Thursday, June 06, 2013

Tropical Storm Andrea: June 6, Update A

Oeuf, what a day! (or ‘Eggs, quelle journee!’ if you prefer the French translation ;-)). Storms and big meetings shouldn’t be allowed to be on the same day… it wreaks havoc on one’s shoes! Time for a cuppa tea. J

It’s been mostly dry and even sunny in St. Petersburg (Florida) since this afternoon. We did have a bit of a soggy night and morning with about an hour of thundery weather which, like some of our normal daily summer thunderstorms, dumped a few more drops of rain and gave us a few tornadoes. Places south of Tampa Bay had more thundery weather but by 5pm I heard that in Ft. Myers there was just “A bit of nagging rain” left. And I just heard from Mitch R. in Melbourne (on the east coast of Florida, not Australia!) that it was sunny over there by 7pm.

TS Andrea officially made landfall today at 5.45pm EST in the big bend area of Florida, right on target. The exact location was 29.5N, 83.4W, a mere 35 miles north of Cedar Key. Officially her central pressure was 993mb with winds of 65mph, which makes her a strong Tropical Storm (range: 39-73mph). She was moving at a fairly brisk 17mph in a NE direction.

I think today she was actually grown-up enough to be named Tropical Storm… but only just! I don’t think that she had sustained winds of 60-65 mph. I looked at every on-the-ground wind observation I could find in her path today (though they were few and far between) and none of them showed a maximum sustained wind speed stronger than about 45mph. You can see for yourself…

Dear Members of the Jury, I present Exhibit A:

This is a graph from the NOAA coastal station at Cedar Key (35 miles from landfall) showing wind speed before, during and after the storm passed by. This is the same data that you see in the Tides Online graphs but it is presented differently. The green line is the pressure which dropped as the storm approached, reached a low point as the storm was closest, and then started to increase as the storm went by. The blue line is the sustained wind speed and the red line are the wind gusts. You can see that the maximum sustained wind speed is about 36 knots, or 41.4 mph (1 kt = 1.15mph) (gusts are about 51mph).

And Exhibit B:

Another example are the observations from NOAA buoy 42036 in the Gulf, located at 28.5N, 84.5W (about 130 miles NW of Tampa). The center of Andrea passed very close to this location at 11am EDT (center was 28.2N, 84.3W). Again, the maximum wind speed was 35 knots, or just over 40 mph.

And Exhibit C (which I’ve not attached because my briefcase was a bit full, but I can upon request): The closest non-NOAA buoy was not quite as close to the center of the storm as the two examples above, but it was closer to Florida than the storm as she went by. The USF/COMPS mooring at 27.5N, 83.7 W showed a max wind speed of 31 mph.

Although the sustained winds were relatively weak (and hence her official winds should be lower), there were still some gusts which caused a bit of damage here and there – a branch falling on a fence or roof, or, as Jackie D. in St. Petersburg found when she got home, a glass table that lost a battle with a runaway umbrella (thanks for sharing!):

Overall though, TS Andrea was mostly a watery event with rain and storm surge. In St. Pete, the maximum storm surge was just over 2 feet above the normal tides. At Cedar Key, just south of the center at landfall, the storm surge so far has been about 4.5 ft above the normal tide… that would probably cover my car completely! Here is a photo of Gulfport from Randy L. (thanks!), showing the surge and waves:

TS Andrea is now over northern Florida at 30.3N, 82.4W, moving NE at 15mph. Officially her winds are 45mph, central pressure is 993mb. I think she is weaker than this at the moment and should really be downgraded to a Tropical Depression (17-38mph). She’s mostly just cloudy, with some pockets of rain, as you can see in this infrared (IR) satellite image (the main convective activity is offshore, over the deep warm waters of the Gulf Stream):

What is interesting is that she is quite large – extending all the way from Florida to the DC area (the patch of clouds over New England are from a different source). I think the NHC forecast track is pretty good, but I am not sure she will remain at Tropical Storm strength for the next 4 days.

There is an Atlantic Blob out there… it has some pretty good circulation in the lower half of the troposphere and some reasonable convection. The NHC give him a 10% chance of developing in the next 2 days. I’ll look at him properly tomorrow.

I was going to talk about the pathetic state of our critical observation capabilities which is hampering what we know about storms (including accurate forecasts), but I’ve rambled on long enough for one sitting! I’ll have to save that for a rainy day (well… maybe the next rainy day J). It’s half past wine o’clock! ;-)

Tally ho!

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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