WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.5N 137.5E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 382 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 27W HAS CONTINUED ITS RAPID INTENSIFICATION TREND AND HAS
INTENSIFIED 20 KNOTS OVER THE LAST SIX HOURS, 35 KNOTS IN THE LAST
12 HOURS AND AN AMAZING 55 KNOTS IN THE PAST 24 HOURS. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 25NM RAGGED EYE
FEATURE, WITH EYE TEMPERATURES AROUND -3C AND CLOUD TOP
TEMPERATURES AT OR NEAR -83C. THE INITIAL POSITION IS ASSESSED WITH
HIGH CONFIDENCE BASED BOTH ON THE EIR EYE FEATURE AND A VERY WELL
DEFINED MICROWAVE EYE IN A 021706Z AMSR2 COLOR ENHANCED 37GHZ
MICROWAVE IMAGE. AGENCY DVORAK CURRENT INTENSITY ESTIMATES HAVE
JUMPED UP TO T6.5 (PGTW AND KNES), AND ADT FINAL T WAS T6.6. RAW
ADT VALUES HAVE BEEN RUNNING ABOVE T7.0 FOR THE PAST EIGHT HOURS,
AT TIMES MOVING ABOVE T7.5 AND A SATCON ESTIMATE AT 021604Z WAS 136
KNOTS. THE INITIAL INTENSITY IS ASSESSED AT 125 KNOTS BASED ON THE
CONGRUENCE OF THE ABOVE NOTED DATA, BUT CONFIDENCE REMAINS MEDIUM
BASED ON THE DRAMATIC INTENSIFICATION TRENDS. THE SYSTEM IS
TRACKING NORTHEASTWARD AT A FAIRLY RAPID CLIP (16 KNOTS), ALONG THE
STRONG GRADIENT BETWEEN A SUBTROPICAL RIDGE (STR) TO THE EAST AND A
STRONG MID- TO UPPER-LEVEL TROUGH TO THE WEST. FOR THE TIME BEING, 
UPPER-LEVEL OUTFLOW REMAINS ROBUST, OFFSETTING THE INCREASING
WESTERLY VWS, CURRENTLY ASSESSED AS MODERATE TO HIGH (25-35 KTS)
AND THE ENCROACHMENT OF MID-LEVEL DRY AIR.

INITIAL WIND RADII BASIS: PERSISTENCE WITH EARLIER SCATTEROMETER
DATA. 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF DEEP-LAYER
SUBTROPICAL RIDGE TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 136 KTS AT 021609Z
   CIMSS ADT: 132 KTS AT 021740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT FROM THE WEST. 

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: TY 27W HAS UNDERGONE AN IMPRESSIVE PERIOD OF
EXTREMELY RAPID INTENSIFICATION OF AT LEAST 55 KNOTS IN THE PAST 24
HOURS. HOWEVER, THE SYSTEM HAS LIKELY REACHED ITS PEAK INTENSITY,
AS ANIMATED EIR IS BEGINNING TO SHOW THE CLOUD STRUCTURE BECOMING
INCREASINGLY RAGGED, PARTICULARLY ON THE NORTHERN SIDE. CIMSS VWS
ANALYSIS CONFIRMS THE HWRF AND GFS MODEL-DERIVED HODOGRAPHS AND
SKEW-T, WHICH INDICATE SHARPLY INCREASING SHEAR, WITH A COLUMN
AVERAGE OF 33 KNOTS AND A MAXIMUM NEAR 40 KNOTS IN THE MID-LEVELS.
ADDITIONALLY, HWRF CROSS-SECTIONS STRONGLY SUGGEST THE PRESENCE OF
A WEDGE OF VERY DRY MID-LEVEL AIR DIVING TOWARDS THE SURFACE AND
BEGINNING TO IMPINGE ON THE LOW LEVEL VORTEX. THESE ANALYSES MARK
THE BEGINNING OF THE END FOR TY 27W, AS SHEAR AND DRY AIR
ENCROACHMENT WILL ONLY INCREASE THROUGH THE FORECAST PERIOD. IN
FACT BY TAU 48, SHEAR VALUES ARE EXPECTED TO APPROACH 50 KNOTS,
WHILE THE ENTIRE COLUMN ABOVE 850MB WILL DRY OUT. AS THE SYSTEM
RAPIDLY INTENSIFIED, IT IS FORECAST TO JUST AS RAPIDLY WEAKEN AND
IS EXPECTED TO DISSIPATE TO JUST 20 KNOTS WITHIN THE NEXT 72 HOURS.
AS THE SYSTEM WEAKENS TO BELOW 50 KNOTS BY TAU 36, IT WILL COME
UNDER THE STEERING INFLUENCE OF THE LOWER LEVEL FLOW, AND THUS TURN
SHARPLY SOUTHWARD AFTER TAU 48, ULTIMATELY DISSIPATING WHILE MOVING
QUICKLY SOUTHWESTWARD, AHEAD OF STRONG NORTHERLY LOW LEVEL FLOW. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE
NEXT 24 TO 36 HOURS, THOUGH FORWARD SPEED HAS INCREASED BETWEEN TAU
24 AND 36 SINCE THE PREVIOUS RUN. WITH THE EXCEPTION OF EGRR AND
GALWEM, ALL MODELS CONCUR ON THE SYSTEM SLAMMING ON THE BRAKES NEAR
25N, THEN TURNING SHARPLY EQUATORWARD. THERE IS A FAIR AMOUNT OF
DISAGREEMENT ON THE TIMING OF THE TURN TO THE SOUTH, WITH HWRF AND
NAVGEM TURNING THE EARLIEST, BY TAU 24, WHILE THE REMAINDER
DELAYING THE TURN UNTIL TAU 36. AFTER THE TURN, THE GFS, HWRF AND
NAVGEM RACE THE SYSTEM SOUTHWESTWARD MUCH FASTER THAN THE REMAINDER
OF THE GUIDANCE. THE JTWC FORECAST LIES NEAR THE CENTER OF THE
ENVELOPE THROUGH TAU 24, THEN MOST CLOSELY TRACKS THE GFS
THEREAFTER, THOUGH AT A SLOWER OVERALL TRACK SPEED. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT, WITH ALL MODELS INDICATING THE
SYSTEM HAS PEAKED, AND SHOWING RAPID WEAKENING FROM ANALYSIS TIME
THROUGH THE FORECAST PERIOD. THE JTWC FORECAST IS SLIGHTLY ABOVE
THE CONSENSUS MEAN THROUGH THE DURATION OF THE FORECAST. OVERALL
CONFIDENCE IN BOTH THE TRACK AND INTENSITY IS MEDIUM. 

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