WESTERN PACIFIC:TY 07W(MEKKHALA) approaching OKINAWA while weakening/08W(HIGOS) to merge with 07W in approx 60h/Invest 95W//24@1030 UTC

JTWC FACEBOOK
Joint Typhoon Warning Center

 

WDPN31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (MEKKHALA) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.8N 124.8E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 326 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 31 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE LOW-LEVEL 
CIRCULATION CENTER (LLCC) OF 07W PARTIALLY EXPOSED IN THE NORTHERN 
SEMICIRCLE, WITH SIGNIFICANT DEEP CONVECTION LIMITED TO THE SOUTHERN 
SEMICIRCLE. STRONG NORTHEASTERLY VERTICAL WIND SHEAR HAS CONTINUED TO 
DISALLOW THE DEEP CONVECTION TO WRAP AROUND TO THE NORTHERN SIDE. 
MODERATE EQUATORWARD OUTFLOW IS EVIDENT IN THE ANIMATED WATER VAPOR 
IMAGERY, ALONG WITH A WEDGE OF DRY AIR TO THE NORTH OF THE SYSTEM 
THAT HAS YET TO PENETRATE THE CORE. THE INITIAL POSITION IS PLACED 
WITH HIGH CONFIDENCE BASED ON THE INTERMITTENTLY EXPOSED CENTER OF 
THE LLCC IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 70 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE OBSERVED STEADY 
WEAKENING OF THE SYSTEM, ON THE HIGHER END OF THE AGENCY DVORAK 
FIXES. THE ENVIRONMENT IS CHARACTERIZED AS UNFAVORABLE, WITH STILL-
WARM SEA SURFACE TEMPERATURES BEING OVERCOME PRIMARILY BY HIGH (30-35 
KTS) VWS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: THE WESTERN PERIPHERY OF THE 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: T4.0 - 65 KTS
   CIMSS ADT: 47 KTS AT 240600Z
   CIMSS AIDT: 52 KTS AT 240600Z
   CIMSS D-MINT: 45 KTS AT 240528Z
   CIMSS D-PRINT: 47 KTS AT 240600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30-35 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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: TYPHOON (TY) 07W (MEKKHALA) HAS CONTINUED ON A
NORTHWARD TRAJECTORY AS IT ROUNDS THE WESTERN PERIPHERY OF A DEEP-
LAYER STR CENTERED TO THE NORTHEAST. SPEED OF ADVANCE HAS SLOWLY 
INCREASED OVER THE LAST 12 HOURS AND IS EXPECTED TO CONTINUE TO DO SO 
OVER THE NEXT 48 HOURS AS IT RECURVES TOWARD THE NORTHEAST. THE 
FORECAST TRACK WILL PASS PARALLEL TO THE NORTHWEST COAST OF OKINAWA 
BEGINNING AROUND TAU 36, WITH THE CPA TO KADENA AB EXPECTED AT 
251900Z. AFTER TAU 48 THE TRACK SPEED CONTINUES TO ACCELERATE AT A 
HIGHER RATE AS THE NORTHEASTWARD MOTION TAKES 07W ON A TRACK THAT 
PARALLELS THE SOUTHEASTERN COAST OF HONSHU, JUST OFFSHORE. OF NOTE, 
THE KANTO PLAIN IS WELL WITHIN THE UNCERTAINTY ENVELOPE OF TRACK 
GUIDANCE AS THE SYSTEM APPROACHES THE TOKYO BAY REGION JUST AFTER TAU 
72. THE INTENSITY IS FORECAST TO CONTINUE ITS STEADY DECLINE 
THROUGHOUT THE FORECAST PERIOD, WITH A BRIEF PERIOD OF SUSTAINED 
INTENSITY BETWEEN TAUS 48-60 WHEN VWS DECREASES TO LESS HOSTILE 
VALUES AND POLEWARD OUTFLOW GETS A BOOST FROM A JET STREAK TO THE 
NORTH. THE SYSTEM WILL BEGIN EXTRATROPICAL TRANSITION BEFORE TAU 72 
AS IT MOVES POLEWARD INTO THE MIDLATITUDE WESTERLIES, COMPLETING THE 
TRANSITION BEFORE TAU 96.

