Tropical Storm CALVIN

ZCZC MIATCDEP3 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM CALVIN DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT MON JUN 27 2005
 
ACAPULCO RADAR IMAGES SUGGEST LITTLE CHANGE IN ORGANIZATION OVER THE
LAST SEVERAL HOURS.  IN FACT...THE SPIRAL BANDING IS NOT AS WELL
DEFINED AS IT WAS THIS MORNING.  GEOSTATIONARY SATELLITE IMAGES
ALSO SUGGEST LITTLE CHANGE.  DVORAK T-NUMBERS REMAIN AT 3.0 AND THE
CURRENT INTENSITY ESTIMATE IS HELD AT 45 KT FOR THIS PACKAGE. 
CALVIN IS EXPECTED TO REMAIN IN AN ENVIRONMENT OF MODERATE EASTERLY
VERTICAL SHEAR OVER THE NEXT FEW DAYS SO ONLY SLOW STRENGTHENING IS
ANTICIPATED.  THE OFFICIAL WIND SPEED FORECAST IS A BLEND OF THE
LATEST GFDL AND SHIPS MODEL OUTPUT.  BY 72 HOURS...THE CYCLONE WILL
BE TRAVERSING COOLER WATERS AND ENCOUNTERING A MORE STABLE AIR MASS
SO WEAKENING SHOULD HAVE COMMENCED BY THAT TIME.

THERE IS A LOT OF SCATTER IN THE CENTER FIXES BUT THE STORM HAS
APPARENTLY TURNED TOWARD THE WEST-NORTHWEST.  INITIAL MOTION
ESTIMATE IS 300/9.  THE TRACK FORECAST APPEARS TO BE RELATIVELY
STRAIGHTFORWARD...WITH A MID-LEVEL RIDGE EXPECTED TO PERSIST TO THE
NORTH OF THE TROPICAL CYCLONE...AND PROVIDING AN EAST-SOUTHEASTERLY
STEERING FLOW.  BECAUSE OF THE FASTER INITIAL MOTION ESTIMATE...
THIS OFFICIAL TRACK FORECAST IS SOMEWHAT FASTER THAN THE PREVIOUS
ONE DURING THE FIRST FEW DAYS OF THE FORECAST PERIOD.  LATER IN THE
PERIOD...THE WEAKENING CYCLONE IS FORECAST TO TURN WESTWARD UNDER
THE INFLUENCE OF SHALLOW-LAYER FLOW.

THE WEST-NORTHWESTWARD MOTION REDUCES THE THREAT TO THE COAST...AND
THE TROPICAL STORM WATCH CAN PROBABLY BE DISCONTINUED LATER TODAY. 
HOWEVER...LOCALLY HEAVY RAINFALL ASSOCIATED WITH THE OUTER
CIRCULATION IS EXPECTED TO CONTINUE TO AFFECT PORTIONS OF THE
SOUTHERN COAST OF MEXICO OVER THE NEXT DAY OR SO.
 
FORECASTER PASCH
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/2100Z 15.4N 100.9W    45 KT
 12HR VT     28/0600Z 15.8N 102.2W    50 KT
 24HR VT     28/1800Z 16.3N 104.2W    55 KT
 36HR VT     29/0600Z 16.8N 106.5W    60 KT
 48HR VT     29/1800Z 17.3N 108.6W    60 KT
 72HR VT     30/1800Z 18.0N 112.0W    50 KT
 96HR VT     01/1800Z 18.0N 115.0W    30 KT
120HR VT     02/1800Z 18.0N 117.5W    20 KT
 
$$
NNNN