Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 13w Warning Nr 12//

From: SIU Weather Processor <[email-masked]>
Date: Wed, 22 Sep 2010 21:44:03 -0500

WDPN32 PGTW 230300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 13W WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 13W (MALAKAS), LOCATED APPROXIMATELY 295 NM SOUTH
OF IWO TO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 04 KNOTS AND HAS
INTENSIFIED BY 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY SHOWS IMPROVED CENTRAL CONVECTION
OVER THE TIGHTLY WRAPPED LOW LEVEL CIRCULATION CENTER (LLCC). A
222113Z 37V SSMIS MICROWAVE IMAGE SHOWS THE MAJORITY OF THE DEEPEST
CONVECTION IS LOCATED TO THE SOUTHEAST OF THE LLCC. THE INITIAL
POSITION IS BASED ON THE AFOREMENTIONED SSMIS AND MULTISPECTRAL
IMAGERY AS WELL AS POSITION ESTIMATES FROM A 222351Z ITOP VORTEX
MESSAGE. THE INITIAL INTENSITY IS BASED ON PGTW AND RJTD DVORAK
ESTIMATES RANGING FROM 55 TO 77 KNOTS, IN ADDITION TO THE VORTEX
MESSAGE REPORTING 69 KNOT WINDS. UPPER LEVEL ANALYSIS INDICATES THAT
A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) TO THE NORTH HAS MOVED
FARTHER NORTHWARD ALLOWING FOR A DECREASE IN SUBSIDENCE ALONG THE
NORTHERN PERIPHERY, WHICH HAS ALLOWED FOR FURTHER INTENSIFICATION.
EQUATORWARD OUTFLOW AND OUTFLOW INTO A TUTT CELL TO THE NORTHEAST
REMAINS GOOD.
3. FORECAST REASONING.
   A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TY 13W IS CURRENTLY TRACKING ALONG THE SOUTHWESTERN PERIPHERY
OF A SUBTROPICAL STEERING RIDGE. A MID-LATITUDE, UPPER LEVEL TROUGH
TO THE NORTHWEST IS EXPECTED TO CONTINUE TRACKING EASTWARD AND
WEAKEN THE STEERING RIDGE TO THE NORTH WITHIN THE NEXT 12 HOURS.
THIS WILL ALLOW TY MALAKAS TO TURN POLEWARD. TY 13W IS EXPECTED TO
CONTINUE INTENSIFYING AS POLEWARD OUTFLOW IMPROVES INTO THE
APPROACHING MID-LATITUDE TROUGH. AROUND TAU 36, TY 13W WILL ROUND
THE RIDGE AXIS AND BEGIN TO RECURVE INTO THE MID-LATITUDE
WESTERLIES. BY TAU 72, THE SYSTEM IS FORECAST TO TRANSITION FULLY
INTO AN INTENSE EXTRATROPICAL LOW AS IT GAINS THE UPPER LEVEL
SUPPORT OF THE APPROACHING TROUGH. NUMERICAL MODEL GUIDANCE IS IN
VERY GOOD AGREEMENT. THEREFORE, THIS FORECAST IS IN AGREEMENT WITH
THE MODEL CONSENSUS.//

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