Frequently Asked Questions, Primer and Glossary
Many clients use our Custom (vessel-specific) email forecasts.
Forecasts (except general 10-day Outlook) generally includes:
Ideally, we will send your custom forecast to you the day ahead of departure. In circumstances in which the weather is uncertain and it is beneficial to wait for the newest information, we will email your forecast closer to the departure time.
When you order your initial Custom email forecast, please schedule it for 1-3 days before your 1st possible departure date. You will want to schedule the forecast for the day on which you will begin to make final departure preparations/decisions.
We will assess conditions ahead of your departure and contact you (by email or phone) to confirm when you'll be ready to depart, and that the weather looks good.
If you are not ready to depart, or the weather is not good, then we'll re-schedule an assessment for 1-2 days later...and we'll keep doing this until you're ready to go and the weather is good.
The forecast is a single forecast (for 2 days or 5 days, whichever you choose). To order additional forecasts, please contact us at 863-248-2702 or order online at mwxc.com.
On the day before your forecast is due (2 days prior to your earliest departure date), we will send an assessment of conditions for your desired departure date/time. If conditions do not look acceptable, we will suggest rescheduling your forecast.
We will continue doing this as many times as necessary to identify a departure opportunity you deem acceptable.
Of course, once we agree on a departure date/time and send you the detailed forecast, if you later decide not to go, the order will still be considered to be completed.
Yes. We work with many vessels each year on both E-bound and W-bound Crossings of the Atlantic.
We can work via SSB Voice Nets, voice telephone, email, SMS text messaging, or any combination.
SSB Nets should work all the way to the Coast of Europe, depending on propagation and the quality of your radio installation.
No SSB? Many folks prefer email and/or voice telephone or have no SSB, so we can communicate via email and/or voice telephone or even SMS text messaging for any part of the trip.
Cost varies depending on how self-reliant you are, and how bad or changeable weather conditions are.
Some self-reliant folks cross the Atlantic with a few "general 10-day Outlook" and a few "2-day or 5-day forecasts" when there's a significant upcoming weather event. Forecasts for their entire Atlantic crossing can be $100-or-so.
Other folks prefer more input on forecasting and routing and will ensure each day of the trip is covered in detail. Most folks request about $100 of forecasts each week on extended offshore passages.
No. Some folks might object to a forecaster contacting them (and billing them) for a forecast when they don't need it. We have no desire to charge you for anything you don't feel you need.
Instead, each forecast includes a recommendation on when you should contact us for another forecast.
Although not every forecast verifies with 100% precision, each forecast includes a discussion of uncertainties, forecast confidence, and possibility for severe weather. Almost all forecasts which require revision do so because of uncertainties or potential for severe weather which we discussed previously.
If you notice your weather conditions are beginning to deviate from the previous forecast, then you can decide to request an earlier update.
In general, for extended offshore passages, clients usually request 2-3 forecasts per week.
Self-reliant folks may only need 1 forecast or outlook each week on a passage. It is more typical for a client to request 1 or 2 detailed 5-day forecasts per week, and 1 or 2 detailed 2-day forecasts the day before inclement weather.
Occasionally there's a good reason to aim for a specific waypoint, and, when this is the case, we will provide specific waypoints in your forecast.
However, clients are best served by sailing their vessel in a manner which is fast and comfortable, while heading basically in the right direction. General suggestions are typically easier to follow than the exact coordinates of a waypoint.
We offer a service where we monitor possible Tropical threats, and if we identify a threat to your location, we'll contact you to establish a dialog.
We normally classify a threat as any meaningful chance an approaching Tropical LO (or potential Tropical LO) could bring you TropicalStorm (35k+ sustained) winds from any direction, or more than 10k of wind from a direction from which you might not be protected.
Cost is $65 (or 2 Custom forecast credits) to monitor and alert you to a possible threat, and to provide Regional forecasts which cover the potential threat as the system approaches. This also includes consultation on whether we recommend you take action ahead of the approaching threat.
If you decide to take action by getting underway to avoid the threat (or if you want a Custom forecast for where you are), your 1st Custom forecast is included at no extra charge. Additional Custom forecasts are $35 (or 1 Custom forecast credit), or a phone call is $30 (or 1 Custom forecast credit). You might need a couple of Custom forecasts immediately before and during the event.
When that Tropical threat has passed, we can schedule another monitoring type forecast for $65 for the next possible Tropical threat.
You can participate in interactive, real-time SSB Voice Nets from almost any Internet-connected device.
As of January 1, 2021, code is in HTML5, which means it works well on almost any device, including computers, tablets, and phones.
