Advisories

WDPN32 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (PEILOU) 
WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.4N 162.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 534 NM NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 13W (PEILOU) WITH A TIGHTLY COILED LOW-LEVEL CIRCULATION
CENTER PEAKING OUT FROM BENEATH THE NORTHERN EDGE OF A CLUMP OF
DEEP CONVECTION. VERTICAL SHEAR IS BEGINNING TO INCREASE OUT OF THE
NORTHWEST AT 10-15 KT, WITH UPPER-LEVEL OUTFLOW VISIBLY RESTRICTED
ON THAT SIDE. THE REMNANTS OF 15W CAN BE SEEN ROTATING SOUTHWARD
AROUND THE WESTERN SIDE OF 13W, MANIFESTING AS A TROUGH EXTENSION
TOWARDS THE WEST. THE STORM IS APPROACHING A BAROCLINIC LOW TO THE
NORTHEAST, BUT REMAINS WELL SOUTH OF THE ASSOCIATED THERMAL
BOUNDARY. THE INITIAL INTENSITY IS HELD AT 30 KT BASED ON AGENCY
DVORAK INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: MONSOONAL SOUTHWESTERLY FLOW BELT ALONG
THE NORTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T2.0 - 30 KTS
   CIMSS D-PRINT: 38 KTS AT 112300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 26-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL DEPRESSION 13W (PEILOU) CONTINUES TO
TRACK NORTHEASTWARD WITHIN THE EXTENDED SOUTHWESTERLY MONSOON BELT.
THE STORM IS APPROACHING A BAROCLINIC LOW TO ITS NORTHEAST, AND IS
LIKELY TO ULTIMATELY WASH OUT WITHIN ITS MUCH BROADER CIRCULATION
DURING THE NEXT 24 TO 36 HOURS. ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO MARKEDLY DETERIORATE, WITH SEA SURFACE TEMPERATURES
DECREASING TO 26C TO 27C AND NORTHWESTERLY VERTICAL SHEAR STEADILY
INCREASING TO MORE THAN 30 KT IN ABOUT 24 HOURS AS THE SUBTROPICAL
JET STRENGTHENS OVERHEAD. WEAKENING OF 13W IS THUS FORECAST TO BEGIN 
IN 12 HOURS, A LITTLE LATER THAN PREVIOUSLY ANTICIPATED DUE TO THE
PERSISTENT LOW-LEVEL CIRCULATION AND ASSOCIATED CONVECTIVE CORE
DURING THE PAST SIX HOURS. THE FORECAST NOW EXTENDS TO 36 HOURS TO
ACCOUNT FOR NUMERICAL MODELS MAINTAINING A WELL-DEFINED CIRCULATION
FOR SLIGHTLY LONGER THAN BEFORE, BUT DISSIPATION COULD OCCUR
SOONER.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS, LEANING TOWARDS AI-BASED MEMBERS, WITH THE
OVERALL GUIDANCE PACKAGE IN GOOD AGREEMENT. THE JTWC INTENSITY
FORECAST RUNS BELOW THE MODEL CONSENSUS DUE TO ITS MEMBERS
ERRONEOUSLY INCORPORATING THE BROADER WIND FIELD OF THE NEARBY
BAROCLINIC LOW.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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