Tropical Storm Don (Updated: 8:00pm CDT, 7/28/2011)

Watches/Warnings:
A TROPICAL STORM WARNING IS IN EFFECT FOR…
* TEXAS COAST FROM PORT MANSFIELD TO SAN LUIS PASS

A TROPICAL STORM WATCH IS IN EFFECT FOR…
* TEXAS COAST SOUTH OF PORT MANSFIELD TO THE MOUTH OF THE RIO GRANDE

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.

Here is the latest on TS Don, as of 7:00pm CDT:

LOCATION…24.7N 91.8W
ABOUT 410 MI…655 KM ESE OF CORPUS CHRISTI TEXAS
ABOUT 365 MI…590 KM E OF BROWNSVILLE TEXAS
MAXIMUM SUSTAINED WINDS…45 MPH…75 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…1004 MB…29.65 INCHES

—————————————————————————————

Believe it or not, there is a lot that has transpired since my last update at 5:00pm CDT.  A couple of recon airplanes have flown into the storm since then.  As of right now, the minimum central pressure that the Air Force recovered was 995.4mb. 996.1mb was the minimum central pressure recorded from the NOAA recon plane.  So what does this mean?

This means that Don strengthened quite a bit over the course of 3 or 4 hours (from 1004mb to 995.4mb).   The National Hurricane Center will come out with another full update at 10:00pm CDT.  I expect the maximum sustained winds to be a bit higher, in the range of 50-55mph, maybe even more.  In their full update, NHC will update any tropical storm watches/warnings, update strength, coordinates of the storm, and forecast track, as well as a written discussion.

Water vapor imagery continues to show dry air ahead of TS Don.  This may be the only thing that prevents it from becoming a Category 1 hurricane at landfall.  Wind shear has improved around the storm, with the exception of the southwest part.  This may be a reason why pressure dropped so much in the center.  Convection has plumed around the center since my last update, and because of the location of the convection, it may steer the storm a little bit further south than what the models have it, currently.  This is still questionable at this time.

Figure 1. 00Z 110729 Shear tendency values(past 24 hours). Don is moving toward an area with decreasing shear.

Figure 2. 0015Z 110729 Water vapor imagery showing the dry air ahead of TS Don. This may limit its intensity. Pinks and purples show greater amounts of water vapor.

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About Brian

University of Oklahoma graduate with a degree in Meteorology. Follow me on Twitter: @WeatherInformer
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