WDPS31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23P (URMIL) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.7S 170.0E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 154 NM SOUTHEAST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A HIGHLY
OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC) WITH PERSISTENT DEEP
CONVECTION SLIGHTLY OFFSET TO THE EAST AND SOUTHEAST. ENVIRONMENTAL
CONDITIONS ARE CURRENTLY FAVORABLE WITH LOW VERTICAL WIND SHEAR
(VWS)  (10-15 KTS), WARM SEA SURFACE TEMPERATURES (28 C TO 29 C),
AND MODERATE POLEWARD AND EQUATORWARD OUTFLOW. THROUGHOUT THE
WESTERN SEMICIRCLE, THE AFOREMENTIONED MID-LEVEL VWS AND DRY AIR
HAS BECOME EVIDENT OVER THE LAST SIX HOURS, LEAVING MUCH OF THE
REGION CONVECTION FREE. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON EXTRAPOLATION FROM A 271756Z WSFM 89 GHZ
MICROWAVE IMAGE DIRECTLY OVER THE LLCC. THE INITIAL INTENSITY OF 60
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 271819Z RCM-1 SAR
DATA.

INITIAL WIND RADII BASIS: 271420Z AMSR2 DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   PHFO: T3.5 - 55 KTS
   CIMSS SATCON: 55 KTS AT 271530Z
   CIMSS ADT: 63 KTS AT 271900Z
   CIMSS AIDT: 55 KTS AT 271900Z
   CIMSS D-MINT: 38 KTS AT 271659Z
   CIMSS D-PRINT: 56 KTS AT 271800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: SHORTWAVE TROUGH PASSING SOUTH OF TC 23P CENTER,
SLOWLY INTRODUCING MODERATE MID-LEVEL WESTERLY SHEAR

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 23P (URMIL) WILL
CONTINUE SOUTHEASTWARD FOR THE REMAINDER OF THE FORECAST PERIOD
UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE (STR) POSITIONED TO
THE NORTHEAST. OVER THE NEXT 24 HOURS THE CIRCULATION WILL CONTINUE
TO GRADUALLY INTENSIFY AS IMPROVING OUTFLOW AND LOW VERTICAL WIND
SHEAR ENHANCE THE VORTEX STRUCTURE AFTER ITS EAST-SOUTHEASTWARD
TRACK OVER THE SOUTHERN ISLES OF VANUATU. THIS IMPROVEMENT WILL BE
SHORT LIVED AS THE SYSTEM WILL TRACK OVER COOLER SEA SURFACE
TEMPERATURES (26 C TO 27 C) BY TAU 36, WHILE BECOMING UNFAVORABLY
IMPACTED BY WESTERLY JET FLOW TO THE SOUTH AND DRY AIR ENTRAINMENT
AROUND THE NORTHERN QUADRANT. ENVIRONMENTAL CONDITIONS WILL
INITIATE SUBTROPICAL TRANSITION BY TAU 36, WITH SUBTROPICAL
TRANSITION COMPLETING BY TAU 48. 

MODEL DISCUSSION: MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE
CONTINUED SOUTHEASTWARD TRACK OF 23P AS IT IS DRIVEN POLEWARD BY
THE STR TO THE NORTHEAST. CROSS TRACK SPREAD IS 90 NM BY TAU 48.
THE JTWC FORECASTED TRACK IS PLACED CLOSE TO THE MULTI MODEL
CONSENSUS WITH MEDIUM CONFIDENCE, ACCOUNTING FOR SOME UNCERTAINTY
REGARDING THE TIMING OF IMPACTS FROM THE MID-LATITUDE WESTERLY FLOW
TO THE SOUTH. INTENSITY GUIDANCE CONTINUES TO AGREE ON A SHORT TERM
WINDOW FOR INTENSIFICATION UNTIL TAU 24, WITH A TERMINAL WEAKENING
TREND THEREAFTER. THE JTWC FORECASTED INTENSITY IS PLACED SLIGHTLY
ABOVE THE MULTI MODEL CONSENSUS WITH MEDIUM CONFIDENCE, ACCOUNTING
FOR THE FORECASTED POLEWARD OUTFLOW, AND SHORT WINDOW OF
INTENSIFICATION OVER THE NEXT 24 HOURS.

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