WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (GONI) WARNING NR 
034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 22W (GONI), LOCATED APPROXIMATELY 216 NM 
EAST-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-SOUTHWESTWARD 
AT 04 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY (MSI) REVEALS A BROAD, FULLY-EXPOSED LOW LEVEL 
CIRCULATION CENTER (LLCC) WITH THE ASSOCIATED DEEP CONVECTION 
SHEARED TO THE NORTHWEST. DUE TO THE FULLY-EXPOSED NATURE AND A 
TIMELY 050540Z AMSR2 89 GHZ MICROWAVE IMAGE DEPICTING BANDING 
WRAPPING INTO THE LLCC, THERE IS HIGH CONFIDENCE IN THE INITIAL 
POSITION. THE INITIAL INTENSITY IS SET AT 35 KTS BASED ON A 050609Z 
SATELLITE CONSENSUS ESTIMATE OF 37 KTS AND DVORAK CURRENT INTENSITY 
ESTIMATES OF T2.0-2.5 (30-35 KTS) BY PGTW AND RJTD. FURTHERMORE, A 
050240Z ASCAT-C IMAGE SHOWS A BROAD SWATH OF 30-34 KT WINDS OVER THE 
WESTERN SEMICIRCLE. ALL WIND RADII HAVE BEEN UPDATED BASED ON THE 
AFOREMENTIONED ASCAT IMAGE. TS 22W IS TRACKING THROUGH A MARGINAL 
ENVIRONMENT CONSISTING OF MODERATE (15-20 KT) VERTICAL WIND SHEAR 
(VWS) OFFSET BY DIVERGENT FLOW ALOFT AND WARM (26-27 CELSIUS) SEA 
SURFACE TEMPERATURES (SST). TS 22W IS TRACKING WEST-SOUTHWESTWARD 
UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO THE 
NORTHEAST. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TS 22W WILL CONTINUE TO TRACK GENERALLY WESTWARD FOR THE 
DURATION OF THE FORECAST PERIOD UNDER THE INFLUENCE OF THE 
AFOREMENTIONED STR. DUE TO PERSISTENT MODERATE VWS, THE SYSTEM 
SHOULD STEADILY WEAKEN AS IT APPROACHES THE COAST, MAKING LANDFALL 
IN CENTRAL VIETNAM AROUND TAU 18. AFTERWARDS, INTERACTION WITH THE 
RUGGED TERRAIN WILL CONTINUE TO WEAKEN THE SYSTEM, LEADING TO 
DISSIPATION OVER LAND BY TAU 36. NUMERICAL MODEL GUIDANCE IS IN FAIR 
AGREEMENT SHOWING A 76 NM SPREAD IN THE SOLUTIONS AT LANDFALL AND 
THEN INCREASING TO 126 NM BY TAU 36 AS THE SYSTEM TRACKS INLAND. 
THIS INCREASING SPREAD PLACES FAIR CONFIDENCE IN THE JTWC FORECAST 
TRACK WHICH IS POSITIONED JUST SOUTH OF THE MULTI-MODEL CONSENSUS.//
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