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Tropical Storm RICHARD


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TROPICAL STORM RICHARD DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL192010
1100 AM EDT THU OCT 21 2010
 
AIRCRAFT DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTERS SHOWED
PEAK FLIGHT WINDS OF 40 KT...RELIABLE SFMR VALUES OF 37 KT...AND A
MINIMUM PRESSURE OF ABOUT 1006 MB.  BASED ON THE ABOVE DATA...THIS
SYSTEM IS UPGRADED TO A TROPICAL STORM WITH AN INITIAL INTENSITY OF
35 KT.  THE CENTER IS LOCATED JUST TO THE WEST OF INCREASING MASS
OF THUNDERSTORMS...WITH A WEAK LOW-LEVEL SWIRL SEEN FARTHER TO THE
SOUTHWEST IN THE HIGH RESOLUTION VISIBLE IMAGES.  OVERALL...THE
CLOUD PATTERN HAS BECOME MORE CONCENTRATED NEAR THE CENTER...WITH
MANY CURVED BANDS IN THE EASTERN SEMICIRCLE.   

GRADUAL INTENSIFICATION SEEMS TO BE THE BEST BET IN THE SHORT-TERM.
WHILE SHEAR HAS DECREASED FROM YESTERDAY...THERE IS STILL A FAIR
AMOUNT OF MID- TO UPPER-LEVEL DRY AIR PRESENT TO THE NORTHWEST OF
THE CYCLONE. THIS DRY AIR WILL HAVE A DECENT CHANCE OF SLOWING THE
STRENGTHENING RATE FOR THE NEXT DAY OR SO AS IT CONTINUES TO BE
ADVECTED TOWARD THE TROPICAL CYCLONE BY A TROUGH OVER THE EXTREME
NORTHWESTERN CARIBBEAN SEA ACROSS FLORIDA. HOWEVER...IN A COUPLE OF
DAYS...UPPER-LEVEL RIDGING IS FORECAST TO BUILD OVER THE CYCLONE...
CREATING A RATHER LOW SHEAR ENVIRONMENT...WHICH SHOULD CUT DOWN ON
ANY DRY AIR ENTRAINMENT. THE NHC INTENSITY FORECAST IS SIMILAR TO
THE PREVIOUS ONE THROUGH 48 HOURS...THEN IS HIGHER THEREAFTER. THE
NEW FORECAST IS BETWEEN THE STATISTICAL MODELS AND THE INTENSITY
MODEL CONSENSUS. IT IS WORTH NOTING THAT THE GFDL AND HWRF
STRENGTHEN THIS SYSTEM INTO A MAJOR HURRICANE IN A FEW DAYS...WHICH
IS NOT OUT OF QUESTION IF RICHARD DEVELOPS THE RIGHT INNER CORE
STRUCTURE.

THE STORM HAS BEEN ERRATICALLY MOVING DURING MOST OF ITS LIFE...AND
A LONG-TERM MOTION IS ABOUT 135/5.  CURRENTLY RICHARD IS UNDERGOING
AN ANTICYCLONIC LOOP AS IT IS CAUGHT IN AN AREA OF RELATIVELY LIGHT
STEERING BETWEEN A TROUGH TO THE NORTH AND A DISTANT RIDGE OVER THE
TROPICAL ATLANTIC.  BY LATE TOMORROW...RIDGING SHOULD REBUILD OVER
THE GULF OF MEXICO...WHICH SHOULD CAUSE THE SYSTEM TO MOVE MORE TO
THE WEST...AND EVENTUALLY WEST-NORTHWEST TO NORTHWEST IN A FEW DAYS. 
THE STRENGTH OF THE RIDGE OVER THE GULF OF MEXICO APPEARS TO BE THE
KEY FEATURE IN THE LONG-RANGE FORECAST.  GENERALLY THE GLOBAL
MODELS WITH A STRONG RIDGE...SUCH AS THE GFS/NOGAPS...KEEP RICHARD
ON A MORE NORTHWESTERLY HEADING WHEN THE CYCLONE APPROACHES THE
GULF OF MEXICO.  HOWEVER...THE MODELS WITH A WEAKER RIDGE...SUCH AS
THE UKMET/ECMWF...AND TO AN EXTREME DEGREE THE HWRF/GFDL...SHOW THE
RIDGE BEING ERODED RATHER QUICKLY AS A NEW UPSTREAM TROUGH DIVES
INTO THE CENTRAL PLAINS.  THE BULK OF THE GUIDANCE IS NOW
SUGGESTING THE WEAKER RIDGE IS MORE LIKELY...AND THE NHC FORECAST
IS SHIFTED TO THE NORTHEAST AT DAYS 4 AND 5.  CONSIDERING THAT THE
NEW FORECAST IS STILL ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE...
FURTHER NORTHEASTWARD ADJUSTMENTS MAY BE REQUIRED IF CURRENT MODEL
TRENDS CONTINUE.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      21/1500Z 16.2N  80.4W    35 KT
 12HR VT     22/0000Z 16.0N  80.4W    40 KT
 24HR VT     22/1200Z 15.9N  80.9W    50 KT
 36HR VT     23/0000Z 16.0N  81.6W    55 KT
 48HR VT     23/1200Z 16.2N  82.4W    65 KT
 72HR VT     24/1200Z 17.4N  85.2W    80 KT
 96HR VT     25/1200Z 19.5N  88.0W    45 KT...INLAND
120HR VT     26/1200Z 22.0N  89.0W    35 KT...OVER WATER
 
$$
FORECASTER BLAKE
 
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