Tropical Storm Don

[Ari Brown]

The NHC as of 2 pm EDT is now giving 90L a near 100% chance of development and is planning to start advisories at 5. HH is on route and will be starting the first NW to SE pass through the storm shortly. Only question now is whether we have TD 4 or TS Don at 5. I won't be surprised if a hurricane watch is posted for parts of Texas later this afternoon.

 

[Ari Brown]

Tropical Depression Four

We now have Tropical Depression Four, according to the NHC ATCF server.

invest_RENUMBER_al902011_al042011.ren

AL, 04, 2011072718, , BEST, 0, 223N, 873W, 30, 1008, TD,

18z information from above:
Location is 22.3N, 87.3W
Wind is 30 knots, 35 mph
Minimum central pressure is 1008 millibars/hPa

Recon is still sampling TD 4 so by the time the 5 pm advisory comes out we may have Tropical Storm Don.

 

[Ari Brown]

And now we have Tropical Storm Don:

AL, 04, 2011072718, , BEST, 0, 221N, 868W, 35, 1004, TS, 34,

The NHC's ATCF system now indicates 35 kt/40 mph winds, so we now have the fourth named storm of the 2011 Atlantic season. The first advisory is scheduled for 5pm EDT but I'd imagine it's currently subject to how soon recon can post a vortex message.

Also -- what recon has found so far indicates an estimated 10 mb pressure drop in Don since this morning. I'd say it's at serious risk of bombing into a stronger storm as soon as it gets away from the Yucatan.

 

[Stuart Robinson]

IMO this will become TS Don and then affect the south Texas coast with much needed rain.

RECON now supports TC DON

 

[Randall Marable]

Can one of the MODS update the name of this thread for me? Thanks.

 

[Ari Brown]

Surprisingly, no watches or warnings posted for the first advisory. NHC sends Don into the TX coast between Corpus Christi and Matagorda. Though the NHC intensity forecast maxes out at 55 kt, they kinda hinted that it could get up to 65 kt before landfall.

 

[MClarkson]

Too much shear. You can see a bit of northeasterly shear on the satellite loop, but it really looks bad on the NAM upper level forecasts for the next few days. 200mb winds reach 50 knots at one point along the likely track... TCs don't like that at all. The GFS doesn't have quite as strong upper level winds, but its still not that good(for the storm).

 

[Ari Brown]

Too much shear. You can see a bit of northeasterly shear on the satellite loop, but it really looks bad on the NAM upper level forecasts for the next few days. 200mb winds reach 50 knots at one point along the likely track... TCs don't like that at all. The GFS doesn't have quite as strong upper level winds, but its still not that good(for the storm).

That's an issue that Don is dealing with right now, along with dry air and close proximity to land. As time moves forward, shear is forecast to lessen and Don will move further into the GOM, and it appears that Don should at least be able to meet the NHC forecast intensity, IMO.

CIMSS ADT numbers are looking good. A little high on the vmax (estimated wind speed) but looks good in general.

----- Current Analysis -----
Date : 28 JUL 2011 Time : 011500 UTC
Lat : 22:33:10 N Lon : 87:41:20 W


CI# /Pressure/ Vmax
3.1 / 998.2mb/ 47.0kt


Final T# Adj T# Raw T#
3.1 2.9 2.5

 

[MClarkson]

GFS and NAM have increasing shear, at least for the next day or so.

http://mag.ncep.noaa.gov/NCOMAGWEB/...AMER&currKey=model&returnToModel=&imageSize=M

 

[cdcollura]

Good day all,

MODS: can you set this thread to "Don"?

Ugh, the "S" word (shear). Shear when you don't want it.

Reminds me of the "R" word (ridge) in May (during bad years).

I actually had my schedule cleared for Friday, but now I'm not so sure (to "waste" a free plane ticket to Austin).

Don is caught on the eastern side of an upper-trough and just west of a deep tropical ridge separating a weak high to the west.

I'd say about 60 MPH at landfall on a best-case scenario.

Very SMALL wind field too (had the shear relaxed a bit, then it would strengthen rapidly - Remember Charley in '04)?

 

[Mike Moore]

Yeah not even worth an Airtran ticket.

 

[Randall Marable]

TROPICAL STORM DON INTERMEDIATE ADVISORY NUMBER 6A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011
100 AM CDT FRI JUL 29 2011

...DON CONTINUES MOVING WEST-NORTHWEST WITH LITTLE CHANGE IN
STRENGTH...


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...25.0N 93.0W
ABOUT 335 MI...540 KM SE OF CORPUS CHRISTI TEXAS
ABOUT 285 MI...455 KM ESE OF BROWNSVILLE TEXAS
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES



With this motion continuing through the night I can imagine watches may have to be extended down the coast even more. The latest models continue to shift southward with landfall meaning bad news for most portions of Texas who were looking forward to the rain.