Tropical Depression TWENTY-ONE-E

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TROPICAL DEPRESSION TWENTY-ONE-E DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP212006
200 AM PDT TUE NOV 14 2006
 
SATELLITE IMAGERY THIS MORNING INDICATES THAT THE TROPICAL
DEPRESSION IS NEAR TROPICAL STORM STRENGTH.  A SMALL AREA OF
PERSISTENT CONVECTION HAS FORMED NEAR THE CENTER AT THE END OF A
BAND THAT WRAPS IN FROM NORTHWEST TO SOUTHWEST TO SOUTHEAST OF THE
CENTER.  SATELLITE INTENSITY ESTIMATES ARE 30 KT FROM TAFB AND
SAB...AND 25 KT FOR AFWA.  BASED ON THAT...THE SYSTEM WILL REMAIN A
DEPRESSION FOR THIS ADVISORY.

THE CYCLONE HAS SLOWED ITS FORWARD MOTION TO 300/5.  IT IS EMBEDDED
IN AN AREA OF WEAK STEERING CURRENTS AS A SERIES OF MID/UPPER-LEVEL
WESTERLY TROUGHS CROSS NORTHERN MEXICO...AND A MID/UPPER-LEVEL
RIDGE AMPLIFIES WEST OF THE DEPRESSION.  THE LARGE-SCALE MODELS
FORECAST THIS COMBINATION OF FEATURES TO CREATE A LIGHT NORTHERLY
MID-LEVEL FLOW NEAR THE DEPRESSION DURING THE NEXT 24-48 HR. 
SHOULD THIS VERIFY...THE DEPRESSION WOULD MAKE LITTLE PROGRESS
TOWARD THE NORTHWEST...AND INDEED THE GFDL CALLS A LOOPING TRACK
DURING THIS PERIOD.  STARTING IN ABOUT 72 HR...A MID/UPPER-LEVEL
SHORTWAVE TROUGH WILL DROP SOUTHWARD NEAR CLARION ISLAND AND BECOME
A CUT-OFF LOW.  THIS WOULD ALLOW THE TROPICAL CYCLONE TO ACQUIRE A
FASTER NORTHWESTWARD OR NORTHWARD MOTION...WITH THE GFDL
FORECASTING THE SYSTEM TO REACH CABO CORRIENTES MEXICO IN 96-108
HR.  THE OFFICIAL FORECAST CALLS FOR A SLOWER NORTHWESTWARD MOTION
THAN THE PREVIOUS PACKAGE FOR THE FIRST 72 HR...FOLLOWED BY A
SLIGHTLY FASTER MOTION.  IF CURRENT MODEL TRENDS CONTINUE...THE
TRACK MAY HAVE TO BE ADJUSTED SOUTHWARD IN SUBSEQUENT ADVISORIES.

THE DEPRESSION IS CURRENTLY IN AN AREA OF LIGHT VERTICAL WIND SHEAR
WHICH SHOULD ALLOW STRENGTHENING.  LARGE-SCALE MODELS FORECAST A
GENERALLY FAVORABLE SHEAR ENVIRONMENT SOUTH OF 15N NEAR THE
FORECAST TRACK FOR THE NEXT SEVERAL DAYS.  THE GFDL MODEL FORECASTS
THE SYSTEM TO BECOME A MAJOR HURRICANE IN 96 HR...WHILE THE SHIPS
MODEL FORECAST IT TO PEAK JUST UNDER HURRICANE STRENGTH IN 60-72
HR.  THE NEW INTENSITY FORECAST CALLS FOR MORE STRENGTHENING THAN
PREVIOUSLY...BUT IS STILL BELOW THE SHIPS AND GFDL GUIDANCE.  THERE
ARE TWO CONCERNS ABOUT THE INTENSITY FORECAST.  FIRST...THE
ENVIRONMENT IS FAVORABLE ENOUGH THAT THERE IS A 40-50 PERCENT
CHANCE OF RAPID STRENGTHENING DURING THE NEXT 24 HR ACCORDING TO
THE INDEX ATTACHED TO THE SHIPS MODEL.  SECOND...ANY MOTION THAT
DELAYS THE CYCLONE REACHING THE STRONGER SHEAR NORTH OF 15N WOULD
ALLOW IT MORE TIME IN A FAVORABLE ENVIRONMENT.  THUS...THE SYSTEM
COULD GET CONSIDERABLY STRONGER THAN FORECAST HERE.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0900Z 13.0N 104.6W    30 KT
 12HR VT     14/1800Z 13.2N 105.0W    40 KT
 24HR VT     15/0600Z 13.6N 105.5W    45 KT
 36HR VT     15/1800Z 13.9N 105.8W    50 KT
 48HR VT     16/0600Z 14.4N 106.1W    55 KT
 72HR VT     17/0600Z 15.5N 106.5W    55 KT
 96HR VT     18/0600Z 16.5N 107.0W    50 KT
120HR VT     19/0600Z 17.5N 108.0W    45 KT
 
$$
FORECASTER BEVEN
 
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