It figures that a hurricane’s projected track aimed right at our Stevens 47, Totem, while we were an ocean away from it, having traveled by jet from Mexico to Europe and South Africa. That was Hurricane Kay, in early September. Last week brought Hurricane Ian, which we watched approach Florida, glued to updates, fearing for the boats and livelihoods of friends along Florida’s west coast.  

Actively tracking weather is one of the most consistent features of life on a cruising boat. You don’t just feel the elements more directly; your immediate security is weather-driven. Looking at GRIBs through PredictWind remains our mainstay weather tool. And, we love the new GMDSS addition: graphical display of GMDSS text forecast details (lows, highs, tropical depressions, fronts) over a GRIB. Anyone in my husband Jamie’s classes at Cruisers University in Annapolis from October 10-16 will see a bunch of these. 

Other specialty tools provide input to keep informed and make decisions about our everyday comfort and safety. Writing recently about chubascos, a weather phenomenon in the Sea of Cortez, we focused on how valuable the GOES band 11 viewer is for anticipating these weather bombs. Here are other tools that may be less commonly tapped, but helpful for those of us living at weather level. 

Weather Radar

Radar is an excellent tool when it’s available. Radar on a boat is a fine way to get squall size, location and tracking to mitigate the conditions (Squall tracking, more than avoiding hazards at the night or in fog, is the #1 use of Totem’s radar, in fact). Weather service radar, accessed via the internet, offers a dynamic wider-region view. This requires internet bandwidth.  

A weather radar source with a time loop helps visualize movement and the squall or front’s increasing or decreasing footprint, to preemptively adjust course and or speed. You may not be able to bypass the weather, but even reducing the duration of your exposure to volatile weather is useful. 

On our last days in South Africa, we actually had more wind than Puerto Peñascohad, Mexico, from Hurricane Kay’s attempted swipe—this front line brought 50-plus knots. It was wild to watch (from inside a cozy beach house), but for locals, was “just another Sunday.” 

Real-Time Lighting

Real-Time lighting strike maps show where the sky is more or less electric. Like radar, this tool provides a visual for a storm’s size, intensity and track. For folks on boats, the devastating power of lightning can be even more daunting than wind and rain. 

We like the display on the website Blitzortung for this, and there are a range of real-time lightning map mobile apps as well.

Satellite Imagery

Another satellite imagery resource is Zoom.earth. It’s instructive, but not targeted. Still, for sharing satellite-informed views of your location without freaking out your kids or in-laws, try giving them this view. The red areas show heat detected by satellites. This tool influenced our driving route to avoid hot-season wildfires.

Surge Estimators

Hurricane Kay ended up tracking outside of Baja, California, a much lower risk to Totem than it might have been if it tracked up the Sea of Cortez. But it was late when we considered that, even though the system was relatively distant, there might be a surge effect near our boat’s location. And, as Murphy’s Law would dictate, of course it would coincide with peak tidal swings in an area notorious for extremes (22 feet isn’t unusual). We watched CERA, a collaboration between the National Oceanic and Atmospheric Administration and Louisiana State University, for modeling surge. It indicated that water might not just rise above the level of the slipway, but also spill further into the yard. Not so good for boats in sand or gravel, and not good news for things on the ground. Like our new-in-the-box engine.

Water level exceeding the slipway would have been a first at the boatyard. (We still, by the way, feel this is the best possible option for hurricane season on the Pacific side of Mexico.) From South Africa, we watched and waited for updates. 

And recently, we watched as the surge forecast from Hurricane Ian developed for Florida—especially Southwest Florida, where folks we care about in Punta Gorda have their catamaran. It was tough to see the surge increase and consider the havoc it caused. NOAA’s estimate was 12 to 18 feet. There’s not much good that comes from an 18-foot surge (or even “just” 12 feet) when you’re tied to a fixed dock. 

Wave And Swell

Boaters tend to focus on the wind forecast, the sea state tends to be a much bigger influence for real feel on a boat. And yet, wave and swell forecasts have long been the least accurate reflection of real feel in the weather toolkit. GRIB Wave forecasts only display one wave forecast at a time. Secondary or tertiary waves and swell, such as a swell from a far-off gale, can really increase the motion of the ocean. The information is often available, but clunky to view and interpret. PredictWind has a new tool set that uses all wave and swell data, and then models roll, pitching and slamming based on specific dimensions of a given boat. Its new Automatic Wave Routing feature is a big step toward interpreting a real-feel to make go or no-go decisions. 

If we’re near a surfing region, we also sometimes use surfer websites such as Magic Seaweed to understand the magnitude of local swells. Farther offshore, there might be a weather buoy near a planned route. Looking at real-time data, such as NOAA’s National Data Buoy Center site, can help determine the accuracy of forecast information.  

Tsunami Danger

This isn’t something we really thought about a lot before cruising, but we’ve ended up needing to track tsunamis a few times when we were potentially in risk zones. It’s no joke, and we know enough people who have had truly dangerous tsunami events while cruising. 

While our first tsunami was a nonevent, the second warranted more attention: We watched as the depth changed 6 feet up then 6 feet down in 15-minute intervals. One boat missed a swing and ran aground in a channel.

What are your tools for this? A U.S. Geological Survey website details earthquakes worldwide, and a global scattering of tsunami monitoring stations are on this UNESCO-funded site.  

The 2022 hurricane season finally did get spicy, as promised. While Hurricane Ian left a trail of heartbreak in Florida, we received news that our friends’ boat in Punta Gorda came through nearly unscathed. So many others did not. Neighboring boats were found sunk, or on top of the dock, or in the adjacent yard. And now, on the Pacific side, we watch Orlene. The tropical depression is expected to become a hurricane, and is tracking toward Mazatlan and the Sea of Cortez, where we lie at the northern tip.

The post Sailing Totem: Adding Tools to the Weather Toolbox appeared first on Cruising World.

Studying weather forecasts is so much a part of the morning ritual on our boat that we automatically associate the smell of coffee with weather bulletins and surface-analysis charts. It doesn’t matter where we are—near a city with speedy Wi-Fi and downloads, anchored in a remote corner of the globe with text bulletins, or underway with the Pactor modem screeching and rumbling for half an hour to get a GRIB file—weather and morning coffee just go together. 

As sailors, we live much closer to the elements than most people. Keeping an eye on forecasts is imperative for the safety of the boat and the well-being of the crew. It’s also a fun and interesting pastime.

Get your bearings. When you start exploring a ­cruising area, the local weather might seem indecipherable. Get a good introduction to the ­dominant systems by ­reading a few articles about the ­regional weather. When is the rainy season? Is there a hurricane season? 

Guidebooks offer a helpful, albeit simplified, overview. For instance, guides to French Polynesia, where we’ve been cruising aboard our 1988 Sparkman & Stephens 41, Pitufa, for the past eight seasons, describe the area as having two distinct seasons: a dry and windy season between May and October, and a cyclone season from November to April with generally rainy, hot weather. This is true for Tahiti and the Society Islands, but the Marquesas are usually dry with two short rainy seasons in spring and fall, while the Gambier and Austral Islands have proper seasons with hot summers and cool winters. If you don’t study this kind of information beforehand, you’ll be in for a few surprises.

Pilot charts. Take a look at pilot charts as well. What’s the strength and direction of the predominant winds? How often do passing low-pressure systems interrupt them? Get an overview, and then choose a few reliable weather sources from the jumble of available information. Check them on a daily basis.

