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JTWC IS ISSUING 6 HOURLY WARNINGS AND 3 HOURLY SATELLITE BULLETIN ON 07W
WESTERN NORTH PACIFIC: TS 07W(MEKKHALA). WARNING 7 ISSUED BY JTWC @20/0900 UTC
TC WARNING GRAPHIC
PROGNOSTIC REASONING
WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 14.1N 136.8E
INITIAL INTENSITY: 45 KTS
GEOGRAPHIC REFERENCE: 286 NM NORTH-NORTHWEST OF YAP
MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
SIGNIFICANT WAVE HEIGHT: 21 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 07W (MEKKHALA) PARTIALLY EXPOSED TO THE SOUTHEAST OF THE
CENTRAL DEEP CONVECTION. AFTER A BRIEF PERIOD WHEN THE CENTER WAS COMPLETELY EXPOSED TO THE SOUTHEAST OF THE CENTRAL DENSE OVERCAST
(CDO), THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS RECENTLY BEGUN TO TUCK UNDER THE CONVECTION, SIGNALING THE VORTEX IS BECOMING MORE VERTICALLY STACKED. A 200420Z AMSR2 MICROWAVE IMAGE CONFIRMS THE DEEP CONVECTION REMAINS CONFINED TO THE NORTHWESTERN QUADRANT AND SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION,CHARACTERIZED BY WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), AND STRONG POLEWARD OUTFLOW SUPPORTED BY AN UPPER-LEVEL ANTI-CYCLONE, WITH A SMALL WEDGE OF RELATIVELY DRIER AIR PRESENT ALONG THE SOUTHERN
SEMICIRCLE. THE LIMITING FACTOR FOR DEVELOPMENT REMAINS THE TILTED VORTEX. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATED LISTED BELOW.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.0 - 45 KTS
RJTD: T2.5 - 35 KTS
RCTP: T3.0 - 45 KTS
KNES: T3.0 - 45 KTS
CIMSS SATCON: 53 KTS AT 200700Z
CIMSS ADT: 51 KTS AT 200700Z
CIMSS AIDT: 44 KTS AT 200700Z
CIMSS D-MINT: 39 KTS AT 200420Z
CIMSS D-PRINT: 37 KTS AT 200700Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
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 CONTINUE ITS GENERAL WEST-NORTHWESTWARD TRAJECTORY AS IT TRACKS AROUND THE STEERING STR
CENTERED TO THE NORTH. MEKKHALA HAS ASSUMED A DUE WESTWARD TRACK OVER THE PAST 6 HOURS, HOWEVER, BEGINNING IMMINENTLY, THE STR IS
EXPECTED TO SHIFT EASTWARD AND ALLOW 07W TO TRACK NORTHWESTWARD THROUGH TAU 60. THE SHORT-TERM TRACK MAY REMAIN WESTWARD IF THE STR SHIFTS SLOWER THAN ANTICIPATED. TS 07W IS FORECAST TO SLOW ITS TRANSLATIONAL SPEED AND TRACK INTO A WEAKNESS IN THE STR AROUND TAU
72. MEKKHALA IS ANTICIPATED TO ROUND THE RIDGE AXIS AROUND TAU 96 AND TRACK NORTH-NORTHEASTWARD FROM TAU 96-120. REGARDING INTENSITY,07W IS EXPECTED TO STEADILY INTENSIFY FOR THE NEXT 24 HOURS AS THE STORM CONTINUES TO ORGANIZE. ONCE THE VORTEX BECOMES VERTICALLY ALIGNED AROUND TAU 24, INTENSIFICATION IS FORECAST TO BECOME MORE
VIGOROUS, WITH THE FAVORABLE ENVIRONMENT SUPPORTING LIKELY RAPID INTENSIFICATION (RI) BETWEEN TAU 36-60. 07W IS FORECAST TO REACH
ITS PEAK INTENSITY AT TAU 72, JUST PRIOR TO ROUNDING THE RIDGE.MEKKHALA IS EXPECTED TO WEAKEN QUICKLY THEREAFTER AS IT ENTERS INTO
A HIGH SHEAR ENVIRONMENT INDUCED BY STRONG UPPER-LEVEL EASTERLIES NEAR 20N. UPWELLING AND DRY AIR ENTRAINMENT MAY CONTRIBUTE TO
ADDITIONAL WEAKENING, THOUGH THE DRIVING FACTOR WILL BE VWS.
MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 60, WITH MINIMAL SPREAD IN THE ALONG-TRACK OR
CROSS-TRACK DIRECTIONS. GUIDANCE DIVERGES AROUND TAU 72 AS 07W BEGINS TO ROUND THE RIDGE, CAUSING AN INCREASING CROSS-TRACK SPREAD
FROM TAU 72 ONWARD. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE AND MEDIUM CONFIDENCE FROM TAU 72 THROUGH THE
END OF THE FORECAST PERIOD. RELIABLE INTENSITY AIDS ARE IN POOR AGREEMENT FOR THE DURATION OF THE FORECAST PERIOD. SEVERAL JTWC RI
AIDS HAVE TRIGGERED, INDICATING IMMINENT RI, HOWEVER RI IS NOT FORECAST TO OCCUR UNTIL AFTER TAU 24 DUE TO THE CURRENT DISORGANIZATION OF THE STORM. MESOSCALE AND GLOBAL MODELS ARE SPLIT IN THE PEAK INTENSITY OF 07W: GFS INDICATES A PEAK OF 65-70 KTS AT TAU 48 AND COAMPS-TC (NAVGEM BOUNDARY CONDITIONS) INDICATES A PEAK
OF OVER 125 KTS AT TAU 72, WITH OTHER MODELS FALLING SOMEWHERE IN THE MIDDLE. THE JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL
LOW CONFIDENCE AS A RESULT OF THE SIGNIFICANT UNCERTAINTY REGARDING INTENSIFICATION RATE AND PEAK.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
TRACK 72-120 HR: MEDIUM
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING NR
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 14.1N 136.8E
INITIAL INTENSITY: 45 KTS
GEOGRAPHIC REFERENCE: 286 NM NORTH-NORTHWEST OF YAP
MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
SIGNIFICANT WAVE HEIGHT: 21 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM (TS) 07W (MEKKHALA) PARTIALLY EXPOSED TO THE SOUTHEAST OF THE
CENTRAL DEEP CONVECTION. AFTER A BRIEF PERIOD WHEN THE CENTER WAS COMPLETELY EXPOSED TO THE SOUTHEAST OF THE CENTRAL DENSE OVERCAST
(CDO), THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS RECENTLY BEGUN TO TUCK UNDER THE CONVECTION, SIGNALING THE VORTEX IS BECOMING MORE VERTICALLY STACKED. A 200420Z AMSR2 MICROWAVE IMAGE CONFIRMS THE DEEP CONVECTION REMAINS CONFINED TO THE NORTHWESTERN QUADRANT AND SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION,CHARACTERIZED BY WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS), AND STRONG POLEWARD OUTFLOW SUPPORTED BY AN UPPER-LEVEL ANTI-CYCLONE, WITH A SMALL WEDGE OF RELATIVELY DRIER AIR PRESENT ALONG THE SOUTHERN
SEMICIRCLE. THE LIMITING FACTOR FOR DEVELOPMENT REMAINS THE TILTED VORTEX. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATED LISTED BELOW.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.0 - 45 KTS
RJTD: T2.5 - 35 KTS
RCTP: T3.0 - 45 KTS
KNES: T3.0 - 45 KTS
CIMSS SATCON: 53 KTS AT 200700Z
CIMSS ADT: 51 KTS AT 200700Z
CIMSS AIDT: 44 KTS AT 200700Z
CIMSS D-MINT: 39 KTS AT 200420Z
