
WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (NOUL) WARNING NR 18//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 06W (NOUL), LOCATED APPROXIMATELY 735 NM EAST-SOUTHEAST
OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. TY 06W CONTINUES TO TRACK WEST-
NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL STEERING RIDGE TO THE NORTH. THE CURRENT POSITION IS
BASED ON A 070532Z PGTW SATELLITE EYE FIX WITH HIGH CONFIDENCE. THE
INTENSITY OF 90 KNOTS IS CONSISTENT WITH RECENT DVORAK SATELLITE
INTENSITY ESTIMATES FROM PGTW AND RJTD. A FAVORABLE UPPER-LEVEL
PATTERN PROVIDING STRONG WESTWARD AND EQUATORWARD OUTFLOW AND LOW
VERTICAL WIND SHEAR HAS ALLOWED TY 06W TO MAINTAIN INTENSITY OVER
THE PAST SIX HOURS. MULTISPECTRAL SATELLITE IMAGERY SHOWS A FAIRLY
SYMMETRIC CONVECTIVE PATTERN SURROUNDING A 17 NM EYE.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY 06W IS EXPECTED TO TRACK WEST-NORTHWESTWARD UNDER THE
CONTINUED STEERING INFLUENCE OF THE SUBTROPICAL RIDGE OVER THE NEXT
72 HOURS, MAKING LANDFALL ON THE ISLAND OF LUZON BY TAU 72.
GENERALLY FAVORABLE UPPER-LEVEL OUTFLOW, LOW VERTICAL WIND SHEAR,
AND WARM WATER SHOULD SUPPORT ADDITIONAL INTENSIFICATION PRIOR TO
LANDFALL. NUMERIC MODELS ARE IN FAIR AGREEMENT THROUGH TAU 72, WITH
THE GFDN SHOWING A TRACK SLIGHTLY TO THE WEST AND ECMWF A TRACK
SLIGHTLY TO THE EAST OF THE PRIMARY GROUPING. THE JTWC FORECAST LIES
WITHIN THE PRIMARY GROUPING NEAR THE MULTI-MODEL CONSENSUS. BECAUSE
THERE IS SOME UNCERTAINTY REGARDING ORIENTATION OF THE STEERING
RIDGE DURING THIS PERIOD, CONFIDENCE IN THE NEAR TO MEDIUM-TERM JTWC
TRACK FORECAST IS LOW.
C. IN THE EXTENDED PERIOD, A DEVELOPING MID-LATITUDE TROUGH WILL
WEAKEN THE STEERING RIDGE, ALLOWING TY 06W TO ROUND THE RIDGE AXIS
AND TURN TOWARD THE NORTHEAST. SOME REINTENSIFICATION IS EXPECTED
AFTER THE SYSTEM MOVES BACK OVER WATER AFTER CROSSING LUZON,
ALTHOUGH THE INTENSITY INCREASE SHOULD BE LIMITED BY MODERATE
VERTICAL WIND SHEAR AND DECREASING ALONG TRACK SEA SURFACE
TEMPERATURES. THERE IS A CONSIDERABLE MODEL SPREAD IN THE EXTENDED
FORECAST PERIOD, PARTICULARLY WITH RESPECT TO TRACK SPEED. HOWEVER,
NEARLY ALL DEPICT THE SYSTEM TRACKING JUST SOUTHEAST OF TAIWAN.
GIVEN HIGH UNCERTAINTY IN THE EXTENDED PERIOD, THE CURRENT JTWC
TRACK FORECAST LIES NEAR THE MULTI-MODEL CONSENSUS, WITH LOW
CONFIDENCE.//
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