Tropical Storm SERGIO

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TROPICAL STORM SERGIO DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP212006
800 AM PDT TUE NOV 14 2006
 
AN AMSR-E MICROWAVE PASS AT 09Z SHOWED A WELL-DEFINED CORE BAND. 
DVORAK INTENSITY ESTIMATES WERE 30 KT FROM TAFB AND AFWA ...AND 35
KT FROM SAB.  BASED ON THE STRONG MICROWAVE PRESENTATION...THE
ADVISORY INTENSITY WILL FAVOR THE HIGHER ESTIMATE...AND THE
DEPRESSION IS UPGRADED TO A TROPICAL STORM.  THIS IS THE FIRST TIME
SINCE 1961 THAT TWO TROPICAL STORMS HAVE FORMED IN THE EASTERN
PACIFIC BASIN IN NOVEMBER...AND ONLY FIVE STORMS HAVE FORMED LATER
IN THE SEASON THAN SERGIO.

A REPRESENTATIVE INITIAL MOTION MIGHT BE 315/3...SLOWER THAN BEFORE. 
GLOBAL MODEL GUIDANCE SUGGESTS THAT THE ALREADY WEAK RIDGING TO THE
NORTH OF SERGIO WILL CONTINUE TO BREAK DOWN...AND ALL OF THE
PRIMARY DYNAMICAL MODELS INDICATE A LOOP OR A STALL OVER THE NEXT
COUPLE OF DAYS.  AFTER THAT...A MID- TO UPPER-LEVEL LOW IS FORECAST
TO DROP SOUTHWARD ACROSS BAJA CALIFORNIA TO THE WEST OF THE
CYCLONE...WHICH SHOULD INDUCE A NORTH OR NORTHWESTWARD MOTION TO
RESUME.  WITHIN THIS BASIC SCENARIO THERE IS CONSIDERABLE MODEL
SPREAD...HOWEVER...WITH THE GFDL ON THE RIGHT WITH A TRACK VERY
CLOSE TO THE MEXICAN COAST...AND THE ECMWF ON THE LEFT WELL
OFFSHORE.  THE OFFICIAL FORECAST IS SLOWER THAN THE PREVIOUS
ADVISORY EARLY IN THE FORECAST PERIOD...AND SHIFTED A LITTLE TO THE
RIGHT LATER ON TO BE IN BETTER AGREEMENT WITH THE DYNAMICAL MODEL
CONSENSUS.

FIRST VISIBLE SATELLITE IMAGES SEEM TO CONFIRM THE GOOD CORE BANDING
STRUCTURE SEEN IN THE EARLIER MICROWAVE DATA...AND SERGIO IS
UNDERNEATH AN UPPER ANTICYCLONE WITH LIGHT SHEAR.  WATER
TEMPERATURES ARE ABOVE 29C...AND THE ENVIRONMENT IS MOIST.  I DON'T
SEE ANY REASON WHY THIS SYSTEM SHOULD NOT DEVELOP FURTHER IN THE
SHORT RUN...AND PERHAPS QUITE RAPIDLY.  THE SHIPS R-I INDEX
CONTINUES TO INDICATE A STRONG POSSIBILITY OF RAPID
INTENSIFICATION...AS DOES THE GFDL MODEL.  THE OFFICIAL INTENSITY
FORECAST IS ADJUSTED UPWARD AND IS CLOSE TO AN AVERAGE OF THE SHIPS
AND GFDL GUIDANCE.  WHILE THERE IS UNFAVORABLE SHEAR TO THE NORTH
OF THE CYCLONE...THE CURRENT FORECAST PRESUMES THAT SERGIO WILL
REMAIN FAR ENOUGH TO THE SOUTH TO AVOID THE SHEAR. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/1500Z 13.2N 104.5W    35 KT
 12HR VT     15/0000Z 13.4N 104.7W    45 KT
 24HR VT     15/1200Z 13.5N 105.0W    55 KT
 36HR VT     16/0000Z 13.5N 105.0W    65 KT
 48HR VT     16/1200Z 14.0N 105.0W    70 KT
 72HR VT     17/1200Z 15.5N 105.5W    70 KT
 96HR VT     18/1200Z 17.0N 106.0W    70 KT
120HR VT     19/1200Z 18.5N 107.0W    65 KT
 
$$
FORECASTER FRANKLIN/BLAKE
 
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