WDPN31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (PEWA) 
WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 01C (PEWA), LOCATED APPROXIMATELY 242 NM
NORTHEASTWARD OF WAKE ISLAND, HAS TRACKED NORTH-NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY DEPICTS BUILDING CENTRAL CONVECTION WITH A FRAGMENTED 
BANDING FEATURE WRAPPING INTO A PARTIALLY EXPOSED LOW-LEVEL 
CIRCULATION CENTER (LLCC). THE WESTERN THROUGH SOUTHERN PERIPHERIES
OF THE STORM CONTINUE TO BE STRONGLY SHEARED. A 220157Z AMSU-B 
MICROWAVE IMAGE BETTER REVEALS THE POSITION OF THE PARTIALLY EXPOSED 
LLCC RELATIVE TO THE CENTRAL CONVECTION AS WELL AS DRY AIR
APPROACHING FROM THE NORTH AND SOUTH OF THE SYSTEM. THE IMAGE ALSO 
SHOWS THE FRAGMENTED NATURE OF THE WEAKENING BANDING FEATURE TO THE 
EAST OF THE LLCC. THE INITIAL POSITION IS BASED ON THE ABOVE 
ANIMATION AND THE AFOREMENTIONED IMAGERY WITH FAIR CONFIDENCE. THE 
INITIAL INTENSITY OF 35 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES 
FROM PGTW AND RJTD. PERSISTENT VERTICAL WIND SHEAR (VWS) ASSOCIATED 
WITH THE PERIPHERAL FLOW AROUND A TROPICAL UPPER TROPOSPHERIC TROUGH 
(TUTT) CELL TO THE NORTHWEST OF THE SYSTEM CONTINUES TO REMAIN A 
MAJOR LIMITING FACTOR TO THE DEVELOPMENT OF THE SYSTEM. THE CYCLONE 
CONTINUES TO TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF 
A SUBTROPICAL RIDGE (STR) TO THE EAST.
 3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING BULLETIN.
   B. TS 01C WILL CONTINUE TO TRACK NORTHWESTWARD THROUGH TAU 48 
UNDER THE INFLUENCE OF THE STR. THE NUMERICAL MODEL GUIDANCE IS IN 
GOOD AGREEMENT DURING THIS PERIOD, LENDING HIGH CONFIDENCE TO THIS 
PORTION OF THE FORECAST TRACK. THE CYCLONE IS EXPECTED TO INTENSIFY 
SLOWLY AS THE TUTT CELL MOVES NORTHWESTWARD A BIT FASTER THAN TS 
01C. THIS OPENING DISTANCE WILL ALLOW THE VWS TO SLOWLY DECREASE AND 
POLEWARD OUTFLOW TO IMPROVE AS THE SYSTEM CONTINUES TO TRACK ACROSS 
WARM WATER AND INCREASE TO A PEAK INTENSITY OF 60 KNOTS. AT THIS 
POINT, APPROXIMATELY TAU 72, THE NUMERICAL GUIDANCE BECOMES SPREAD 
AS TS O1C MOVES INTO A WEAK STEERING ENVIRONMENT AS AN APPROACHING 
MID-LATITUDE TROUGH BREAKS THE STEERING RIDGE.
   C. IN THE EXTENDED PERIOD, THE TRACK SPEEDS ARE EXPECTED TO SLOW 
CONSIDERABLY DUE TO THE WEAK STEEERING ENVIRONMENT. ADDITIONALLY,
THE NUMERICAL GUIDANCE DIVERGES WITH RESPECT TO THE LOCATION AND 
TIMING OF THE SLOW-DOWN. THEREFORE, THE FORECAST TRACK CONFIDENCE 
FOR THE EXTENDED PERIOD IS LOW. AS TS 01C MEANDERS IN THE WEAK 
STEERING ENVIRONMENT, COOLER SSTS AND DRY INTRUSION ARE EXPECTED 
TO WEAKEN THE SYSTEM.//
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