Tropical Storm SURIGAE Advisory 4月17日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
    TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 192 NM
NORTHWEST OF KAYANGEL, PALAU, HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY REVEALS THAT TY 02W HAS RAPIDLY INTENSIFIED
OVER THE PAST SIX HOURS. THE INITIAL POSITION IS SET WITH HIGH
CONFIDENCE BASED ON A 6 NM EYE OBSERVED IN THE EIR. THE INITIAL
INTENSITY HAS BEEN INCREASED TO 115 KTS, HEDGED BETWEEN DVORAK
CURRENT INTENSITY ESTIMATES OF T5.5 (RJTD), T6.0 (PGTW), AND T6.5
(KNES). OF NOTE, PGTW OBSERVED AN INSTANTANEOUS DATA T OF 6.5, BUT
MAINTAINED A SLIGHTLY LOWER ESTIMATE BASED ON AN OBSERVED WEAKNESS
OBSERVED ALONG THE SOUTHWESTERN PERIPHERY OF THE EYE. ADDITIONALLY,
THE ADVANCED DVORAK TECHNIQUE OF T5.9 (112 KTS) AND A 161713Z SATCON
OF 121KTS ARE SUPPORTIVE OF THE INITIAL INTENSITY. THE 34- AND 50-KT
WIND RADII HAVE BEEN ADJUSTED BASED ON THE 161255Z ASCAT-C DATA.
ENVIRONMENTAL ANALYSIS REVEALS LOW (10-15 KT) VERTICAL WIND SHEAR,
ROBUST EQUATORWARD AND POLEWARD OUTFLOW, AND WARM (29-30 CELSIUS)
SEA SURFACE TEMPERATURES CONTRIBUTING TO AN OVERALL HIGHLY FAVORABLE
ENVIRONMENT. TY 02W IS CURRENTLY TRACKING WEST-NORTHWESTWARD TOWARDS
A WEAKNESS IN THE STEERING SUBTROPICAL RIDGE (STR) CAUSED BY AN
APPROACHING MID-LATITUDE TROUGH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TY 02W IS EXPECTED TO TRACK NORTHWESTWARD
TOWARDS THE WEAKNESS IN THE STR. AROUND TAU 48, THE SYSTEM WILL SLOW
AS IT ENTERS THE COL. DURING THIS TIME, THE STR TO THE EAST IS
FORECAST TO BUILD AND TAKE OVER AS THE PRIMARY STEERING INFLUENCE,
DRIVING THE SYSTEM TO THE NORTH. TY 02W WILL CONTINUE TO INTENSIFY
THROUGH TAU 24, REACHING A PEAK INTENSITY OF 125 KTS. AFTERWARDS,
DECREASING DIVERGENCE ALOFT WILL BEGIN TO IMPACT THE SYSTEM AND
CAUSE IT TO SLOWLY WEAKEN. IN THE LATEST MODEL RUNS, THE ECMWF AND
GFS TRACK SOLUTIONS HAVE SHIFTED SLIGHTLY TO THE EAST, COMING INTO
BETTER AGREEMENT WITH THE MAJORITY OF THE NEAR TERM MODEL GUIDANCE.
HOWEVER, THE JGSM, UKMET, AND UKMET ENSEMBLE SOLUTIONS CONTINUE TO
BE THE EASTERNMOST SOLUTIONS. BASED ON THE VARIATION IN MODEL
GUIDANCE, THERE IS FAIR CONFIDENCE IN THE EARLY PORTION OF THE JTWC
FORECAST TRACK.
   C. AFTER TAU 72, TY 02W WILL TURN TO A NORTHWARD TRACK THROUGH
TAU 120, TRACKING ALONG THE WESTERN PERIPHERY OF THE STR POSITIONED
TO THE EAST. THE ENVIRONMENT WILL SLOWLY BECOME LESS FAVORABLE AS
UPPER LEVEL DIVERGENCE BEGINS TO SIGNIFICANTLY DECREASE AFTER TAU
72. THIS WILL RESULT IN THE SYSTEM SLOWLY WEAKENING TO 90 KTS BY TAU
120. IN THE EXTENDED RANGE, NUMERICAL MODEL TRACK SOLUTIONS DIVERGE
TO A CROSS-TRACK SPREAD OF 535 NM AT TAU 120. OF NOTE, THE ECMWF
SOLUTION CONTINUES TO BRING THE SYSTEM OVER LUZON BY TAU 120 DESPITE
HAVING SHIFTED SLIGHTLY EASTWARD FROM THE PREVIOUS MODEL RUN. BASED
ON THIS UNCERTAINTY BETWEEN THE MODELS, THERE IS LOW CONFIDENCE IN
THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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