WDPN31 PGTW 202100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 134.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 794 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) CONTINUING TO ORGANIZE AS THE UPPER LEVEL
CONVECTION WRAPS AROUND THE SOUTHWESTERN QUADRANT, OBSCURING THE
ELONGATED LOW LEVEL CIRCULATION CENTER (LLCC). INTENSE CONVECTIVE
BURSTS, WITH CLOUD TOP TEMPERATURES OF -90C IN IR IMAGERY CAN ALSO
BE OBSERVED, WHICH PAIRED WITH THE INCREASE IN INTENSITY COULD
POSSIBLY INDICATE BETTER VERTICAL ALIGNMENT BETWEEN THE UPPER AND
LOWER LEVEL CIRCULATIONS. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON A 201646Z ATMS 88.2 GHZ PASS AND A
201632Z AMSR2 WINDSPEED IMAGE WHICH DEPICT DEEP CONVECTIVE BANDING
WRAPPING INTO THE SOUTHWEST QUADRANT OF TS 07W. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK
FIXES AND OBJECTIVE ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS
REVEALS FAVORABLE CONDITIONS WITH LOW TO MODERATE (15-20 KTS)
VERTICAL WIND SHEAR (VWS), WARM (29-30 C) SEA SURFACE TEMPERATURES
(SSTS), AND MODERATE OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: PERSISTENCE 

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: T3.0 - 45 KTS
   CIMSS SATCON: 54 KTS AT 201800Z
   CIMSS ADT: 53 KTS AT 201800Z
   CIMSS AIDT: 45 KTS AT 201800Z
   CIMSS D-MINT: 52 KTS AT 201800Z
   CIMSS D-PRINT: 46 KTS AT 201730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 MEKKHALA IS FORECAST TO TRACK
WEST-NORTHWESTWARD UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE NORTH OF THE SYSTEM THROUGH TAU 48. PAST TAU 48,
THE SYSTEM IS FORECAST TO SLOW IN TRANSLATIONAL SPEED AND BEGIN
TRACKING POLEWARD AS THE RIDGE BREAKS DOWN TO THE NORTH. AS IT
PROGRESSES POLEWARD BEYOND TAU 60, THERE IS SLIGHT DISAGREEMENT
ACROSS MODEL GUIDANCE IN HOW SHARP OF A TURN THE SYSTEM WILL MAKE
TO THE NORTHEAST, BUT THE STORM IS NOT ASSESSED TO BE WITHIN A
RECURVATURE SCENARIO THAT WOULD CAUSE SUCH A TIGHT TURN IN THE
TRACK, AND THUS NOT REFLECTED IN THE OFFICIAL JTWC FORECAST. IN
TERMS OF INTENSITY, TS 07W IS EXPECTED TO INTENSIFY RAPIDLY BETWEEN
TAUS 24 TO 60 AS IT BECOMES STACKED VERTICALLY AND CONTINUES TO
EXPERIENCE FAVORABLE ENVIRONMENTAL CONDITIONS. TS 07W IS EXPECTED
TO REACH ITS PEAK INTENSITY BETWEEN TAUS 48 AND 60, COINCIDING WITH
THE TURN POLEWARD. AFTER THIS PEAK INTENSITY, A SHARP INCREASE IN
VWS (OVER 30 KTS) IS EXPECTED TO START IMPACTING THE SYSTEM
RESULTING IN A STEADY WEAKENING TREND THEREAFTER. ADDITIONALLY, THE
SLOWING OF THE FORECAST TRACK MAY CAUSE TS 07W TO STALL OVER COOLER
SSTS UPWELLED IN ITS TRACK, POTENTIALLY ENHANCING THE DECREASE IN
INTENSITY PAST TAU 60.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 72 WITH THE EXCEPTION OF THE MAJOR OUTLIERS, GFS AND JGSM,
WHICH TRACK THE SYSTEM SHARPLY WESTWARD AFTER TAU 36 TOWARD
NORTHERN LUZON AND THE LUZON STRAIT. PAST THE POLEWARD TURN,
GUIDANCE IS MORE SPREAD, WITH THE AI CONSENSUS AND EXPERIMENTAL
GOOGLE DEEP MIND ENSEMBLE DEPICTING A POLEWARD TRACK, WHILE THE
MULTI-MODEL CONSENSUS AND ECMWF SHOW A SHARPER TURN TO A
NORTHEASTWARD TRACK. THE OFFICIAL JTWC TRACK FORECAST IS THUS LAID
WITH HIGH CONFIDENCE FROM TAU 0 TO 72 AND A MEDIUM CONFIDENCE PAST
TAU 72, HEDGING THE OFFICIAL FORECAST CLOSER TO THE AI CONSENSUS,
BUT KEEPING IN AGREEMENT WITH THE SLOWER ALONG TRACK SPEED DEPICTED
BY THE MULTI-MODEL CONSENSUS. INTENSITY MODEL GUIDANCE HAS A LARGE
SPREAD BETWEEN STATISTICAL AND DYNAMICAL MODELS IN HOW RAPIDLY TS
07W WILL INTENSIFY. RAPID INTENSIFICATION GUIDANCE HAS TRIGGERED WITH 
CTCXEPS CONTINUING TO PREDICT 100 PERCENT PROBABILITY AT TAU 24-48. 
THE OFFICIAL JTWC INTENSITY FORECAST IS THUS ASSESSED WITH LOW 
CONFIDENCE THROUGHOUT THE FORECAST PERIOD, ABOVE THE MULTI-MODEL 
CONSENSUS.

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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