Full Multimedia (you hear us, see our webcam, and you also see our desktop. You text questions in the chat box and we answer verbally):
https://web.conferenceconsole.com/99910131
Access code = 560446 (see NOTE below)
Audio/Text chat ONLY (to conserve bandwidth, this is audio and texting only. You text questions in the chat box, and we answer verbally):
https://web.conferenceconsole.com/4634056
Access Code = 316121 (see NOTE below)
We may be able to provide a phone-in option at a later date.
Youtube VIDEO explaining how Webcasts function: https://youtu.be/myt-iKz6Y3s
NOTE: Occasionally a client will have difficulty getting the website to accept the Access Code. This typically only happens the 1st time you access the Webcast from that browser (the website remembers you after that and you no longer need the Access Code). The workaround is to try refreshing the browser and re-entering the Access Code a couple times.If copying and pasting the Access Code still fails after several attempts, please try typing the Access Code manually. The above has worked in every instance thus far.
You can sign-up on the website by selecting a single forecast or a package of custom forecast credits. You can use these forecasts by phone, InReach, or other device (mix-and-match).
IMPORTANT:
Prior to departure, we need to test communication with the InReach (or Zoleo or other satellite text messaging). Message from your device to: forecast@mwxc.com
When you message us, please ask us to reply. When you receive our reply, you will know we have established reliable 2-way communication.
The < symbol indicates a change in conditions over the relevant time period. Read "<" as "becoming".
"090@12-15g18k<16-20g25k today" means the wind will be 090-degrees (due East), starting the day between 12 and 15 knots with gusts to 18 knots, then building to between 16 and 20 knots with gusts up to 25 knots by the end of the day.
The Bahamas Regional Email forecast offers specific forecast and recommendations on the Gulf Stream between:
N ROUTE: Fort Pierce / Lake Worth - to - Matanilla Shoal / Memory Rock / West End
S ROUTE: Miami / Ft. Lauderdale / Key Largo - to - Bimini / S Riding Rock / Great Bahama Bank
All locations are in degrees-minutes....NOT decimal degrees!!!!
Example: “24-30N / 77-20W” is “24 degrees, 30 minutes North and 77 degrees, 20 minutes West”
ALWAYS do your own navigation to ensure you remain clear of navigation hazards.
Yes, mwxc.com website has a SSL 3.0 security certificate (notice the "https" on the sign-up form).
We follow credit card industry "best practices", and every 3 months we re-verify "PCI-compliance".
Neither the www.mwxc.com website nor ePN ever store your entire credit card number.
Instead, we store the last 4 digits and expiration date. We also store a unique code which the Card Network assigns to purchases by you at Marine Weather Center.
When you renew, or purchase additional weather services with the same card you used previously, we submit to the Card Network the last 4 digits of your credit card, the expiration month/year, and the unique code, and the transaction processes just as if a full credit card number was submitted.
You are purchasing limited rights to use our intellectual property on your vessel and, unless you have our express permission, you may NOT redistribute, or cause to be redistributed, our forecasts for use on a vessel you are not physically on.
However, there are some ways you can share:
Feel free to put my forecast into your own words, and share this with others. Be sure you note it's your interpretation of my forecast.
If you believe sharing a forecast on a single occasion may motivate a potential new client to purchase our services, then it's acceptable to share our forecast on that one occasion. However, this is NOT ACCEPTABLE on a recurring basis, or if you do not think there's a reasonable chance the sharing could prompt the person you're sharing with to purchase services.
The "Primer" below is specific to our "Regional Daily Email" forecasts, which cover the E Caribbean, W Caribbean, Bahamas, and US E Coast waters.
TYPES of Regional Daily Email forecasts:
"Early Briefing" for the Bahamas/FL, focusing primarily on Gulf Stream Crossings, so vessels can start their day with the newest information. Other regions may receive an early briefing if necessary.
Normal 5-day forecast usually arrives midday.
"Interim Tropical" is issued for ALL REGIONS when significant Tropical weather is possible.
Other "Interim" emails may be issued for Earthquakes/Tsunamis or significant weather events or emergencies.
"Schedule" emails alert you to changes to Marine Weather Center operations.
Forecasts are split into several parts:
Recent observational data, often including satellite-derived winds (ASCAT, others), BUOYs, and vessel observations. Observations generally start at one end of the forecast area and move logically to the other end, and focus on data which is “curated” by us as representative of conditions you’re likely experiencing now or in the recent past.
Analysis of current satellite and radar imagery.
