Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 16w Warning Nr 17//

From: SIU Weather Processor <[email-masked]>
Date: Mon, 25 Oct 2010 08:44:03 -0500

WDPN32 PGTW 251500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 16W (CHABA), LOCATED APPROXIMATELY 525 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWEST-
WARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED WATER VAPOR
SATELLITE IMAGERY SHOWS DEEP CONVECTIVE BANDING ALONG THE SOUTHERN
AND WESTERN PERIPHERY OF THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS
FURTHER CONSOLIDATED. ADDITIONALLY, A POLEWARD OUTFLOW CHANNEL HAS
EMERGED AS A MID-LATITUDE TROUGH DIGGING IN FROM THE NORTHWEST CLOSES
IN. THE INITIAL POSITION IS EXTRAPOLATED FROM 251032Z SSMI-S
MICROWAVE IMAGE, WHICH DEPICTS A HOOK FEATURE TIGHTLY WRAPPED INTO
THE LLCC.
THE INITIAL INTENSITY IS BASED ON PGTW, KNES AND RJTD DVORAK
ESTIMATES OF T3.5. TS 16W IS CURRENTLY TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF A MID-LEVEL SUBTROPICAL STEERING RIDGE
ANCHORED EAST OF JAPAN.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE TRACK FORECAST
PHILOSOPHY, HOWEVER, THE FORECAST INTENSITIES ARE SLIGHTLY HIGHER.
   B. TS 16W WILL CONTINUE TO INTENSIFY AS VERTICAL WIND SHEAR
DECREASES AND POLEWARD OUTFLOW IMPROVES AS IT ROUNDS THE WESTERN EDGE
OF THE STEERING RIDGE. AFTER TAU 36, THE SYSTEM WILL VEER MORE TO THE
RIGHT AS IT GETS ABSORBED INTO THE WESTERLIES AFTER THE PASSAGE OF
THE AFOREMENTIONED MID-LATITUDE TROUGH. ITS INITIAL EXPOSURE TO THE
STRONG WESTERLIES WILL FURTHER INCREASE POLEWARD OUTFLOW ALLOWING THE
SYSTEM TO PEAK INTENSITY PRIOR TO TAU 72.
   C. AFTER TAU 72, TS CHABA IS EXPECTED TO RECURVE AND ACCELERATE TO
THE NORTHEAST AND BEGIN EXTRATROPICAL TRANSITION. ITS PROLONGED
EXPOSURE TO THE PREVAILING WESTERLIES AND DECREASING OCEAN HEAT
CONTENT WILL GRADUALLY WEAKEN THE SYSTEM DURING THIS TRANSITION. WITH
THE EXCEPTION OF GFDN, NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH THIS TRACK FORECAST WHICH IS SLIGHTLY TO THE RIGHT OF CONSENSUS
TO OFFSET THE UNREALISTICALLY ABRUPT WESTWARD GFDN SOLUTION.//

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