Tropical Storm KUJIRA Advisory 9月27日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 15W (FIFTEEN), LOCATED APPROXIMATELY 409
NM WEST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 11 KNOTS (KTS)
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC)
WITH PERSISTENT CONVECTION IN THE SOUTHERN AND EASTERN SEMICIRCLES.
OVER THE PAST SIX HOURS, CONVECTION HAS BEGUN TO BUILD OVERHEAD THE
LLCC. A 261757Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALS CONVECTIVE
BANDING WRAPPING INTO THE LLCC FROM THE SOUTH AND THE EAST, LENDING
GOOD CONFIDENCE TO THE INITIAL POSITION. FURTHERMORE, THIS MICROWAVE
IMAGE REVEALS A LACK OF DEEP CONVECTION OVER THE NORTHWESTERN
QUADRANT WHICH IS BEING INHIBITED BY AN UPPER LEVEL LOW POSITIONED
TO THE NORTHWEST. DESPITE THE EFFECTS OF THE UPPER LEVEL LOW, TD 15W
IS IN AN OVERALL MARGINALLY FAVORABLE ENVIRONMENT AS A POINT SOURCE
DIRECTLY OVERHEAD IS ENHANCING UPPER LEVEL DIFFLUENCE. THE INITIAL
INTENSITY IS ASSESSED AT 25 KTS BASED ON MULTI-AGENCY DVORAK CURRENT
INTENSITY ESTIMATES OF T1.5 (25 KTS) BY PGTW, RJTD, AND KNES ALONG
WITH A SWATH OF 25-29 KT WINDS WITHIN THE EASTERN QUADRANT OF THE
SYSTEM OBSERVED IN A 261054Z METOP-C ASCAT IMAGE. TD 15W IS
EXPERIENCING LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS)
AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST). TD 15W IS
TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE FOR THIS
SYSTEM AND SETS THE FORECAST PHILOSOPHY.
   B. TD 15W IS FORECAST TO TRACK NORTH-NORTHWESTWARD THROUGH TAU 36
AS IT STEADILY INTENSIFIES. THE SYSTEM WILL BEGIN TO TURN TO A
GENERALLY NORTHWARD TRACK THROUGH TAU 48 AND THEN RECURVE NORTH-
NORTHEASTWARD THROUGH TAU 72 AS THE SYSTEM ROUNDS THE STR AXIS. THIS
RECURVE IS ENHANCED BY A DEEP MIDLATITUDE TROUGH APPROACHING FROM
THE EAST. THROUGH THE RECURVE, TD 15W SHOULD STEADILY INTENSIFY TO
75 KTS BY TAU 72 DUE TO CONTINUED LOW VWS AND WARM SST. HOWEVER, THE
SYSTEM'S PEAK INTENSITY MAY BE SLIGHTLY HIGHER AND OCCUR PRIOR TO
TAU 72, AROUND TAU 60. INTERACTION WITH THE MIDLATITUDE TROUGH AND
THE BAROCLINIC ZONE WILL CAUSE TD 15W TO BEGIN EXTRATROPICAL
TRANSITION (ETT) BY TAU 72. NUMERICAL MODEL GUIDANCE SHOWS TIGHT
AGREEMENT IN THE NEAR TERM, WITH THE MAXIMUM (123 NM) CROSS-TRACK
SPREAD OCCURRING AT TAU 36 AND THEN DECREASING THROUGH TAU 72.
OVERALL, THERE IS HIGH CONFIDENCE IN THE NEAR TERM JTWC TRACK
FORECAST DUE TO LOW ALONG-TRACK SPREAD AND GOOD AGREEMENT IN THE
TIMING OF THE RECURVE BETWEEN MODEL SOLUTIONS.
   C. AFTER TAU 72, INCREASING VERTICAL WIND SHEAR AND COOLING (<26
CELSIUS) SST WILL CAUSE THE SYSTEM TO STEADILY WEAKEN THROUGH THE
REMAINDER OF THE FORECAST PERIOD. TD 15W WILL TURN TO AN EAST-
NORTHEASTWARD TRACK AFTER TAU 72, TRACKING ALONG THE PERIPHERY OF
THE AFOREMENTIONED STR. BY TAU 96, THE SYSTEM WILL WEAKEN TO 45 KTS
AND COMPLETE ETT, GAINING FRONTAL CHARACTERISTICS AS IT BECOMES
EMBEDDED IN THE JET FLOW. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT THROUGH THE EXTENDED FORECAST WITH A 100 NM SPREAD AT TAU
72. ADDITIONALLY, THE ECMWF ENSEMBLE SOLUTIONS ARE IN EXCELLENT
AGREEMENT, PLACING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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