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Tropical Storm BUD Forecast Discussion Number 9

Issued at 800 PM PDT TUE MAY 22 2012

000
WTPZ42 KNHC 230242
TCDEP2
 
TROPICAL STORM BUD DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP022012
800 PM PDT TUE MAY 22 2012
 
THERE HAS BEEN A BURST OF CONVECTION NEAR THE LOW-LEVEL CENTER OF
BUD DURING THE PAST FEW HOURS. HOWEVER...A 2243 UTC TRMM OVERPASS
SUGGESTED THAT THE CENTER IS LOCATED ON THE EASTERN EDGE OF THE NEW
CONVECTIVE GROWTH.  THE OVERALL CLOUD PATTERN OF THE CYCLONE HAS NOT
CHANGED MUCH SINCE THE PREVIOUS ADVISORY...NOR HAVE SATELLITE
CLASSIFICATIONS WHICH ARE AT T2.5 FROM TAFB AND SAB. BASED ON THE
LACK OF CHANGE SINCE THAT TIME...THE INITIAL INTENSITY IS HELD AT
35 KT.
 
IT REMAINS A BIT PUZZLING AS TO WHY BUD HAS NOT STRENGTHENED SINCE
CURRENT SHEAR ANALYSES CONTINUE TO INDICATE LESS SOUTHEASTERLY
SHEAR OVER BUD THAN WHAT THE CURRENT CLOUD PATTERN WOULD SUGGEST. 
EVEN THOUGH THE TROPICAL CYCLONE SHOULD BE TRAVERSING WARM WATERS
AND ENCOUNTERING EVEN LOWER VERTICAL SHEAR DURING THE NEXT DAY OR
TWO...THE INTENSITY GUIDANCE SHOWS LITTLE STRENGTHENING. AS BUD
APPROACHES SOUTHWESTERN MEXICO IN 2-3 DAYS...INCREASING SOUTHERLY
TO SOUTHWESTERLY FLOW ALOFT AND A DEEP LAYER OF DRY AIR IMPINGING
ON THE WESTERN SIDE OF THE CIRCULATION SHOULD RESULT IN WEAKENING.
LARGE-SCALE MODELS INDICATE A DECOUPLING OF THE LOW- TO MID-LEVEL
FLOW FROM THE UPPER-LEVEL FLOW LATER IN THE FORECAST PERIOD WHICH
COULD RESULT IN AN EVEN FASTER RATE OF WEAKENING AT THAT TIME. THE
OFFICIAL NHC INTENSITY FORECAST IS REDUCED RELATIVE TO THE PREVIOUS
ONE AND NO LONGER CALLS FOR BUD TO BECOME A HURRICANE. THE NEW
FORECAST REMAINS ABOVE THE STATISTICAL GUIDANCE AT NEARLY ALL
TIMES.
 
THE INITIAL MOTION ESTIMATE IS 315/12.  BUD SHOULD MOVE GENERALLY
NORTHWESTWARD FOR THE NEXT 12-24 HOURS AROUND THE WESTERN PERIPHERY
OF A MID-LEVEL RIDGE EXTENDING WESTWARD FROM THE CARIBBEAN SEA.  IN
24-48 HOURS...GLOBAL MODELS SHOW THE CYCLONE SLOWING DOWN AND
TURNING NORTHWARD AS IT ENCOUNTERS A WEAKNESS IN THE RIDGE ALONG
107W AND EVENTUALLY NORTHEASTWARD AS IT FEELS THE INFLUENCE OF
A DEEP-LAYER TROUGH FORECAST TO AMPLIFY OVER THE WESTERN U.S. AS BUD
APPROACHES THE COAST OF SOUTHWESTERN MEXICO IN 72-120 HOURS...THE
CYCLONE SHOULD COME TO A HALT AND TURN SOUTHWESTWARD AS A
PRESUMABLY WEAKER AND INCREASINGLY SHALLOWER SYSTEM BECOMES
EMBEDDED IN NORTHERLY LOW- TO MID-LEVEL AROUND A RIDGE TO ITS WEST. 
THE NEW NHC FORECAST IS SIMILAR TO THE PREVIOUS ONE BUT IS NOW ON
THE RIGHT SIDE OF THE GUIDANCE ENVELOPE THROUGH 72 HOURS AND
REPRESENTS A BLEND OF THE ECMWF/GFS MODELS ON DAYS 4 AND 5.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0300Z 12.9N 105.9W   35 KT  40 MPH
 12H  23/1200Z 13.7N 106.7W   40 KT  45 MPH
 24H  24/0000Z 14.5N 107.1W   45 KT  50 MPH
 36H  24/1200Z 15.4N 107.0W   50 KT  60 MPH
 48H  25/0000Z 16.5N 106.3W   55 KT  65 MPH
 72H  26/0000Z 18.5N 105.3W   50 KT  60 MPH
 96H  27/0000Z 19.0N 105.5W   35 KT  40 MPH
120H  28/0000Z 18.5N 106.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER KIMBERLAIN
 

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