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Hurricane MIRIAM


ZCZC MIATCDEP3 ALL
TTAA00 KNHC DDHHMM
 
HURRICANE MIRIAM DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132012
200 AM PDT MON SEP 24 2012
 
MIRIAM HAS CONTINUED TO RAPIDLY STRENGTHEN. A SMALL 10 N MI DIAMETER
COULD-FILLED EYE IS EMBEDDED IN THE NORTHWEST QUADRANT OF A COLD
CENTRAL DENSE OVERCAST FEATURE THAT HAS BECOME MORE CIRCULAR OVER
THE PAST FEW HOURS. SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS
T5.0/90 KT FROM TAFB AND SAB...AND THE LATEST UW-CIMSS ESTIMATE IS
T5.6/105 KT. BASED ON THESE DATA...THE INITIAL INTENSITY HAS BEEN
INCREASED TO 90 KT...WHICH COULD BE ON THE CONSERVATIVE SIDE.

THE INITIAL MOTION ESTIMATE 305/11 KT. MIRIAM IS BASICALLY ON
TRACK...SO THERE IS NO CHANGE TO THE PREVIOUS FORECAST TRACK
THROUGH 36 HOURS. AFTER THAT...HOWEVER...THE TRACK HAS BEEN SHIFTED
TO THE EAST OF AND A LITTLE FASTER THAN THE PREVIOUS ADVISORY DUE
TO MIRIAM FORECAST TO BE A DEEPER AND MORE ROBUST CYCLONE SIMILAR
TO WHAT THE GFS AND ECMWF MODELS ARE INDICATING. THE UKMET MODEL
WAS COMPLETELY DISCOUNTED SINCE IT WAS WAS POORLY INITIALIZED AND
IS ONLY FORECASTING A VERY WEAK AND SHALLOW CYCLONE THAT DISSIPATES
AND MOVES SLOWLY NORTHWEST AND WESTWARD WITH TIME...WHICH HAS
RESULTED IN A DEGRADATION OF THE CONSENSUS MODELS TV15 AND TVCE. A
BROAD MID-LEVEL TROUGH CURRENTLY ALONG THE U.S. WEST COAST IS
FORECAST TO SLOWLY AMPLIFY SOUTHWARD OFF THE COAST OF BAJA
CALIFORNIA AND CREATE A LARGE BREAK IN THE SUBTROPICAL RIDGE TO THE
NORTH OF THE CYCLONE BY 48 HOURS. THIS CHANGING FLOW PATTERN IS
EXPECTED TO GRADUALLY TURN MIRIAM NORTHWARD BY 72 HOURS...AND THEN
RECURVE THE SYSTEM SLOWLY TO THE NORTHEAST TOWARD BAJA CALIFORNIA
ON DAYS 4 AND 5. GIVEN THE PERSISTENT WEST BIAS OF THE UKMET...
GFDL...AND HWRF MODELS...THE OFFICIAL FORECAST IS SIMILAR TO BUT
SLOWER THAN A BLEND OF THE GFS...GFS-ENSEMBLE MEAN...AND ECMWF
FORECAST TRACKS.

GIVEN THE SMALL-DIAMETER EYE AND LOW SHEAR EXPECTED FOR THE NEXT 12
HOURS OR SO...ADDITIONAL RAPID STRENGTHENING INTO A MAJOR HURRICANE
SEEMS HIGHLY PLAUSIBLE. IT IS POSSIBLE THAT MIRIAM COULD EVEN REACH
CATEGORY 4 INTENSITY...BUT THE RATHER SMALL EYE COULD NEGATE THAT
POSSIBILITY DUE TO A PROBABLE EYEWALL REPLACEMENT CYCLE SOMETIME
DURING THE NEXT 24 HOURS. BY 36 HOURS AND BEYOND...MODERATE
SOUTHWESTERLY SHEAR AHEAD OF THE AFOREMENTIONED MID-/UPPER-LEVEL
TROUGH IS EXPECTED TO INDUCE GRADUAL WEAKENING. HOWEVER...THE
WEAKENING TREND IS NOT EXPECTED TO BE AS FAST AS INDICATED IN
PREVIOUS ADVISORIES NOW THAT MIRIAM IS FORECAST TO BE FARTHER EAST
AND...THEREFORE...OVER WARMER SSTS. THE NHC INTENSITY FORECAST IS
ABOVE ALL OF THE GUIDANCE FOR THE NEXT 24 HOURS...AND THEN FOLLOWS
THE INTENSITY CONSENSUS MODELS TV15 AND IVCN.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 17.3N 112.2W   90 KT 105 MPH
 12H  24/1800Z 18.0N 113.2W  105 KT 120 MPH
 24H  25/0600Z 18.8N 114.3W  110 KT 125 MPH
 36H  25/1800Z 19.6N 114.8W  100 KT 115 MPH
 48H  26/0600Z 20.4N 115.2W   90 KT 105 MPH
 72H  27/0600Z 22.2N 115.5W   75 KT  85 MPH
 96H  28/0600Z 24.0N 115.5W   60 KT  70 MPH
120H  29/0600Z 25.5N 114.5W   50 KT  60 MPH
 
$$
FORECASTER STEWART
 
NNNN


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Page last modified: Monday, 31-Dec-2012 12:10:38 UTC