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Hurricane MIRIAM Forecast Discussion Number 14

Issued at 200 AM PDT TUE SEP 25 2012

000
WTPZ43 KNHC 250843
TCDEP3
 
HURRICANE MIRIAM DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132012
200 AM PDT TUE SEP 25 2012
 
MICROWAVE AND INFRARED SATELLITE IMAGERY INDICATE MIRIAM HAS
COMPLETED ITS EYEWALL REPLACEMENT CYCLE AND A 30 N MI DIAMETER EYE
APPEARS TO HAVE STABILIZED. CLOUD TOPS HAVE COOLED SIGNIFICANTLY
AROUND THE EYE OVER THE PAST 4 HOURS...AND UW-CIMSS ADT AND NHC
AODT SATELLITE INTENSITY ESTIMATES HAVE INCREASED TO T5.3/97 KT AND
T5.6/105 KT...RESPECTIVELY. AS A RESULT...THE INITIAL INTENSITY IS
BEING MAINTAINED AT 90 KT...WHICH COULD BE CONSERVATIVE.
 
THE INITIAL MOTION ESTIMATE IS 310/05 KT. MIRIAM IS ON TRACK AND...
AS A RESULT...THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS
FORECAST TRACK OR REASONING. MIRIAM IS EXPECTED TO GRADUALLY TURN
TOWARD THE NORTHWEST LATER TODAY AND TURN NORTHWARD IN 24-36 HOURS
AS THE CYCLONE BECOMES EMBEDDED IN WEAK SOUTHERLY STEERING FLOW
BETWEEN A SUBTROPICAL RIDGE SITUATED TO THE EAST AND A MID- TO
UPPER-LEVEL LOW LOCATED TO ITS WEST AND NORTHWEST. THE UKMET MODEL
REMAINS A SIGNIFICANT OUTLIER WITH A STRONG WEST BIAS AND HAS...
THEREFORE...BEEN DISCOUNTED FOR THIS FORECAST CYCLE. AS A RESULT...
THE OFFICIAL FORECAST TRACK REMAINS TO THE EAST OF THE CONSENSUS
MODELS TV15 AND TVCE...AND IS FAIRLY CLOSE TO A BLEND OF THE GFS
AND ECMWF MODELS...WHICH BETTER DEPICT A STRONGER AND MORE
VERTICALLY DEEP CYCLONE AS CURRENTLY ANALYZED.
 
GRADUAL WEAKENING IS FORECAST DURING THE NEXT 24 TO 36 HOURS AS
SOUTHWESTERLY SHEAR INCREASES AHEAD OF A SLOWLY ADVANCING
MID-/UPPER-LEVEL TROUGH NOTED TO THE WEST AND NORTHWEST OF MIRIAM
IN WATER VAPOR IMAGERY. BY DAYS 3-5...THE GLOBAL MODELS ARE
FORECASTING A LARGE MID-/UPPER-LEVEL LOW DEVELOPING NEAR 30N 130W.
THIS LOW IS EXPECTED TO INCREASE THE VERTICAL SHEAR ABOVE 30 KT...
WHICH SHOULD INDUCE MORE RAPID WEAKENING AND POSSIBLE DISSIPATION
BEFORE MIRIAM REACHES BAJA CALIFORNIA. THE OFFICIAL FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY AND FOLLOWS A BLEND OF THE SHIPS
AND LGEM MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0900Z 18.7N 114.3W   90 KT 105 MPH
 12H  25/1800Z 19.3N 114.7W   85 KT 100 MPH
 24H  26/0600Z 20.1N 115.0W   80 KT  90 MPH
 36H  26/1800Z 21.1N 115.2W   70 KT  80 MPH
 48H  27/0600Z 22.1N 115.3W   65 KT  75 MPH
 72H  28/0600Z 24.0N 115.3W   50 KT  60 MPH
 96H  29/0600Z 25.7N 114.9W   40 KT  45 MPH
120H  30/0600Z 27.2N 114.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

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