WDPN31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 138.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 272 NM NORTH OF YAP
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 07W (MEKKHALA) WITH A PERSISTING CENTRAL DENSE OVERCAST
(CDO) PARTIALLY OBSCURING BUT OFFSET NORTHEAST OF THE LOW LEVEL
CIRCULATION CENTER (LLCC). TS 07W REMAINS TILTED TO THE NORTHEAST
DUE TO LIGHT SOUTHWESTERLY SHEAR, BUT THE TILT IS LESSENING AS
ENVIRONMENTAL CONDITIONS IMPROVE AND THE SYSTEM CONTINUES TO
STRENGTHEN. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS
WITH WARM (29-30 C) SEA SURFACE TEMPERATURES (SSTS), LOW TO
MODERATE (10-15 KTS) VERTICAL WIND SHEAR (VWS), AND MODERATE RADIAL
OUTFLOW ALOFT. THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON TRACING THE PARTIALLY OBSCURED LLCC EMBEDDED
NEAR THE SOUTHWESTERN EDGE OF THE CDO. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND AUTOMATED OBJECTIVE AIDS LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 44 KTS AT 191800Z
   CIMSS ADT: 45 KTS AT 191800Z
   CIMSS AIDT: 37 KTS AT 191800Z
   CIMSS D-MINT: 31 KTS AT 191612Z
   CIMSS D-PRINT: 36 KTS AT 191730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 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: TROPICAL STORM MEKKHALA IS FORECAST TO TRACK
WEST-NORTHWESTWARD UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE TO
THE NORTH OVER THE NEXT 72 HOURS. THEREAFTER, A WEAKNESS IN THE
DEEP-LAYER SUBTROPICAL RIDGE IS EXPECTED TO CAUSE SLOWING OF THE
FORWARD MOTION AND A NORTHWARD TURN TO THE SOUTHEAST OF TAIWAN
AFTER TAU 96. IN TERMS OF INTENSITY, TS MEKKHALA IS EXPECTED TO
INTENSIFY STEADILY OVER THE NEXT 24 HOURS, BUT LIKELY NOT RAPIDLY
UNTIL THE INNER CORE HAS FULLY MATURED AND THE VORTEX HAS BECOME
MORE VERTICALLY STACKED AND SYMMETRIC. AFTER 24 HOURS, MORE RAPID
INTENSIFICATION (RI) IS EXPECTED IN RESPONSE TO FAVORABLE
ENVIRONMENTAL CONDITIONS. THE PEAK INTENSITY IS FORECAST TO OCCUR
AROUND TAU 72, AT WHICH POINT VERTICAL SHEAR IS EXPECTED TO SPIKE 
AS THE STORM MOVES INTO A REGION WITH SOUTHWESTERLY MONSOON
LOW-LEVEL FLOW AND STRONG UPPER-LEVEL EASTERLIES. THIS IS EXPECTED
TO CAUSE STEADY WEAKENING AFTER TAU 72, POSSIBLY COMPOUNDED BY
DYNAMIC OCEAN COOLING AS THE STORM'S FORWARD MOTION SLOWS.
DYNAMICAL MODELS DISAGREE STARKLY REGARDING THE DEGREE TO WHICH TS
MEKKHALA WILL SUCCUMB TO THE RISING SHEAR BEYOND TAU 72,
CONTRIBUTING TO LOWER THAN AVERAGE CONFIDENCE IN THE INTENSITY
FORECAST DURING THAT PERIOD.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 72 WITH THE EXCEPTION OF THE UKMET MODELS WHICH DISPLAY A MORE
DIRECT WESTWARD TRACK. THE OFFICIAL JTWC TRACK FORECAST WAS LAID
WITH HIGH CONFIDENCE THROUGH TAU 72, THEN MEDIUM CONFIDENCE
THEREAFTER, UTILIZING A BLEND OF ECMWF, ECMWF ENSEMBLE MEAN, GFS
ENSEMBLE MEAN, AIFS, AIFS ENSEMBLE MEAN, NAVGEM, JMA, AND THE
EXPERIMENTAL GOOGLE DEEP MIND ENSEMBLE MEAN MODELS AS GUIDANCE.
INTENSITY GUIDANCE ALSO DISPLAYED SOME DISAGREEMENT IN HOW QUICKLY
TS 07W WOULD INTENSIFY, WITH STATISTICAL MODELS BEING SLOWER TO
STRENGTHEN. THE OFFICIAL JTWC INTENSITY FORECAST IS ASSESSED WITH
MEDIUM CONFIDENCE THROUGH TAU 72, ABOVE THE CONSENSUS AND MORE IN
FAVOR OF THE DYNAMICAL MODELS SUCH AS HAFS AND THE VARIOUS RI AIDS,
ALTHOUGH HEDGING THE ONSET OF RI TO TAU 12-24 TO ACCOUNT FOR THE
CURRENT LEVEL OF DISORGANIZATION. BEYOND TAU 72, THE INTENSITY
FORECAST IS ASSESSED WITH LOW CONFIDENCE DUE TO STRONG MODEL
DISAGREEMENT IN THE WEAKENING TREND DURING THAT PERIOD.

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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