Advisories

WDPN32 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (KUJIRA) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 141.5E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 162 NM SOUTH OF IWO TO
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 13W (KUJIRA) REGAINING A WELL-DEFINED LOW-LEVEL CIRCULATION 
CENTER (LLCC) AFTER A LONG TREK OF THE REMNANT VORTICITY ALL THE WAY 
FROM LUZON. THE MSI SHOWS A COMPACT, PARTIALLY EXPOSED LLCC WITH 
BURSTS OF CONVECTION PRIMARILY LOCATED WITHIN THE SOUTHEASTERN 
QUADRANT. A 082105Z F17 SSMIS 91 GHZ MICROWAVE IMAGE REVEALED THE LOW-
LEVEL CLOUD LINES TIGHTLY WRAPPING INTO THE COMPACT CORE WITH A 
FRAGMENTED BAND OF CONVECTION ALONG THE SOUTHERN SEMICIRCLE. THE 
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY 
EXPOSED LLCC IN ANIMATED MSI. THE INITIAL INTENSITY OF 25 KTS IS 
ASSESSED WITH LOW CONFIDENCE DUE TO THE LACK OF AGENCY DVORAK AND 
CIMSS OBJECTIVE ESTIMATES. ENVIRONMENTAL ANALYSIS INDICATES THAT 13W 
IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG 
EASTWARD AND EQUATORWARD OUTFLOW ALOFT, LOW TO MODERATE (15-20 KTS) 
WESTERLY VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE 
TEMPERATURES.

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

CURRENT STEERING MECHANISM: THE COMBINED INFLUENCE OF AN ELONGATED
NEAR-EQUATORIAL RIDGE (NER) AND A BELT OF STRONG LOW-LEVEL
WESTERLIES TO THE SOUTH OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS D-PRINT: 27 KTS AT 090000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EASTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: AVAILABLE METEOROLOGICAL DATA SUPPORTS 
THE REGENERATION OF TD 13W, THEREFORE, JTWC IS RESUMING WARNINGS. 
THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST 
PHILOSOPHY. 

FORECAST DISCUSSION: TD 13W IS FORECAST TO TRACK EAST-SOUTHEASTWARD
THROUGH TAU 24 UNDER THE INFLUENCE OF THE NER AND LOW-LEVEL WESTERLIES 
TO THE SOUTH. AFTER TAU 24, 13W IS EXPECTED TO BEGIN TURNING POLEWARD 
AS IT FOLLOWS A LARGE-SCALE CYCLONIC FLOW ASSOCIATED WITH TS 13W ALONG 
WITH THE WESTERN EXTENT OF A BUILDING NER POSITIONED NEAR 20N 165E. TD 
13W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 36 DUE TO AN 
ENHANCED POLEWARD OUTFLOW CHANNEL CAUSED BY AN INTERACTION WITH AN 
UPPER-LEVEL TROUGH TO THE NORTH OF THE SYSTEM. VERTICAL WIND SHEAR IS 
EXPECTED TO REMAIN LOW TO MODERATE, HOWEVER, THIS IS HIGHLY DEPENDENT 
ON THE POSITION OF THE UPPER-LEVEL TROUGH RELATIVE TO 13W. IF THE 
TROUGH DIGS DOWN FURTHER EQUATORWARD, THERE COULD BE MORE SHEAR ACTING 
ON THE SYSTEM, LEADING TO LESS INTENSIFICATION. AS IT STANDS, A PEAK 
INTENSITY OF AROUND 40 KTS IS FORECAST TO OCCUR NEAR TAU 36. AFTER TAU 
36, 14W IS FORECAST TO BEGIN WEAKENING AS DRY AIR BEGINS TO ENTRAIN 
INTO THE VORTEX FROM THE WEST AND SOUTHWESTERLY VERTICAL WIND SHEAR 
INCREASES. DISSIPATION IS FORECAST TO OCCUR AROUND TAU 72, BUT THIS 
REMAINS UNCERTAIN DUE TO THE SMALL NATURE OF THE VORTEX BEING MORE 
SUSCEPTIBLE TO THE SURROUNDING ENVIRONMENT. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH A CROSS-TRACK SPREAD
OF 220 NM AT TAU 72 AND NO NOTABLE OUTLIERS. THE JTWC TRACK FORECAST 
IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. 
INTENSITY GUIDANCE AGREES ON INTENSIFICATION THROUGH TAU 36 FOLLOWED 
BY GRADUAL WEAKENING THEREAFTER. PEAK INTENSITIES ARE ALL AROUND 40-45 
KTS. THE MOST UNCERTAINTY COMES AFTER TAU 60, WHERE MANY MODELS SHOW 
13W MAINTAINING AN INTENSITY OF ABOVE 25 KTS FOR LONGER THAN THE 
FORECASTED 72 HOURS. THE JTWC INTENSITY FORECAST IS PLACED LOWER THAN 
MODEL GUIDANCE SUGGESTS AFTER TAU 60 DUE TO THE EXPECTED HOSTILE 
ENVIRONMENT. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY 
FORECAST.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: LOW//
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