Lee, Soon To Form? (8/30/2011)

I will get to tropical development in the Caribbean that will trek into the Gulf of Mexico later.  Right now, I want to focus on Tropical Storm Katia in the open Atlantic and what it might do and where it might go.

Tropical Cyclone Katia

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...12.7N 35.4W
ABOUT 750 MI...1210 KM W OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 20 MPH...32 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES

Katia is currently a tropical storm with maximum sustained winds of 60 mph, moving towards the west-northwest at 20 mph.  Katia is forecast to be a hurricane in the next 12-24 hours.  With the Bermuda High centered over the north-central Atlantic, Katia will likely flow the flow around the high.  Exactly where it will go and if it will strike land is still uncertain and depends on the strength and location of the high.  People living in the Lesser Antilles, Puerto Rico, and even Hispaniola need to keep monitoring this storm, even though it is forecast to move to the north of these areas over the next 3-5 days.

Figure 1. 12Z ECMWF 24-hr forecast of Katia.

Figure 2. NHC's 5-day forecast of Katia

Tropical Wave In The Caribbean

 

Figure 3. Tropical wave in question is circled in yellow.

An area of disorganized thunderstorms is causing some concerns for future development.  This area of thunderstorms is slowly moving northwest and many computer forecast models have this area moving into the western Gulf of Mexico as a tropical depression and even some even have it developing into a Tropical Storm Lee by this weekend.  Although models are beginning to agree on intensity of this area in the next 2-3 days, they all disagree on the track.  The North American Model (NAM) model has is entering the Gulf of Mexico in the next 24-36 hours and becoming a tropical storm and trekking towards the LA/TX border as early as Friday.  The Global Forecast System (GFS) model is having trouble developing the area of low pressure, but does have it forming, and then stalling just south of LA by Sunday afternoon through Monday evening, which it then pushes east.  The ECMWF (Euro model) and NOGAPS models doesn’t really have a structural storm forming, but does bring a lot of rain to the Rio Grande Valley starting tomorrow (Wednesday).

Having said all of that, the models are having trouble with a path because of the position of the mid-level ridge and a surface front that will be draped across central TX and northern LA.  I believe there are two scenarios can occur IF something does happen to form over the next couple of days:

  1.  If mid-level ridge dominates, the storm will move southwest (from the LA/TX border), towards the RGV, giving the Valley a better chance of rain.
  2. If the surface front dominates (or mid-level ridge shifts/weakens), the storm will move east or east-northeast, away from the RGV, leaving the Valley high and dry.

It’s important to note that these two possibilities are likely to happen if a tropical cyclone were to develop.  If it stays disorganized, all bets are off.

Figure 4. Surface analysis on day 6 (Monday morning, Sept 5) from HPC. Cold front draped across TX and LA will affect the track of tropical low pressure in the Gulf of Mexico.

About Brian

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