WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4N 133.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 727 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) DEVELOPING MORE DEFINED SPIRAL BANDING
WITH STRONG CONVECTIVE BURSTS IN THE CENTRAL DENSE OVERCAST (CDO).
ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS WITH WARM
(29-30 C) SEA SURFACE TEMPERATURES (SSTS), LOW (10-15 KTS) VERTICAL
WIND SHEAR (VWS), AND MODERATE RADIAL OUTFLOW ALOFT. VISIBLE
STRIATIONS IN THE CIRRUS CLOUDS ALOFT FURTHER POINT TO THE LOW
SHEAR AND IMPROVED OUTFLOW. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON A 210034Z METOP-B ASCAT PASS DEPICTING A
WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
INTENSITY IS ASSESSED WITH  MEDIUM CONFIDENCE BASED ON THE 10 KT
SPREAD OF AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: ADJUSTED BASED ON THE 202059Z RCM-3 SAR
IMAGE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 59 KTS AT 210000Z
   CIMSS AIDT: 51 KTS AT 210000Z
   CIMSS D-PRINT: 51 KTS AT 210000Z

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

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: TS 07W IS FORECAST TO TRACK WEST-NORTHWESTWARD
OUT TO TAU 48 UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE (STR)
CENTERED TO THE NORTH. AFTER TAU 48, TS 07W IS EXPECTED TO TURN
POLEWARD FOLLOWING A WEAKENING IN THE STR, ACCOMPANIED BY A
DECREASE IN TRACK SPEED. NEAR THE END OF THE FORECAST PERIOD, TS
07W WILL TRACK GENERALLY NORTH-NORTHEASTWARD ALONG THE WESTERN
PERIPHERY OF A BROAD STR. IN REGARDS TO THE INTENSITY FORECAST, TS
07W IS EXPECTED TO INTENSIFY RAPIDLY FROM TAU 12 TO 48, AND
REACHING PEAK INTENSITY FROM TAU 48 TO TAU 60. FOLLOWING THIS PEAK,
HOWEVER, TS 07W IS EXPECTED TO WEAKEN STEADILY AS IT EXPERIENCES A
SEVERE INCREASE IN VWS OF UP TO 30-40 KTS, INCREASED DRY AIR
ENTRAINMENT, AND POTENTIAL UPWELLING OF COOLER SSTS AS TS 07W SLOWS
IN SPEED. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT WITH
THE EXCEPTION OF JGSM, WITH A CLOSER AGREEMENT ON THE TIMING AND
FINAL HEADING OF THE FORECAST POLEWARD TURN, HOWEVER, ALONG TRACK
SPEED DOES SPREAD OUT BETWEEN MODELS AS THE FORECAST PERIOD
PROGRESSES. THE OFFICIAL JTWC TRACK FORECAST IS THUS LAID WITH HIGH
CONFIDENCE OUT TO TAU 72 AND MEDIUM CONFIDENCE THEREAFTER,
SPLITTING THE DIFFERENCE BETWEEN THE AI CONSENSUS AND MULTI-MODEL
CONSENSUS. MODEL INTENSITY GUIDANCE REMAINS SPREAD WITH A 75 KT
DIFFERENCE AT THE PEAK INTENSITY TIME. THE OFFICIAL JTWC INTENSITY
FORECAST IS THEREFORE ASSESSED WITH LOW CONFIDENCE THROUGHOUT THE
FORECAST PERIOD, IN LINE WITH THE MULTI-MODEL CONSENSUS UNTIL TAU
36 AND THEN HEDGED IN FAVOR OF THE MULTIPLE RAPID INTENSIFICATION
(RI) AIDS. OF NOTE, THE CTCXEPS RI AID HAS BACKED OFF FROM 100
PERCENT PROBABILITY OF RI TO 70 PERCENT FROM TAUS 24-48.

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