Look at the big picture. When we have a strong internet connection, we download wind forecasts for a large area to observe the distant systems behind the local winds. This technique helps us, for example, keep an eye on passing troughs that interrupt the trade winds, or take note of an acceleration zone on top of a high-pressure system. 

We like to compare the American Global Forecast System model with the one from the European Centre for Medium-Range Weather Forecasts. That way, we can ​see how they differ. We also like to check the models after the fact and keep track of which one was more accurate.

Surface-analysis charts allow us to visually interpret the isobars, and they turn features such as fronts, troughs and lows into comprehensible images.

Some cruisers crop too small of a frame when forecasting and download data on an immediate area without seeing the bigger picture. They’re often flabbergasted (and curse the stupid forecast!) if the wind blows from the opposite direction. By contrast, if you download a larger GRIB file, you might see a convergence zone with northwest winds on one side and southeast winds on the other. The big picture is important to understand because minor inaccuracies in the forecast can result in a major predicament that leaves you pitching and rolling off a lee shore. 

Looking at the big picture also means that you can prepare for multiple scenarios and have alternative anchorages in mind. We like to explore cruising areas thoroughly and have our own GPS tracks to follow to a safe anchorage in the event of a windshift—a tool that is especially helpful if a move must be made during a squall or in the middle of the night.

Get a feel for weather patterns. During a prolonged stay in a protected anchorage, it’s interesting to look at the forecasts every day. What’s typical for the season and area? Do forecasts tend to overestimate or underestimate weather features? How do systems move? What can you expect from windshifts from certain directions—sunny skies or squalls? If you know your weather, then you can enjoy fair-weather sailing downwind or use the windshifts that passing troughs generate to make miles against the prevailing trades. 

Wait for proper windows. Losing your patience and sailing out on a suboptimal weather window is tempting, but it often leads to frustration. Flogging sails in fickle winds, or too much wind from the wrong direction, is worse than waiting. 

Once you find your window, make sure that you have a reliable source for forecasts underway. Whether you’re using an SSB or Iridium, monitoring forecasts means you can change course if needed, or head for an alternative destination. 

Each year, we sail east from Tahiti toward the Tuamotus in September or October, and each year neighbors ask us which island we’re headed for. The answer’s always the same: “Where the wind will allow us to go.” Setting out with winds from the northerly quadrant, we make miles eastward and try to get as far as we can. If the wind shifts back to the east earlier than expected, or has less of a northerly component than hoped for, we have half a dozen atolls from which to choose. 

Keep it up. Continue to look at forecasts even at anchor, and be prepared to move. What looks like a benign calm in the anchorage might, in reality, be an approaching system loaded with squalls. Being prepared with information is better than trying to ride out nasty conditions on the wrong side of an atoll. Fetch can build quickly, and waves can reach surprising heights. We were anchored recently on the east side of Maupihaa in the Society Islands when we noticed that the GRIB files showed a major wind shift within the next two days. Those shifts often come with squally fronts, so we warned our neighbors in the anchorage and set out to explore alternative spots in the atoll that might be safer in the clocking winds. When the front arrived with 30 knots from the northwest, we were comfortably anchored behind a beautiful motu on the northwest side. Unfortunately, the boats that decided to ride out the shift on the east side spent “the worst night of their cruising lives,” according to the skipper of a 50-foot catamaran, even though they were anchored just 2 miles away from us on the other side of the tiny lagoon. 

Birgit Hackl and her partner, Christian Feldbauer, have cruised French Polynesia for eight seasons. For more information, visit their blog.

Check the Charts for Patterns

Cross-referencing pilot charts, local guides, and anchorage guides can offer a good overview and insight into the weather patterns of an area. 

See our satellite data-based global interactive wind atlas at pitufa.at/oceanwinds.

Pacific Weather

The weather in the South Pacific is dominated by two big highs—the Kermadec high and the Easter Island high—with the South Pacific Convergence Zone in between. The trade winds here are not as stable as Atlantic and Caribbean trades, and can be frequently interrupted by troughs that travel along the convergence zone. Every couple of weeks, a passing trough lets the winds clock around, which is annoying when passagemaking westward but handy when hopping eastward along the islands.

We use Meteo France’s weather bulletins and surface ­analysis, NOAA’s surface analysis and cyclone warning site, and the weekly summaries of MetBob’s Bob McDavitt. All of those sites are embedded here: pitufa.at/weather-fp.

For Fiji, see the weather forecasts on the government’s ­official site (met.gov.fj), which includes the marine forecast.

These sources provide a general overview: 

Pacific Crossing Guide (Adlard Coles Nautical); South Pacific Anchorages (Imray); Cruising World, July 2019, “Pacific Weather Routing”; and Cruising World, July 2019, “Pacific Passage Planning”.

We use an SSB radio in combination with a Pactor modem to download forecasts underway, or when in remote areas. SSB propagation is limited to certain times of the day, so some cruisers prefer a satellite phone. No matter which medium you use, saildocs.com provides a great free service to download forecasts, using small files to save data. For French Polynesia, visit pitufa.at/weather-fp.

The post Pilot Charts, GRIB Files and Wind Patterns: Understanding Weather Bulletins, Models and Forecasts Makes for Safer, Happier Cruising. appeared first on Cruising World.

Marine weather guru and well-known seminar lecturer Lee Chesneau passed away Thanksgiving Day, 2021, three years after suffering a major stroke. 

According to an obituary posted on the Dignity Memorial website, after serving in the U.S. Navy, Chesneau spent his career with the National Weather Service, retiring in the late 1990s. He then went on to teach and speak about weather, eventually forming his own consulting business to promote safety at sea. In that role he helped train commercial fishing and recreational mariners on becoming self-reliant on vessel routing and prudent decision making. Together with Capt. Ma-Li Chen from Taipei, Chesneau published Heavy Weather Avoidance and Route Design: Concepts and Applications of 500Mb Charts and numerous other works. He was one of only a few to be certified as an USCG Standard Training, Certification, and Watch Standing instructor for basic and advanced meteorology.

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NOAA’s Climate Prediction Center is predicting another above-normal Atlantic hurricane season. Forecasters predict a 60% chance of an above-normal season, a 30% chance of a near-normal season, and a 10% chance of a below-normal season. However, experts do not anticipate the historic level of storm activity seen in 2020.

For 2021, a likely range of 13 to 20 named storms (winds of 39 mph or higher), of which 6 to 10 could become hurricanes (winds of 74 mph or higher), including 3 to 5 major hurricanes (category 3, 4 or 5; with winds of 111 mph or higher) is expected. NOAA provides these ranges with a 70% confidence. The Atlantic hurricane season extends from June 1 through November 30.

“Now is the time for communities along the coastline as well as inland to get prepared for the dangers that hurricanes can bring,” said Secretary of Commerce Gina Raimondo. “The experts at NOAA are poised to deliver life-saving early warnings and forecasts to communities, which will also help minimize the economic impacts of storms.”

Last month, NOAA updated the statistics used to determine when hurricane seasons are above-, near-, or below-average relative to the latest climate record. Based on this update an average hurricane season produces 14 named storms, of which 7 become hurricanes, including 3 major hurricanes. Watch this video summary of the Outlook:

El Nino Southern Oscillation (ENSO) conditions are currently in the neutral phase, with the possibility of the return of La Nina later in the hurricane season. “ENSO-neutral and La Nina support the conditions associated with the ongoing high-activity era,” said Matthew Rosencrans, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center. “Predicted warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and Caribbean Sea, weaker tropical Atlantic trade winds, and an enhanced west African monsoon will likely be factors in this year’s overall activity.” Scientists at NOAA also continue to study how climate change is impacting the strength and frequency of tropical cyclones.

