Tropical Storm SURIGAE Advisory Tue Apr 13

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (TWO) WARNING
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
    TROPICAL DEPRESSION (TD) 02W (TWO), LOCATED APPROXIMATELY  107 NM
SOUTH-SOUTHWEST OF YAP, HAS TRACKED NORTHWESTWARD AT 06 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
SHOWS THE SYSTEM HAS FURTHER DEVELOPED AS THE MAIN FEEDER BAND,
STRETCHED ALONG THE NORTHERN PERIPHERIES, SIGNIFICANTLY CONSOLIDATED
AND WRAPPED TIGHTER INTO A MORE COMPACT AND DEEP CENTRAL DENSE
OVERCAST. THE INITIAL POSITION AND INTENSITY OF 25KTS ARE
EXTRAPOLATED WITH GOOD CONFIDENCE FROM A 130907Z HY-2 SCATTEROMETER
BULLSEYE PASS AND SUPPORTED BY THE DVORAK ESTIMATES OF T1.5/25KTS
FROM PGTW AND RJTD. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT
INCLUDING ROBUST RADIAL OUTFLOW WITH A STRONG POLEWARD BIAS, LOW (05-
10KT) VERTICAL WIND SHEAR, AND VERY WARM (30-31C) SEA SURFACE
TEMPERATURE IN THE PHILIPPINE SEA. THE CYCLONE IS TRACKING  ALONG
THE NORTHWEST PERIPHERY OF A LOW REFLECTION OF THE NEAR EQUATORIAL
RIDGE TO THE EAST-SOUTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY FOR THIS SYSTEM.
   B. TD 02W WILL TRACK SLOWLY NORTHWARD OR MAY EVEN BECOME QUASI-
STATIONARY OVER THE NEXT 24HRS AS A SUBTROPICAL RIDGE (STR) TO THE
NORTHWEST BUILDS AND COMPETES FOR STEERING. AFTERWARD, A MIDLATITUDE
TROUGH DIGGING IN FROM CHINA WILL BREAK THE RIDGE. THE EASTERN SIDE
OF THE STR TO THE NORTHEAST WILL ASSUME STEERING AND DRIVE TD 02W
NORTHWESTWARD. THE AFOREMENTIONED FAVORABLE ENVIRONMENT WILL PROMOTE
STEADY INTENSIFICATION TO 70KTS BY TAU 72. NUMERICAL MODELS ARE IN
OVERALL GOOD AGREEMENT WITH A GRADUAL SPREAD TO 155NM BY TAU 72 WITH
ECMF ON THE LEFT- AND AVNO ON THE RIGHT-MARGIN OF THE ENVELOPE.
HOWEVER, GIVEN THE UNCERTAINTY IN THE INITIAL STORM MOTION SECONDARY
TO THE COMPETING STEERING MECHANISMS, THERE IS LOW CONFIDENCE IN
THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TD 02W WILL CONTINUE NORTHWESTWARD TOWARD THE
BREAK IN THE RIDGE UNDER THE STEERING INFLUENCE OF THE SAME STR. A
RAPID INTENSIFICATION IS EXPECTED AS THE FAVORABLE CONDITIONS ARE
FURTHER ENHANCED BY INCREASED POLEWARD OUTFLOW. BY TAU 120, TD 02W
WILL SURGE TO 115KTS, POSSIBLY HIGHER. NUMERICAL MODELS SPREAD OUT
EVEN MORE TO OVER 480NM BY TAU 120, LENDING LOW CONFIDENCE TO THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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