WDPS31 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08P (PITA) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.9S 167.6W
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 139 NM EAST-SOUTHEAST OF NIUE
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 27 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE 08P (PITA) IS RUNNING THE SHOOT THROUGH THE
SOUTHERN PACIFIC CONVERGENCE ZONE (SPCZ). TWO SCATTEROMETRY PASSES
AT 100926Z AND 102035Z VERIFY THAT GALE FORCE WINDS EXTENDED OVER
MULTIPLE SECTORS OF THE STORM. AGENCY DVORAKS ARE WIDELY SCATTERED
AND MOSTLY ABOVE WHAT THE SCATTEROMETRY SUPPORTS BUT IT IS CLEAR
THAT THE SYSTEM CONSOLIDATED IN THE SPCZ OVERNIGHT AND DEEPENED TO
TROPICAL STORM STRENGTH. THE LATEST DVORAKS FROM JTWC AND THE RSMC
IN FIJI HAVE ALIGNED AND ARE COHERENT WITH THE SCATTEROMETRY.
CONVECTION HAS ORGANIZED AROUND ALL SIDES OF THE LOW LEVEL
CIRCULATION CENTER (LLCC) AND THE JTWC FIX PLACES THE LLCC AT THE
UPSHEAR SIDE OF THE CONVECTIVE MASS. 08P EXISTS IN A NARROW BUT
FAVORABLE ENVIRONMENT THAT WILL ALLOW IT TO MAINTAIN INTENSITY AS
IT RUNS TO THE EAST-SOUTHEAST. ANIMATED WATER VAPOR IMAGERY REVEALS
SOME IMPINGEMENT TO OUTFLOW ON THE POLEWARD SIDE BUT FAVORABLE
OUTFLOW TO THE EQUATORWARD SIDE.

INITIAL WIND RADII BASIS: 102035Z ASCAT.

CURRENT STEERING MECHANISM: THE SPCZ

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T4.0 - 65 KTS
   NFFN: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 18-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 08P WILL RUN RAPIDLY DOWN THE SPCZ FOR THE
FIRST 48 HOURS BEFORE IT IS OVERCOME BY WESTERLY VERTICAL WIND
SHEAR (VWS) AND SPINS OFF AND WEAKENS NEAR THE TROPIC OF CAPRICORN,
WELL CLEAR OF ANY ISLAND NATIONS AND SHIPPING ROUTES. ALTHOUGH THE
SYSTEM MAY HAVE ALREADY PEAKED, THE ENVIRONMENT ALONG TRACK IS
HOMOGENEOUS ENOUGH TO SUSTAIN THE SYSTEM AT ITS CURRENT INTENSITY
FOR THE FIRST 48 HOURS. SEA SURFACE TEMPERATURES ALONG TRACK WILL
HOLD ABOVE 27C THROUGHOUT AND COUPLE WITH SLOWLY RISING VWS TO
CAUSE A DISSIPATION OVER WATER SCENARIO. 

MODEL DISCUSSION: MODEL GUIDANCE IS JUST COMING IN AFTER A LATE
START. THE SPCZ TRACK IS SIMPLE AND AIDS ARE CONSISTENT IN SHOWING
THE LLCC BREAK OFF AND SPIN DOWN JUST AFTER TAU 48.  THE JTWC TRACK
FORECAST STICKS CLOSE TO THE MULTI-MODEL CONSENSUS IN BOTH TRACK
AND INTENSITY. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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