Planning for a Weather Window

03 November 2015

A fall passage to the Caribbean from the northeast US is undoubtedly one of the more challenging offshore undertakings, both once at sea and indeed during the preparation stages. Here at the Caribbean 1500 headquarters in Portsmouth, VA, we write about the weather every year – about how difficult it is to find a weather window this time of year, as we’re squeezed between the winter gale season and the end of tropical cyclone season.

And of course, the weather is all the talk on the docks. Skippers and crews can’t help themselves but talk about it as nervous energy (no matter how many times you’ve made this passage) builds up about the things we cannot control. Nevermind that the planned departure date is still five days away and this time of year, a lot can change over the long-term forecast.

All of that said, we thought it useful to provide some insight into how and where we get the weather info we use for planning purposes and what goes on behind the scenes. I always look at the rally departure as a skipper, not an event manager – meaning, I’m looking for weather patterns that I’d feel most comfortable departing in if I were actually sailing (I’m not), but also taking into account the varied experience of the fleet.

So, in the bigger picture, what weather patterns do we look for?

One challenge of leaving from the northeast is the Gulf Stream crossing (though it’s not nearly as big a deal as some people make it out to be – IF you leave in the right weather conditions). Logic would dictate departing on a southwesterly wind – wind with the flow of the current, which sets to the NE. BUT, a southwesterly wind this time of year often indicates an approaching cold front. The interaction of this especially cold air moving out over the much warmer water of the Gulf Stream creates volatile localized weather, meaning increased wind, thunderstorms, rain and otherwise lousy conditions. Fronts can stall over the stream and intensify even further. This is what plagued the Salty Dawg rally a few years back (though their troubles were more down to not being prepared for those escalating conditions, which in reality weren’t that bad).

Anyway. I like to depart, and look for a window for the rally to depart, just AFTER the passage of a cold front. The weather clears, the incoming High pressure creates a more stable, fair-weather pattern, and the wind, which starts in the west and quickly veers around to east-northeast, is from behind, making for reaching to broad-reaching conditions. However, especially this time of year, it’s usually a strong wind from the northerly quadrants, so you’ve got to be ready for 20-25, sometimes 30 knots of wind coming over the quarter. It’s a baptism by fire sometimes, but makes for fast sailing.

The real challenge is timing the departure so that you can get across the axis of the Stream before the wind goes all the way into the NE and E. Even a 25-knot wind from the northeast is not a real problem in the Stream. Yes, it’s wind against current, but not enough wind to be dangerous. It’ll be bumpy, for sure, but there’s a difference. And, due to the incoming High, even a strong northeasterly wind will normally blow itself out in a few days as the High drifts farther offshore.

Sometimes, as we’re seeing in the forecasts now, the incoming High interacts with the outgoing Low and causes steep High-pressure ridging over an area just offshore. The pressure gradient gets tight, and the wind can blow hard for days from the NE and E. This can make the Gulf Stream uncomfortable, but furthermore can hinder progress to the east. Generally, sailing directions dictate getting east early, while you’re still up north, to setup for the run south once into the Trades. If you miss it, you’ll be close-hauled for almost half the passage, once you’re into the Trades, and wind up with an easier sail to Puerto Rico than to the BVI!

In the here and now, we’re looking at two weather patterns that will tell us when to depart. A strong cold front created by a Low pressure system up north over the Great Lakes is marching across the US right now. It’s just dumped 12” of snow in the Sierra Nevada out west. The speed of this cold front is one factor that will dictate when we set sail. As it clears out and offshore, we’ll experience exactly what I’ve described above. The timing is everything, and right now (fingers crossed), it looks to be cleared out by Sunday.

The other factor of course is tropical weather. And while the tropics are quiet now, the long-term forecast is indicating a small low forming north of the BVI and Leeward Islands early next week. You’ve got to keep it in perspective though – that low is merely a mathematical model at this point based on current atmospheric conditions, and it’s still a week away from forming. But we’ve got to keep it in mind, and keep an eye on that area. IF (and that’s a big IF), it does form, it’s strength and track will play into our decision of when to depart.

So, fittingly perhaps, the weather pattern this week is shaping up to be the classic conundrum – stuck between a fall cold front and a potential tropical system.


Free Online Weather Sources

• National Hurricane Center:
• Coastal & Offshore Text Forecasts:
• Interactive Wind & Currents Globe:
• Global Sailing Weather (Wind & Currents):
• Saildocs (subscribe to receive GRIBS offshore):
• ZyGRIB: GRIB reader for Apple (search online)
• PocketGRIB: Smartphone App (search in app store)

Besides the standard sources of weather available free and online to anyone, we work closely with Weather Routing Inc. (WRI) to determine a good weather window, and we use their text forecasts for the rally fleet once everyone gets offshore (a big benefit of the 1500). I wanted to give some insight into how this back-and-forth works with WRI, so have included an email exchange from just this morning with a discussion between myself and David Cannon of WRI. The full text is below.

We’ll of course have more updates on the weather here at the Caribbean 1500 rally start in the days to come, so stay tuned to!