“Although NOAA scientists don’t expect this season to be as busy as last year, it only takes one storm to devastate a community,” said Ben Friedman, acting NOAA administrator. “The forecasters at the National Hurricane Center are well-prepared with significant upgrades to our computer models, emerging observation techniques, and the expertise to deliver the life-saving forecasts that we all depend on during this, and every, hurricane season.”

In an effort to continuously enhance hurricane forecasting, NOAA made several updates to products and services that will improve hurricane forecasting during the 2021 season.

• In March, NOAA upgraded the flagship Global Forecast System (GFS) to improve hurricane genesis forecasting and coupled GFS with a wave model extending ocean wave forecasts from 10 days out to 16 days. Additionally, Global Positioning Satellite Radio Occultation (GPS-RO) data are now included in the GFS model, providing an additional source of observations to strengthen overall model performance.
• Forecasters at the National Hurricane Center are now using an upgraded probabilistic storm surge model — known as P-Surge — which includes improved tropical cyclone wind structure and storm size information that offers better predictability and accuracy. This upgrade extends the lead time of P-Surge forecast guidance from 48 to 60 hours in situations where there is high confidence.
• NOAA’s Atlantic Oceanographic and Meteorological Laboratory will deploy its largest array of air and water uncrewed systems to gather data designed to help improve hurricane intensity forecasts and forecast models. New drones will be launched from NOAA Hurricane Hunter aircraft that will fly into the lower part of hurricanes, and in the ocean, saildrones, hurricane gliders, global drifters, and air-deployable technology — called ALAMO floats — will track various parts of the life cycle of tropical storms.

Last year’s record-breaking season serves as a reminder to all residents in coastal regions or areas prone to inland flooding from rainfall to be prepared for the 2021 hurricane season.

“With hurricane season starting on June 1, now is the time to get ready and advance disaster resilience in our communities,” said FEMA Administrator Deanne Criswell. “Visit Ready.gov and Listo.gov to learn and take the steps to prepare yourself and others in your household. Download the FEMA app to sign-up for a variety of alerts and to access preparedness information. Purchase flood insurance to protect your greatest asset, your home. And, please encourage your neighbors, friends and coworkers to also get ready for the upcoming season.”   

NOAA also issued seasonal hurricane outlooks for the Eastern and Central Pacific basins, and will provide an update to the Atlantic outlook in early August, just prior to the peak of the season.

Visit FEMA’s Ready.gov to be prepared for the start of hurricane season and the National Hurricane Center’s website at hurricanes.gov throughout the season to stay current on watches and warnings.

The post For 2021 NOAA Predicts Another Active Atlantic Hurricane Season appeared first on Cruising World.

Weather always wins. Schedules are the enemy. Between these two principles for safe cruising, Totem and crew have remained in Santa Rosalia for an extended stay – weeks more than anticipated. Our goal destination is only about 250nm to the north: returning to Cabrales Boatyard in Puerto Peñasco to dig into our engine issues. Why is this distance, which we’d normally do in 40 or so hours, proving to be so complicated?

Weather drives our decisions, and it’s the primary reason we are still cemented to the dock. We want easy conditions: partly for our personal comfort, and partly to avoid any situation that could over-work our somewhat compromised engine. We’re a sailboat, so what’s the big deal?

In the wintertime, strong northerly winds dominate the Sea of Cortez. They make slab-faced waves two or three seconds apart. Wind and water from the direction we want to go. We like to live by the code that “misery is optional,” and bashing into square seas for 250 nm is not consistent with that tenet.

These frequent northers generate over the Four Corners in the US southwest and are readily forecasted. But Sea of Cortez weather is also affected by Pacific Ocean weather, complicating the gaps between northers. This diagram helps illustrate: the red boxes are areas between mountain ranges, flatter terrain where gap winds accelerate across to the sea. Those yellow boxes are the dominant ranges, which fuel katabatic (falling) winds.

Our juggle: to find three days of mellow weather that let us get back north. We really need only two days to transit 250 nm, but prefer the extra day to allow seas whipped up by the prior system to flatten. Misery is optional!

This is where our second factor kicks in: TIME. If we are willing to spend a week or more offline, we’d hop one day north to Bahia San Francisquito or Isla Partida in a weather window otherwise too short for the entire trip. We’d wait out 25-knot to 50-knot winds tucked in there, looking for the next window to proceed north. The catch is that waiting period is often about a week.

We are a victim of our success at the moment, unable to take a week off from high-bandwidth internet. Our coaching business is thriving, and frankly, we love it (how lucky are we to be able to help people realize the cruising dream?!), and frankly, we need the income (that engine…).

Supporting between 45 and 50 clients has kept us pretty busy. Almost half of the TRU crew we’re actively working with are recently launched as cruisers, navigating the hurdles of their new lifestyle. Others are more tenured, and it was pretty exciting this week to see our third TRU client close the loop on a three-year circumnavigation. A big congratulations to the Mirabella crew!

While we’re away from cell towers, we keep up with email via our Iridium GO, but our days are filled with video chats to talk about a prospect boat, zooming in to high resolution images of chainplates or GRIB files for weather routing. Adding a number of seminars into the mix means more bandwidth. Text-only connectivity of the GO email is fine for normal cruising, but it isn’t good enough to keep up with those demands.

Are we frustrated or disappointed? No, not really. Sure, we’d really like to be back at Cabrales Boatyard among friends (it’s special! Read our Ode to a Shipyard Community to see why). Santa Rosalia is nice, but there’s no cruiser community to partake in. We miss camaraderie of sharing meals, laughs, and tools with the friends back at Cabrales. Our teens missed another teens birthday, one we were SURE we’d be able to make… by February 28.

In many ways this is a good reminder of some cruising principles that bear repeating. Weather always wins. Schedules are the enemy. In this case, schedules are our inability to be away. That can apply to cruisers who are trying to juggle working while afloat like we are. But it can also apply to those who are trying to get to that next island to meet friends flying in that they’ve invited for a holiday. It’s easy to be tempted into making bad decision that result in being miserable at best, and unsafe at worst, when letting a schedule convince you that it’s OK to tempt the weather.

Meanwhile, we are in early transition away from the northerlies towards what will become light southerly winds, which dominate weather in the relatively airless hot months of summer. And meanwhile, we make the most of where we are.

Marking the one-year anniversary of the pandemic’s arrival in our reality, we look back with the benefit of optimism that there is a better, freer time coming soon. Our daughters turned 16 and 18, milestone birthdays that passed while in isolation instead of being celebrated. They’ve been incredibly patient throughout. Their maturity is a testament to the flexibility bestowed upon them by growing up as cruising kids: change happens, and you adapt. Not all phases are fun, but you make the most of them and carry on to a better time.

Jamie and I wanted to do something special for them. And the happenstance of being parked at this particular corner of Baja, at this particular time of year, suddenly came into focus: directly across the peninsula, the San Ignacio lagoon carves in from the Pacific – and teems with grey whales. For about two months a year, this UNESCO world heritage site is the mating and calving grounds for the migratory whales. And so, we went.