MODEL DISCUSSION: MODEL TRACK GUIDANCE FROM THE ECMWF DETERMINISTIC, 
ECMWF ENSEMBLE, AND GALWEM SOLUTIONS HAVE BECOME MUCH FASTER WESTERN 
OUTLIERS, A NOTABLE DEVIATION FROM PREVIOUS MODEL RUNS. THIS TRIO HAS 
SKEWED THE MULTI-MODEL CONSENSUS CONSIDERABLY IN THE LATEST MODEL RUN 
AND HAVE BEEN REMOVED FROM THE MODIFIED MULTI-MODEL CONSENSUS. THE 
MEMBERS OF THE MODIFIED CONSENSUS ARE IN VERY GOOD AGREEMENT THROUGH 
TAU 72 WITH MINIMAL ALONG- AND ACROSS-TRACK SPREAD. AFTER TAU 72 THE 
ALONG-TRACK SPREAD INCREASES AS UNCERTAINTY ABOUT THE EXTRATROPICAL 
TRANSITION SCENARIO BECOMES EVIDENT. THE JTWC TRACK FORECAST IS 
PLACED CLOSE TO THE MODIFIED CONSENSUS WITH HIGH CONFIDENCE THROUGH 
TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. THE INTENSITY GUIDANCE IS IN 
GOOD AGREEMENT ABOUT THE OVERALL WEAKENING TREND THROUGHOUT THE 
FORECAST PERIOD BUT WITHIN AN ENVELOPE OF 15-20 KTS. THEREFORE, THE 
JTWC INTENSITY FORECAST IS PLACED SLIGHTLY ABOVE THE CONSENSUS WITH 
MEDIUM CONFIDENCE THROUGHOUT. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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WDPN32 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 08W (HIGOS) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.7N 140.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 266 NM WEST-NORTHWEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION 08W (HIGOS) WITH A SMALL, WEAKLY-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC) THAT HAS RECENTLY TUCKED BACK UNDER THE
FLARING CONVECTION. THERE CONTINUES TO BE A NORTHWARD TILT IN THE
VORTEX WITH HEIGHT AND THE ASSOCIATED CONVECTION REMAINS CONFINED
TO THE NORTHERN SEMICIRCLE OF THE SYSTEM. A 240356Z AMSR2 89 GHZ
MICROWAVE IMAGE REVEALED RAGGED LOW-LEVEL CLOUD LINES WRAPPING INTO
THE COMPACT CENTER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON TRACKING THE EXPOSED LLCC BEFORE THE
OBSCURATION OF THE CENTER. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL
ANALYSIS INDICATES THAT 08W IS IN A MARGINAL ENVIRONMENT
CHARACTERIZED BY WEAK OUTFLOW ALOFT, LOW (10-15 KTS) SOUTHEASTERLY
VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 41 KTS AT 240610Z
   CIMSS AIDT: 38 KTS AT 240610Z
   CIMSS D-MINT: 29 KTS AT 240439Z
   CIMSS D-PRINT: 25 KTS AT 240610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TRUNCATED THE FORECAST TO 60 HOURS,
NOW SHOWING DISSIPATION DUE TO INTERACTION WITH 07W

FORECAST DISCUSSION: 08W IS FORECAST TO CONTINUE ROUNDING THE
WESTERN EXTENT OF THE SUBTROPICAL RIDGE THROUGH TAU 48. AFTER TAU
48, THE FORECAST PHILOSOPHY FOR THE SYSTEM HAS CHANGED
SIGNIFICANTLY. THE SYSTEM IS NOW FORECAST TO BECOME ABSORBED AND
MERGE WITH THE WIND FIELD OF TY 07W (MEKKHALA). THE TIMING OF THE
MERGE IS UNCERTAIN DUE TO THE RELIANCE ON THE FORWARD TRACK SPEED
OF BOTH 08W AND 07W. AS IT STANDS, A MERGE IS FORECAST TO OCCUR
NEAR TAU 60, SOUTH OF HONSHU. REGARDING INTENSITY, 08W IS NOW
FORECAST TO ONLY MAINTAIN ITS CURRENT INTENSITY THROUGH THE TIMING
OF THE INTERACTION WITH 07W RATHER THAN HAVING A PERIOD OF
INTENSIFICATION. THIS IS MOSTLY ATTRIBUTED TO A PERSISTENT
ASYMMETRY IN THE WIND FIELD AND VORTEX TILT. ONCE THE MERGE OCCURS,
08W IS EXPECTED TO OPEN UP INTO A WAVE AND BECOME UNTRACKABLE,
HOWEVER, THERE WILL LIKELY BE AN ISOLATED AREA OF NEAR-GALE FORCE
WINDS ASSOCIATED WITH THE REMNANT VORTICITY OF THE SYSTEM AS THE
CIRCULATION UNRAVELS. THERE STILL REMAINS A POSSIBILITY THAT 08W
OUTRUNS 07W AND RECURVES BEFORE ENOUGH INTERACTION WITH 07W OCCURS,
BUT THAT SCENARIO IS NOW ANALYZED TO BE LESS LIKELY.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 48 WITH A GENERAL AGREEMENT ON A
NORTHWESTWARD TRACK THROUGH TAU 24 FOLLOWED BY A NORTHWARD TURN.
HOWEVER, AFTER TAU 48, THERE IS SIGNIFICANT VARIATION BETWEEN
MODELS. SOME MODELS LOSE THE VORTEX AT TAU 48 FURTHER TO THE WEST,
NEAR MINAMI DAITO JIMA, WHILE OTHERS ATTEMPT TO TURN THE SYSTEM
NORTHEASTWARD. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
CONSENSUS THROUGH TAU 48, THEN CLOSER TO THE GFS THROUGH TAU 60
WITH LOW CONFIDENCE. THE AVAILABLE INTENSITY GUIDANCE HAS MARKEDLY
DROPPED COMPARED TO THE PREVIOUS MODEL RUN. THE JTWC INTENSITY
FORECAST IS IN LINE WITH THE GFS AND ECMWF DEPICTION WITH LOW
CONFIDENCE DUE TO THE INHERENT UNCERTAINTY REVOLVING AROUND THE
MERGE WITH 07W.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   INTENSITY 00-72 HR: LOW//
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