Tropical Storm SURIGAE Advisory 4月16日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
    TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 42 NM
NORTHEAST OF KAYANGEL, HAS TRACKED WEST-SOUTHWESTWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS CENTRAL COLD COVER CONTINUES TO BUILD UP DIRECTLY OVER
THE LOW-LEVEL CIRCULATION CENTER (LLCC), COMPLETELY OBSCURING THE
POSITION OF THE LLCC. THE INITIAL POSITION IS PLACED WITH GOOD
CONFIDENCE BASED ON A 151659Z AMSR2 37GHZ IMAGE THAT REVEALS A CLEAR
MICROWAVE EYE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON THE
DVORAK CURRENT INTENSITY ESTIMATES OF T4.0 (65 KNOTS) BY PGTW, RJTD
AND KNES AND AN ADVANCED DVORAK TECHNIQUE ESTIMATE OF 65 KNOTS.
ENVIRONMENTAL ANALYSIS INDICATES AN OVERALL FAVORABLE ENVIRONMENT
FOR DEVELOPMENT WITH LOW (10-15KT) VERTICAL WIND SHEAR (VWS),
DESPITE OUTFLOW ALOFT CONTAINED TO THE WESTERN SEMICIRCLE WITH
PRESSURE ON THE EASTERN SIDE OF THE STORM. VERY WARM (29-30C) SEA
SURFACE TEMPERATURE (SST) IN THE PHILIPPINE SEA IMPROVES THE OVERALL
ENVIRONMENT FOR DEVELOPMENT. TY 02W IS CURRENTLY MOVING VERY SLOWLY,
TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE DEEP
LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 02W IS FORECAST TO GRADUALLY TRANSITION TO A NORTHWESTWARD
TRACK AS A MIDLATITUDE TROUGH DIGS IN, BREAKING THE EXTENSION OF THE
STR, ALLOWING TY 02W TO TRACK TOWARD THIS WEAKNESS IN THE STR. THE
SYSTEM WILL STEADILY INTENSIFY AS THE PRESSURE ON THE EASTERN SIDE
GRADUALLY SUBSIDES, LEADING TO ROBUST, DUAL CHANNEL OUTFLOW THAT
WILL SIGNIFICANTLY IMPROVE THE ENVIRONMENT FOR DEVELOPMENT, WITH TY
02W REACHING 95KTS BY TAU 48 AND 115KTS BY TAU 72. NUMERICAL MODEL
GUIDANCE HAS SPREAD SLIGHTLY OVER THE PAST SIX HOURS WITH A CROSS-
TRACK SPREAD OF 180NM AT TAU 72 WITH ECMWF AND ECMWF ENSEMBLE MEAN
FURTHER WEST BEFORE RECURVING AND JGSM RECURVING MORE ABRUPTLY. THE
JTWC TRACK HAS BEEN PLACED NEAR THE MULTI-MODEL CONSENSUS. THERE IS
FAIR CONFIDENCE IN THE EARLY PORTION OF THE JTWC TRACK FORECAST DUE
TO ITS UNEXPECTED RECENT DIP OFF OF GUIDANCE TO THE SOUTHWEST.
   C. AFTER TAU 72, THE BREAK IN THE STR RESULTS IN THE STR TO THE
EAST TAKING OVER AS THE PRIMARY STEERING MECHANISM, SENDING TY
SURIGAE POLEWARD AS IT TRACKS AROUND THE WESTERN PERIPHERY OF THIS
RIDGE. THE ENVIRONMENTAL CONDITIONS WILL BECOME SLIGHTLY LESS
FAVORABLE AS THE AMOUNT OF UPPER-LEVEL DIVERGENCE DECREASES AND SEA
SURFACE TEMPERATURES LOWER THROUGH THE END OF THE FORECAST PERIOD.
THE SYSTEM WILL DECREASE DOWN TO 100KTS BY TAU 120. NUMERICAL MODEL
CROSS-TRACK SPREAD IS 290NM AT TAU 120 AS THE TWO SOLUTIONS
DESCRIBED ABOVE DIVERGE FURTHER, LENDING LOW CONFIDENCE TO THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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