Synopsis of weather features, and their likely influence on your weather for the next 5 days. The format of Synopsis varies as necessary to best describe weather patterns.
Outlook for 5-10 days, or as far into the future as we can make an informed guess.
SUGGEST section (E Caribbean, GulfStream Crossing between S FL and Bahamas, and US E Coast regions): Our forecasts are geared to help you make informed weather-based decisions. To further support decision-making, many of our forecasts include SUGGEST sections where we offer our suggested conclusions regarding travel (which days are best for motoring or sailing in one direction or the other).
Specific forecasts for Precipitation (and wind in squalls) / Winds (excluding squalls) / Swell.
Because one of the most common forecast errors is a slight error in location of predicted weather, we typically divide forecasts by weather-parameter (Precipitation first, then Wind, then Seas), so you see forecasts for adjacent areas above and below your forecast.
More information on sections of the forecasts:
SYNOPSIS:
We often CAPITALIZE weather features, so they stand out in the email. For more information/education, we suggest you start with Chris Parker's book, "Coastal & Offshore Weather, the essential Handbook", available here:
https://www.mwxc.com/order_books.php
LO = low pressure system
2nd-ary LO = LO which forms along FRONT trailing from a LO, generally causing inclement weather to persist or worsen
HI = high pressure system
RIDGE = flat, weak, high pressure system along an axis
TROF (and ColdFRONT / WarmFRONT) = flat, weak area lower pressure along an axis, typically causing nasty weather
2nd-ary FRONT = often a LO supports more than one ColdFRONT. 2nd-ary FRONT(s) reinforce the established flow and often bring more veering of wind direction
WAVE = Tropical WAVE, a TROF (an area of lower pressure along an axis) in the Tropics usually moves from E-to-W, and is accompanied by squalls. Most Tropical LOs (Tropical Storms / Hurricanes) develop along a WAVE…and generally do so at the “Apex” of WAVE. Apex is a point usually in N portion of WAVE with greatest pressure drop and vorticity (spin), and winds are usually stronger N of Apex / lighter S of Apex.
IMPULSE = Sometimes we have a piece of energy in the atmosphere which is not necessarily a LO (though it may become one). Maybe it’s an area along a TROF (or a ColdFRONT or a WarmFRONT) where there’s more wind / seas / squalls. Usually forecast models have a hard time with such small, weak areas of energy, so forecast details (and the evolution of the feature) are usually uncertain.
We think it’s important to address such an area of energy, and referring to it as an IMPULSE (of energy) is descriptive. When we use this term, you should think about it as an area of more windy, squally weather, which might get worse, but the evolution of which is uncertain.
FORECAST:
Detailed forecasts in 3 parts: Precip (and associated wind), Wind (gradient wind and wind-chop), Swell.
Times-of-day convention: Whether you can see (daylight), or not (night) is often crucial.
So by "day" we mean when there is enough light to see / "night" is when it's dark.
Further...
Morning = Dawn-Noon
Afternoon = Noon-Sunset
Evening = Sunset-Midnight
Overnight = Midnight-Dawn
PRECIP – We usually discuss coverage of showers and squalls (in order of increasing coverage: stray / isolated / scattered / numerous or widespread), see below for detail. We also estimate wind speeds in the precip – sometimes as wind speed “added to gradient wind.” For example, if "+10k" then you add 10k to our gradient wind forecast to account for squalls. Wind in precip is usually listed as total wind in squalls (for example, if "40k", then squalls may pack wind to 40k).
Precipitation coverage: Terms like Stray, Isolated, Scattered, Numerous/Widespread are often misunderstood, and there's a big difference between the chance of any given location seeing precipitation (at a single moment of time or over a period of hours or days)....versus any precipitation occurring in a given geographic area (at a specific moment in time or over a period of time).
Stray = mostly dry, but slight chance you may see a shower or squall during specified forecast interval.
Typically 50%+ chance 1 or more showers/squalls in the area (not necessarily your location) at some time during the forecast interval, but less than 5% areal coverage (of the whole forecast area) at any moment, and your chance of seeing one is low (less than 20%) during the forecast interval.
Isolated = mostly dry, but there's a 20%-50% chance you see 1 or more showers/squalls during specified forecast interval.
Typically 80%+ certain some showers/squalls in the area (not necessarily your location) at some time during the forecast interval, but less than 15% areal coverage (of the whole forecast area) at any moment, and 20%-50% chance you see 1 or more showers/squalls during specified forecast interval.
Scattered = there will be showers & squalls around, and you'll almost certainly see some - maybe quite a few.
