Tropical Storm MUIFA Advisory Do, 08.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (MUIFA) WARNING NR
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 17.1N 133.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 634 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN
ASYMMETRIC SYSTEM WITH PERSISTENT DEEP CONVECTION DISPLACED TO THE
SOUTH OF A PARTIALLY OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC).
ANIMATED WATER VAPOR IMAGERY, CIMSS ATMOSPHERIC MOTION VECTORS
(AMVS) AND JTWC HAND ANALYSIS REVEALS AN ELONGATED TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) POSITIONED TO THE NORTH OF THE LLCC,
IMPARTING A WEST-NORTHWEST SHEAR VECTOR OVER TOP OF THE SYSTEM,
AND SOME CONVERGENCE ALOFT TO THE NORTHWEST, LEADING TO THE CURRENT
ASYMMETRIC STRUCTURE OF THE SYSTEM. A EARLIER 072124Z SSMIS 91GHZ
MICROWAVE IMAGE DEPICTED THE LLCC FULLY EXPOSED TO THE NORTH OF
SLIGHTLY CURVED DEEP CONVECTION, AND EXTRAPOLATION OF THIS FEATURE
AND ANALYSIS OF LOW-LEVEL SPIRAL BANDS LENT MEDIUM CONFIDENCE TO
THE INITIAL POSITION. REANALYSIS OF PREVIOUS POSITIONS BASED ON
EARLIER SCATTEROMETER DATA WITH WINDS LESS THAN 35 KNOTS RESULTED IN A
DOWNWARD ADJUSTMENT IN THE PREVIOUS ANALYSES. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF AGENCY DVORAK
CURRENT INTENSITY ESTIMATES, THE ADT AND THE SATELLITE CONSENSUS.
OVERALL THE CURRENT ENVIRONMENT IS GENERALLY FAVORABLE WITH THE
EXCEPTION OF THE SIGNIFICANT TILT AND ASYMMETRIC CORE STRUCTURE.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SOUTHERN SIDE OF MID-LEVEL SUBTROPICAL
RIDGE (STR) CENTERED TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 44 KTS AT 072125Z
   CIMSS ADT: 37 KTS AT 072350Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: WEAK POLEWARD OUTFLOW INTO A TUTT CELL FAR TO THE
NORTHEAST
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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. HOWEVER, THE PREVIOUS
INTENSITY ESTIMATES HAVE BEEN LOWERED FIVE KNOTS BASED ON
REANALYSIS.
FORECAST DISCUSSION: TS MUIFA HAS TRACKED WESTWARD OVER THE PAST 12
HOURS OR SO ALONG THE SOUTHERN SIDE OF AN ELONGATED LOW TO
MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH. THIS GENERAL MOTION
IS EXPECTED TO CONTINUE FOR THE NEXT 12 HOURS BUT THEN THE SYSTEM
IS EXPECTED TO TURN SHARPLY NORTHWESTWARD AS THE STR BUILDS SOUTH
OF HONSHU AND REORIENTS TO A MORE SOUTHEAST TO NORTHWEST AXIS.
TRACK MOTION SLOWS AFTER TAU 72 AS THE STEERING PATTERN WEAKENS
SLIGHTLY, THEN THE SYSTEM TURNS SHARPLY POLEWARD AND ACCELERATES
INTO THE EAST CHINA SEA AS THE STEERING RIDGE ERODES TO THE EAST
AHEAD OF A VERY DEEP UPPER-LEVEL TROUGH MOVING IN FROM THE WEST. IN
THE SHORT-TERM, THE CONVERGENCE ALOFT TO THE NORTHWEST AND
PERSISTENT MID-LEVEL SHEAR (15 KNOTS) MEANS THE SYSTEM WILL BE SLOW
TO CONSOLIDATE AND INTENSIFICATION IS EXPECTED TO BE RATHER SLOW
FOR THE NEXT 12 HOURS. BUT THEN THE GLOVES COME OFF, AS THE