CIMSS D-PRINT: 37 KTS AT 200700Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
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 CONTINUE ITS GENERAL WEST-NORTHWESTWARD TRAJECTORY AS IT TRACKS AROUND THE STEERING STR
CENTERED TO THE NORTH. MEKKHALA HAS ASSUMED A DUE WESTWARD TRACK OVER THE PAST 6 HOURS, HOWEVER, BEGINNING IMMINENTLY, THE STR IS
EXPECTED TO SHIFT EASTWARD AND ALLOW 07W TO TRACK NORTHWESTWARD THROUGH TAU 60. THE SHORT-TERM TRACK MAY REMAIN WESTWARD IF THE STR SHIFTS SLOWER THAN ANTICIPATED. TS 07W IS FORECAST TO SLOW ITS TRANSLATIONAL SPEED AND TRACK INTO A WEAKNESS IN THE STR AROUND TAU
72. MEKKHALA IS ANTICIPATED TO ROUND THE RIDGE AXIS AROUND TAU 96 AND TRACK NORTH-NORTHEASTWARD FROM TAU 96-120. REGARDING INTENSITY,07W IS EXPECTED TO STEADILY INTENSIFY FOR THE NEXT 24 HOURS AS THE STORM CONTINUES TO ORGANIZE. ONCE THE VORTEX BECOMES VERTICALLY ALIGNED AROUND TAU 24, INTENSIFICATION IS FORECAST TO BECOME MORE
VIGOROUS, WITH THE FAVORABLE ENVIRONMENT SUPPORTING LIKELY RAPID INTENSIFICATION (RI) BETWEEN TAU 36-60. 07W IS FORECAST TO REACH
ITS PEAK INTENSITY AT TAU 72, JUST PRIOR TO ROUNDING THE RIDGE.MEKKHALA IS EXPECTED TO WEAKEN QUICKLY THEREAFTER AS IT ENTERS INTO
A HIGH SHEAR ENVIRONMENT INDUCED BY STRONG UPPER-LEVEL EASTERLIES NEAR 20N. UPWELLING AND DRY AIR ENTRAINMENT MAY CONTRIBUTE TO
ADDITIONAL WEAKENING, THOUGH THE DRIVING FACTOR WILL BE VWS.
MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 60, WITH MINIMAL SPREAD IN THE ALONG-TRACK OR
CROSS-TRACK DIRECTIONS. GUIDANCE DIVERGES AROUND TAU 72 AS 07W BEGINS TO ROUND THE RIDGE, CAUSING AN INCREASING CROSS-TRACK SPREAD
FROM TAU 72 ONWARD. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE AND MEDIUM CONFIDENCE FROM TAU 72 THROUGH THE
END OF THE FORECAST PERIOD. RELIABLE INTENSITY AIDS ARE IN POOR AGREEMENT FOR THE DURATION OF THE FORECAST PERIOD. SEVERAL JTWC RI
AIDS HAVE TRIGGERED, INDICATING IMMINENT RI, HOWEVER RI IS NOT FORECAST TO OCCUR UNTIL AFTER TAU 24 DUE TO THE CURRENT DISORGANIZATION OF THE STORM. MESOSCALE AND GLOBAL MODELS ARE SPLIT IN THE PEAK INTENSITY OF 07W: GFS INDICATES A PEAK OF 65-70 KTS AT TAU 48 AND COAMPS-TC (NAVGEM BOUNDARY CONDITIONS) INDICATES A PEAK
OF OVER 125 KTS AT TAU 72, WITH OTHER MODELS FALLING SOMEWHERE IN THE MIDDLE. THE JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL
LOW CONFIDENCE AS A RESULT OF THE SIGNIFICANT UNCERTAINTY REGARDING INTENSIFICATION RATE AND PEAK.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
TRACK 72-120 HR: MEDIUM
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
AI Model Track Forecasts
Ensemble Track Ellipses
Radius of Maximum Wind (RMW)
INVEST 93W
