Tropical Storm KALMAEGI Advisory 11月17日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KALMAEGI)
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 27W (KALMAEGI), LOCATED APPROXIMATELY 284 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 02
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS A LARGE AREA OF DEEP CONVECTION LOOSELY WRAPPING
INTO A BROAD AND OBSCURED LOW LEVEL CIRCULATION (LLC). THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON A WEAK, FRAGMENTED
BUT DISCERNIBLE LLC FEATURE IN THE 161750Z MKIVB STRATUS-ENHANCED IR
IMAGE. THE INITIAL INTENSITY OF 35KTS IS BASED ON THE DVORAK
ESTIMATES OF T2.5/35KTS FROM RJTD AND PGTW. ANALYSES INDICATE A
MARGINAL ENVIRONMENT WITH A VIGOROUS POLEWARD OUTFLOW AND
WARM (29C) SSTS OFFSET BY MODERATE (15-20KT) RELATIVE VERTICAL WIND
SHEAR (VWS) AND COOL/DRY NORTHEASTERLY SURGE OVER THE PHILIPPINE
SEA. THE CYCLONE IS QUASI-STATIONARY (QS) IN A WEAK STEERING
ENVIRONMENT IN A COL BETWEEN THE SUBTROPICAL RIDGE (STR) TO THE WEST
AND THE STR TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THE STR TO THE EAST WILL ASSUME STEERING AND SLOWLY DRIVE THE
SYSTEM NORTHWESTWARD UP TO TAU 36. AFTERWARD, THE STR TO THE WEST
WILL BUILD, REORIENT NORTHWARD, AND GRADUALLY STEER THE CYCLONE
WESTWARD THEN SOUTHWESTWARD INTO NORTHERN LUZON. THE MARGINALLY
FAVORABLE ENVIRONMENT WILL FUEL SLOW INTENSIFICATION TO A PEAK OF
55KTS BY TAU 48, JUST BEFORE LANDFALL. AFTERWARD, INCREASING VWS AND
LAND INTERACTION WILL ERODE THE SYSTEM DOWN TO 40KTS BY TAU 72 AS
THE SYSTEM EXITS INTO THE SOUTH CHINA SEA. THERE IS A DISTINCT
POSSIBILITY THAT THE STRONG VWS, COLD/DRY SURGE, AND LAND
INTERACTION WILL GREATLY OFFSET THE STRONG OUTFLOW AND ERODE THE
SYSTEM MORE RAPIDLY AND INTO DISSIPATION BY TAU 72.
   C. AFTER TAU 72, TS KALMAEGI IS EXPECTED TO CONTINUE
SOUTHWESTWARD UNDER THE SECONDARY STR, IN THE SOUTH CHINA SEA WHERE
THE COLD/DRY NORTHERLY SURGE IS MORE VIGOROUS. THIS, PLUS THE HIGH
VWS, WILL RESULT IN DISSIPATION BY TAU 120. THE NUMERICAL MODELS ARE
IN VERY BROAD AGREEMENT TO THE FORECAST TRACK BUT WITH SIGNIFICANT
DIFFERENCES IN TRACK SPEED GIVEN THE UNCERTAINTIES IN THE STORM
MOTION IN THE COL AND ACROSS THE RUGGED LUZON TERRAIN. IN VIEW OF
THESE, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC TRACK FORECAST.//
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