WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.5N 135.6E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 445 NM NORTH-NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT TY NYATOH
CONTINUES TO VALIANTLY IN AN ATTEMPT TO ESTABLISH AN EYE. OVER THE
PAST SIX HOURS, A TRANSIT, RAGGED EYE HAS BRIEFLY BEEN EVIDENT IN
THE MSI AND INFRARED IMAGERY, BUT HAS FAILED TO PERSIST FOR MORE
THAN AN HOUR OR SO. VORTICAL HOT TOWERS (VHT) WITH CLOUD TOPS
COLDER THAN (-90C) CONTINUE TO FLARE UP ALONG THE WESTERN AND
SOUTHERN PERIPHERY OF THE CENTER, PROVIDING STRONG INDICATIONS THAT
THE APPEARANCE OF THE EYE MAY BE IMMINENT. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE NASCENT EYE FEATURE SEEN
IN THE 0000Z MSI AND IR IMAGERY, THOUGH SUBSEQUENT IMAGERY SUGGESTS
THE EYE FEATURE HAS ONCE AGAIN DEGRADED. THE INITIAL INTENSITY OF
80 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, CONSISTENT WITH THE
AVERAGE OF AGENCY CURRENT INTENSITY ESTIMATES BETWEEN T3.5 AND
T5.0. OF NOTE, THE ADT CONTINUES TO USE THE UNIFORM CDO SCENE TYPE,
LEADING TO AN UNREALISTICALLY LOW ESTIMATE, WHICH IS ALSO DRAGGING
DOWN THE SATCON ESTIMATE, BOTH OF WHICH HAVE BEEN DISREGARDED IN
THIS ANALYSIS. THE SYSTEM IS TRACKING NORTHWARD ALONG THE WESTERN
PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR), THROUGH A
FAVORABLE ENVIRONMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER STR
CENTERED FAR TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 65 KTS AT 012243Z
   CIMSS ADT: 61 KTS AT 012340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: WHILE TY 27W HAS YET TO DEVELOP A DISCRETE
AND PERSISTENT EYE FEATURE, IT HAS STILL MANAGED TO STEADILY,
ALBEIT, SLOWLY INTENSIFY UNDER HIGHLY FAVORABLE CONDITIONS OF LOW
VWS, WARM SSTS AND EXTREMELY ROBUST POLEWARD OUTFLOW.  THE
ALIGNMENT OF FAVORABLE CONDITIONS IS NOT EXPECTED TO LAST FOR MUCH
LONGER HOWEVER, AND THE LIMITED TIME LEFT BEFORE CONDITIONS
DETERIORATE WILL LIMIT THE ULTIMATE PEAK INTENSITY. THE SYSTEM IS
FORECAST TO INTENSIFY TO 95 KNOTS WITHIN THE NEXT 12 HOURS, THEN
MAINTAIN THAT INTENSITY THROUGH TAU 24. BASED ON MODEL
CROSS-SECTIONS AND ANIMATED WATER VAPOR IMAGERY, DRY AIR ASSOCIATED
WITH ROBUST NORTHERLY FLOW ON THE WESTERN SIDE OF THE CIRCULATION
IS ALREADY BEGINNING TO WRAP INTO THE CORE FROM THE SOUTH. THIS
TREND IS EXPECTED TO CONTINUE AND STRENGTHEN FROM HERE ON OUT. AT
THE SAME TIME, WHILE VWS IS CURRENTLY LOW DUE TO THE PRESENCE OF A
STRONG SECONDARY CIRCULATION ALOFT, SHEAR IS FORECAST TO INCREASE
SHARPLY AFTER TAU 18. COMBINED, THESE FACTORS WILL SERVE TO BOTH
DECAPITATE AND DRY OUT THE SYSTEM, LEADING TO RAPID WEAKENING AFTER
TAU 24. AS THE SYSTEM WEAKENS, IT WILL SLOW DOWN AS IT APPROACHES
STRONG NORTHERLY FLOW ASSOCIATED WITH A STRONG HIGH PRESSURE SYSTEM
OVER EASTERN CHINA. AFTER TAU 48, THE SYSTEM WILL BE UNDER
EXTREMELY HIGH SHEAR (50+ KTS) AND DRY AIR WILL ENVELOPE THE ENTIRE
COLUMN ABOVE 850MB, LEADING TO VERY RAPID DISSIPATION BY TAU 96.
WHILE DISSIPATING, THE REMNANT VORTEX WILL TURN SHARPLY SOUTHWARD
UNDER THE INFLUENCE OF THE LOW LEVEL FLOW FROM THE NORTH-NORTHEAST.


MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU
36, WITH ALL CONSENSUS MEMBERS IN A TIGHT, 65NM ENVELOPE. HOWEVER
BY TAU 48, MODELS BEGIN TO SHARPLY DIVERGE IN ALONG TRACK SPEED,
WITH THE GFS AND NAVGEM IN PARTICULARLY SLOWING SIGNIFICANTLY AND
BEGINNING THE SHARP TURN SOUTHWARD BY TAU 48, WHILE THE REMAINDER
OF THE GUIDANCE CONTINUES THE NORTHEAST TRACK FOR ANOTHER 12 TO 24
HOURS. ALL REMAINING MEMBERS EXCEPT GALWEM AND EGRR TURN THE SYSTEM
SOUTHWARD BETWEEN TAUS 60 AND 72, WHILE THE GFS AND GFS ENSEMBLE
RACE THE SYSTEM SOUTHWESTWARD AT HIGH SPEED THROUGH TAU 72 AND
LATER. THE JTWC FORECAST TRACK FOLLOWS THE CONSENSUS MEAN THROUGH
TAU 36, THEN MOST CLOSELY TRACKS THE UKMET AND NAVGEM SOLUTIONS
THROUGH THE REMAINDER OF THE FORECAST. OVERALL CONFIDENCE IS MEDIUM
IN THE NEAR-TERM AND LOW AFTER TAU 48 DUE TO THE DIVERGENCE IN THE
GUIDANCE AND THE UNCERTAINTY OF THE TIMING AND STRENGTH OF THE TURN
SOUTHWARD. INTENSITY GUIDANCE REMAINS MIXED, WITH THE HWRF
CONTINUING IN ITS ATTEMPT TO RAPIDLY INTENSIFY THE SYSTEM TO A PEAK
OF 105 KTS BY TAU 24. THE REMAINDER OF THE GUIDANCE PACKAGE PEAKS
BETWEEN 80-90 KTS, FOLLOWED BY A RAPID AND DRAMATIC WEAKENING
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE JTWC FORECAST
LIES 10 KTS HIGHER THAN THE CONSENSUS MEAN THROUGH TAU 24 AND ABOUT
FIVE KTS HIGHER THEREAFTER WITH LOW CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN