WDPS32 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11P (OSAI)
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8S 164.6W
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 312 NM EAST-NORTHEAST OF NIUE
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 11P (OSAI) HAVING BEGUN EXPERIENCING STRONG (20-25KTS)
VERTICAL WIND SHEAR (VWS) OVER THE PAST SIX HOURS, WITH CENTRALIZED
DEEP CONVECTION OFFSET EASTWARD OF THE LOW LEVEL CIRCULATION CENTER
IN A 071800Z HIMAWARI-9 VISIBLE SATELLITE IMAGE. HIGH (29C) SEA
SURFACE TEMPERATURES AND MODERATE DIVERGENCE ALOFT ARE OFFSET BY A
TILTED VORTEX (SOUTHEASTWARD WITH HEIGHT) AND THE AFOREMENTIONED
STRONG VWS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON 071700Z SSMIS 37GHZ AND 89GHZ MICROWAVE SATELLITE IMAGERY.
THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NER TO THE NORTHWEST AND STR TO THE
SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 55 KTS AT 071740Z
   CIMSS AIDT: 44 KTS AT 071940Z
   CIMSS DPRINT: 40 KTS AT 072000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 11P IS FORECAST TO TRACK
SOUTH-SOUTHEASTWARD THROUGH TAU 24, FOLLOWING THE STEERING
INFLUENCE OF A WEAK STR TO THE SOUTHWEST. THE AFOREMENTIONED STRONG
VWS IS ANTICIPATED TO GRADUALLY WEAKENING THE SYSTEM DESPITE
FAVORABLE SST AND DIVERGENCE ALOFT, COMING TO A FORECASTED
INTENSITY OF 40KTS BY TAU 24. AFTER TAU 24, A BUILDING STR SOUTH OF
THE LLCC WILL CAUSE THE SYSTEM TO TURN EASTWARD TO TAU 36 AND THEN
STAY ON AN EASTWARD TRACK THROUGH DISSIPATION PRIOR TO TAU 48.
SEVERAL MEMBERS OF THE JTWC INTENSITY CONSENSUS SHOW A POTENTIAL
FOR REINTENSIFICATION TO 35KTS OR ABOVE SOMETIME AFTER TAU 48, 
RANGING FROM TAU 48 TO TAU 120. FURTHER ANALYSIS OF THE ENVIRONMENT 
AND MODEL GUIDANCE ON THE NEXT WARNING MAY EXTEND THE FORECAST OF TC 
11P AS CONDITIONS WARRANT.

MODEL DISCUSSION: GLOBAL NUMERICAL GUIDANCE IS IN EXCEPTIONAL
AGREEMENT THROUGH TAU 12, AND THEN MEMBERS OF THE JTWC CONSENSUS
SHARPLY DIVERGE FROM ON ANOTHER OFFERING SEVERAL DIFFERENT
SOLUTIONS THEREAFTER. MOST MEMBERS TURN THE SYSTEM EASTWARD BETWEEN
TAU 24 AND TAU 36, AS THE JTWC FORECAST RESPECTIVELY SHOWS. THE GFS
ENSEMBLE MEAN SUGGESTS A WESTWARD TRACK NEAR TAU 24, AND THE ECMWF
ENSEMBLE MEAN SUGGESTS AN EXTENSION OF THE SOUTH-SOUTHEASTWARD
TRACK THROUGH TAU 36 BEFORE EVENTUALLY TURNING EASTWARD AFTER THE
FORECAST INTERVAL. INTENSITY GUIDANCE IS IN BETTER AGREEMENT THAN
TRACK GUIDANCE, BUT STILL YIELDS MODERATE UNCERTAINTY.  THE
INTENSITY SPREAD, EXCLUDING STATISTICAL-DYNAMICAL GUIDANCE, AT TAU
48 IS 10 KTS CENTERED AROUND 30 KTS.

FORECAST CONFIDENCE:
   TRACK 0 - 48 HR: LOW
   INTENSITY 0 - 48 HR: MEDIUM//
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