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Tropical Storm IVO


ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM IVO DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP122007
200 PM PDT WED SEP 19 2007
 
IVO CONTINUES TO STRENGTHEN..WITH INCREASED CONVECTIVE BANDING
AROUND THE CENTER AND THE POSSIBLE BEGINNING OF EYE FORMATION IN
BOTH VISIBLE AND MICROWAVE IMAGERY.  SATELLITE INTENSITY ESTIMATES
ARE 65 KT FROM SAB AND 55 KT FROM TAFB.  THE INITIAL INTENSITY IS
INCREASED TO 60 KT...AND IF IVO IS NOT YET A HURRICANE IT SHOULD
BECOME ONE SHORTLY.  THE CIRRUS OUTFLOW IS GOOD TO THE SOUTHWEST
AND NORTHEAST AND FAIR TO POOR ELSEWHERE.
 
THE STORM HAS MOVED A LITTLE TO THE LEFT OF THE PREVIOUS TRACK...
WITH AN INITIAL MOTION OF 290/9.  IVO REMAINS SOUTH OF A MID-LEVEL
RIDGE EXTENDING WESTWARD FROM NORTHERN MEXICO.  THE LARGE-SCALE
MODELS ARE IN GOOD AGREEMENT THAT A DEEP-LAYER LOW CURRENTLY MOVING
SOUTHWARD INTO CALIFORNIA WILL DROP FAR ENOUGH SOUTH TO BREAK THE
RIDGE NORTH OF IVO...ALLOWING THE STORM TO RECURVE TO THE NORTHEAST
DURING THE NEXT 48-96 HR.  HOWEVER...IT STILL APPEARS THE LOW WILL
NOT COME FAR ENOUGH SOUTH TO ACCELERATE THE STORM NORTHEASTWARD...
SO THE MOTION AFTER RECURVATURE IS LIKELY TO BE SLOW. 
ADDITIONALLY...THE MODELS ARE FORECASTING THE RIDGE TO RE-BUILD
EAST OF IVO IN 96-120 HR...AND THEY RESPOND TO THIS BY SHOWING A
MORE NORTHWARD MOTION BY THE END OF THE FORECAST PERIOD.  THE NEW
FORECAST TRACK IS SHIFTED A LITTLE TO THE LEFT DURING THE FIRST
PART OF THE FORECAST DUE TO THE INITIAL POSITION AND MOTION...AND A
LITTLE TO THE LEFT OF THE PREVIOUS TRACK AT THE END OF THE FORECAST
DUE TO THE BUILDING RIDGE.  IT IS IN BEST OVERALL AGREEMENT WITH
THE CCON CONSENSUS.  IT SHOULD BE NOTED THAT THE ECMWF MODEL DOES
NOT FORECAST IVO TO RECURVE...AS IT TRAPS THE STORM SOUTH OF THE
RE-BUILDING RIDGE.
 
IVO IS FORECAST TO REMAIN IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT
FOR THE NEXT 24-36 HR...SO CONTINUED STRENGTHENING IS FORECAST
IN AGREEMENT WITH THE SHIPS MODEL.  BEYOND THAT TIME...THE
LARGE-SCALE MODELS CONTINUE TO DISAGREE ON HOW MUCH WIND SHEAR IVO
WILL ENCOUNTER.  THE GFS AND ECMWF FORECAST INCREASING SHEAR...
WHILE THE UKMET AND THE NOGAPS FORECAST A MORE FAVORABLE
ENVIRONMENT.  BECAUSE IT IS NOT CLEAR WHICH MODEL IS ON THE RIGHT
TRACK...THE INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS
PACKAGE.   THE TWO ALTERNATIVE SCENARIOS FROM THE PREVIOUS PACKAGE
REMAIN.  FIRST...THE FORECAST TRACK BRINGS IVO OVER WARMER WATER BY
120 HR...AND IF THE SHEAR IS LIGHT IVO COULD BE STRONGER THAN
FORECAST AT THAT TIME.  SECOND...IF IVO TRACKS NORTH OF THE
FORECAST TRACK...IT WOULD LIKELY ENCOUNTER BOTH STRONGER SHEAR AND
COLDER WATER...WHICH SHOULD CAUSE A FASTER WEAKENING.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/2100Z 15.4N 111.9W    60 KT
 12HR VT     20/0600Z 16.0N 113.0W    70 KT
 24HR VT     20/1800Z 16.8N 113.7W    75 KT
 36HR VT     21/0600Z 17.9N 114.0W    75 KT
 48HR VT     21/1800Z 18.9N 113.7W    75 KT
 72HR VT     22/1800Z 21.0N 112.5W    70 KT
 96HR VT     23/1800Z 22.0N 111.5W    60 KT
120HR VT     24/1800Z 23.0N 109.5W    55 KT
 
$$
FORECASTER BEVEN
 
NNNN


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Page last modified: Friday, 02-Nov-2007 21:21:04 UTC