WDPN31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.5N 130.6E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 620 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 07W (MEKKHALA) WITH A WARM SPOT PRESENT IN THE CENTRAL DENSE
OVERCAST, INDICATING 07W IS TRYING TO FORM AN EYE. ADDITIONALLY,
07W IS ASSESSED TO BE BEGINNING RAPID INTENSIFICATION (RI), HAVING
ALREADY INTENSIFIED 20 KTS IN 12 HOURS. A 210906Z WSFM MICROWAVE
IMAGE REVEALED MEKKHALA HAD A WELL-DEFINED MICROWAVE EYE IN THE
LOWER-LEVELS, BUT HAD NOT QUITE FORMED A MICROWAVE EYE IN THE UPPER
LEVEL. ENVIRONMENTAL ANALYSIS INDICATED A HIGHLY FAVORABLE
ENVIRONMENT CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR
(VWS), WARM (29-30 C), AND STRONG RADIAL OUTFLOW SUPPORTED BY A
POINT SOURCE ALOFT. THE INITIAL POSITION AND INITIAL INTENSITY ARE
ASSESSED WITH HIGH CONFIDENCE BASED ON THE BULLSEYE 211142Z METOP-B
ASCAT DATA.

INITIAL WIND RADII BASIS: 211142Z METOP-B SCATTEROMETER DATA

CURRENT STEERING MECHANISM: A WESTWARD EXTENSION OF A WEAK
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 79 KTS AT 211300Z
   CIMSS AIDT: 80 KTS AT 211300Z
   CIMSS D-PRINT: 71 KTS AT 211300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 07W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD FOR THE NEXT 24 HOURS WHILE IT REMAINS LOCATED ON THE
SOUTHERN PERIPHERY OF THE EXTENSION OF THE STEERING STR. BETWEEN
TAU 24-36, 07W WILL BEGIN TO ENCOUNTER A WEAKNESS IN THE RIDGE AND
BEGIN TO CURVE NORTH-NORTHWESTWARD. FROM TAU 36 TO TAU 60, MEKKHALA
WILL ROUND THE RIDGE AXIS, INDUCING A NORTH-NORTHEASTWARD
TRAJECTORY FROM TAU 60 THROUGH THE END OF THE FORECAST. REGARDING
INTENSITY, 07W IS FORECAST TO CONTINUE RAPIDLY INTENSIFYING FOR THE
NEXT 24-36 HOURS, WHILE IT REMAINS IN THE HIGHLY FAVORABLE
ENVIRONMENT UNTIL REACHING THE PEAK INTENSITY AT TAU 36-48. BETWEEN
TAU 48-60, 07W WILL ENTER A HOSTILE ENVIRONMENT, CHARACTERIZED BY
HIGH (30-40 KTS) VWS AND SIGNIFICANT DRY AIR, INDUCING DRASTIC
WEAKENING. COOL WATER UPWELLING IS ALSO POSSIBLE AROUND TAU 36-60
AS MEKKHALA SLOWS WHILE ROUNDING THE RIDGE, FURTHER HASTENING THE
WEAKENING TREND. 

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGH TAU 48, BUT DIVERGES SLIGHTLY IN THE CROSS-TRACK
AND ALONG-TRACK DIRECTIONS THEREAFTER, AS MODELS STRUGGLE TO
INTERPRET THE RECURVATURE SCENARIO AND ASSOCIATED TRANSLATION
SPEEDS. HOWEVER, GUIDANCE REMAINS IN MODERATE AGREEMENT THROUGH THE
END OF THE FORECAST, SUPPORTING THE JTWC TRACK FORECAST WITH HIGH
CONFIDENCE FROM TAU 0-72 AND MEDIUM CONFIDENCE FROM TAU 72-120.
RELIABLE INTENSITY GUIDANCE IS IMPROVING IN TERMS OF GENERAL
AGREEMENT, AND DEPICTS A MODERATE RANGE OF 90-125 KTS AT THE TIME
OF FORECASTED PEAK INTENSITY. HAFS AND COAMPS-TC (GFS BOUNDARY
CONDITIONS) DEPICT RI, IN ADDITION TO SEVERAL JTWC RI AIDS REACHING
THRESHOLD, SUPPORTING THE JTWC RI FORECAST. THE JTWC INTENSITY
FORECAST IS PLACED NEAR THE HAFS MODEL SOLUTION WITH MEDIUM
CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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