Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 10w Warning Nr 18//

From: SIU Weather Processor <[email-masked]>
Date: Sun, 5 Sep 2010 21:21:03 -0500

WDPN33 PGTW 060300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W WARNING NR 18//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 10W (MALOU), LOCATED APPROXIMATELY 55 NM
SOUTH-SOUTHWEST OF CHEJU ISLAND, HAS TRACKED NORTH-NORTHEASTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS TIGHTLY CURVED BANDING WRAPPING INTO THE LLCC WITH
DEEP CONVECTION BEING SHEARED NORTHEAST OF THE SYSTEM CENTER. THERE
IS POOR CONFIDENCE IN THE CURRENT POSITION BASED ON A 052303Z 37H
SSMIS MICROWAVE PASS WHICH INDICATES MULTIPLE LOW LEVEL VORTICES MAY
STILL EXIST WITHIN THE BROAD CIRCULATION PATTERN. THE CURRENT
INTENSITY IS BASED ON DVORAK ESTIMATES RANGING FROM 35 TO 45 KNOTS
FROM PGTW, KNES, AND RJD, AS WELL AS SURFACE OBSERVATIONS ON CHEJU
ISLAND INDICATING INCREASING EASTERLY WINDS (23 KNOTS AT 00Z AND 27
KNOTS AT 01Z). UPPER LEVEL ANALYSIS REVEALS THE SYSTEM HAS IMPROVED
EQUATORWARD OUTFLOW ASSOCIATED WITH AN UPPER LEVEL LOW TO THE SOUTH,
HOWEVER, INTERACTION WITH THE MID-LATITUDE WESTERLIES IS IMPINGING
OUTFLOW ALONG THE WESTERN FLANK OF THE SYSTEM AND CAUSING A MAJORITY
OF THE DEEP CONVECTION TO BE SHEARED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE FROM THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 10W IS CURRENTLY TRACKING ALONG THE WESTERN EXTENT OF A
LOW TO MID-LEVEL SUBTROPICAL STEERING RIDGE. THE SYSTEM IS FORECAST
TO TURN NORTHEASTWARD AS IT TRACKS NORTH OF THE RIDGE AXIS AND
BEGINS TO INTERACT WITH THE BAROCLINIC BOUNDARY TO THE NORTH. TS 10W
IS FORECAST TO CROSS CHEJU ISLAND WITHIN THE NEXT 12 HOURS AND
GRADUALLY WEAKEN AS IT MAKES LANDFALL IN SOUTHERN SOUTH KOREA. BY
TAU 36, TS 10W IS EXPECTED TO BECOME FULLY ABSORBED INTO THE MID-
LATITUDE WESTERLY FLOW. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF NOGAPS WHICH LOSES THE SYSTEM AFTER
TAU 48, AND GFDN WHICH ERRONEOUSLY TRACKS THE SYSTEM NORTHWARD ALONG
THE WESTERN COAST OF SOUTH KOREA. THIS FORECAST IS IN GOOD AGREEMENT
WITH MODEL CONSENSUS AND IS WITHIN THE TIGHT PACKING OF GFS, JGSM,
ECMWF, EGRR, AND WBAR.//

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