It’s unusual for us to splash out like this. It took a lot of time for me to figure out how we could do this in a way that aligned with our risk tolerance. But with work going well, and money saved from, well, not going out much this year – the splurge wasn’t hard. The ability to book an entire boat to ourselves instead of sharing it with folks who may not share our risk profile made it possible.

Can you imagine the feeling of being checked out by a whale? We first experienced it in Papua New Guinea when false killer whales made flyby passes, rocketing by our dinghy. The Greys were entirely different: the massive mother parking herself immediately below, and perpendicular to our panga. Her curious calf first spyhopping, then riding up on her back to get a closer look at the above-water creatures.

We’ve seen a lot of badly done whale watching, with aggressive guides bent on delivering “the experience” to the benefit of tips and the detriment of whales. This bore no resemblance, and our captain’s respect for the whales and other boats in the area unquestionable. Despite 27 years’ experience driving boats in the lagoon, his unjaded enthusiasm greeting the whales that approached our small vessel was the best and only kind of contagion we encountered.

It’s a bright spot, one among many which feel like they are gathering to move us all forward, slowly, surely!

The post Sailing Totem: Weather and Schedules, the Laws of Cruising appeared first on Cruising World.

—Behan

On this day, I have two boats galloping north at 10 knots. The sailing is nice, boosted by 3 knots of Gulf Stream current along Florida’s east coast. This has elements of a unicorn passage. After dark, it’ll be all dragons. I’m anxious for both families. I didn’t exactly send them out into this night. But I didn’t stop them either. Realtime weather radar shows heavier rain approaching. Florida now has tornado and flood warnings. Damn. Lightning hotspots continue to increase along the coastline. The dragons are coming. 1,700 miles west, Totem bobs in softening afternoon wind waves in the Sea of Cortez. We haven’t had a drop of rain in 6 months. No dragons either. We’ll have a gorgeous full moon rising over Isla Carmen in a few hours. Nothing like my Gulf Stream boats speeding through darkness and dragon fire. I am the chess master, sliding pieces past danger. I am the fool, thinking I control the board.

I’ve only recently come to accept that I provide a weather routing service. I’m not a meteorologist, not even a pretend one. I’m never the assertive voice when a group of sailors debate a weather window for the next passage. Information sharing is helpful. Selling an interpretation only masks a hidden agenda. I thought I understood weather forecasting pretty well when I was a racing sailor. Weather had tactical value and I was competitive. Then came the first big and very unexpected squall while delivering a J/35 to Newport, RI. Didn’t see that coming, but could have if I’d known where to look.

Family cruising in Puget Sound and beyond shifted desired weather traits from tactical to comfortable. The unicorn passage: fully at ease with surroundings in the magic and enchantment of glorious sailing. Unicorns are rare, elusive. Waiting is tedious; not getting you to that next beautiful anchorage you’ve dreamt of, frustrating. Instead, interpret the forecast and go. Rarely expecting unicorns, always hoping not to see dragons. Sometimes getting it right. Sometimes not, always comparing and contrasting forecast and reality after the anchor dropped. After hundreds of passages and assessments, my technical weather knowledge is hopelessly mediocre. My particular weather superpower is translating meteorological data into “this is what it’s going to be like.”

My Gulf Stream boats aren’t off to the next dreamy anchorage. They’re retreating to neutral territory. Like many, they’d been COVID-19 restricted in the Caribbean. Uncertainty of a global pandemic and hurricane season looming like a nightmare monster set them on a path to Maine. It’s a return to home for one family. A gorgeous new cruising region for the other. A big step closer to predictability for both. The path is about 2,500 NM long. Beginning in turquoise water of the US Virgin Islands, where warming temperatures bring increasingly volatile weather. Going north in May and June quickly bumps into colder weather and frequent gales springing from the East Coast out into the cold Atlantic.

A few weeks before picking a good enough window to depart paradise, we began the conversation of which route home. We sailed Totem from the Caribbean to New England in 2016, on a direct route via Bermuda. This shaved 1,000 NM from a path along the US coast. Due to COVID-19, Bermuda was now closed, and the likelihood of gales was high, so, no go. A less offshore route meant skirting the Bahamas, but they were also closed—even for vessels in transit. This longer path without bailout options suddenly got riskier. Fortunately, Salty Dawg Rally organizers stepped in to help. They worked with Bahamian officials to create an innocent passage status list of boats for cruisers repatriating the US and Canada. Once on this list, crews could stop in Bahamas to wait out weather, or procure food and fuel.

With a bailout in Bahamas possible, most of the dozen boats that sought out professional weather guidance from this amateur router preferred to skirt east of Bahamas and make landfall in Chesapeake Bay. This unlikely outcome wasn’t realized by any of them. Through the weather window, I could point out dragons lurking. Boats began peeling off to take innocent passage through the Bahamas. Better to make some progress than wait and wait for the unicorn passage. These boats leap frogged through the Bahamas, unable to step ashore but grateful for the respite. Each made landfall in Florida.

My last two boats, patient or stubborn I won’t say. As their weather router, it’s not my role to tell them when or where to go. It has to be their choice. It can be frustrating, when they don’t follow what I think they should do. Then I remember the times I chose poorly. This includes last night on Totem. I thought the afternoon swell would fade for a flat night and easy sleeping. Instead it was a restless, rolly night at anchor. There is no crystal ball. I don’t push my interpretation, only describe what I see.

A huge low off of New England, with a trough extending to the Bahamas, blah, blah, blah. I picture myself with the young families. One with some offshore experience. The other hadn’t sailed overnight before. I picture the headlines: Virgin family departs Virgin Islands for innocent passage to Bahamas. What could go wrong…? Both boats added experienced crew. With a gift of easier whether, they managed nicely. Weather got more complicated as they went, but they arrived in Florida without drama.

On this night, northbound along the Florida coast, finesse is the key. I described volatile conditions before they set off. No bad wind or waves, but potential squalls to 40 knots, and lightning. Those dragons are real and can be terrifying. A quick start guide to successful family cruising would do well starting with this rule #1: Avoid Terrifying.

My guidance was for a slow start to let the band of unsettled weather pass ahead. I watched the satisfying progress on their satellite tracker positions. They were only 50 miles offshore, within real-time weather radar range. With another online resource I could track real-time lightning strikes. On another browser tab I rechecked the GRIB Rain forecast for the 20th time. Lifeless gray blobs, with smaller pink ones denoting rain intensity. Lifeless, almost meaningless until you see the dull blobs as the smoke and flames from dragon fire. That gets the heart rate up.

The tools I used aren’t meant for piloting, but that’s how I used them. To navigate around hazards. Crudely plotting the lightning’s advance (radar and lightning screens didn’t show lat/long lines) I went against my own rule not to tell them what to do. “Speed now please, all you can make. And change course ten degrees to starboard,” I typed into the message box. The screen confirmed the message sent. Several minutes passed before the reply arrived, “Headsail out, sails trimmed, and course changed. Making out lightning in the distance.”

Virtual chess and mythical creatures. I could feel their tension as lightning approached. Almost hear the voice crack, if there was a voice in the next message, “lighting is getting intense, will we miss it?” With a few more course adjustments, volatile weather passed just south of the two boats. Actual conditions reflected forecast conditions pretty well, except for being 40 miles closer to my boats then the lifeless gray blobs showed. I learned a long time ago that the weather isn’t supposed to do what the forecast says. The dragon that was supposed to strike fear deeper into the night, was now gorgeous lightning safely astern. Another experience. Another assessment. Another way to express lifeless gray blobs.

