Tropical Storm SANBA Advisory 2月15日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (SANBA)
WARNING NR 25//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 02W (SANBA), LOCATED APPROXIMATELY 447 NM
SOUTH-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED IMAGERY SHOWS A PARTIALLY EXPOSED AND ELONGATING LOW LEVEL
CIRCULATION CENTER WITH FLARING CONVECTION IN THE NORTHWEST
QUADRANT. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED
ON THE INFRARED LOOP AND A 141801Z 37 GHZ GMI MICROWAVE IMAGE
DEPICTING AN ELONGATED LLCC WITH WEAK, POORLY ORGANIZED BANDING. THE
INITIAL INTENSITY OF 25 KNOTS IS BASED ON MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATE OF T1.5 (25 KNOTS) FROM PGTW AND KNES.
ENVIRONMENTAL ANALYSIS REVEALS THE SYSTEM IS IN AN AREA OF MODERATE
TO STRONG (20-25 KNOT) VERTICAL WIND SHEAR AND IS TRACKING THROUGH
MARGINALLY FAVORABLE (27 CELSIUS) SEA SURFACE TEMPERATURES. UPPER
LEVEL ANALYSIS REVEALS THAT THE MARGINALLY FAVORABLE ENVIRONMENT IS
BEGIN OFFSET BY A STRONG POLEWARD OUTFLOW CHANNEL THAT IS ALLOWING
THE SYSTEM TO MAINTAIN 25 KNOTS INTENSITY AND ENABLING FLARING
CONVECTION. TD 02W IS CURRENTLY TRACKING WEST-NORTHWEST ALONG THE
SOUTHERN PERIPHERY OF AN EXTENSION OF THE SUB TROPICAL RIDGE LOCATED
TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD SANBA IS FORECAST TO INITIALLY TRACK WEST-NORTHWEST THROUGH
THE BALABAC STRAIT INTO THE SOUTH CHINA SEA. THE RIDGE EXTENSION IS
FORECAST TO BUILD AS THE RIDGE SHIFTS TO THE WEST CAUSING THE SYSTEM
TO TRACK MORE WESTWARD AND EVENTUALLY TO THE SOUTHWEST AFTER TAU 48.
THOUGH THE SYSTEM HAS TRACKED AT A SLOW SPEED OVER THE LAST 18 HOURS
TD SANBA IS FORECAST TO ACCELERATE AFTER ENTERING THE SOUTH CHINA
SEA AS THE STEERING STR BUILDS IN FROM THE NORTHEAST.  THE INTENSITY
IS FORECAST TO PLATEAU AT 25 KTS, AS INCREASING VWS AND COOLING SSTS
ARE OFFSET BY STRONG POLEWARD OUTFLOW. AFTER TAU 48, TD 02W WILL
TRACK INTO INCREASINGLY COOLER (<26 CELSIUS) SSTS, CAUSING
DISSIPATION BY TAU 72. AVAILABLE DYNAMIC MODEL GUIDANCE IS IN
GENERAL AGREEMENT ON THE WESTWARD TRACK HOWEVER, VARY AS SEVERAL
INITIALLY TRACK MORE TO THE WEST-NORTHWEST, AND OTHERS DIVERGE TO
THE WEST. DUE TO THE LARGE SPREAD IN MODEL GUIDANCE, AND THE WEAK
NATURE OF THE SYSTEM, THERE IS OVERALL A LOW CONFIDENCE IN THE
JTWC FORECAST TRACK.//
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