Tropical Depression SEVEN-E

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TROPICAL DEPRESSION SEVEN-E DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP072008
200 AM PDT WED JUL 16 2008
 
THE AREA OF LOW PRESSURE SOUTH OF THE GULF OF TEHUANTEPEC HAS BEEN
MAINTAINING CONVECTION CLOSE TO THE CENTER OF A WELL-DEFINED
CIRCULATION.  THIS CONVECTION HAS BEEN GRADUALLY INCREASING IN
EXTENT AND VIGOR OVER THE PAST 12-24 HOURS...AND AT 06Z THE SYSTEM
GARNERED CONSENSUS DVORAK T2.0 CLASSIFICATIONS.  ON THIS
BASIS...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION SEVEN-E.

THE CENTER IS HARD TO LOCATE PRECISELY...BUT IS SOMEWHERE NEAR THE
EASTERN EDGE OF THE DEEP CONVECTION.  THE INITIAL MOTION IS
ESTIMATED TO BE 310/8.  DEEP-LAYER HIGH PRESSURE OVER THE
SOUTHWESTERN UNITED STATES IS EXPECTED TO STEER THE CYCLONE TO THE
WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS...AND THE MODEL
GUIDANCE IS IN GOOD AGREEMENT TO THAT POINT.  IN THE LATTER PART OF
THE FORECAST PERIOD...THERE ARE LARGE DIFFERENCES IN HOW THE GLOBAL
MODELS HANDLE A MID- TO UPPER-LEVEL TROUGH CURRENTLY NEAR 40N/150W. 
THE OFFICIAL FORECAST FAVORS THE ECMWF SOLUTION...WHICH MAINTAINS A
SOMEWHAT WEAKER RIDGE THROUGHOUT AND IN PARTICULAR NEAR THE END OF
THE PERIOD DUE TO THE LOCATION OF THE UPPER TROUGH.  MOST OF THE
REMAINING TRACK GUIDANCE IS SOUTH OF AND FASTER THAN THE OFFICIAL
FORECAST.

THE DEPRESSION IS IN AN ENVIRONMENT OF MODERATE EASTERLY SHEAR...AND
THIS IS EXPECTED TO CONTINUE FOR MOST OF THE FORECAST PERIOD.  THE
EXPLICIT DYNAMICAL GUIDANCE...THE HWRF AND GFDL MODELS...SHOW THE
SYSTEM BECOMING A MID-RANGE TROPICAL STORM...WHILE THE STATISTICAL
SHIPS MODEL PEAKS OUT NEAR 75 KT IN THREE DAYS.  THIS IS ALL THE
MORE REMARKABLE GIVEN THAT THE CURRENT SHIPS RUN IS BASED OFF THE
MEDIUM BAM...WHICH REACHES COLDER WATER A DAY SOONER THAN THE
OFFICIAL FORECAST.  THE GFS/UKMET/NOGAPS/ECMWF LARGE-SCALE MODELS
ALL INDICATE THAT THE CYCLONE SHOULD BE ABLE TO FIGHT OFF THE SHEAR
AND THRIVE...AND OUT OF RESPECT FOR THAT UNANIMITY OF OPINION THE
OFFICIAL FORECAST WILL BE ABOVE THE ICON INTENSITY CONSENSUS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/0900Z 10.1N  95.3W    30 KT
 12HR VT     16/1800Z 10.6N  96.9W    35 KT
 24HR VT     17/0600Z 11.3N  99.6W    40 KT
 36HR VT     17/1800Z 11.8N 102.0W    45 KT
 48HR VT     18/0600Z 12.5N 104.0W    50 KT
 72HR VT     19/0600Z 14.0N 106.5W    60 KT
 96HR VT     20/0600Z 16.0N 109.0W    65 KT
120HR VT     21/0600Z 18.0N 112.0W    65 KT
 
$$
FORECASTER FRANKLIN
 
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