Tropical Storm SANBA Advisory 2月12日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (SANBA)
WARNING NR 13//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 02W (SANBA), LOCATED APPROXIMATELY 67 NM WEST-
NORTHWEST OF ANGAUR, HAS TRACKED WEST-NORTHWESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS THE CENTRAL DEEP CONVECTION HAS DISSIPATED SOME AND
THE FLARING IS STARTING TO REVEAL A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ON THE ANIMATED LOOP AND AN 111741Z 37GHZ SSMI
MICROWAVE IMAGE. THE AFOREMENTIONED MICROWAVE IMAGE SHOWS WEAK
BANDING WRAPPING INTO A CENTRAL NOTCH FEATURE. THE INITIAL INTENSITY
OF 35 KNOTS IS HEDGED SLIGHTLY ABOVE CONCURRENT DVORAK INTENSITY
ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW AND RJTD. ENVIRONMENTAL
ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF MODERATE (15-20 KNOT)
VERTICAL WIND SHEAR AND IS TRACKING THROUGH AN AREA OF WARM (29
CELSIUS) SEA SURFACE TEMPERATURES. UPPER LEVEL ANALYSIS REVEALS THAT
THE SYSTEM HAS STRONG POLEWARD OUTFLOW ENHANCED BY MID-LATITUDE
WESTERLIES. TS 02W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 02W WILL TRACK GENERALLY WEST-NORTHWESTWARD ALONG AN
EXTENSION OF THE STR TOWARD THE SOUTHERN PHILIPPINES, MAKING
LANDFALL AROUND TAU 30. MARGINALLY FAVORABLE ENVIRONMENTAL
CONDITIONS WILL ALLOW FOR ADDITIONAL INTENSIFICATION UP TO 45 KNOTS
PRIOR TO LANDFALL. ONCE OVERLAND, THE SYSTEM WILL WEAKEN SLIGHTY AND
A BUILDING EXTENSION OF THE STR WILL CAUSE THE SYSTEM TO TRACK
WESTWARD AND INTO THE SULU SEA. MARGINAL CONDITION OVER THE SULU SEA
WILL ALLOW THE SYSTEM TO MAINTAIN WEAK TROPICAL STORM STRENGTH AS IT
TRACKS SOUTH OF PUERTO PRINCESA. DYNAMIC MODEL GUIDANCE IS IN TIGHT
AGREEMENT THROUGH TAU 72, LENDING HIGH CONFIDENCE IN THIS PORTION OF
THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TS SANBA WILL TRACK MORE NORTHWESTWARD, AS THE
STR RECEDES AND THE SYSTEM ROUNDS THE SOUTHWESTERN PERIPHERY OF THE
EXTENSION. MARGINAL CONDITIONS IN THE SOUTH CHINA SEA, THE RESULT OF
A COLD SURGE, WILL CAUSE THE SYSTEM TO GRADUALLY WEAKEN TO 30 KNOTS
BY TAU 120. AVAILABLE DYNAMIC MODEL GUIDANCE SPREADS SIGNIFICANTLY
IN BOTH TRACK DIRECTION AND ALONG TRACK SPEED, SPECIFICALLY IN THE
TURN TO THE NORTHWEST. THE LARGE SPREAD IN MODEL GUIDANCE AFTER TAU
72 LENDS LOW CONFIDENCE IN THE LONG RANGE JTWC TRACK FORECAST.//
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