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Tropical Depression THIRTEEN-E Forecast Discussion Number 1

Issued at 100 PM PST SAT NOV 19 2011

000
WTPZ43 KNHC 192039
TCDEP3
 
TROPICAL DEPRESSION THIRTEEN-E DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132011
100 PM PST SAT NOV 19 2011
 
THE LOW-LEVEL CENTER OF THE AREA OF LOW PRESSURE SOUTH OF THE
MEXICAN COAST HAS BECOME BETTER DEFINED DURING THE DAY...AND A 1645
UTC ASCAT PASS INDICATES THAT THE SYSTEM IS PRODUCING WINDS OF AT
LEAST 30 KT.  IT COULD BE ARGUED THAT THE ASSOCIATED CONVECTION IS
NOT ALL THAT INTENSE...BUT IT IS JUST DEEP AND ORGANIZED ENOUGH FOR
SAB AND TAFB TO PROVIDE DVORAK ESTIMATES OF 25 AND 30 KT...
RESPECTIVELY.  THE SYSTEM IS THEREFORE BEING DESIGNATED AS A
TROPICAL DEPRESSION WITH AN INTENSITY OF 30 KT.
 
THE DEPRESSION IS CURRENTLY LOCATED TO THE SOUTH OF A MID-LEVEL
RIDGE THAT EXTENDS FROM THE SOUTHWESTERN GULF OF MEXICO
WEST-SOUTHWESTWARD ACROSS SOUTHERN MEXICO...AND IT HAS AN INITIAL
MOTION OF 280/10 KT.  AS WOULD BE EXPECTED FOR NOVEMBER...A BROAD
BUT DEEP MID/UPPER-LEVEL TROUGH EXTENDS WEST OF THE U.S./MEXICAN
COAST TO ABOUT 140W WITH THE MID-LATITUDE WESTERLIES EXTENDING DOWN
TO 16N.  EVEN THOUGH A VIGOROUS CLOSED MID-LEVEL LOW IS EXPECTED TO
DIG SOUTHWARD ALONG THE CALIFORNIA COAST OVER THE NEXT COUPLE OF
DAYS...THE SUBTROPICAL RIDGE IS EXPECTED TO BUILD AND EXPAND
WESTWARD AT THE SAME TIME.  THIS SHOULD INDUCE THE DEPRESSION ON A
WEST TO WEST-NORTHWESTWARD COURSE WITH A NEARLY CONSTANT FORWARD
SPEED THROUGH THE NEXT FIVE DAYS.  WITH THE EXCEPTION OF THE
HWRF...WHICH SHOWS A MORE POLEWARD MOTION BEYOND DAY 3...THE TRACK
GUIDANCE IS TIGHTLY CLUSTERED...AND THE OFFICIAL FORECAST IS VERY
CLOSE TO THE MODEL CONSENSUS TVCE.
 
THE THERMODYNAMIC ENVIRONMENT NEAR THE DEPRESSION MAY NOT BE IDEAL
FOR CONVECTIVE DEVELOPMENT SINCE THE SYSTEM MOVED OVER COOL WATERS
AND THROUGH A REGION OF DRY AIR RESULTING FROM A GAP WIND EVENT
OVER THE GULF OF TEHUANTEPEC.  HOWEVER...THE SYSTEM IS MOVING
TOWARDS A MORE CONDUCIVE ENVIRONMENT...AND DEEP CONVECTION SHOULD
BEGIN TO SLOWLY FILL IN OVER THE CIRCULATION.  VERTICAL SHEAR IS
EXPECTED TO BE RELATIVELY LIGHT THROUGH THE FORECAST PERIOD...SO
STEADY STRENGTHENING IS EXPECTED.  THERE IS SOME DIVERGENCE BETWEEN
THE SHIPS AND LGEM GUIDANCE BEYOND 24 HOURS...WITH THE SHIPS
SHOWING MORE AGGRESSIVE INTENSIFICATION.  GIVEN THE UNCERTAINTY IN
HOW MUCH THE THERMODYNAMIC ENVIRONMENT WILL IMPROVE...THE OFFICIAL
INTENSITY FORECAST LIES CLOSER TO THE LGEM MODEL.
 
BASED ON HISTORICAL RECORDS...TROPICAL DEPRESSION THIRTEEN-E IS THE
LATEST-FORMING TROPICAL CYCLONE IN THE EASTERN NORTH PACIFIC BASIN
SINCE TROPICAL DEPRESSION TWENTY-TWO-E IN 1987...WHICH FORMED ON
NOVEMBER 24.  IF IT BECOMES A TROPICAL STORM...IT WOULD BE THE
LATEST-FORMING NAMED STORM SINCE HURRICANE WINNIE IN 1983...WHICH
FORMED ON DECEMBER 4.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/2100Z 10.0N 101.0W   30 KT  35 MPH
 12H  20/0600Z 10.2N 102.5W   35 KT  40 MPH
 24H  20/1800Z 10.9N 104.5W   40 KT  45 MPH
 36H  21/0600Z 11.4N 106.8W   45 KT  50 MPH
 48H  21/1800Z 11.6N 109.0W   50 KT  60 MPH
 72H  22/1800Z 12.0N 113.0W   60 KT  70 MPH
 96H  23/1800Z 12.5N 118.0W   65 KT  75 MPH
120H  24/1800Z 13.5N 122.5W   55 KT  65 MPH
 
$$
FORECASTER BERG
 

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