Thursday, August 24, 2017

Tropical Storm Harvey: August 23, Update A

Well, as I think they say in some horror movie or other which I can’t recall at the moment… Heee’s Baaaack.

Tropical Storm Harvey took a little hiatus as he was crossing the Caribbean to watch the solar eclipse, and a lovely shiny red eclipse it was too...
Credit: Unknown - Internet (brought to my attention by Ben A.)

(What sort of nerd would I be if I let the big science event of the week just pass us by? ;-))

But today Harvey returns to us as a Tropical Storm in the Gulf. His circulation never really went away and after crossing the Yucatan Peninsula and moving over the warm waters of the Bay of Campeche, he has slowly been gathering his wits and is now a Tropical Storm. Again. Sigh.

Currently he is at 22.6N, 92.6W, heading NW at 7mph. His central pressure is 1001mb, with winds of 45mph which makes him a weak Tropical Storm (TS range: 39-73mph). He is very disorganized and it is not easy to see his center of circulation in this mess…

I am going to assume it is where the NHC say it is (they sent a plane in to investigate, so they will have the best available data). He does have circulation in the lower half of the troposphere but it is not as well defined in the mid-levels (vorticity map below is at 500mb - the mid-level) which is another sign he is a very weak Tropical Storm:

He is forecast to head generally northwest, making landfall in Texas on Friday night/Saturday as a very weak category 1 hurricane:

I think there is a bit more uncertainty with this track than usual because he is such a weak storm and also because he almost stalled today – which always adds a little hiccup. The southern Texas track is reasonable, but there’s a chance he will be a little more to the right, maybe northern Texas (or Louisiana)…  it is really tricky to assess this today given what a mess he is. We’ll have a much better idea tomorrow I hope.

Regarding the intensity, there is room for him to grow slowly and for now the thinking of a very weak cat 1 hurricane or strong Tropical Storm in a couple of days seems about right. Looking at the ocean: the sea surface water is very warm – around 29-31 deg C in the northern Gulf ahead of him and the upper 50-75 m is warmer than 26 deg C, which is enough to allow him to grow, but he won’t be a really big storm. Looking at the atmosphere, there is some wind shear that is impacting him at the moment (the clouds are mostly to the northeast in the satellite images which is an indication of wind shear), but it looks like that will get lighter in the next day or so, which will also allow him to grow a bit.

There will be some rain and some storm surge along the northern Gulf coast – don’t forget, look on for the sea level along the coast (see this post for the Technical Alert on how to use the Tides Online site).

I’ll be back tomorrow, by which time we should have a much better handle on the track.

Night for now!

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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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