Tropical Storm SANBA Advisory 2月13日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (SANBA)
WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 02W (SANBA), LOCATED APPROXIMATELY 496 NM
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 19
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A RAPIDLY MOVING SYSTEM WITH DEEP CONVECTION
CONFINED TO THE NORTHERN SEMI-CIRCLE. THERE IS HIGH CONFIDENCE IN
THE INITIAL POSITION WHICH IS BASED ON A LOW REFLECTIVITY
CIRCULATION FEATURE OBSERVED IN A 121811Z 89GHZ GMI IMAGE WITH A
PATCH OF DEEP CONVECTION EMANATING FROM THE CENTER AND A BAND OF
DEEP CONVECTION ON THE NORTHERN PERIPHERY. THE INITIAL INTENSITY IS
ASSESSED AT 35 KNOTS WHICH IS HEDGED TO THE HIGHER END OF CURRENT
INTENSITY DVORAK ESTIMATES RANGING FROM T2.0 TO T2.5 (25 TO 30
KNOTS). A 121320Z METOP-B ASCAT IMAGE SHOWS THE INTACT LOW LEVEL
CIRCULATION CENTER WITH THE HIGHEST WINDS LOCATED TO THE NORTH AND
EXTENDING NORTHWEST JUST OFFSHORE FROM THE PHILIPPINES. TS 02W IS
TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN BOUNDARY OF A DEEP-
LAYERED SUBTROPICAL RIDGE (STR) ANCHORED TO THE NORTHEAST AND
EXTENDING WESTWARD OVER THE SOUTH CHINA SEA. THE POSITION OF THE
RIDGE AXIS IS CREATING GOOD DIFFLUENT CONDITIONS ALOFT AND TS 02W IS
TRACKING RAPIDLY IN PHASE WITH THE EASTERLY FLOW MINIMIZING THE
INFLUENCE OF VERTICAL WIND SHEAR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 02W WILL CONTINUE TRACKING GENERALLY WESTWARD OVER THE
FORECAST PERIOD ALONG THE SOUTHERN BOUNDARY OF THE STR EXTENSION. AN
ONGOING COLD SURGE EVENT IN THE MID-LATITUDES OFF THE ASIAN COAST IS
BRINGING ENHANCED NORTHEASTERLY WINDS INTO THE REGION AND FEEDING
INTO TS 02W AND EXPANDING THE GALE WIND RADII TO MAINLY THE NORTHERN
PORTIONS OF THE FORECAST TRACK. THE ENHANCED FLOW IS EXPECTED TO
PERSIST OVER THE NEXT 36 TO 48 HOURS AND, WITH AN OTHERWISE
FAVORABLE ENVIRONMENT, LEAD TO A MAXIMUM INTENSITY OF 40 KNOTS AT
TAU 48. BUT TS 02W WILL FIRST WEAKEN SLIGHTLY AS IT TRACKS OVER THE
SOUTHERN ISLANDS OF THE PHILIPPINES. THE LOW LEVEL CIRCULATION IS
EXPECTED TO REMAIN INTACT RECONSOLIDATING QUICKLY AS IT EMERGES OVER
THE SULU SEA.
   C. IN THE EXTENDED TAUS, TS 02W WILL WEAKEN GRADUALLY AS IT
TRACKS WEST-NORTHWESTWARD OVER THE SOUTH CHINA SEA AND ENCOUNTERS
COOLER SEA SURFACE TEMPERATURES AS IT APPROACHES VIETNAM. VERTICAL
WIND SHEAR IS ALSO EXPECTED TO INCREASE UNDER THE PREDOMINANT
EASTERLY FLOW ALOFT. TS 02W IS FORECAST TO DISSIPATE COMPLETELY
SHORTLY AFTER MAKING LANDFALL OVER VIETNAM NEAR TAU 102. DYNAMIC
MODEL GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 48 LENDING HIGH
CONFIDENCE TO THIS PORTION OF THE FORECAST TRACK. BEYOND TAU 48 THE
GUIDANCE DIFFERS SOMEWHAT WITH COAMPS SHOWING A TRACK SOUTH OF 10
DEGREES NORTH. NAVGEM AND THE JAPANESE ENSEMBLE ARE THE NORTHERN
MOST OUTLIERS SHOWING A MORE PRONOUNCED TURN TO THE NORTHWEST. DUE
TO THE FADING CONFIDENCE IN THE EXTENDED FORECAST TRACK, THERE IS
OVERALL LOW CONFIDENCE IN THE FORECAST TRACK.//
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