Tropical Storm TAPAH Advisory Mon Apr 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (TAPAH) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 06W (TAPAH), LOCATED APPROXIMATELY 121 NM
SOUTHEAST OF SAIPAN, HAS TRACKED NORTHWARD AT 06 KNOTS OVER THE PAST
SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS DECREASING
CENTRAL CONVECTION AND AN OVERALL DECREASE IN CONVECTIVE
ORGANIZATION. HOWEVER, GUAM RADAR IMAGERY CONTINUES TO INDICATE
TIGHTLY-CURVED BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC). A 281117Z METOP-B 89 GHZ IMAGE DEPICTS A
WELL-DEFINED CENTER LOCATED ON THE WESTERN EDGE OF THE DEEP CENTRAL
CONVECTION. DESPITE THE GENERAL WEAKENING TREND, A 281118Z ASCAT
SHOWS 45 TO 50 KNOT WINDS, WHICH SUPPORTS THE CURRENT INTENSITY OF
50 KNOTS. BASED ON THE RADAR AND MICROWAVE IMAGERY, THERE IS GOOD
CONFIDENCE IN THE INITIAL POSITION. UPPER-LEVEL ANALYSIS REVEALS A
FAVORABLE ENVIRONMENT WITH LOW (05 TO 10 KNOTS) VERTICAL WIND SHEAR
(VWS) AND GOOD POLEWARD OUTFLOW; HOWEVER, POLEWARD OUTFLOW IS
WEAKENING AS THE DEEP MIDLATITUDE LOW QUICKLY SHIFTS NORTHEASTWARD.
TS 06W IS BEGINNING TO TRACK NORTHWARD AND PERHAPS EVEN NORTH-
NORTHWESTWARD AS THE SUBTROPICAL RIDGE (STR) BUILDS IN NORTHEAST OF
THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 06W IS FORECAST TO TRACK NORTHWARD THROUGH TAU 12 THEN
NORTH-NORTHWESTWARD TO NORTHWESTWARD ALONG THE SOUTHWEST PERIPHERY
OF THE BUILDING STR TO THE NORTH. TS 06W IS FORECAST TO INTENSIFY
FOR THE NEXT 24 HOURS AS FAVORABLE ENVIRONMENTAL CONDITIONS OF GOOD
POLEWARD OUTFLOW AND WARM SEA SURFACE TEMPERATURES (NEAR 28 DEGREES
CELSIUS) PERSIST. AFTER TAU 24, POLEWARD OUTFLOW IS FORECAST TO
WEAKEN AS AN UPPER-LEVEL RIDGE BUILDS SOUTH OF JAPAN.
   C. IN THE EXTENDED TAUS, TS 06W IS FORECAST TO RE-CURVE AHEAD OF
AN APPROACHING SHORTWAVE TROUGH AND SHOULD ENCOUNTER INCREASING
VERTICAL WIND SHEAR, DECREASING SEA SURFACE TEMPERATURES, AND BEGIN
TO INTERACT WITH THE BAROCLINIC ZONE AT WHICH POINT THE SYSTEM IS
FORECAST TO QUICKLY WEAKEN AND DISSIPATE BY TAU 96. THE DYNAMIC
MODEL GUIDANCE IS NOW IN GOOD AGREEMENT, THEREFORE, THE FORECAST IS
POSITIONED NEAR THE MULTI-MODEL CONSENSUS AND IS CONSISTENT WITH THE
PREVIOUS JTWC FORECAST. DUE TO THE TIGHT GROUPING OF MODEL GUIDANCE,
THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.//
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