Typically 95%+ certain some showers/squalls in the area (not necessarily your location) at some time during the forecast interval, and up to 15-50% areal coverage at any moment, and more than 50% chance you see 1-or-more (probably at least a couple) showers/squalls during the forecast interval.
Numerous/Widespread = it'll be very wet, with lots of showers/squalls much of the time.
Typically 100% showers/squalls in the area (not necessarily your location) at some time during the forecast interval, and over 50% areal coverage at times, and close to 100% chance you see 1-or-more (and probably many) showers/squalls during the forecast interval.
WIND – speed & direction:
Direction: Usually in degrees TRUE (for example 060), but when we can't be that specific we'll use cardinal directions (for example ENE). The forecast is NOT so accurate that you should really expect wind exactly 060-degrees. Instead, specificity highlights TRENDs in wind direction: 060-degrees is just about ENE. 070-degrees is also ENE. A change from 060 to 070 suggests a VEERING TREND to the wind direction.
Speed: In knots (nautical miles per hour - 1k = 1.15mph), often in the format 12-15g19k, which should be read as 12 knots to 15 knots, gusting to 19 knots.
L&V = light and variable
Most weather forecasts from other sources give forecast details for each day. However, weather is fluid and tends to evolve in some sort of a pattern or trend…and we feel it’s wrong to describe something like weather in discrete, arbitrary intervals (like days).
Instead, when there are trends in conditions, our forecasts describe those trends over the time period during which the trend unfolds. For instance, some forecasts might say NE@12k Sun1, ENE@15k Mon2 and E@18k Tue3. But, if this is a gradual TREND, which unfolds at a steady progression, then it’s far more useful to say today starts at 040@10k, and wind gradually, steadily increases & veers to 100@20k by the end of Tue3. And the way we write this is 040@10k<100@20k Sun1-Tue3.
The “<” symbol tells you we’re describing a TREND in conditions over the time we specify at the END of the phrase, and the “<” symbol should be read as the word BECOMING.
So a more complex phrase 060@10-13g16k<080@16-20g25k Wed16-Thu17 night is read:
Wind 060-degrees True at 10 knots to 13 knots, gusting to 16 knots, BECOMING 080-degrees True at 16 knots to 20 knots, gusting to 25 knots from Wed16 through Thu17 night.
During some intervals, there’s no trend – just steady conditions, so in that case we would not note a trend.
Another unconventional part of our forecast: We describe the weather FIRST, and THEN tell you what timeframe those conditions will be in effect. Whether it’s squall activity, gradient wind, or seas, we generally explain what the weather will be like…THEN we tell you what time period will experience that sort of weather. This may seem counter-intuitive, but it allows you to easily identify good or bad weather conditions, and then see during what interval of time those conditions are predicted to occur. Our format also facilitates describing trends. (In some extreme weather events the formatting will change, but it will be obvious, and we’ll note the non-standard formatting in the forecast).
All of the above actually helps you make better decisions based on the weather forecast, since you can see how & when the weather is evolving/trending (for better or worse).
REMEMBER TO CONSIDER WIND IN SQUALLS! Our “Wind” forecast is generally for wind in the absence of significant squalls. ALWAYS refer to the “PRECIP” forecast for wind in squalls!
SEAS – There are 3 types of wave forecasts:
"Wind-chop": waves attributable to local wind. These waves are typically steep, but as long as they are not large, they're not problematic.
"Swell", "Primary wave" (and Secondary and Tertiary) waves. Computer model forecasts generally focus on the Primary wave, specifically the "Primary Significant Wave" (the mathematical average of the 33% of largest waves in the largest wave train). If this is wind-driven, then interval of this wave is about 1 second per foot of wave height (6'/6sec). If this is swell (driven by wind somewhere else) then the wave interval will be longer than 1 second per foot of wave height.
"Seas": the aggregate "Significant Wave", (mathematical average of the 33% of largest waves), combining wind-chop and all other wave trains. NOAA's NWS predicts "Seas".
At Marine Weather Center, we examine seas in 2 ways:
For wind-chop:
In the E Caribbean and US E Coast forecasts, we specify wind-chop embedded within the WIND forecast (following a "/" after the wind forecast), so you'll see something like this:
090@15/4'
predicting 4' wind-chop. These are generally wind-driven seas, and include seas resulting from locally-higher wind in any predicted squalls.
