Tropical Depression FOUR-E

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TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP042008
800 PM PDT TUE JUL 01 2008
 
ASCAT DATA AT AROUND 16Z SHOWED THAT THE LOW PRESSURE AREA SOUTHWEST
OF MANZANILLO MEXICO HAD A BROAD CENTER ELONGATED NORTH-NORTHWEST
TO SOUTH-SOUTHEAST.  SINCE THAT TIME...SATELLITE IMAGERY INDICATES
THAT THE CIRCULATION AND ASSOCIATED SHOWER ACTIVITY HAS SOMEWHAT
CONSOLIDATED AT THE SOUTHERN END OF THE ELONGATION.  BASED ON
THIS...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION FOUR-E.  THE
INITIAL INTENSITY IS 30 KT IN AGREEMENT WITH SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB...AS WELL AS THE OBSERVED WINDS IN THE
EARLIER ASCAT DATA.

THE INITIAL MOTION IS 315/6.  THE DEPRESSION IS ON THE SOUTHWEST
SIDE OF A WEAK MID-LEVEL RIDGE EXTENDING FROM THE SOUTHWESTERN
UNITED STATES INTO MEXICO.  THE LARGE-SCALE MODELS FORECAST THE
RIDGE TO WEAKEN DURING THE NEXT 48-72 HR...WHICH RESULTS IN WEAK
STEERING CURRENTS.  THE ECMWF AND THE NOGAPS...WHICH KEEP THE
CYCLONE ALIVE FOR 5 DAYS...FORECAST A SLOW NORTHWESTWARD MOTION FOR
48-72 HR AND A SLOW WESTWARD MOTION THEREAFTER.  THIS IS SUPPORTED
BY THE UKMET AND GFS UNTIL THEIR MODEL CYCLONES DISSIPATE NEAR 96
HR.  THE FORECAST TRACK FOLLOWS THIS SCENARIO IN BEST AGREEMENT
WITH THE ECMWF.  THERE IS A CHANCE OF ERRATIC MOTION DURING THE
FIRST 24 HR AS THE CYCLONE CONSOLIDATES.

THE DEPRESSION IS CURRENTLY UNDER A LARGE UPPER-LEVEL ANTICYCLONE
WITH WITH FAIR TO GOOD CIRRUS OUTFLOW IN ALL DIRECTIONS.  THIS
SHOULD ALLOW GRADUAL STRENGTHENING UNTIL THE CYCLONE REACHES COOLER
SEA SURFACE TEMPERATURES IN 36-48 HR.  THE GFS...ECMWF...AND NOGAPS
FORECAST INCREASED VERTICAL WIND SHEAR AFTER 72-96 HR.  SHOULD THIS
VERIFY...THE SYSTEM COULD WEAKEN FASTER THAN CURRENTLY FORECAST.

THE ASCAT DATA SHOWED 25-30 KT WINDS IN A BAND THAT IS CURRENTLY
ABOUT 200 N MI FROM THE CENTER IN THE NORTHEASTERN QUADRANT.  WHILE
THE CENTER OF THE CYCLONE IS EXPECTED TO REMAIN WELL OFFSHORE...
INTERESTS ALONG THE WEST COAST OF MEXICO FROM ZIHUATANEJO TO PUERTO
VALLARTA SHOULD MONITOR ITS PROGRESS IN CASE IT COMES CLOSER THAN
CURRENTLY FORECAST OR THE WIND FIELD IS LARGER THAN FORECAST. 
RAINBANDS ASSOCIATED WITH THE SYSTEM COULD AFFECT PORTIONS OF THE
WESTERN COAST OF MEXICO TONIGHT AND WEDNESDAY.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0300Z 15.9N 107.0W    30 KT
 12HR VT     02/1200Z 16.4N 107.7W    35 KT
 24HR VT     03/0000Z 17.0N 108.5W    40 KT
 36HR VT     03/1200Z 17.5N 109.0W    45 KT
 48HR VT     04/0000Z 18.0N 109.5W    40 KT
 72HR VT     05/0000Z 19.0N 110.5W    35 KT
 96HR VT     06/0000Z 19.5N 112.0W    30 KT
120HR VT     07/0000Z 19.5N 113.5W    25 KT
 
$$
FORECASTER BEVEN
 
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