1/14/2013

Very Long Range Weather Outlook, Key West 2013

Chris Bedford, Sailing Weather Service

North Sails has overnight sail care & repair available during Race Week

FORECAST SCHEDULE: This is a long-range outlook forecast for Key West Race Week 2012. An updated forecast for the week will be issued on Sunday (20th), with daily race week forecasts commencing Monday (21st) and continue through the last day of racing on Friday (25th).

FEEDBACK: Sailing Weather Service and North Sails encourage feedback. When able, please send us daily weather notes so we can improve YOUR forecast at: feedback@sailwx.com. Thanks!

OVERVIEW: With a week still to go before race week commences, it is still far too early to gain much confidence OR detail as to what weather/wind conditions are likely to occur during race week. However, Sailing Weather Service is a leader in the application of long range ensemble forecasting techniques to regattas and ocean racing.

This outlook has involved review of an ensemble of over 40 forecast models the last few days. These model change and most certainly struggle to predict details of the weather beyond 5-7 days. However where there are consistent patterns between the models beyond the 7 day forecast, we can make some reasonable assertions regarding the MOST LIKELY – though not certain – weather that will occur. Even still, details beyond assessment forecast suggesting below normal, normal, or above normal are difficult (or actually impossible) to make. Indeed, where there are no discernible consistent patterns, we can only say that the pattern is completely unpredictable and that virtually any outcome is possible.

Below, we apply the ensemble pattern recognition techniques as well as our experience in forecasting the weather in Key West to present some of the trends and possible conditions for race week.

NOTE: This information is for preliminary planning and guidance purposes only. You should monitor conditions on your own over the next week and then reference the latest forecasts once race week starts. REMEMBER that the US National Weather Service is the sole source of OFFICIAL warnings and advisories and should be monitored at all times.

DISCUSSION: Much of the eastern US and Gulf of Mexico has experienced an unusual period of mild weather over the last week or so. This represented a significant change from the cold outbreak late in December through the New Year. The cause of this change was development of a upper level ridge over the eastern US which pushed storms and cold air north into eastern Canada. This effectively protected the east coast from cold intrusions from the north, and allowed development of a persistent high pressure off the east coast – analogous to a Bermuda High pressure pattern – which supported fresh E/SE trade winds across the FL Keys.

The breakdown of this ridge pattern is imminent. A cold front moving through the Mississippi River valley will gradually push east, supported by a weakening of the upper level ridge pattern. Eventually, this ridge will be replaced by a tough over the eastern US, allowing more typical temperature patterns to return as well as bring a return of progressive weather patterns including cold front and possibly some snow storms or nor’easters to the Great Lakes and northeastern US, respectively.

This process of change will be well underway over much of the east this week. However, it may take well into next weekend before the upper level trough is deep enough to bring change to the Key West. In fact, the cold front passage may not occur until Sunday in Key West, meaning that right up until the start of Race Week, trade wind conditions may continue in Key West. So, just to play with competitors heads, any training or preparations in Key West prior to the start of race week will likely take place the waning “warm winter” pattern of the last week to 10 days. However either by Sunday or almost certainly by Monday, a dramatic change to a more typical winter pattern is expected, with more changeable conditions expected day-to-day.

GENERAL OUTLOOK FOR KEY WEST RACE WEEK:

A brief description of expect weather map patterns is provided for each day of Race Week below. In addition, the probability of occurrence of various wind speeds and rain is given.

*** KEY TO ASSESSMENTS OF WIND AND WEATHER ***

PREDOMINANT WIND – Light: < 10 kts | MODERATE: 10-15 kts | FRESH: 15-20 kts | STRONG: > 20 kts
WEATHER (RAIN) BASELINE DAILY PROBABILITY – 20%

SUBJECTIVE CONFIDENCE:
- POOR: Models show little or no consistency. At best, the forecast is a guess
- BELOW AVERAGE: Some consistency, but models changing and timing may be indefinable. The forecast is an educated guess.
- AVERAGE: Models are consistent within a reasonable range. The forecast has statistical significance.
- ABOVE AVERAGE: Unusually strong model consistency leads to expectations of a reliable forecast. Statistically reliable.
- HIGH: Sorry, this is never used on a 7+ day forecast!

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MONDAY (21 Jan 2013): Ensemble trends suggest a post-frontal pattern on Monday with new high pressure building north of the Keys. In this pattern, N’ly winds are possible, gradually veering with time to the NE. Winds may be Fresh to strong early in the high pressure build, but easing and unstable winds will develop as the wind veers right. There may be some lingering post-frontal showers depending on how quickly the front expected Saturday or Sunday moves away to the south.

WIND - LIGHT: 20%| MODERATE: 30% | FRESH: 40% | STRONG: 10% RAIN – 30% (Above normal)
SUBJECTIVE CONFIDENCE: ABOVE AVERAGE

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TUESDAY (22 Jan 2013): High pressure moves relatively quickly off the US east coast and the next front appears over the Mississippi River valley moving toward the gulf coast. A high pressure ridge should hold across northern FL turning winds from NE to E as weak gradient. This tends to be a lighter, more unstable wind pattern. The weather is generally good as cool air from the FL peninsula drains southwest across the Keys.

WIND - LIGHT: 35%| MODERATE: 40% | FRESH: 20% | STRONG: 5% RAIN – 10% (Normal)
SUBJECTIVE CONFIDENCE: AVERAGE

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WEDNESDAY (23 Jan 2013): High pressure moves further east into the Atlantic but a ridge hold across central FL. This will promote a return of trade winds to the waters off the keys. E tending SE wind should be a bit stronger and more consistent. There is a small chance of some trade wind showers, especially off the Gulf Stream in the morning.

WIND - LIGHT: 25%| MODERATE: 60% | FRESH: 25% | STRONG: 0% RAIN – 20% (Below normal)
SUBJECTIVE CONFIDENCE: AVERAGE

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THURSDAY (24 Jan 2013): The pattern starts to fall apart and become less predictable as the next cold front is expected to push into the eastern Gulf and toward Key West. There is a spread in the forecasts regarding the strength of this front ranging from weak to very strong. In addition, there is no consensus on the timing of weather features, this leads to little confidence and difficulty in defining the wind regime. The front is likely to bring some rain with it, so risk of adverse weather increases.

WIND - LIGHT: 20%| MODERATE: 30% | FRESH: 30% | STRONG: 20% RAIN – 40% (Above normal)
SUBJECTIVE CONFIDENCE: BELOW AVERAGE

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FRIDAY (25 Jan 2013): The uncertainty brought by the uncertainty on Thursday carries over into Friday. If the front does go through, then a push of stronger N’ly wind can be expected and this is reflected in the forecast wind range probabilities. However this is an educated guess based only on past experiences with trends. Above normal on rain probabilities give the possible proximity of any front or frontal remnants.

WIND - LIGHT: 10%| MODERATE: 30% | FRESH: 40% | STRONG: 20% RAIN – 30% (Above normal)
SUBJECTIVE CONFIDENCE: POOR

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Forecast prepared by Sailing Weather Service, LLC
Learn more at www.sailwx.com

OVERNIGHT SAIL CARE & REPAIR
North Sails will have overnight sail care & repair available during Key West Race Week 2013. North Sails Loft will be located at 2928 N. Roosevelt Blvd, Key West, Florida (in Key Plaza next door to K-mart). North Sails Van will be available at all times downstairs at 201 William Street for pick up/delivery. Call Yana Meerson at 631-805-4949 or 954-663-4556 for more information.


NORTH SAILS

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