Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Storm 15w (megi) Warning Nr

From: SIU Weather Processor <[email-masked]>
Date: Wed, 13 Oct 2010 10:02:29 -0500

WDPN31 PGTW 131500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (MEGI) WARNING NR
03//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 15W (MEGI) LOCATED APPROXIMATELY 200 NM
NORTHEAST OF YAP, HAS TRACKED WESTWARD AT 04 KNOTS OVER THE PAST 06
HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY AND A 130915Z SSMIS
91 GHZ MICROWAVE IMAGE INDICATE A RAPIDLY DEVELOPING SYSTEM WITH
TIGHTLY CURVED CONVECTIVE BANDING WRAPPING INTO A WELL-DEFINED LOW
LEVEL CIRCULATION CENTER (LLCC). ANIMATED WATER VAPOR IMAGERY SHOWS
GOOD OVERALL OUTFLOW WITH ENHANCED POLEWARD OUTFLOW OVER THE
NORTHERN QUADRANT DUE TO A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT)
CELL TO THE NORTHEAST. THE SYSTEM IS CURRENTLY TRACKING WESTWARD
ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL STEERING RIDGE
(STR). THE CURRENT INTENSITY IS BASED ON THE HIGHER END OF DVORAK
ESTIMATES RANGING FROM 30 TO 45 KNOTS FROM KNES, RJTD, AND PGTW.
3. FORECAST REASONING.
   A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN
   B. TS 15W IS EXPECTED TO STEADILY INTENSIFY THROUGHOUT THE
FORECAST PERIOD AS IT TRACKS ALONG THE SOUTHERN FLANK OF THE
STEERING RIDGE. BETWEEN TAU 12 AND TAU 24 THE SYSTEM IS EXPECTED TO
REACH TYPHOON INTENSITY AND BEGIN TRACKING WEST-NORTHWESTWARD AS AN
APPROACHING MID-LATITUDE TROUGH WEAKENS THE RIDGE SLIGHTLY. AFTER
TAU 36, THE RIDGE IS EXPECTED TO REORIENT AND RE-BUILD WESTWARD
ALLOWING THE SYSTEM TO STAIR-STEP BACK TO THE WEST AND SIGNIFICANTLY
INTENSIFY AS POLEWARD OUTFLOW IS ENHANCED BY THE PASSING MID-
LATITUDE TROUGH. BETWEEN TAU 48 AND TAU 72, TS 15W IS EXPECTED TO
MERGE WITH A TROPICAL DISTURBANCE TO THE WEST.
   C. AFTER TAU 72, TS MEGI IS FORECAST TO CONTINUE TO INTENSIFY AS
IT TRACKS WESTWARD TOWARD NORTHERN LUZON OVER HIGHLY FAVORABLE SEA
SURFACE TEMPERATURES AND HIGH OCEAN HEAT CONTENT (OHC). NUMERICAL
MODEL GUIDANCE IS IN VERY GOOD AGREEMENT WITH THIS FORECAST TRACK,
THEREFORE THIS FORECAST IS CLOSE TO MODEL CONSENSUS.//

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