Tropical Storm YUTU Advisory 10月29日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (YUTU) WARNING NR 30//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 31W (YUTU), LOCATED APPROXIMATELY 385 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-SOUTHWESTWARD
AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY SHOWS UNRAVELING AND COLLAPSING RAIN BANDS FEEDING
INTO A CENTRAL CONVECTION THAT CONTINUED TO WEAKEN, AS EVIDENCED BY
WARMING CLOUD TOPS. THE SYSTEM, HOWEVER, HAS MAINTAINED A 30-NM
RAGGED EYE THAT LINED UP WELL WITH A MICROWAVE EYE IN THE 281721Z
AMSR2 PASS AND USED FOR THE INITIAL POSITION WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 105 KNOTS IS AVERAGED FROM AGENCY AND
OBJECTIVE DVORAK ESTIMATES RANGING FROM T5.0-T6.0. THE ENVIRONMENT
IS LESS FAVORABLE WITH REDUCED UPPER LEVEL OUTFLOW AND MODERATE (15-
20 KNOT) VERTICAL WIND SHEAR (VWS). HOWEVER, ALONG-TRACK SST AND OHC
VALUES REMAIN CONDUCIVE. TY 31W IS TRACKING ALONG THE SOUTHERN
PERIPHERY OF AN EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 31W WILL CONTINUE ON A WEST-SOUTHWESTWARD TRACK TOWARD LUZON
AS THE STR BUILDS, MAKE LANDFALL JUST SOUTH OF PALANAN, ISABELA
SHORTLY AFTER TAU 24, DRAG QUICKLY ACROSS THE RUGGED TERRAIN OF LUZON
AND EXIT INTO THE SOUTH CHINA SEA (SCS) JUST AFTER TAU 36. AFTERWARD,
 A MID-LATITUDE SHORTWAVE TROUGH APPROACHING FROM THE NORTHWEST WILL
WEAKEN THE STR AND ALLOW THE CYCLONE TO TRACK NORTHWESTWARD. DUE TO
THE DEGRADED ENVIRONMENT, THE SYSTEM WILL CONTINUE TO SLOWLY WEAKEN
TO 95 KNOTS BEFORE LANDFALL, THEN RAPIDLY ERODE TO 60 KNOTS BY TAU 36
DUE TO LAND INTERACTION AND INCREASING VWS AS IT EXITS INTO THE SOUTH
CHINA SEA. AFTERWARD, INCREASED POLEWARD OUTFLOW AHEAD OF THE
SHORTWAVE TROUGH WILL OFFSET THE MARGINAL ENVIRONMENT AND STOKE A
SLIGHT INTENSIFICATION TO 70 KNOTS BY TAU 72. NUMERICAL GUIDANCE IS
IN TIGHT AGREEMENT WITH MINIMAL SPREADING TO 120 NM AT TAU 72,
LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST THAT IS
LAID VERY CLOSE TO CONSENSUS.
   C. BEYOND TAU 72, TY YUTU WILL CREST THE STR AXIS AND TRACK MORE
NORTHWARD. INCREASING VWS AND A COLD SURGE EVENT IN THE SCS WILL
GRADUALLY ERODE THE SYSTEM DOWN TO 45 KNOTS BY TAU 120. NUMERICAL
MODEL GUIDANCE AGREEMENT CONTINUES TO TIGHTEN WITH GRADUAL SPREADING
TO 290 NM AT TAU 120. NOTABLE LEFT-OF-TRACK OUTLIERS ARE GFS AND JGSM
FAVORING A DELAYED, WIDER RECURVATURE. THERE IS FAIR CONFIDENCE IN
THE EXTENDED PORTION OF THE JTWC FORECAST TRACK THAT IS LAID JUST
RIGHT OF CONSENSUS TO OFFSET THE LESS LIKELY LEFTWARD MODEL
OUTLIERS.//
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