NOTE: No actual decision has been made regarding the actual departure date and time for the 2015 Caribbean 1500. As of today, the start is still set for Sunday, November 8. We like to allow the weather to play itself out and leave out options open before making a concrete announcement. Typically, any delays will only be announced the day before the scheduled start.


From: Andy Schell
Sent: Tuesday, November 03, 2015 13:23
To: Director of Yacht Ops, WRI; Weather Routing Inc
Subject: Carib1500 / Tropical Outlook

Hi David, Jeremy et al,

The Caribbean 1500 is in full swing here in Portsmouth, VA, and I’m starting to look at the weather patterns for our planned Sunday departure on November 8. I’d like some feedback from you on what I’m seeing:

• Cold front approaches later in the week – when that passes normally dictates our departure on the back of it when the weather clears and the wind goes into the north. I’m seeing stronger north-northeasterlies behind the front, but diminishing and then veering more easterly. Does this jibe with what you’re seeing?
• On the tropical side, I’m starting to hear rumors of a tropical wave forming well into the eastern Atlantic, which is something we need to account for. Do you have any information/outlook on what it’s going to do, and if there exists something you’re watching in the first place?

Andy Schell


From: David Cannon
Sent: Tuesday, November 03, 2015 13:49
To: Andy Schell
Subject: RE: Carib1500 / Tropical Outlook

Hi Andy,

Thanks very much for your e-mail. Great to hear from you. We have actually begun looking into the expected conditions for the planned departure on the 08th and beyond when considering both of the items you mention below. Here is our thinking as it stands now, addressing both items below:

• We are watching the next in a series of cold fronts, which will pass through the Southern Chesapeake Bay and Virginia Tidewater during the night of the 06th (Friday Night) and early morning of the 07th. From there, the front will continue on an eastward motion across adjacent waters west of 65W-70W during the remainder of the 07th as high pressure ridging builds e’ward toward U.S. Mid-Atlantic coastal areas in the wake of the front. As the front moves even farther east, the ridge will continue to move east to southeastward during the 08th, and slowly weaken as it gradually moves farther east late on the 08th and on the 09th through 10th.

• All of this will mean a period of N-NE winds developing behind the front on the 07th, more so during the afternoon and night of the 07th as ridging establishes itself along the Virginia and North Carolina Coasts and east of there to 73W. In this region, N-NE sustained winds will reach as high as 25-30kts on the night of the 07th and early morning of the 08th. These winds will tend near the high end of this range farther south along the North Carolina Coast, particularly near Cape Hatteras, where periods 30-35kts cannot be ruled out. Additionally, NE combined seas in the Gulfstream will develop and build, reaching as high as 8-10ft during the night of the 07th and during the day of the 08th.

• As the ridge moves farther east, winds do indeed become NE-E during the night of the 08th and will persist on the 09th and 10th given the very expansive coverage and slow motion of the ridge. Easing will occur, but gradually. Case in point, even on the night of the 08th, there will still be period of NE winds near 25kts along the North Carolina Capes from Cape Hatteras south. Elsewhere, from the Virginia/North Carolina Coasts to 70W, NE-E winds will likely average from 17-22 kts on the night of the 08th, easing to 15-20kts on the 09th, and 12-17kts on the 10th. NE-E combined seas in the Gulfstream will still reach 7-9ft on the night of the 08th, though otherwise will range generally from 5-7ft during this time and on the 09th and 10th.

• As for the tropics, indications do not point toward development in the Central or Eastern Atlantic, as the tropical convergence zone will likely remain along and south of 15N during the next 10 days at least. However, we are closely monitoring the development of a surface low some 200-250 nautical miles north of the Virgin and Northern Leeward Islands on the 09th. The aforementioned high pressure will pass to the north of this feature during the 09th and 10th, acting as a “blocking” feature, which would effectively mitigate any significant northward or eastward motion of the low. Rather, the low will likely meander or only gradually drift toward the north, remaining south of 23N and between 60W and 65W during the 09th through 11th before moving farther north all the while intensifying before another cold front moves off the U.S. East Coast and allows for a more northward acceleration on the 12th/13th.

Further, the low will be in an environment when sea surface temperatures will at least be marginally conducive for tropical development during the 09th through 11th, before more significant northward motion (toward cooler waters and a more “hostile” environment aloft) allows for any transition toward a non-tropical entity.

In summation, while easing of more NE-E winds and abatement of NE-E seas on the 09th would in fact allow for more favorable Gulfstream transits, we do need to closely the monitor the development of the low north of the Virgin/Northern Leeward Islands, as this will likely have an effect on routing for several days to come given its very slow track. Its placement and exact track will be critical … *any* westward shifts in the track will either require more western routing (west of 70W toward the Southern Bahamas) or delays in the start of the rally would be required to allow the low to “play itself out” and essentially become a non-factor.

The biggest item to take from this of course are the *potential* for shifts in the projected placement and track of the developing mentioned above, which of course will be fine-tuned in the days ahead through the remainder of the week on into the weekend. 

I understand that this is a lot of information to consider, and I do suggest we discuss once again on Thursday, the 05th as we continue to evaluate matters further. Please let us know your thoughts. Thanks again.

Best Regards,

David Cannon
Director of Yacht Operations/Meteorologist
Racing/Tournament Specialist,

Weather Routing Inc. (WRI)