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Alex Slowly Gains Strength

By: Dr. Jeff Masters, 6:35 AM GMT on June 29, 2010

Hello, it's Dr. Rob Carver substituting for Jeff on the late shift.

As of the 0100 EDT advisory, Alex is 475 miles SE of Brownsville TX moving NNW at 8 mph. The advisory wind speed is 65 mph with a minimum central pressure of 985 mb. The most recent vortex fix was at 1225EDT with an unchanged pressure reading. Alex is expected to take a turn to the NW and make landfall just south of Brownsville late Wednesday night/early Thursday morning. The government of Mexico has issued a hurricane warning from the mouth of the Rio Grande south to La Cruz. NHC has hoisted the hurricane warning flag from the Rio Grande north to Baffin Bay. A tropical storm warning extends from Baffin Bay to Port O'Connor. Alex is expected to expand in size so it will be much larger than Hurricane Dolly, which was the last storm to affect the region in 2008.

Hurricane Local Statements are now being issued by the Brownsville and Corpus Christi NWS offices. These statements provide a detailed look at how Alex will affect the region and summarize how local emergency management is responding to the situation.

Alex has three different ways to negatively impact the Rio Grande Valley: storm surge, heavy rains, and strong winds.

Risk of Storm Surge
NHC is forecasting a storm surge of 3-5 feet along the coast north of where Alex makes landfall. The exact details of the surge's extent depend on where Alex makes landfall and how big it gets while it is over the open water. I've include a plot of the statistical storm surge forecast product. Unless Alex refuses to make it's left turn, I don't think there's a chance of storm surge north of Port O'Connor.

Plot of experimental storm surge forecast.

Threat from Rain
NHC thinks 5 to 10 inches of rain over southern Texas/northern Mexico is possible when Alex makes landfall. This is why the Brownsville office thinks the primary threat from Alex will be inland flooding in areas with poor drainage.

Alex has a history of producing torrential amounts of rain as shown by this estimate of rainfall during Alex's passage over the Yucatan Peninsula.

Satellite-derived rainfall estimates for June 27, 2010 using data from the Climate Prediction Center.

Threat from Wind
Alex is currently forecast to reach hurricane status. There will likely be hurricane force winds along the coast where Alex makes landfall. The current hurricane wind probabilities show that Brownsville has a 77% chance of experiencing tropical storm force winds and a 18% chance of experiencing hurricane force winds. Corpus Christi has a 44 % chance of tropical storm winds and a 4% chance of hurricane force winds. There is also the possibility of tornadoes forming in outer rainbands as Alex makes landfall.

The Curious Incident of the Hurricane Dynamical Models
One thing that strikes me as odd about Alex is that neither the GFDL nor the HWRF have been intensifying the storm into a hurricane in the past few model runs. This is intriguing because Alex is already a strong tropical storm. It will bear watching to see if GFDL/HWRF continue this pattern for future storms.

Next Update
Jeff will post an entry sometime this morning, and I'll have another entry late Tuesday night.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.