WDPN33 PGTW 040300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W WARNING NR 28//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TROPICAL STORM (TS) 22W (NALGAE), LOCATED APPROXIMATELY 340 
NM EAST-SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD 
AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY SHOWS A PARTIALLY EXPOSED BROAD LOW LEVEL 
CIRCULATION CENTER (LLCC) WITH MINIMAL DEEP CONVECTION OVER THE 
WESTERN PERIPHERY. THE INITIAL POSITION IS BASED ON THE PGTW CENTER 
FIX AND THE ANIMATED MSI WITH GOOD CONFIDENCE. ADDITIONALLY, A 
032243Z SSMIS 91 GHZ IMAGE VERIFIES THE INITIAL POSITION AND DETAILS 
THE LACK OF ANY ORGANIZED DEEP CENTRAL CONVECTION. THE INITIAL 
INTENSITY LIES IN THE MIDDLE OF PGTW, KNES, AND RJTD DVORAK 
ESTIMATES RANGING FROM 35 TO 45 KNOTS. RECENT ANIMATED WATER VAPOR 
IMAGERY AND UPPER LEVEL ANALYSIS INDICATES THE LLCC IS LOCATED SOUTH 
OF THE SUBTROPICAL RIDGE AXIS IN AN AREA OF MODERATE EASTERLY 
VERTICAL WIND SHEAR (VWS).     
3.  A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY.
    B. TS 22W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF 
A DEEP LAYER SUBTROPICAL STEERING RIDGE, WHICH IS EXPECTED TO REMAIN 
THE PRIMARY STEERING INFLUENCE THROUGHOUT THE FORECAST PERIOD. 
NALGAE IS FORECAST TO WEAKEN DUE TO CONTINUED MODERATE EASTERLY VWS 
AND LAND INTERACTION BY TAU 12 AS THE SYSTEM SKIRTS THE SOUTHERN 
COAST OF HAINAN. AS TS 22W EMERGES OVER THE SOUTHERN GULF OF TONKIN 
IT WILL MAINTAIN TROPICAL STORM STRENGTH UNTIL IT MAKES LANDFALL 
SHORTLY AFTER TAU 48. THE SYSTEM WILL THEN BEGIN TO WEAKEN AS IT 
INTERACTS WITH LAND. BY TAU 72 TS 22W WILL DISSIPATE OVER VIETNAM. 
NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT EXCEPT FOR WBAR, WHICH 
ERRONEOUSLY TRACKS THE SYSTEM NORTHWARD INTO THE SUBTROPICAL 
STEERING RIDGE. THIS FORECAST IS SLIGHTLY SOUTH OF MODEL CONSENSUS 
TO ACCOUNT FOR THIS ERROR.//
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