Sunday, August 16, 2009

TD Ana, TS Bill, TS Claudette & Whirlygig: August 16 Update B

TD Ana:
Formerly known as TS Ana. Poor Ana isn't looking so hot anymore. The dry
air and wind shear has mussed up her hair and make-up to the point that
she's now downgraded to a TD. Winds are 35mph and central pressure is
1008mb. There is still some convection and some circulation, so we should
keep half an eye on her. The center is somewhere around 15.1N, 58.8W, and
she's moving west (ish) near 23mph. She's expected to make a W-NW turn
later tonight, but looks like she'll pass south of the VIs and into the
Caribbean by tomorrow.

TS Bill:
I can't see him staying as a TS for long, and I agree with the NHC that
he'll be a hurricane within the next few hours. He has grown quite quickly
over the last three to four hours. He is in a low wind shear environment,
with plenty of water vapor surrounding him, and water temperatures of 29
deg C beneath. His current wind speed is near 65 mph (TS range: 39-73mph)
and Central pressure at 994 mb. He's moving WNW at 16mph and is currently
centered at about 12.8N, 40W.

The forecast track currently takes him north of the VIs and towards
Bermuda in a few days. I am not 100% convinced of this track. I can see
why they are saying it... there's a low (trough) in the pressure field
that is moving east and will begin to erode the high pressure over the
Atlantic, which will effectively create a path for him to turn NW. But it
is days away, and if that 'trough' does not extend far enough south, then
the high pressure will force him westward for longer than they are
currently forecasting and towards the Caribbean. So, everyone from Bermuda
to the Caribbean, continue to keep both eyes on Bill (which means that
along with Ana, we're keeping 2.5 eyes on these systems... hmmm).

TS Claudette:
She's quite close to the Florida panhandle now, at about 29.5N, 85.6W.
She's a weak TS, with winds of 50mph and central pressure of 1008mb, and
is moving (according to the NHC) NW at 14mph. I'll buy this as it's
difficult to tell exactly where the center is in such a weak system, and
the NHC have planes flying through etc. So it looks like landfall
somewhere between Appalachicola and Pensacola tonight.

But I'm not sure I agree with how the NHC have decided to phrase the water
level information (from the latest advisory): "STORM TIDE IS EXPECTED TO

"Storm tide above ground level". What, may I ask, is 'ground level'?? Yes,
I'm confused by this rather vague terminology. Is it relative to mean low
level water? Which is what is used by the Tides Online site
( I directed you towards
in the previous entry. I much prefer the Tides Online version of how high
the water level will get. It gives you what is normally predicted (blue) -
i.e. your normal high and low tides. Then it shows you what the actual
observations are (red). And finally, the green is the residual, which is
the difference between the observed and predicted levels - i.e. the water
level change because of something other than tides. From that, it looks
like water levels at Appalachicola are about 2 ft above normal, and Cedar
Key is about 1.5 ft above normal. I'm not sure anywhere will get to the
3-5 ft above normal, but we'll know by tomorrow.

Whirlygig north of Bahamas:
There's some dry air moving in a circular manner north of the Bahamas.
It's not got any convection but circulation is good. Just thought I'd
mention it because this entry is rather short (!?!). Not likely to

That's all from me for today. I hear from folks that it was cloudy, wet
and windy along the west coast of Florida. And apparently some of you are
awake at 5am! ... getting your surf boards out. ;)

I'll tune in at some point tomorrow, not sure when. Big day for me. I'm
having tea with the Queen. Ha. Not really. First day at work. Oooh. Aaah.

Night night,

Blog entries archived at:

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,
hypothetically, I was there and I was, hypothetically, going to "run away,
run away" (Monty Python), I'd let you know.

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