In other geographic areas, you can estimate wind-chop yourself based on this rule-of-thumb: Wind blowing for more than an hour-or-so even over modest fetch, as long as depth does not restrict wave height, will be (or wind-driven waves will be so steep they will feel like):
10k = 2′
13k = 3′
15k = 4′
18k = 5′
20k = 6′
25k = 8-9′
30k = 10-12′
Where water depth limits wave height, you can think of the following descriptors: calm, light chop, moderate chop, choppy. We typically avoid detailing waves where water depth limits wave height, because wave height and steepness vary dramatically as depth changes. Instead, we detail wave height as if water were deep, and let you adjust downward for your specific water depth.
Under "SWELL", we predict height, periodicity, and direction of the Primary (largest) wave train, as well as any meaningful Secondary and Tertiary wave trains.
Our forecasts assume waves are not limited by water depth or fetch (the distance wind blows over water between you and any upwind landmass or upwind very shallow water). In areas where fetch and depth are limited (parts of Bahamas, Virgin Islands, along any Coast where wind is blowing from land, and areas in the lee of islands in the Caribbean) fetch (and often water depth) limit wave height - the extent to which wave height is limited depends on your precise location, so we always assume unrestricted depth and fetch. Therefore, in E Caribbean and Bahamas our seas forecast is for E of the islands.
Stated differently:
We want to predict unfiltered seas (not filtered by the islands)...we want to do this because the amount of filtering from islands varies significantly depending on the user's exact location (which changes minute-to-minute if you're underway), and we can't know that, so unfiltered seas are best.
Additionally, particularly in E Caribbean, seas (and wind) between Islands in the Windwards/Leewards are typically higher (due to funneling / compression) than over open waters away from Islands...and the Islands also bend wind & sea directions locally. Because the extent to which wave height is larger and wave direction is different depends on your precise location, you must adjust for this.
Again, our forecasts for wind & seas assumes you're in exposed areas, and away from the local effects imparted by Islands, shallow waters, etc.
Along US E Coast and Florida, seas immediately following wind forecast (090@15/4') are wind-chop, but if we include interval and direction of seas, then it's swell.
Acceleration: What you really care about is the ACCELERATION of motion of your vessel due to seas. By acceleration, we mean any change in motion versus what you'd have with flat calm seas.
In general, seas with an interval much greater than 1-second-per-foot of height are swells. 6' seas with 6-sec interval is a wind-chop. 6' seas with 8-sec interval are short-interval swells. 6' seas with a 12-sec interval are long-interval swells. Swells are less-steep, and, therefore, impart less acceleration on the vessel for a given height.
Acceleration (and implications for boat handling) also vary considerably on your vessel's length, beam, weight (and weight distribution), and hull shape. The acceleration imparted by 6' wind-chop with 6-sec interval will be very different on a heavy 30' sailboat versus a light 30' sailboat, a 50' sailboat or a 30' powerboat.
Also, apparent wave interval (and acceleration) change depending on your direction of motion relative to seas: apparent wave interval shortens (usually increasing acceleration) when heading into waves / lengthens (usually decreasing acceleration) when heading with waves.
HOW TO INTERPRET OUR WIND-CHOP and SWELL FORECASTS:
For wave HEIGHT: we suggest you start with wind-chop forecast, then add 50% of our swell forecast.
Here's an example: in Leewards we can get unfiltered swell by looking just E of Guadeloupe-Barbuda, and just N&E of Barbuda-StMartin. For that area, let's say
Wind is 090@18-20, so wind-chop forecast is 6' (6-seconds interval is implied because it's wind-chop).
Primary wave (Swell) forecast is 8-10'/12secNE (that's 8-10 seconds feet with 12-seconds interval from the NE).
Based on our rule-of-thumb assumption for phasing of wave trains we add wind-wave of 6' + 50% of swell (4-5') = 10-11' perceived wave height.
The added benefit of knowing the wave components (wind-chop and swell) is you can further assess comfort by considering swell interval and direction.
The 12-seconds interval of the swell is about 2x the 6-seconds interval of wind-chop, so you will see a swell wave about the same time as every-other wind-chop wave.
For wave DIRECTION: Swell direction is NE, which is 45-degrees from the 090T wind direction. So the overall seastate described above is a 6' wave from the E, followed 6 seconds later by a 10-11' wave from the NE & E (triangular wave peak), then 6 seconds later a 6' wave from E, followed 6 seconds later by another 10-11' wave from NE & E (triangular wave peak).
That's 10-11' of motion 5x a minute (every 12 seconds), and in a jerky, confused motion. Sounds very uncomfortable! Without describing the wind-chop and swell individually, we would not be able to appreciate the actual overall seastate and its influence on our vessel.
Why do we not add the full height of both wave trains (6' + 8-10' = 14-16')? Because wave height is from trough-to-crest (not from mean sealevel to crest), and because wind-chop and swell are of different intervals, both trough and crest will not phase in the same wave. Adding 50% of swell to wind-chop is a reasonable approximation.