The post Sailing Totem: Unicorns and Dragons—Confessions of an Amateur Weather Router appeared first on Cruising World.

What cruiser hasn’t blamed a meteorologist for a bad forecast when caught “unexpectedly” in a boisterous blow? “It was only supposed to be 15 knots, but that forecaster couldn’t get it right if Mother Nature shouted the answer.” 

Supposed to be—as if a forecast were instructions for atmosphere and ocean to follow. I have a whimsical theory, in fact: Impugned for ruined weddings and rough days on the water, clever and dedicated meteorologists created computer-derived weather forecasts packed into a digital file called a gridded binary, or GRIB file. These GRIB forecasts deflect hurtful sentiments away from sensitive scientists and onto emotionless computers—and that’s how meteorologists get the last laugh: The various computer models require an understanding of how the data should be interpreted. In other words, a faulty forecast might be user error after all. 

Picture, if you will, weather geeks in a breakroom, pocket protectors and all: 

Wx Geek 1: “So this saltier- than-thou type returned to the marina complaining about the GRIB forecast—it was only supposed to be 15 knots he said.”

Wx Geek 2: “Let me guess, he thought that meant maximum wind speed?”

Wx Geek 1: “Better still, he never checked the gust forecast that showed 30 knots!”

Cruising our Stevens 47, Totem, through Papua New Guinea was a stark reminder that we take weather tools for granted. On Panapompom Island, children gawked at us, the strange visitors, and squalls seemed always on the horizon as we walked the beach talking to islanders. Tumbling in the surf was the carved bow section torn from a canoe. Lateen-rigged outrigger canoes are the primary mode of transportation throughout Papuan islands. One woman matter-of-factly said, “Sometimes they don’t return.” 

Conditions in the region were tough due to a stalled low-pressure system. We expected it well before heavy grayscale clouds arrived, thanks to a GRIB forecast downloaded with our SSB and Pactor modem. Papuan sailors are skilled and tough as nails, but the destroyed canoe in the surf exposed the consequences of a thousand-year technological gap between us. 

Safety at sea is immeasurably better because of weather forecasting. Weather predictions are imperfect, but here’s the catch: GRIB forecasts are a series of images with symbolic meaning; the forecast is how you interpret those images. Put another way, you are the forecaster.

Van Gogh’s “Starry Night” has nothing to do with weather forecasting, but the celestial whorls share more than passing resemblance to the swirling flows in a GRIB image. My untrained interpretation of “Starry Night” is thin: captivating colors that seem alive with movement. That’s all I’ve got. Professional interpretations online speak of turbulence, agitation, a cypress tree representing a bridge between life and death. It’s easy to have an interpretation of GRIB images, but is it the whole meaning? Or do you need to dig deeper?

A GRIB Is Not an App!

There are a number of meteorological agencies worldwide that create global and regional GRIB forecasts. Agencies within the National Ocean and Atmospheric Administration and the European Center for Medium-Range Weather Forecasting are the biggest GRIB sources. Each produces multiple forecasts, called GRIB models. For example, a few of the GRIB models created by NOAA agencies include: 

• Global Forecast System, depicting surface wind, ­pressure, precipitation, etc.
• Real Time Ocean Forecast System, displaying ocean currents.
• Wave Watch 3, predicting waves and swells.

In addition to national sources, private companies produce GRIBs, such as PredictWind’s PWE and PWG models. On the whole, it’s a dizzying display of acronyms! The takeaway is knowing that GRIB sources and GRIB models are different than the app or viewing tool.

Windy, Passage Weather, Ventusky and many other apps/viewers don’t create a GRIB forecast, they only display it. An app is like a theater, and the GRIB model is the film being shown.

GRIB viewers are set apart based on which models they offer and what control features are available. Maybe they show only one model, or don’t reveal important information about the GRIB. Or perhaps they don’t have the option to limit file sizes for offshore or remote downloads using a satellite device or Pactor Modem.

When choosing and analyzing GRIB files, here are technical criteria to consider:

Geographic area: The bigger the forecast area, the bigger the file size. If bandwidth is constrained, it’s best to use a GRIB viewer that enables a user-defined area to manage download size. How much area do you need? Your planned route is the obvious starting point, but sometimes a broader area can show weather systems that will affect you later.

In 2016, we sailed 9,614 nautical miles from South Africa to the US. Between Bermuda and Connecticut, a maze of current eddies, meanders and filaments splintered away from the Gulf Stream to make it one of our least comfortable passages. We used GRIB current forecasts to minimize foul eddies and wind against current situations, but water flow was too dynamic. Had I not been so miserly and insistent on small area, small file size, I might have seen current flow patterns to pick a cleaner, more comfortable path.

Resolution: Often overlooked, GRIB resolution is a major reason that cruisers get the forecast wrong. The color shading on GRIBs applied by some viewers is used to represent wind speed, wave height, etc. At first glance, it appears as though a supercomputer calculated forecast data for every pixel on the screen. But it hasn’t. Resolution refers to the spacing between the actual calculated data points. Wind-barb symbols, when shown, reveal the real spacing. All spaces between them are shaded by the viewer, which is making its best guess at what the wind speed will be. At the source, GFS model resolution is 18 miles (28 kilometers) and ECMWF models can be 5.6 miles (9 kilometers) or 11.2 miles (18 kilometers), depending on the model. For perspective, 18 miles’ resolution means that one data point represents 324 square miles. One data point per 5.6-mile spacing covers 31 square miles. High resolution means less estimated information but creates a problem for sailors. The GRIB file size quickly becomes too large to download offshore or in remote areas using an SSB radio or budget satellite communications. Fortunately, GRIB resolution can be dialed back. A medium resolution of 31 miles (50 kilometers) has one data point per 961 square miles; low-resolution spacing, with data points 62 miles apart (100 kilometers) has one data point per a whopping 3,844 square miles! If there aren’t features in a 3,844-square-mile area affecting your weather, then that might be all you need. Add land, though, and the low-resolution forecast won’t show wind deflected, blocked or funneled—or seriously altered as land heats and cools on a daily cycle. Along a coastline, the gap between data points that span land and sea, and estimated wind speeds displayed by a viewer’s color shading, can be seriously flawed with low resolution. The overland prediction often has little resemblance to wind over water. With big spacing, the viewer’s color shading could, for example, show 30 knots of wind 30 miles offshore and 10 knots nearshore because the overland data points skew the speed estimates in between data points. In reality, those 30 knots could carry to just off the coast, causing problems for a coastal sailor. Always know GRIB resolution, and use high resolution when you have the bandwidth on board. When you don’t, remember that land has a big impact on any forecast.

Duration: The number of days covered by the forecast is known as duration. It can range from one to 16 days. Forecast accuracy tends to be high for the first three days, then decline with each successive day. What value does a 16-day forecast have if only the first three are accurate? It can show trends. 

Let’s say you’re in the British Virgin Islands and want to make the 170-mile trip to Antigua. This is against prevailing easterly trade winds and can be a slog. Looking at longer-duration forecasts reveals trends that help find a better window for the passage. Trade winds blow with consistency but still cycle up and down, and occasionally break down completely. Using a large-area and long-­duration GRIB forecast, tracking weather across the broader area can hint at local conditions days later. For instance, maybe a gale flowing east from the Carolinas will have enough impact to shut down the trade winds for a smoother ride across the Anegada Passage.

