[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 200234
TCDAT1
TROPICAL STORM JEANNE DISCUSSION NUMBER  26
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SUN SEP 19 2004

A NOAA HURRICANE HUNTER FOUND 60 KT FLIGHT-LEVEL WINDS AT 925 MB
ABOUT 25 N MI FROM THE CENTER IN BOTH THE NORTHEASTERN AND
SOUTHEASTERN QUADRANTS...ALONG WITH A CENTRAL PRESSURE OF 994 MB.
SURFACE WINDS FROM THE STEPPED FREQUENCY MICROWAVE RADIOMETER ON
THE AIRCRAFT WERE NEAR 50 KT.  THE INITIAL INTENSITY IS THUS
INCREASED TO 50 KT.  WHILE CONVECTIVE BANDING HAS INCREASED AND
MOVED CLOSER TO THE CENTER SINCE YESTERDAY...THE STORM IS STILL NOT
THAT WELL ORGANIZED AS REFLECTED IN SATELLITE INTENSITY ESTIMATES
OF 35 KT.  CIRRUS OUTFLOW IS POOR IN THE SOUTHERN QUADRANT AND FAIR
TO GOOD ELSEWHERE.

THE INITIAL MOTION IS 010/7...ALTHOUGH THE MOTION DURING THE NOAA
FLIGHT WAS CLOSER TO 030/7.  JEANNE IS CURRENTLY BETWEEN A DEEP
LAYER RIDGE TO THE EAST AND AN UPPER-LEVEL TROUGH/COLD FRONT TO THE
NORTHWEST.  TRACK GUIDANCE AGREES THIS PATTERN SHOULD GRADUALLY
TURN JEANNE NORTHEASTWARD THROUGH 36 HR.  SERIOUS MODEL DIVERGENCE
THEN ARISES.  THE GFS AND GUIDANCE BASED ON IT...INCLUDING THE
GFDL...MARCH JEANNE STEADILY TOWARD THE EAST OR EAST-NORTHEAST
SOUTH OF A STRONG DEEP-LAYER TROUGH THROUGH 120 HR...WITH THE GFS
SHOWING JEANNE FOLLOW KARL NORTHEASTWARD TO HIGHER LATITUDES.  ON
THE OTHER HAND...THE UKMET AND NOGAPS TURN JEANNE SOUTHEASTWARD AND
SOUTHWARD THROUGH ABOUT 96 HR AS KARL PASSES TO THE EAST AND A
DEEP-LAYER RIDGE BUILDS TO THE NORTHWEST...THEN MOVE IT NORTHWEST
AS THE RIDGE WEAKENS.  AT THE MOMENT...IT CANNOT BE DETERMINED
WHICH OF THESE TWO OPTIONS WILL VERIFY.  THEREFORE...THE OFFICIAL
FORECAST TRACK SPLITS THE DIFFERENCE BETWEEN THE TWO EXTREMES AND
CALL FOR A SLOW EASTWARD DRIFT AFTER 36 HR.  THIS CONTINUES TO BE A
LOW CONFIDENCE FORECAST.

THE INTENSITY FORECAST REMAINS PROBLEMATIC.  FOR NOW...THE UPPER-
LEVEL WINDS ARE FAVORABLE AND THE BROAD CIRCULATION SHOULD GRADUALLY
CONSOLIDATE.  AFTER 24-36 HR...THE GFS AND THE NOGAPS INDICATE
SIGNIFICANT UPPER-LEVEL WESTERLIES IMPACTING JEANNE.  DESPITE
SHOWING MORE THAN 20 KT OF SHEAR...THE SHIPS MODEL CALLS FOR
STRENGTHENING DURING THIS PERIOD AS DOES THE GFDL.  ANOTHER
COMPLICATION IS THAT THE COLD FRONT MAY INTERACT WITH JEANNE IN
ABOUT 36 HR.  THE INTENSITY FORECAST CALLS FOR STRENGTHENING TO 70
KT BY 48 HR...WHICH IS LESS THAN THE 78 KT FROM SHIPS OR THE 86 KT
FROM THE GFDL.  AFTER 48 HR...THE ENVIRONMENT WILL LIKELY BECOME
HOSTILE ENOUGH TO STOP INTENSIFICATION AND CAUSE SLIGHT WEAKENING.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      20/0300Z 25.2N  72.0W    50 KT
 12HR VT     20/1200Z 26.2N  71.7W    55 KT
 24HR VT     21/0000Z 27.0N  71.0W    60 KT
 36HR VT     21/1200Z 27.3N  70.0W    65 KT
 48HR VT     22/0000Z 27.0N  69.0W    70 KT
 72HR VT     23/0000Z 26.5N  68.5W    70 KT
 96HR VT     24/0000Z 26.5N  68.0W    65 KT
120HR VT     25/0000Z 27.0N  67.5W    60 KT


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