Example B: wind 090@10-13, wind-chop 2-3', swell 6'/12secE. Wind-chop is 2-3' every 2-3 seconds, which is benign for all but very small fast dinghies because it's so small. There will be a larger wave (2-3' + 50% of 6' (3'), so that's 2-3' + 3' = 5-6') every 12 seconds. But this is only 5-6' of motion 5x per minute, and the motion is very regular because wind-chop and swell are from same direction. This sea would be very comfortable on most boats.
Decision making based on our seastate forecasts:
Start by considering wind-chop and any swell independently. Are both acceptable by themselves?
If so, then consider how wind-chop and swell phase. Start with wind-chop and add 50% of swell height. Still acceptable?
If so, then consider whether wind-chop and swell are from similar directions? If so, then wave motion will be in a consistent direction / if not, then wave motion will be confused.
Currents / GulfStream: When wind blows against any strong current (tidal or geostrophic (non-tidal, such as GulfStream)), sea height is commonly 50% larger than without current, and wave interval is similar or even steeper than without current. So in GulfStream or in tidal current of 3-4k a 6'/6sec wind-chop may really be 9'/5sec, which imparts close to 2x the acceleration on the vessel. In addition, wave direction often becomes somewhat random, so the acceleration is confused.
GEOGRAPHY:
ALL FORECASTS: For locations near the boundary between areas, you should average conditions in the 2 areas. For instance, if you're transiting waters between StLucia-Guadeloupe, and we give a forecast for SE Caribbean and NE Caribbean, then you'll average the 2 forecasts.
When conditions vary significantly within an area, we'll break that area into smaller pieces.
E CARIBBEAN:
SE Caribbean = Martinique-Trinidad
Windwards = Martinique-Grenada
NE Caribbean = Dominica-Leewards-VI-PR (always S Coast of PR unless specified)
Leewards = Guadeloupe-StMartin/Anguilla
Virgins = British, US, and Spanish Virgins and the E Coast of PR from Fajardo-PlamasDelMar
MonaPsg = route to/from N Coast of the DR via HourglassShoal area toward Mayaguez/PuertoReal
DR = N Coast of DR unless specified
Venezuela = offshore, N of 12N
ABCs = Aruba-Bonaire-Curacao
*.*
BAHAMAS/FL:
CROSSING – waters between Florida and Bahamas (and along Coast of FL)
N ROUTE = MemoryRock-MantanillaShoal-WestEnd…to LakeWorth-FtPierce
S ROUTE = GreatIsaac-Bimini-SouthRidingRock…to FtLauderdale-Miami-KeyLargo
NW Bahamas = all areas N of Eleuthera and N of NewProvidence and N of Andros
C Bahamas = NewProvidence, Andros, Eluthera, Exumas, CatIsland, N part of LongIsland, Conception, Rum, SanSalvador, sometimes Jumentos
SE Bahamas = S part of LongIsland, Crooked, Acklins, and all Islands S&E to Provo Turks & Caicos, sometimes including Jumentos
T&C = T&C and waters between T&C and LuperonDR
Occasionally we’ll reference other areas:
E-most islands of the Bahamas = Mayaguana, Samama, Rum, SanSal, Conception, Cat, Eleuthera, Abaco
SW Bahamas = Andros-CaySalBank and parts of GreatBahamaBank
FLStraits = waters S of FLKeys toward Cuba
N Bahamas = Abaco-GrandBahama-LittleBahamaBank
OTHER AREAS section varies by season:
NFL = FL/GA border to PonceInlet
CFL = S of PonceInlet to FtPierce
CROSSING - N Route, includes FL Coast from FtPierce to N of FtLauderdale
CROSSING - S Route, includes FL Coast from FtLauderdale thru KyLargo
KyW = FL Keys from Islamorada to/from DryTortugas
SW FL = Marathon or KyW to/from Naples-PortCharlotte area (seasonal, not in summer)
*.*
US E COAST, outside the ICW (in the Ocean), seasonal, assuming N-to-S travel (inshore of the GulfStream) from September1-March15 / S-to-N travel (including the GulfStream) from March15-August31:
Maine and YarmouthNS to CpCod, including GulfOfMaine (typically late May-late September)
S of CpCodCanal / NewportRI and SandyHook to CpMay and Norfolk (typically late April-early November)
Norfolk-Hatteras-BeaufortNC (typically April1-November30)
BeaufortNC along entire Coast to FL/GA border (year-round)
*.*
W CARIBBEAN:
For vessels transiting ColombianCoast…
Very briefly…when Trade winds are in place, semi-permanent LO over Colombia causes large compression zone with strong wind. Though this zone moves, it’s typically 20-120 mi from shore, but often penetrates to the Coast from the SantaMarta area to 11N/76W. Our Colombia forecast focuses on the strongest wind you are likely to encounter. Computer models typically fail to mix catabatic / downslope winds to the surface, when in actuality these winds do penetrate to the surface. We know this, and we compensate for it, so our forecasts should be accurate, and are often much higher than computer models predict. If you are plying these waters, you may be well served to purchase a detailed "Custom" forecast (or a subscription to Webcasts/SSB Voice Nets, where we can discuss weather one-on-one).
