#659 Postby euro6208 » Tue Apr 20, 2021 7:34 am
WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 300 NM EAST-
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT
05 KTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT
TY SURIGAE CONTINUES TO MAINTAIN A ROUGHLY 30-NM WIDE EYE, THOUGH AT
LEAST IN THE VISIBLE AND INFRARED BANDS HAS BECOME SLIGHTLY MORE
RAGGED. A 200502Z AMSR2 MICROWAVE PASS CONFIRMED A VERY WELL DEFINED
AND INTENSE 30-NM EYEWALL AND THE 37GHZ IMAGE REVEALED A SMALLER AND
WEAKER INNER EYEWALL AT ABOUT 15-NM FROM THE CENTER. THE INITIAL
INTENSITY REMAINS STEADY AT 115 KTS, SUPPORTED BY MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T6.5 FROM PGTW, AND T6.0 FROM
RJTD AND KNES, AN ADT ESTIMATE OF T6.1 AND A SATCON ESTIMATE OF 121
KTS AND IS HEDGED SLIGHTLY LOWER IN LIGHT OF A 200502Z AMSR2
WINDSPEED MEASUREMENT OF 110 KTS. TY 02W REMAINS IN A GENERALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW (8-12 KTS) AND STRONG
POLEWARD AND EQUATORWARD OUTFLOW. SSTS REMAIN GENERALLY WARM, THOUGH
RECENT HYCOM MODEL ANALYSIS SUGGESTS SIGNIFICANT UPWELLING,
PRIMARILY TO THE SOUTH IN THE STORMS WAKE. HOWEVER, NOW THAT THE
SYSTEM HAS PICKED UP FORWARD SPEED ONCE MORE, IT IS MOVING AWAY FROM
THE INDUCED POOL OF COOLER WATERS AND INTO A REGION OF 27-28C
WATERS.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY SURIGAE IS FORECAST TO TRACK NORTHEASTWARD ALONG THE
WESTERN PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) THROUGH TAU 36,
THEN ROUND THE RIDGE AXIS AND TURN SHARPLY NORTHEAST AHEAD OF STRONG
MID-LATITUDE SHORTWAVE TROUGH MOVING IN FROM THE WEST. BY TAU 72,
SURIGAE WILL BE ON A NEAR EASTWARD COURSE, STEADILY ACCELERATING AS
IT BEGINS TO INTERACT WITH THE SUBTROPICAL JET ALOFT. THERE IS NO
SIGNIFICANT CHANGE EXPECTED IN THE UPPER-LEVEL ENVIRONMENT, WITH LOW
VWS AND STRONG POLEWARD OUTFLOW PERSISTING THROUGH TAU 36. THE
PRIMARY INTENSITY FACTORS ARE THUS THE RELATIVELY MARGINAL SSTS
(27C) AND THE LARGE SIZE OF THE CORE AND THE TWO FACTORS TOGETHER
SUPPORT A STEADY OR GRADUAL DECREASE IN INTENSITY THOUGH TAU 12 AND
THEN STEADIER WEAKENING THROUGH TAU 36. ONCE THE SYSTEM MAKES THE
TURN NORTHEAST BY TAU 48, STEADY WEAKENING IS FORECAST AS THE SYSTEM
ENCOUNTERS STEADILY COOLER SSTS, AT OR BELOW 26C, AND DRAMATICALLY
INCREASED MID-LEVEL SHEAR. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 AND THE JTWC FORECAST TRACK IS SET WITH
HIGH CONFIDENCE. THE INTENSITY FORECAST IS SET ON THE HIGH END OF
THE GUIDANCE ENVELOPE AND CLOSELY TRACKS THE HWRF SOLUTION WITH
MODERATE CONFIDENCE.
C. IN THE LATER PORTION OF THE FORECAST, TY SURIGAE WILL CONTINUE
TO ACCELERATE EAST-NORTHEASTWARD AHEAD OF AN ADVANCING MAJOR
SHORTWAVE TROUGH AND ALONG THE NORTHERN PERIPHERY OF THE STR TO THE
SOUTHEAST. MOST AVAILABLE GUIDANCE SUGGESTS THAT TC 02W WILL NOT BE
CAPTURED BY THE PASSING SHORTWAVE, WHICH WILL MISS THE SYSTEM TO THE
NORTH, BUT WILL CONTINUE TRACKING EASTWARD AS IT WEAKENS. THE
PRIMARY IMPACT OF THE SHORTWAVE WILL BE TO IMPART A STRONG WESTERLY
FLOW ALOFT, INCREASING VWS TO ABOVE 50 KTS. THE SYSTEM WILL TRANSIT
GENERALLY ALONG THE 26C ISOTHERM, BUT DUE TO THE VERY HIGH SHEAR AND
THE CONVERGENT NATURE OF THE WESTERLY FLOW ALOFT, WILL STEADILY
WEAKEN THROUGH TAU 120. AS TY 02W MOVES EASTWARD ALONG THE
BAROCLINIC ZONE AND DEVELOPS A FRONTAL STRUCTURE, IT IS FORECAST TO
BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 96. NUMERICAL MODEL
GUIDANCE IS IN OVERALL GOOD AGREEMENT THOUGH BEGINS TO SHOW
SIGNIFICANT SPREAD IN BOTH ALONG AND CROSS-TRACK UNCERTAINTY AFTER
TAU 96 DUE TO THE UNCERTAINTY SURROUNDING THE IMPACT OF THE
SHORTWAVE TROUGH. THE JTWC FORECAST TRACK IS SET JUST SOUTH FROM THE
PREVIOUS FORECAST AND LIES JUST NORTH OF THE MULTI-MODEL CONSENSUS
WITH MODERATE CONFIDENCE.//
NNNN
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