Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 10w Warning Nr 10//

From: SIU Weather Processor <[email-masked]>
Date: Fri, 3 Sep 2010 23:52:13 -0500

WDPN33 PGTW 040300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 10W (MALOU), LOCATED APPROXIMATELY 135 NM
SOUTH-SOUTHWEST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD
AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) AND A 032330Z SSMIS 91 GHZ MICROWAVE IMAGE SHOW DEEP
CONVECTION ALONG THE SOUTHERN HALF OF A WELL DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH ADDITIONAL DEEP CONVECTION, POSSIBLY
ASSOCIATED WITH A TROPICAL DISTURBANCE, 150 NM EAST OF TS 10W. THE
CURRENT POSITION IS BASED, WITH FAIR CONFIDENCE, ON ANIMATED MSI AND
THE AFOREMENTIONED SSMIS MICROWAVE PASS. THE CURRENT INTENSITY IS
BASED ON DVORAK ESTIMATES RANGING FROM 30 TO 35 FROM PGTW, KNES,
AND  RJTD. THIS INTENSITY IS VERIFIED BY OBSERVATIONS NORTH OF THE
DEEP CONVECTION INDICATING 20 TO 30 KNOTS AND BAROMETER MEASUREMENTS
OF 997 MB  AND 999 MB. AN UPPER LEVEL LOW, PREVIOUSLY IMPINGING
OUTFLOW ALONG THE WESTERN FLANK OF TS 10W, HAS MOVED OFF TO THE
SOUTHWEST ALLOWING THE DIFFLUENT REGION OF THE LOW TO ENHANCE OUTFLOW
OVER THE SYSTEM. THE RECENT STORM MOTION IS SLOWER AND MORE WESTWARD
THEN THE PREVIOUS TRACK WHICH MAY BE AN INDICATION OF DIRECT CYCLONE
INTERACTION (DCI) WITH THE PREVIOUSLY MENTIONED TROPICAL DISTURBANCE
EAST OF OKINAWA.
3. FORECAST REASONING.
   A. THE INITIAL PORTION OF THE FORECAST IS SLOWER AND MORE WESTWARD
THAN THE PREVIOUS FORECAST, HOWEVER THE FUNDAMENTAL PHILOSOPHY OF THE
TRACK AND INTENSITY FORECASTS REMAINS THE SAME.
   B. TS 10W IS CURRENTLY TRACKING UNDER THE INFLUENCE OF A LOW TO
MID-LEVEL SUBTROPICAL RIDGE (STR) ORIENTATED SOUTH OF MAINLAND JAPAN,
HOWEVER INTERACTION WITH A DEVELOPING TROPICAL DISTURBANCE EAST OF TS
10W HAS SLOWED ITS OVERALL SPEED OF ADVANCE. THE SYSTEM IS EXPECTED
TO GRADUALLY INTENSIFY AND CONTINUE TRACKING POLEWARD AS THE WESTERN
EXTENT OF THE STR BREAKS DOWN IN RESPONSE TO A PASSING MID-LATITUDE
TROUGH. HOWEVER, THERE IS SOME UNCERTAINTY IN THE TRACK DUE TO
POSSIBLE DCI WITH THE DEVELOPING TROPICAL DISTURBANCE TO THE EAST.
   C. AFTER TAU 72, TS MALOU IS EXPECTED TO CONTINUE TRACKING
POLEWARD TO NORTHEASTWARD AND WEAKEN AS IT INTERACTS WITH THE
MID-LATITUDE WESTERLIES AND TRACKS OVER COOLER SEA SURFACE
TEMPERATURES IN THE NORTHERN YELLOW SEA. NUMERICAL MODEL GUIDANCE IS
IN POOR AGREEMENT AFTER TAU 24, IN RESPONSE TO A WEAK STEERING
ENVIRONMENT AND POOR HANDLING OF THE INTERACTION WITH THE DEVELOPING
TROPICAL DISTURBANCE EAST OF THE SYSTEM. GFS, EGRR, AND JGSM
TRACK THE SYSTEM WEST TO NORTHWESTWARD INTO EASTERN CHINA, WHILE
NOGAPS, WBAR, AND ECMWF SHOW A MORE POLEWARD TO NORTHEASTWARD TRACK.
THIS FORECAST IS SLOWER THAN MODEL CONSENSUS TO ACCOUNT FOR THESE
UNCERTAINTIES.//

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