* *
Panama: E Panama includes SanBlas/GunaYala & adjacent areas to Linton. C Panama includes the area about 40mi on either side of the Canal. W Panama includes BocasDelToro & adjacent areas.
* *
P-S-A stands for Providencia-SanAndreas-AlbuquerqueCays, and adjacent reefs/islands (generally 12N-14N from 80W-82W).
* *
Honduras forecasts generally focus on the greater BayIslands area (Guanaja, Roatan, Utila) between 86W-87W. Conditions can vary greatly Guanaja, but this area is typically transited briefly, and when plying offshore waters of W Caribbean we suggest you purchase a "Custom" forecast (or a subscription to Webcasts/SSB Voice Nets, where we can discuss weather one-on-one).
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“SW Corner of NW Caribbean” typically includes from Placentia S-ward thru Guatemala's RioDulce, and extreme W Honduras. In this area the seabreeze / landbreeze patterns of Belize and Honduras dominate, often resulting in light wind except for a brief late afternoon-evening NE-ENE seabreeze. However nighttime into morning squalls/T-strms are also common, due in part to the convergence of nighttime landbreezes (daytime seabreezes are divergent and therefore typically suppress squalls).
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During periods of enhanced E-SE wind a large zone of strong catabatic wind blows (late afternoons into overnights) from the Honduran mountains thru waters within 100mi of the BayIslands, and often propagate into parts of Belize and S Mexico. The exact location of these winds shifts, and can result in dramatic differences in wind between Utila and Guanaja.
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ColdFRONTs typically lack much energy when they move thru NW (and SW) Caribbean, and veering S-W wind is unusual (it’s more-common Mexico’sYucatan). Severe weather accompanying a FRONT is due not only to tight gradient, but also to convergence caused by landmasses (often with some instability/convection causing the most-severe squalls along FrontalTROF). It is not uncommon for stronger ColdFRONTs to propagate N wind (and strong squalls) into SW Caribbean, with wind funneling along C America and adjacent waters, all the way to W Panama.
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Mexico forecast focuses on the IslaMujeres-Cozumel area, N of 20N. For S of 20N, average the Mexico & Belize forecasts in all respects, unless specified otherwise.
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Other areas:
Jamaica focuses on waters off PortAntonio (NE Jamaica) and Kingston (SE Jamaica) to approximate weather for vessels approaching / departing via WindwardPsg, S Coast of Hispaniola, P-S-A, Panama, and Colombia. However, vessels transiting offshore waters of Caribbean should purchase a "Custom" forecast (or a subscription to Webcasts/SSB Voice Nets, where we can discuss weather one-on-one).
Caymans: when there is a significant nighttime landbreeze coming off Cuba, it typically takes a few hours to propagate to Caymans, resulting in a diurnal wind pattern in Caymans which peaks early mornings.
Cuba, we focus our Regional Email forecasts on 2 areas:
CayoLargo archipelago, including Juventud and Cienfuegos
Jardines (area N of CaboCruz thru and including TrinidaDeCuba)
We are glad to cover all other areas in Cuba with "Custom" forecasts (or a subscription to Webcasts/SSB Voice Nets, where we can discuss weather one-on-one).
S Coast of Haiti & DomRep / offshore passage routes are not frequented by Cruising vessels (except briefly in-transit), so we suggest you purchase a "Custom" forecast (or a subscription to Webcasts/SSB Voice Nets, where we can discuss weather one-on-one).
If this does not answer all your questions about interpreting Regional Email forecasts, please let us know.
<: The “<” symbol tells you we’re describing a TREND in conditions over the time we specify at the END of the phrase, and the “<” symbol should be read as the word BECOMING.