Increment: A GRIB forecast is a series of snapshots; increment refers to the number of hours between those snapshots. Options are three, six, 12 or 24 hours. Smaller increments help to show changes more clearly over small areas. Larger increments have the benefit of smaller file size while being adequate to look at trends over a large area. 

Work with the Elements

The features that define the forecast are its elements. Wind is the most common used by sailors. It’s a start, but taken at face value, is misleading. Taken without considering other elements underutilizes the full value of GRIB files. Here are tips to get the most out of a GRIB forecast:

Pressure: Differences in pressure make wind. To see this, look at the black lines on a GRIB indicating ­pressure changes. As the gradient spacing gets closer, the wind ­increases. Use pressure to better see the big-picture weather.

Wind: How much does the forecast really indicate? Forecasted wind speed tends to be interpreted by sailors as representing the maximum expected, but in fact, is an average of the top range expected. A blustery spring day showing 20 knots can have wind ranging meaningfully higher and still fit the forecast. Also note that wind forecasts struggle for accuracy in whisper-light conditions. 

Gust: Short bursts of higher wind speed can be much different than the wind forecast. Ignoring the gust forecast is disregarding an excellent indicator of what the highest winds might be. Comparing wind and gust forecasts is a gauge of volatility: the larger the difference between them, the less stable conditions are.

Waves: Sea state affects comfort on board more than wind. Unfortunately, sea-state forecasts require the most experience to conjure an interpretation. Wave forecasts predict height, direction and period. Height is not the maximum size but rather the average significant height. Waves forecast to be 6 feet can have a 1-in-1,000 wave that is 10 feet. 

Forecasts don’t quite ­capture the “real-feel” out there. Prediction algorithms don’t account for local factors such as coastal topography and bottom contours that amplify size, compress period, or make sea state erratic and confused. Multidirection sea states are common offshore but don’t make GRIB forecasts either. To better interpret wave forecasts, consider the things that push and shove water out of pattern. 

Current: Along the coast, tide charts are useful for routing with a speed advantage. Ocean currents are often forgotten about, their forecasts underutilized. Ocean currents are often irregular and shifty, but they are worth identifying to route for efficiency and avoid uncomfortable sea states created by conflicting flows of wind and current. 

Rain: A GRIB rain forecast indicates if it’s time to dust off the foul-weather gear. It has more value as a gauge of volatility. Rain is indicated by inches or millimeters per hour. High rainfall tends to be part of volatile weather conditions.

CAPE: This is an acronym for convective available potential energy. It’s a measure of atmospheric instability, such as thunderstorms and squalls. A high CAPE index doesn’t guarantee their formation but indicates their intensity.  

Cloud: A GRIB cloud forecast is a good indicator of visibility when sailing at night with little moonlight. It also might highlight an area of volatile weather such as a frontal system or trough. 

Indexing: Using a single GRIB model might show the best forecast available. It also might show the worst. Looking at multiple GRIB models sets up a problem: When they differ, how do you know which has the better prediction? I’ve listened in on some group-think weather ­discussions where a participant pushed a particular forecast. Turns out that this GRIB best fit their schedule, so they wanted it to be true. That’s gambling. A better method to follow is what I call indexing the models. 

The idea is simple. Study the GRIB models you have available. When they all agree on conditions, the real weather is likely to be as forecast. When they don’t agree, watch the real weather and make a note of which models trend closest to reality. A pattern will emerge. If you sail to a different region or slide into a different season, then re-index because the most accurate model might change. There might not be a single winner, but one model might be better for wind and gusts, and another for the rain or CAPE. When we crossed the Indian Ocean, PredictWind’s PWE was best by far for wind, GFS was best for rain and CAPE forecasts, and ECMWF was the best read of sea state. It took a little more work to download and view them all, but it made for a sweet trip across a lively ocean.

Just as it’s important to start with multiple GRIB models, it’s best to use multiple forecast resources when facing challenging passages. GRIBs give us convenient information anytime or anywhere, but always remember that you are the forecaster. If that makes you uncomfortable, consider the aid of a professional meteorologist to interpret the data for you. Hiring a weather router is a smart way to start cruising with better weather information, while learning in the process. Just don’t complain when results are imperfect! It’s a tall order to predict the future.

Jamie Gifford is a sailmaker, and along with his wife, Behan, provides coaching to fledgling cruisers. The Giffords have completed one eight-year circumnavigation aboard their Stevens 47 Totem, and are about to set off across the Pacific again. You can follow their travels at cruisngworld.com/sailing-totem.

The post How to Read and Interpret GRIB Weather Files appeared first on Cruising World.

The year was 2000, the location was Ship Channel Cay in the Exumas, and the issue was what it always is in the Bahamas in winter: weather. Like so many new cruisers, Chris Parker and his partner, Michael Zidziunas, in their Cheoy Lee 30 Dragon Lady, had expected cruising in paradise to be, well, paradise. Except on this particular morning, it wasn’t.

“The weather forecast was for the wind to be southeast when we got up in the morning and to come around to the southwest during the day, and a cold front was coming through,” Parker says. “So we wake up, and it’s blowing southwest at 20, and we’re on a lee shore on the wrong side of the island. Not a good situation.”

It didn’t improve. Eventually, they bailed out and slogged upwind 3 miles in three hours to find cover at Allens Cay, the sort of trip that anyone who has ever been caught out in the Bahamas knows embodies that technical weather term “snotty.”

“So that was one,” he says. “And we had two other situations within a month when a cold front came through that was either completely unpredicted or much stronger than predicted, or much earlier. And I said, ‘I’ve got to be able to do a better job than this.’’’

It was a fitting genesis for a weather forecaster who today is practically a household name among cruising sailors in the Caribbean, Bahamas and East Coast. Born of necessity, a love of sailing and a lifelong passion for meteorology, Chris Parker’s Marine Weather Center is the go-to weather service for thousands of cruising sailors who subscribe or who simply listen in on the net each morning.

As his service has grown, he’s added two full-time meteorologists, hardware that uses directional capability to reach vessels going trans-Atlantic and to every corner of the Caribbean via SSB, and livestreamed internet forecasts that complement emailed forecasts for each region between Maine and Panama.

When we were cruising full time aboard Osprey, we started every day (except Sunday) tuning in to USB 4.045 at 0630, listening for that familiar voice: “Good morning, all stations. This is Chris Parker on Bel Ami with Marine Weather Center, whiskey-charlie-yankee,” and I would settle in with my coffee, notebook and pen, ready to be educated. Since I was inexperienced and uncertain at the start, for me Parker’s steady, patient voice on the other end of the SSB was a comfort and a confidence builder. Listening to him every day, studying his forecasts, and talking with him when needed, my husband, Johnny, and I learned enough to become confident in our own abilities to understand and interpret weather patterns and forecasting tools, making us better cruising sailors.

Still, we never made a big passage without consulting Parker, and remarkably, in five years of steady movement across a lot of different water, he never steered us wrong. Even well offshore, his forecasts were accurate not just to the day, but often to the hour, and if he said we should be seeing 20 to 25 knots of wind and 4- to 6-foot seas, almost invariably that’s what we would be seeing.

