Tropical Storm NOUL Advisory Thu May 07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (NOUL) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 06W (NOUL), LOCATED APPROXIMATELY 666 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT
11 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 071132Z PGTW SATELLITE EYE FIX WITH HIGH CONFIDENCE. THE
INTENSITY OF 100 KNOTS IS CONSISTENT WITH RECENT DVORAK SATELLITE
CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES. STRONG WESTWARD AND
EQUATORWARD OUTFLOW AND LOW VERTICAL WIND SHEAR HAVE ALLOWED TY 06W
TO INTENSIFY OVER THE PAST SIX HOURS. INFRARED SATELLITE IMAGERY
SHOWS A FAIRLY SYMMETRIC CONVECTIVE PATTERN SURROUNDING A PINHOLE
EYE.
3. FORECAST REASONING.
   A. THE FORECAST TRACK SPEED FOR THE TAU 96 TO TAU 120 PERIOD HAS
INCREASED FROM THE PREVIOUS WARNING AND THE SYSTEM IS NOW FORECAST
TO BEGIN EXTRATROPICAL TRANSITION BY TAU 120. OTHERWISE, 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 JUST AFTER TAU 48.
GENERALLY FAVORABLE UPPER-LEVEL OUTFLOW, LOW VERTICAL WIND SHEAR,
AND WARM WATER SHOULD SUPPORT ADDITIONAL INTENSIFICATION PRIOR TO
LANDFALL. NUMERIC MODELS ARE IN BETTER AGREEMENT THROUGH TAU 72,
WITH ONLY THE EASTERN-OUTLYING ECMWF SOLUTION TRACKING THE SYSTEM
SLIGHTLY OFFSHORE FROM NORTHEASTERN LUZON WITHOUT MAKING LANDFALL.
BASED ON LOW MODEL FORECAST SPREAD AND INCREASING CERTAINTY IN THE
ANTICIPATED ORIENTATION OF THE STEERING RIDGE, CONFIDENCE IN THE
NEAR TO MEDIUM-TERM JTWC TRACK FORECAST IS HIGH.
   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
ONCE THE SYSTEM MOVES BACK OVER WATER AFTER CROSSING LUZON, ALTHOUGH
THE INTENSITY INCREASE SHOULD BE SHORT-LIVED AS INCREASING VERTICAL
WIND SHEAR AND DECREASING ALONG TRACK SEA SURFACE TEMPERATURES
IMPACT THE SYSTEM. TY 06W IS EXPECTED TO BEGIN EXTRATROPICAL
TRANSITION BY TAU 120 AS IT INTERACTS WITH A DEVELOPING MIDLATITUDE
TROUGH. CONSIDERABLE MODEL SPREAD REMAINS 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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