Surf Forecast Question
Submitted By: surfnews
Date: December 13, 2010

i have a question for dean in regard to forecasting.

this past saturday morning, most forecast services were predicting NW winds for saturday.
i had checked the national weather service marine forecast, magic seaweed, swell info and maybe surfline as well. they all predicted
NW winds. and mind you this was saturday mornings’ forecast for saturday, that same day.
then i checked the saint augustine bouy, and saw that it had been recording westerly winds for several hours already.
but the wind gauge at the pier was northerly all morning. “oh it’ll change” i thought. it will swing around and get in line
with all the forecasters by the time we get to the beach.

dean’s forecast was the only hold out. dean had been predicting N/NE winds for saturday, and had been for the past 2 days.
i figured he was outnumbered this time, and also that maybe he just hadn’t updated his forecast to include the new N/W wind info
which all the other services had come up with.

so, we load up and drive to the beach around 1pm and the surf is totally choppy with a north wind on it. ….WHAT!!!??
HOW DID DEAN DO THAT? was he lucky? does he have access to weather data that other forecast services do not?
i assume he uses the national weather service marine forecast when forming his forecast. or does he?
i have found the NWS to be quite accurate for local winds, 24 hours in advance.

but here is my question….we drove 70 miles from gainesville to st. augustine, and the wind was NW the entire way, even in gainesville.
and the st. augustine buoy, off shore is also showing westerly winds. so how could the shoreline in between the two have a north wind instead?

thanks for your time and for providing an excellent surf forecast.


note: i hope you will print this on your letters or message board, it may be helpful to others.

Surf Station Response:
The system responsible for the variation in wind direction that Saturday was a weak area of low pressure, called a coastal trough, that often develops just offshore of Florida’s east coast in late fall and early winter. Unlike surface lows that occassionally cross the Florida peninsula and exit into the Atlantic with a closed circulations, coastal troughs are elongated areas of low pressure that orient parallel to Florida’s east coast with wind direction nearly always a few degrees either side of due north (either side-on or side-off shore). And also unlike closed surface lows that usually depart to the east or northeast out into the Atlantic fairly quickly, coastal troughs can linger over the near shore waters off Florida’s east coast for days, producing moderate NNE-N-NNW winds, low clouds and/or fog, and moist conditions accompanied by drizzle or occassional light rain along the coast. Due to the elongated orientation of the pressure gradient, the northerly winds can occur in a relatively narrow area along the immediate shorline and in the nearshore waters just offshore from the coast. Go inland 10-20 miles and the sun can be out with winds more NW. Go out to sea 40-50 miles or more and wind can be coming from a completely opposite direction, usually SE.

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