Tropical Storm BAILU Advisory 8月23日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (BAILU) WARNING NR
07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 12W (BAILU), LOCATED APPROXIMATELY 579 NM
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY
SHOWS A LOW LEVEL CIRCULATION CENTER (LLCC) TO THE NORTHEAST OF THE
CENTRAL DENSE OVERCAST, OBSCURED BY AN ISOLATED FLARE OF CONVECTION.
THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE ON LOW LEVEL
INFLOW INTO THE LLCC AND SUPPORTED BY A 1720 ATMS 88.2GHZ MICROWAVE
IMAGE. THE INITIAL INTENSITY OF 50 KNOTS IS BASED ON A 221200Z SMOS
PASS THAT SHOWED 50 KT WINDS IN THE SOUTHEAST QUADRANT OF THE
SYSTEM. THE INTENSITY ESTIMATE IS ABOVE ALL AGENCY DVORAK CURRENT
INTENSITY ESTIMATES OF T3.0 (45 KTS) AND A 221628Z SATCON ESTIMATE
OF 46 KTS. ENVIRONMENTAL ANALYSIS SHOWS THAT TS 12W IS EXPERIENCING
FAVORABLE (10 TO 15 KNOT) VERTICAL WIND SHEAR, ALTHOUGH THE LOCATION
OF A POINT SOURCE JUST TO THE NORTH OF THE SYSTEM IS PUSHING THE
BULK OF THE DEEP CONVECTION TO THE SOUTHWEST OF THE LLCC. THE
EQUATORWARD OUTFLOW CHANNEL REMAINS EXCELLENT, WHILE POLEWARD
OUTFLOW IS DISORGANIZED. SEA SURFACE TEMPERATURES REMAIN FAVORABLE
FOR ADDITIONAL DEVELOPMENT, BETWEEN 29 AND 30 DEGREES CELSIUS. TS
12W IS TRACKING NORTHWARD WHILE UNDER THE
INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. IN THE SHORT TERM, TS 12W WILL TRACK NORTHWESTWARD AS THE
AFOREMENTIONED STR SHIFTS SLIGHTLY EASTWARD, RESPONDING TO A
MIDLATITUDE TROUGH PASSING BY TO THE NORTH. FAVORABLE SEA SURFACE
TEMPERATURES AND LOW VERTICAL WIND SHEAR WILL ALLOW TS 12W TO REACH
65 KNOTS BY TAU 24. THE JTWC PEAK INTENSITY IS HIGHER THAN THE MULTI-
MODEL INTENSITY CONSENSUS INDICATES, BUT UNDER THE HWRF PREDICTION.
SHORTLY AFTER TAU 36, TS 12W WILL MAKE LANDFALL IN SOUTHERN TAIWAN
AND VEER MORE WEST-NORTHWESTWARD AS THE STR BUILDS BACK INTO THE
AREA. TS 12W WILL THEN MAKE LANDFALL IN CHINA AFTER TAU 48. TS 12W
WILL BEGIN TO WEAKEN AS IT CROSSES THE MOUNTAINOUS TERRAIN OF
TAIWAN, THEN WEAKEN MORE RAPIDLY WHEN IT MAKES LANDFALL IN CHINA.
DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH ALL MEMBERS
INDICATING A NORTHWESTWARD TRACK. HOWEVER, THE JTWC FORECAST TRACK
IS PLACED SLOWER THAN THE MULTI-MODEL CONSENSUS IN THE NEAR TERM DUE
TO SLOW PREVIOUS TRACK MOTION AND THE TEMPORARY WEAKENING OF THE
STEERING FLOW AS THE STR SHIFTS TO THE EAST. DUE TO THE FASTER THAN
EXPECTED MODEL TRACK SPEED AND FAIR CERTAINTY IN THE INITIAL
POSITION, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE FORECAST
TRACK.
   C. AFTER TAU 72, TS 12W WILL CONTINUE TO TRACK NORTHWESTWARD
ALONG THE SOUTHERN BOUNDARY OF ANOTHER STR TO THE NORTH. LAND
INTERACTION WITH CHINA WILL CAUSE TS 12W TO WEAKEN TO 20 KNOTS BY
TAU 96. DYNAMIC MODEL GUIDANCE HAS A SPREAD OF 525 NM BY TAU 96,
WITH GFS AND NAVGEM BEING THE SOUTHERN OUTLIERS, AND ECMWF THE
EASTERN OUTLIER. THE JTWC TRACK IS HEDGED EAST OF THE MULTI-MODEL
CONSENSUS BASED ON THE ECMWF SOLUTION. DUE TO THE TIGHT GROUPING OF
MODEL TRACKS, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.//
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