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Hurricane IVAN


ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
HURRICANE IVAN DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE SEP 07 2004
 
IVAN HAS CONTINUED TO STRENGTHEN DURING THE EVENING.  THE LAST PASS
OF AN AIR FORCE RESERVE HURRICANE HUNTER THROUGH THE EYE SHOWED A
CENTRAL PRESSURE NEAR 950 MB AND MAXIMUM FLIGHT-LEVEL WINDS OF 129
KT AT 700 MB.  THE INITIAL INTENSITY IS SET TO 115 KT BASED ON THE
FLIGHT-LEVEL WINDS AND SATELLITE INTENSITY ESTIMATES OF 115 KT FROM
ALL AGENCIES.  IT SHOULD BE NOTED THAT THE SATELLITE SIGNATURE OF
IVAN HAS IMPROVED SINCE 00Z AND THE INITIAL INTENSITY MAY BE
CONSERVATIVE.  THE NEXT AIRCRAFT IS SCHEDULED TO ARRIVE IN IVAN
AROUND 06Z.

THE INITIAL MOTION IS 280/15.  IVAN REMAINS ON THE SOUTH SIDE OF A
STRONG SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC.  LARGE-SCALE
MODELS FORECAST THIS RIDGE TO SLOWLY WEAKEN AS A MID/UPPER-LEVEL
TROUGH APPROACHES IT FROM THE NORTHWEST AND AS AN UPPER-LEVEL LOW
DEVELOPS TO THE EAST.   WATER VAPOR IMAGERY ALSO INDICATES AN
UPPER-LEVEL LOW OVER THE CENTRAL AND WESTERN CARIBBEAN...BUT THIS
SEEEMS TO BE RETREATING WESTWARD AS FAST OR FASTER THAN THE
HURRICANE.  THE SYNOPTIC PATTERN SHOULD PRODUCE A WESTWARD TO
WEST-NORTHWESTWARD MOTION FOR THE NEXT 72 HR OR SO...FOLLOWED BY A
MORE NORTHWESTWARD MOTION AT A SLOWER FORWARD SPEED THEREAFTER. 
UNFORTUNATELY...MODEL GUIDANCE IS NOT VERY CONSISTENT FROM RUN TO
RUN AT THE MOMENT.  THE GFS MADE A HUGE SHIFT TO THE RIGHT...FROM
PASSING WEST OF FLORIDA TO PASSING 200 NM EAST OF FLORIDA.  THE
GFDL ALSO SHIFTED TO THE RIGHT...BUT FROM A LEFT OUTLIER INTO THE
MIDDLE OF THE GUIDANCE ENVELOPE.  THE OFFICIAL FORECAST ALSO
SHIFTS...A LITTLE TO THE SOUTH EARLY IN THE FORECAST TO ALLOW FOR
THE CURRENT POSITION AND MOTION AND A LITTLE TO THE RIGHT LATER IN
THE FORECAST PERIOD.  IT IS IN BEST AGREEMENT WITH THE NOGAPS.

UPPER-LEVEL WINDS ARE FORECAST TO BE GENERALLY FAVORABLE FOR
DEVELOPMENT THROUGH THE FORECAST PERIOD...SO THE INTENSITY OF IVAN
WILL BE MAINLY CONTROLLED BY CONCENTRIC EYEWALL CYCLES...CHANGES IN
SEA SURFACE TEMPERATURE...AND LAND INTERACTION.  AN SSM/I OVERPASS
AT 0105Z SHOWED AN OUTER EYEWALL STARTING TO FORM...WHICH SUGGEST
THE CURRENT INTENSIFICATION CYCLE WILL STOP IN 6-12 HR.  HOWEVER...
BY THAT TIME IVAN MAY BE STRONGER THAN CURRENTLY FORECAST.  THE
HURRICANE WILL PASS OVER SOME SLIGHTLY COOLER SEA SURFACE
TEMPERATURES THROUGH 48 HR...THEN REACH WARMER WATER NORTHWEST OF
JAMAICA AFTER 72 HR.  REGARDLESS OF THE EXACT UPS AND DOWNS IN THE
INTENSITY...IVAN IS EXPECTED TO REMAIN A STRONG HURRICANE THROUGH
THE FORECAST PERIOD...MOST LIKELY CATEGORY 4 BUT POSSIBLY REACHING
CATEGORY 5 AT SOME POINTS.

HURRICANE WARNINGS HAVE BEEN ISSUED FOR ARUBA...BONAIRE...AND
CURACAO...AS ANY MOTION SOUTH OF THE FORECAST TRACK COULD BRING
HURRICANE FORCE WINDS NEAR OR OVER THOSE ISLANDS. 
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 12.1N  63.3W   115 KT
 12HR VT     08/1200Z 12.8N  65.7W   125 KT
 24HR VT     09/0000Z 13.8N  68.8W   130 KT
 36HR VT     09/1200Z 14.9N  71.6W   130 KT
 48HR VT     10/0000Z 16.3N  74.2W   130 KT
 72HR VT     11/0000Z 19.0N  78.5W   120 KT
 96HR VT     12/0000Z 21.0N  81.0W   130 KT
120HR VT     13/0000Z 24.0N  83.0W   120 KT
 
 
$$
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Page last modified: Wednesday, 08-Sep-2004 03:22:53 UTC