WDPS31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01P (LOLA) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.1S 167.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 83 NM WEST-NORTHWEST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
DISORGANIZED AND CLEARLY WEAKENING TROPICAL CYCLONE (TC), WITH TWO
LOBES OF CONVECTION ORIENTED ALONG AN EAST-WEST AXIS. THE EASTERN
LOBE CENTERED ROUGHLY ON EPI ISLAND, IS THE STRONGEST DISPLAYING
INTENSE LIGHTNING ACTIVITY AND VERY COLD CLOUD TOPS. THE WESTERN LOBE
WEST OF MALEKULA ISLAND IS MUCH LESS IMPRESSIVE, WITH ONLY WEAK
CONVECTION AND MINIMAL LIGHTNING ACTIVITY. ANALYSIS OF A 250606Z GMI
PASS INCLUDING BOTH THE 37GHZ AND 89GHZ BANDS SUGGESTS THE SYSTEM
IS STRONGLY TILTED WITH A WEAK UPPER-LEVEL EYE DISPLACED TO EAST OF
A WEAKLY DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS ASSESSED WITH LOW CONFIDENCE, EVEN WITH THE
HIGH-RESOLUTION MICROWAVE IMAGERY, AS THE LOWER-LEVEL BANDING
FEATURES ARE ILL-DEFINED AND WEAK AND THE WHOLE ROTATION IS
OBSCURED BY THE RAGGED AND DISORGANIZED CDO. THE INITIAL INTENSITY
IS ASSESSED WITH MEDIUM CONFIDENCE, HEDGED LOWER THAN THE AGENCY
CURRENT INTENSITY ESTIMATES, IN LIGHT OF THE LOWER CIMSS OBJECTIVE
ESTIMATES. THE ENVIRONMENT IS RAPIDLY DETERIORATING AS EXPECTED,
WITH THE LATEST CIMSS DEEP-LAYER SHEAR ANALYSIS INDICATING 16 KNOTS
OF WESTERLY SHEAR, WHILE THE LATEST GFS MODEL SOUNDING SHOWS 40
KNOTS OF MID-LEVEL SOUTHWESTERLY SHEAR. ANALYSIS OF THE MICROWAVE
IMAGERY SUGGESTS THESE VALUES ARE IN GENERAL ACCURATE AND THE
SYSTEM IS IN THE PROCESS OF DECOUPLING. AT THE SAME TIME IT IS
CROSSING THE 26C ISOTHERM, AND DRY AIR IS BEGINNING TO MOVE IN FROM
THE WEST ABOVE THE 500MB LEVEL, SETTING THE STAGE FOR AN IMMINENT
ONSET OF EXTREMELY RAPID WEAKENING.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR SAMOA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   PHFO: T5.0 - 90 KTS
   CIMSS SATCON: 68 KTS AT 250302Z
   CIMSS ADT: 69 KTS AT 250530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: STRONG MID-LEVEL SHEAR AND DRY AIR

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 01P (LOLA) IS FORECAST TO CONTINUE TRACKING
TOWARDS THE SOUTHWEST THROUGH THE FIRST 24 HOURS OF THE FORECAST,
ALONG THE SOUTHWEST SIDE OF THE STEERING RIDGE TO THE EAST. THE
ONSET OF RAPID WEAKENING IS IMMINENT AS THE STRONG MID-LEVEL SHEAR
IS ANTICIPATED TO INCREASE AND USHER IN A PULSE OF VERY DRY
MID-LEVEL AIR, WHICH COMBINED WITH THE SIGNIFICANT REDUCTION IN
SST, WILL DECAPITATE THE SYSTEM AND SMOTHER ANY POSSIBILITY OF
CONVECTION DEVELOPMENT. BY TAU 24, THE LLCC IS EXPECTED TO BE FULLY
EXPOSED AND DEVOID OF SIGNIFICANT CONVECTION. AS THIS PROCESS
OCCURS, THE STEERING LEVEL WILL RAPIDLY SHIFT TO LOWER LEVELS OF
THE ATMOSPHERE, AND AFTER TAU 24, THE SYSTEM WILL COME UNDER THE
STEERING INFLUENCE OF A LOW-LEVEL ANTICYCLONE TO THE EAST-SOUTHEAST
AND BY TAU 36 WILL TURN SOUTH TOWARDS NEW CALEDONIA. THE REMNANT
VORTEX IS EXPECTED TO TRACK OVER NEW CALEDONIA WHILE CONTINUING TO
WEAKEN, ULTIMATELY DISSIPATING BELOW WARNING CRITERIA JUST SOUTH OF
THE ISLAND BY TAU 48. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE
SHORT DURATION OF THE FORECAST, WITH ALL CONSENSUS MEMBERS CONFINED
TO GRADUALLY EXPANDING ENVELOPE THAT REACHES JUST 100NM BY TAU 48.
THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN THROUGH THE
DURATION OF THE FORECAST WITH MEDIUM CONFIDENCE DUE TO THE
UNCERTAINTY IN THE INITIAL POSITION. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT WITH ALL MODELS INDICATING RAPID WEAKENING THROUGH THE
FORECAST PERIOD, THOUGH SOME GUIDANCE SUGGESTS IT COULD WEAKEN TO
BELOW WARNING THRESHOLD AS EARLY AS TAU 36. THE JTWC FORECAST IS
SET ON THE HIGHER SIDE OF THE GUIDANCE WITH MEDIUM CONFIDENCE. 

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