Jul 29, 2011

DAY 58

Tropical Storm Don was able to strengthen just a bit today. And most of that strengthening occurred within the last couple hours. He continues on a WNW track towards south Texas with maximum sustained winds of 50 mph and his pressure is now at 998 mb. As of about 11pm tonight, Don was firing off some impressive convection with a last ditch effort to strengthen before his landfall tomorrow night.

Earlier today though you can watch Don's struggle to grow in this extended visible satellite loop. Through most of the animation you can see the low level spin exposed on the north side while most of Dons convection is removed to the south. This is a result of that northerly wind shear. Without the convection stacked vertically above the circulation, it is difficult for the storm to organize and grow. Also visible in this image are the low level Arc Clouds being spewed out from the northeast side of the storm, this is an indication that Don is swallowing dry air which also disrupts his ability to strengthen. Thus Don remains a weak tropical storm tonight

The official track from the Hurricane Center brings Don as a tropical storm into Texas just south of Corpus Christi in about 24 hours from now. Tropical Storm Warnings are in effect from Brownsville all the way to Galveston, although the northern sections near Galveston are no longer in the cone of possibility.

Rarely do you see people standing on the shore with open arms with the approach of a tropical system, but that's just what you may see tonight as drought stricken Texas is salivating with the possibility of heavy rainfall. You can see that most of the Texas coastline is in an Exceptional Drought.

It is tough to say exactly how much rain Don will be able to deliver. Often times tropical storms can dump more rain than a hurricane (Fay 2008). But that ridge that is responsible for putting Texas in the drought could zap some of the moisture potential from the approaching Don. He is not yet close enough to pick up any rain bands, but the National Weather Service on the Texas coast is expecting 1-2 inches widespread with up the 4 inches locally. That seems like a logical if not even conservative estimate especially if Don continues to move at 15 or plus mph.

The other feature in the tropical Atlantic that we are continuing to watch is the wave half way between Africa and the windward islands. It has now been dubbed 91L and given a 20% chance of developing into a tropical cyclone in the next 48 hours by the National Hurricane Center. The CMC is developing the system in 4 days and the GFS and NOGAPS are also acknowledging this system for future development. The next named storm in the Atlantic will be Emily.

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