2nd-ary LO: LO which forms along FRONT trailing from a LO, generally causing inclement weather to persist or worsen
ABCs: Aruba-Bonaire-Curacao
Afternoon: Noon-Sunset
Bay Islands: The area between 86W-87W including Guanaja, Roatan, Utila
C Bahamas: NewProvidence, Andros, Eluthera, Exumas, CatIsland, N part of LongIsland, Conception, Rum, SanSalvador, sometimes Jumentos
C Panama: The area about 40mi on either side of the Canal
CFL: Central Florida (S of PonceInlet to FtPierce)
CROSSING: Waters between Florida and Bahamas (and along Coast of FL)
DR: N Coast of DR unless specified
E Panama: SanBlas/GunaYala & adjacent areas to Linton
Evening: Sunset-Midnight
FLStraits: Waters S of FLKeys toward Cuba
HI: high pressure system
IMPULSE: Sometimes we have a piece of energy in the atmosphere which is not necessarily a LO (though it may become one). Maybe it’s an area along a TROF (or a ColdFRONT or a WarmFRONT) where there’s more wind / seas / squalls. Usually forecast models have a hard time with such small, weak areas of energy, so forecast details (and the evolution of the feature) are usually uncertain.
We think it’s important to address such an area of energy, and referring to it as an IMPULSE (of energy) is descriptive. When we use this term, you should think about it as an area of more windy, squally weather, which might get worse, but the evolution of which is uncertain.
Isolated squalls: Mostly dry, but there's a 20%-50% chance you see 1 or more showers/squalls during specified forecast interval.
KyW: FL Keys from Islamorada to/from DryTortugas
L&V: Light and variable
Leewards: Guadeloupe-StMartin/Anguilla
LO: low pressure system
MonaPsg (Mona Passage): Route to/from N Coast of the DR via HourglassShoal area toward Mayaguez/PuertoReal
Morning: Dawn-Noon
N Bahamas: Abaco-GrandBahama-LittleBahamaBank
NFL: North Florida (FL/GA border to PonceInlet)
NE Caribbean: Dominica-Leewards-VI-PR (always S Coast of PR unless specified)
N ROUTE: North Route crossing between MemoryRock-MantanillaShoal-WestEnd and LakeWorth-FtPierce
Numerous/Widespread squalls: It'll be very wet, with lots of showers/squalls much of the time.
NW Bahamas: All areas N of Eleuthera and N of NewProvidence and N of Andros
Overnight: Midnight-Dawn
PRECIP: We usually discuss coverage of showers and squalls (in order of increasing coverage: stray / isolated / scattered / numerous or widespread)
P-S-A: Providencia-SanAndreas-AlbuquerqueCays, and adjacent reefs/islands (generally 12N-14N from 80W-82W).
RIDGE: Flat, weak, high pressure system along an axis
Scattered squalls: There will be showers & squalls around, and you'll almost certainly see some - maybe quite a few.
SE Bahamas: S part of LongIsland, Crooked, Acklins, and all Islands S&E to Provo Turks & Caicos, sometimes including Jumentos
Seas: The aggregate "Significant Wave", (mathematical average of the 33% of largest waves), combining wind-chop and all other wave trains.
S ROUTE: South Route crossing between GreatIsaac-Bimini-SouthRidingRock and FtLauderdale-Miami-KeyLargo
Stray squalls: Mostly dry, but slight chance you may see a shower or squall during specified forecast interval.
SW Bahamas: Andros-CaySalBank and parts of GreatBahamaBank
SW Corner of NW Caribbean: Includes from Placentia S-ward thru Guatemala's RioDulce, and extreme W Honduras
SW FL: Marathon or KyW to/from Naples-PortCharlotte area (seasonal, not in summer)
Swell: Waves driven by wind somewhere else with a wave interval longer than 1 second per foot of wave height.
T&C: Turks and Caicos
TROF (and ColdFRONT / WarmFRONT): flat, weak area lower pressure along an axis, typically causing nasty weather
Virgins: British, US, and Spanish Virgins and the E Coast of PR from Fajardo-PlamasDelMar
W Panama: BocasDelToro & adjacent areas.
WAVE: Tropical WAVE, a TROF (an area of lower pressure along an axis) in the Tropics usually moves from E-to-W, and is accompanied by squalls. Most Tropical LOs (Tropical Storms / Hurricanes) develop along a WAVE…and generally do so at the “Apex” of WAVE. Apex is a point usually in N portion of WAVE with greatest pressure drop and vorticity (spin), and winds are usually stronger N of Apex / lighter S of Apex.
Wind-chop: Waves attributable to local wind. These waves are typically steep, but as long as they are not large, they're not problematic.
Windwards: Martinique-Grenada