It’s this combination of accuracy, breadth of products, local knowledge of the territory he covers, affable professionalism, and an immense well of patience that makes him so valuable an asset for cruising sailors. As someone who knows firsthand how miserable or even dangerous sailing can be when you get the weather wrong, he understands how important it is to get it right—not just for the safety of the boat, but also for the well-being of the boat’s people.

Many of his subscribers are friends and fellow cruisers, so for him, it’s personal. He makes it a point to know his clients, their boats and what they can tolerate, and caters his forecasts to those tolerances.

“Meteorologists with the National Weather Service are graded on whether their forecasts are correct,” he says. “Our goal is not necessarily to be correct; it’s to have you not be surprised by weather that puts you in a bad situation. So, if we have someone going trans-Atlantic in a small sailboat without a lot of fuel, or no engine, if they’re in a light-air situation, we’re going to underpredict the wind so they’re not surprised by being becalmed. And on the other hand, if there’s going to be a lot of wind, we tend to overpredict it so they’re not surprised.”

From a young age, he has been into the weather. In second grade, he had a key to the science lab and examined daily the recording barometer to make a forecast, which he published in the school newspaper. When Parker was 10 years old, his father bought a 27-foot Cruis Along—a classic family runabout built on Chesapeake Bay—and he started boating on the bay’s Sassafras River. By the time he was 12, he was the unofficial tender to the local mooring field, running a 12-foot runabout with a 15 hp Sea King on the back. He fell in love with sailing at summer camp, eventually sailing and racing on Lightnings, Flying Scots, Star boats, Lasers and PHRF boats.

All through high school he kept making forecasts for the school radio station, and meteorology seemed like a no-brainer for college. But two years into a meteorology program, he realized he wasn’t going to make it, so he graduated with a business degree.

For a while, the weather took a back seat to making a living. Then, in 1993, he and Zidzivnas bought Dragon Lady and lived aboard while working in Miami. In 1999, they quit their jobs and went sailing. “The plan was we were going to be out and see as much of the world as we could, and do it until it wasn’t fun anymore.”

They sailed for five years, switching from Dragon Lady to a 1966 Morgan 34 named Bel Ami and traveling the East Coast, and down to the Bahamas and Bermuda. “The joke was, after our second year in the Bahamas, our families said: ‘You said you were going around the world. What happened?’ We said, ‘Well, the Bahamas is part of the world,’ and a pretty good part of the world!”

But it had lousy forecasts, despite the efforts of NOAA and BASRA (Bahamas Air Sea Rescue Association), where sailors got their information. After the back-to-back poorly predicted cold fronts, he started downloading weather fax charts from Coast Guard stations, listening to HF broadcasts, and working with a brand-new tool: GRIB files. He beta-tested OCENS WeatherNet and GRIB Explorer, and started making forecasts for Bel Ami.

Pretty soon, cruising friends wanted to know why and how Bel Ami was making such spot-on weather choices. It wasn’t long before he was creating forecasts for them as well, “and that started growing into a business on its own.”

Like many, Parker also listened to David Jones, who ran Caribbean Weather Center—an SSB-based service out of Tortola—for cruisers in the Eastern Caribbean. He had hoped to be able to apprentice with him, but Jones died in fall 2003. Initially, Jones’ widow didn’t want to continue the business, so on the first Monday in January 2004, Parker started his own marine weather net via SSB.

“On that morning, Bruce Van Sant [author of The Gentleman’s Guide to Passages South] in Luperón heard me on the radio, and he knew David’s widow. And he called her, and he said, ‘You have got to team up with this guy.’’’ So, from 2004 through 2010, Parker was the chief forecaster for Caribbean Weather Center. In 2010, he opened Marine Weather Center, and Caribbean Weather Center ­simultaneously shut down.

Since 2005, Parker has based his forecasting operations from his home in Lakeland, Florida. With the service steadily growing, three years ago he hired Chris “Stormy” Stickle, and more recently Shawn Rosenthal, both young meteorologists.

“We want us all to be trained in everything,” Parker says. So, for example, Stormy handled all the SSB nets while Parker was in Annapolis for the fall boat shows. “It’s a huge relief. I still work six days a week—and actually I still work Sundays too, because custom forecasts have to go out on Sundays. But it’s enabled us to grow the business.”

Two other upgrades have been the addition of a dedicated building on his property for the forecasting operation (rather than a 6-by-6-foot closet in his house), and a directional Yagi antenna, which he installed with the help of cruising sailor and friend Rick Medero aboard S/V Sea Language. German-based OptiBeam custom-built the antenna for Marine Weather Center’s two bands—8 MHz and 12 MHz—and the 20-by-40-foot array stands 85 feet tall and rotates to better pinpoint accuracy to the recipient.

“It used to be beyond about 1,000 miles we had really difficult propagation,” Parker says. “But now we can talk reliably with boats all the way to and from Europe.”

In addition to emailed regional forecasts, livestreamed webcasts, SSB net forecasts, and individual routing, in September 2017 for Hurricane Irma, and again in September 2018 for Hurricane Florence, Parker added Facebook Live to his repertoire.

One of the great bonuses to his job, he says, is maintaining his friendships in the cruising community. He plans to get back out there eventually, after he retires. Meantime, he sees a continuing need for Marine Weather Center, despite constantly evolving technologies that make it easier than ever to get weather from multiple sources.

“I thought maybe my business was eventually going to have to go away. The more technology there is, the better computer forecasts become, and eventually you might think meteorologists wouldn’t be necessary.” But what he has found has been the opposite.

“We’ve gone from just forecasting the weather to more of helping guide them through what decisions to make based on what might happen with the weather,” he says. “Whether it’s going to be 75 and sunny tomorrow is not really what you need to know. What you really need to know is, what plan of action do I need to deal with what the weather’s going to do? We try to make those suggestions.”

Contributing editor Wendy Mitman Clarke is presently landbound but still listens to Chris Parker’s livestream, as much for the weather as to put her in a cruising state of mind. You can see more of her work at wendymitmanclarke.com.

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Occasionally we hear complaints like these from ­fellow cruisers about the unsteady weather here in the South Pacific: “The weather here is lousy. We should have stayed in the Caribbean!” Or, “The Pacific is so cold!” Admittedly, there is some truth in these simplified conclusions; the trade winds are frequently interrupted by disturbances and some areas really do cool down. So, some crews do seem truly surprised by the mixed weather after their arrival in Polynesia. However, by analyzing the patterns responsible for tropical weather in the South Pacific, it’s possible to plan favorable itineraries and perhaps avoid any unpleasant surprises.

Wandering Trades

Trade winds, as we’ve learned from the weather textbooks, are caused by the air-­pressure difference between a high-pressure area (or ridge) in the subtropics and the low-pressure area along the equator. This weather model applies nicely for the North Atlantic, where the Azores High (or Bermuda-Azores High) behaves rather predictably—it’s big and fairly permanent.

In the South Pacific, the model is less reliable; the Pacific Ocean is simply way too big. Instead of a single ridge in the subtropics, there are (at least) two highs. To the east lies the South Pacific High with its center typically close to Easter Island. The other one is farther west, closer to New Zealand. French meteorologists call the first one Anticyclone de Pâques after the French name for Easter Island, and the western one Anticyclone de Kermadec after the subtropical Kermadec island chain between Tonga and New Zealand.

