Tropical Storm VONGFONG Advisory mar, 07.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (VONGFONG) WARNING NR 18//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 19W (VONGFONG), LOCATED APPROXIMATELY 460 NM NORTH-
NORTHWEST OF YAP, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED AND MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS AN IRREGULAR EYE FEATURE HAS DEVELOPED AS THE
DEEP CONVECTIVE BANDING AROUND THE SYSTEM HAS DEEPENED AND BECOME
MORE SYMMETRIC. A 062258Z SSMIS MICROWAVE IMAGE FURTHER REVEALS A
SLIGHTLY ASYMMETRIC EYEWALL FEATURE HAS DEVELOPED WHILE BANDING IN
THE OUTER PERIPHERIES HAS INCREASED. THE INITIAL POSITION IS BASED
ON THE EYE FEATURE OBSERVED IN THE MSI LOOP WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY HAS BEEN INCREASED TO 100 KNOTS BASED ON THE
INCREASING STRUCTURE OBSERVED IN THE AFOREMENTIONED SATELLITE
IMAGERY AND AS DVORAK INTENSITY ESTIMATES HAVE INCREASED TO 102
KNOTS FROM PGTW AND RJTD. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM
REMAINS IN AN AREA OF LOW TO MODERATE (10 TO 20 KNOT) VERTICAL WIND
SHEAR (VWS) THAT IS BEING OFFSET BY EXCELLENT EQUATORWARD OUTFLOW
AND THE MOTION OF THE SYSTEM. TY 19W IS CURRENTLY TRACKING ALONG THE
SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE
NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 19W WILL CONTINUE TRACKING WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR THROUGH TAU 48. AFTERWARDS, IT IS
EXPECTED TO SLOW AND TURN MORE POLEWARD AS THE STR WEAKENS IN
RESPONSE TO A MID-LATITUDE TROUGH WHICH WILL BE APPROACHING FROM THE
NORTHWEST. UPPER-LEVEL CONDITIONS ARE EXPECTED TO IMPROVE WITH THE
DEVELOPMENT OF A POLEWARD OUTFLOW CHANNEL WHICH WILL ALLOW FOR
FURTHER INTENSIFICATION AS THE SYSTEM IS EXPECTED TO REACH 130 KNOTS
BY TAU 48. MODEL GUIDANCE IS IN FAIRLY TIGHT AGREEMENT THROUGH TAU
48 LENDING TO HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST.
   C. TY 19W IS EXPECTED TO TRACK POLEWARD ALONG THE WESTERN EDGE OF
THE AFOREMENTIONED STEERING STR WHICH IS EXPECTED TO BE WEAKENING AS
ANOTHER MID-LATITUDE SHORTWAVE TROUGH DIGS IN FROM THE NORTH.
INCREASING VWS WILL GRADUALLY WEAKEN THE CYCLONE AS IT GAINS
LATITUDE. MODEL GUIDANCE GENERALLY OVERALL AGREES WITH A POLEWARD
TURN AT THIS TIME FRAME BUT AT VARYING EXTENTS AND SPEEDS. DUE TO
THIS, THE FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH LOW CONFIDENCE.//
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