Here is an update on our "State of the Winds."
Any local fisherman, diver or even the average landlubber resident has noticed the relentless breeziness over the Keys and the surrounding waters.
We took a look at more statistics through May 15th, and came up with the obvious conclusion: Our winds are bucking the climatological norms. Stated most simply: The winds have been increasing during a time when average winds in the month of May should be decreasing.
Average wind for April at Sand Key (historical): 12.6 knots
Average wind during April, 2004: 12.5 knots
Conclusion: In spite of the windy periods, there were enough lulls in the wind to yield a near-normal average wind for April. Keep in mind, that an average wind is just that--an average. Therefore, for every hour that the wind was only 5 knots, there was an hour that the wind 20 knots. If the lighter winds do not fall during hours normally spent while fishing or diving, then it does not help.
Average wind for 30 days from April 16 through May 15, 2004 at Sand Key: 15.3 knots
Conclusion: While averages for this interim period are not known, it does show that the lulls in the wind that occurred early in April did not occur later in April. So, while we had a breezy winter season, one can see that the average wind was increasing and remaining steady from late April into the first half of May.
Average wind for May at Sand Key (historical): 10.1 knots Standard Deviation: 5.2 knots 83.5% Percentile of wind: 15.3 knots
Average wind for May 1 to 15, 2004: 15.8 knots
Conclusion: Note that the average is above one standard deviation of the average wind to be expected for May. Roughly, we're in the top 15% of all Mays at Sand Key in terms of wind. This is clearly "unusually windy" weather for May, but not unheard-of. Mays as windy as the one we're having could occur, if we think in terms of a century of history or more, once or twice each decade.
Why has it STAYED so windy?
In the above chart, we are looking at an altitude of roughly 19000 feet. If you notice, there is a pattern in the black lines suggesting a tongue or "ridge" of higher pressure going over Florida and the southeast. Notice the lines are closer together further north...across the Great Lakes and New England. There, stronger southwest and west winds are steering storms and cold fronts well to our north. When high pressure builds strongly at these altitudes, we sometimes get what is called a "blocking" weather pattern. Blocking patterns do just that--they block weather systems from moving into and through the region. Closer to ground level (where we work and play), high pressure has remained bridged from the Atlantic into Georgia. In fact, this high pressure system appears even stronger than what we witnessed in April.
The result is all-to-evident: relentless gusty winds out of the east, and what seems to be a never-ending Small Craft Advisory from your Key West National Weather Service Office.
THE FUTURE -- Unfortunately, using historical averages will not be of much help in an unusual year like this. It appears as if above-normal easterly winds will continue into late May, but could ease a little from the "near 20 knots" levels
By the way, what is meant by all these Advisories and Exercise Caution statements? Here's a reminder:
Small Craft Exercise Caution: Sustained winds of 15 to 20 knots, and/or significant wave heights (seas) to 6 feet. This is not normally a life-threatening situation, but with safe boating practices and good knowledge of your vessel's abilities, you may have a safe trip but one that is uncomfortable for many guests.
Small Craft Advisory: Sustained winds of 20 knots to 33 knots, and/or significant wave heights (seas) to 7 feet or greater. This can be a hazardous situation for small boats, and especially flat-bottomed boats of small dimensions. For many experienced boaters, it is the sign of an uncomfortable trip.
Special Marine Warning: Wind gusts of 34 knots or greater, and/or waterspouts, over a duration of 2 hours or less. You will have to use your knowledge and experience to determine whether you will need to return to port. The National Weather Service advises that your best course of action is to return to port as soon as possible before the arrival of strong winds. We will do our best to include higher wind speeds in the warning message should we expect them, or detect them with National Weather Service Doppler Radar, from any thunderstorms in our vicinity. Knowing the wide variety of vessels in our waters, a Special Marine Warning can be considered the "Adult Swim" of our local waters. And even if you cannot get back to port in time, make sure all those life jackets are handy, and get below deck if possible to lower your chance of a fatal lightning injury.
And what is meant by Moderate Breezes, Fresh Breezes, and Strong Breezes?
These terms are old mariner terms first defined in 1805 by Sir Francis Beaufort of England. His work is known as the Beaufort Scale. A Moderate Breeze is a sustained wind of 11 to 16 knots, accompanied by small waves of 1 to 4 feet on the open sea and numerous whitecaps. A Fresh Breeze is a sustained wind of 17 to 21 knots, accompanied by moderate waves of 4 to 8 feet on the open sea, many whitecaps and some spray. A Strong Breeze is a sustained wind of 22 to 27 knots, accompanied by large waves of 8 feet or more on the open sea, common whitecaps and even more spray. Please note that specifics on wind direction and the possibility of swells originating from distant waters will significantly differ from Sir Beaufort's general scale on seas. Your National Weather Service has access to wave and swell forecast models that are considered when making the local Florida Keys Coastal Waters Forecast.
For more information, including additional terms used in the Beaufort Scale, please visit our National Weather Service Marine Webpage! Marina Operators, Captains and Marine Supply Interests: National Weather Service meteorologists will be more than happy to speak on a wide variety of topics concerning weather safety and access to National Weather Service warnings and forecasts for our local waters. Please e-mail Jon Rizzo if you would like to schedule a talk, visit or presentation!