Like the Azores High, the South Pacific High is quite permanent. As a consequence, steady trade winds prevail in the eastern South Pacific, which make a passage from Galapagos to French Polynesia relatively easy. The Kermadec High, on the other hand, is neither permanent nor stationary. It arises from the Tasman Sea, or north of New Zealand, and travels eastward via the Kermadec Islands and south of the Austral Islands of French Polynesia, and may fade away to be replaced by the next one. More persistent examples travel farther southeast and join the eastward procession of lows in the Roaring 40s. The transitory and wandering nature of the Kermadec High is the main cause of the frequently interrupted trade winds in the western and central tropical South Pacific. In other words, there is quite a bit of weather going on.

The Influential SPCZ

The two separate highs in the subtropics result in a different air-pressure gradient in the tropics than a single ridge. Between the highs, there is clearly an area with lower pressure, and isobars encircle both centers. Where those circles approach each other, air masses from different wind directions collide and cause a zone of convergence—the South Pacific Convergence Zone (SPCZ). This zone typically stretches from the Solomon Islands to Fiji and Tonga, or to Samoa, and often continues farther to the southern Cook Islands or the Austral Islands. As the Kermadec High moves eastward, so does the SPCZ (or a part of it), and often there are several disconnected branches of convergence zones.

To the south (or west) of the SPCZ, dry and cool southerly or southeasterly winds can be found, and to the north (or east) the wind is from the northeast, north or ­northwest and brings warm and humid air. The consequence is cloud formation, squalls and ­thunderstorms, as well as developing fronts. Due to a lingering upward movement of air, the air pressure drops and parts of the zone may evolve into a trough or low pressure.

Around every eight to 10 days, a new transitory high starts its journey eastward, bringing the SPCZ and the accompanying troughs along for the ride. An approaching trough is foreshadowed by the trade winds shifting first northeast, then north. When a trough passes, the wind turns farther to the west and then south. The southerly wind typically arrives with a front and strong squalls. Deepened troughs and lows may also develop a front on their northeastern side where the wind turns north.

When we compare weather charts from different government meteorological offices, we see that even experienced forecasters seem to be divided over how to classify the weather phenomena in the SPCZ. For example, French Meteo may see a convergence zone with an associated front or just a stationary front, while the National Oceanic and Atmospheric Association observes a (weak) trough. A pattern we observed over the last six years is that strong and weak events usually ­alternate. Another observation is that GRIB files based on the Global Forecast System (GFS) model do a poor job at ­depicting those fronts.

Squash Zones

When an east-traveling high is very strong and/or moves very close to the tropics, the isobars on top of it are squeezed together and the resulting trade winds are strong. Such squash zones of enhanced trade winds occur frequently during the southern winter and are called mara’amu in Tahitian. The southeasters generally arrive with a nasty cold front after the convergence zone or trough has passed. The strong winds may last for several days and carry numerous squalls as the agitated sea causes increased vaporization and the formation of cumulus clouds.

Seasonal Variations

During the cyclone season (the Southern Hemisphere ­summer), the subtropical highs are farther away from the tropics than during the colder season. As a consequence, the trade winds are weaker, squash zones are rare and calm periods are more likely. The SPCZ moves slower or tends to become stationary. For instance, a branch likes to linger over the southern Cooks and the Australs and brings rainy weather to those areas as well as the Society Islands. This branch also causes plenty of warm and humid northeasterly and northerly winds over French Polynesia, particularly in December and January.

The SPCZ is the birthplace of most cyclones in the South Pacific. With the warm ocean surface in summer and high activity in the SPCZ, the risk of cyclone formation is great, particularly when an additional, extensive area of cloud formation and rainfall coincides with the SPCZ.

In southern winter—the so-called sailing season—the trade-wind belt paradoxically does not cover the entire tropics. As the highs are so close to the Tropic of Capricorn, the southern fringe lies in the belt of variable winds, particularly in the central and eastern Pacific. In Tonga, it is not unusual to get an extended period (five to six days) of westerly winds around August.

RELATED: Pacific Passage Planning

As to the cooler temperatures, most yachts cross the South Pacific outside the cyclone season, in the Southern Hemisphere winter. When an itinerary then includes places at the fringe of the tropics like Pitcairn and the Gambiers, the Austral Islands, the southern Cooks, Niue, and/or the ­southern parts of Tonga, cold weather is unavoidable, particularly when the fresh southeasters blow hard. In July and August, the water temperature in those areas is not far above 68 degrees F (20 degrees C). Bring a thick wetsuit in case you gather enough willpower to go diving or snorkeling.

Summing Up

The eastern South Pacific has relatively undisturbed trade winds, the result of the big and stable high around Easter Island. Also, there’s a wide equatorial area that has steady trade winds and fine (but hot) weather. When moving closer to the equator and farther away from the subtropical highs, the isobars become more or less straight lines and resemble those caused by a single high-pressure ridge, and so the area does not see a convergence zone. In addition, the Intertropical Convergence Zone (ITCZ) is typically located well north of the equator (around 5-10° N). Apart from occasional warm fronts and squalls, when the trade winds blow strongly, the Marquesas, the Line Islands and Penrhyn in the Northern Cooks are blessed with stable weather all year round. Farther west or south, the SPCZ already starts to influence the weather. On the other hand, New Caledonia lies far enough west to also experience less convergence-zone typical weather.

In summation, it pays to take some time and conduct proper research, including pilot and climate charts—after all, the Pacific is a huge and diverse area. Simplified textbook principles do not always apply everywhere; for instance, it is not true that all archipelagos have their rainy season during the summer months. Avoid extra-tight itineraries as they leave no time to await favorable passage weather when bold plans include picking up and dropping off a constantly changing crew or visitors, especially from ambitiously distant places. With some clever planning, as well as a lot of flexibility, cruising the South Pacific is undeniably an extraordinary experience.

Finally, it is not advisable to solely rely on GRIB files to find good passage weather. An ­additional look at ­surface-analysis weather charts shows where the convergence zone and nasty fronts exist, particularly when sailing between French Polynesia and Fiji, or farther west. The SPCZ that causes so much variable weather in the Pacific also has a good side: the numerous ­­disturbances with shifting winds provide good-weather windows to sail eastward.

Birgit Hackl and Christian Feldbauer set out from the Med in 2011 aboard their 41-foot S&S-designed Pitufa. Two years later, after an Atlantic crossing, time in the Caribbean and a transit of the Panama Canal, they reached French Polynesia, which has become their home base. For more on the couple, visit Pitufa.at.

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Pick up some new cruising skills—without having to leave your house! The American Sailing Association has launched a new webinar series that aim to help students grow as a sailor by providing a deep dive into important topics. The first session, Marine Weather in the Smartphone Era, will be held on June 11, 2019, at 6pm PDT/ 9pm EDT. This live session will be moderated by America’s Cup winner and author Peter Isler. Topics covered will include marine weather basics, apps and online sources for weather, understanding and staying current with the weather during your sail.

On June 18, the webinar topic is Coastal Navigation in the Smartphone Era which will include coastal piloting and navigation 101, preparing for your sail with paper charts and apps, and using apps and other navigation tools to stay safe underway.

June 25th’s webinar topic is Bareboat Chartering Tips for Sailors, and will feature special guest, Cruising World editor Mark Pillsbury. Topics will include how to choose a destination, a charter company and the boat, as well as packing and provisioning for the adventure.

Each session is $19.95 for ASA members ($29.95 for non-members) and sailors of all skill levels are welcome. For more information and to register, visit the website.

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