TUTT-CELL SLIDES TO A POSITION TO THE NORTHWEST OF THE LLCC,
ALLOWING FOR ESTABLISHMENT OF A ROBUST POLEWARD OUTFLOW CHANNEL,
WHICH WILL AMPLIFY AND COMPLEMENT THE EXISTING STRONG EQUATORWARD
CHANNEL. AT THE SAME TIME, HIGH RESOLUTION MODELS SUGGEST
CONVECTIVE HOT TOWERS FIRING OFF AND ROTATING UPSHEAR, LEADING TO
AXISYMMETRIZATION BY TAU 18, MARKING THE ONSET OF RAPID
INTENSIFICATION (RI). ANIMATED VISIBLE IMAGERY FROM THE 0200Z HOURS
SUGGEST THIS PROCESS MAY HAVE ALREADY BEGUN, WITH HOT TOWERS
FORMING AROUND THE ASSESSED CENTER. THE SYSTEM WILL PASS OVER A
POOL OF RELATIVELY LOWER OHC (BUT STILL AT OR ABOVE 75 JOULES PER
KG) AROUND TAU 24, BUT DUE TO THE RELATIVELY QUICK FORWARD SPEED,
THIS SHOULD HAVE LITTLE IMPACT OVERALL. THE SYSTEM REALLY TAKES OFF
AROUND TAU 36 AS IT MOVES AN AREA WITH OHC VALUES EXCEEDING 125
JOULES PER KG, AND THE SYSTEM IS EXPECTED TO PEAK AT 120 KNOTS OR
POSSIBLY SLIGHTLY HIGHER BY TAU 72. AT THIS POINT, THE SYSTEM WILL
MOVE INTO THE AREA PREVIOUSLY VISITED BY STY 12W, WHICH LEFT A
MINEFIELD OF COOL, VERY LOW OHC WATER IN ITS WAKE. AS TS 14W ENTERS
THIS REGION, IT WILL WEAKEN FAIRLY QUICKLY, EVEN AS SHEAR REMAINS
MODERATE AND POLEWARD OUTFLOW REMAINS ROBUST INTO THE DIVERGENT
REGION AHEAD OF A SHARP 200MB TROUGH TO THE WEST. THE COMBINATION
OF THESE FEATURES HOWEVER MEANS THAT TS 14W WILL REMAIN A STRONG
TYPHOON ENTERING THE EAST CHINA SEA.
MODEL DISCUSSION: TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT ON
THE OVERALL SCENARIO, WITH DETERMINISTIC GUIDANCE TRACKERS
GRADUALLY SPREADING TO A MODEST 135NM BT TAU 72. ENSEMBLE GUIDANCE
SHOWS A BIT MORE SPREAD DURING THE FIRST 72 HOURS, WITH THE ECMWF
ENSEMBLE IN PARTICULAR SHOWING A FAIRLY LARGE FAN OF POTENTIAL
TRACKS. THE DETERMINISTIC ENVELOPE IS CONSTRAINED BY JGSM ON THE
RIGHT AND UKMET AND NAVGEM ON THE LEFT. IN THE EXTENDED FORECAST
PERIOD, THE GUIDANCE SHOWS INCREASED UNCERTAINTY, WITH ACROSS AND
ALONG-TRACK SPREAD BOTH INCREASING TO NEARLY 300NM BY TAU 120. THE
JTWC FORECAST LIES A BIT TO THE LEFT OF THE CONSENSUS MEAN, CLOSELY
TRACKING THE ECMWF THROUGH THE FIRST 72 HOURS WITH HIGH CONFIDENCE,
THOUGH CONFIDENCE DECREASES THROUGH TAU 120 DUE TO LARGE SPREAD IN
THE GUIDANCE. INTENSITY GUIDANCE IS IN MARGINAL AGREEMENT, WITH THE
NON-COUPLED GUIDANCE SUCH AS THE DECAY-SHIPS INDICATING A MAXIMUM
NEAR 90 KNOTS, WHILE THE HWRF AND COAMPS-TC COUPLED MODELS SUGGEST
A MUCH HIGHER PEAK, AT 120 KNOTS. MULTIPLE RI AIDS ARE BEING
TRIGGERED WITH THIS RUN AS WELL, PROVIDING INCREASED CONFIDENCE IN
THE FORECAST ONSET OF RI. THE JTWC FORECAST CALLS FOR A SLIGHTLY
SLOWER RATE OF INTENSIFICATION THROUGH TAU 12 THAN MOST OF THE RI
GUIDANCE AS THE SYSTEM NEEDS SOME TIME TO CONSOLIDATE. FOR THERE ON
OUT THE JTWC FORECAST TRACKS THE RI GUIDANCE AND MATCHES THE PEAK
INTENSITY OF THE HWRF AND COAMPS-TC. CONFIDENCE IN THE INTENSITY
FORECAST IS MEDIUM THROUGH TAU 72, THEN LOW DUE TO UNCERTAINTY IN
THE AMOUNT OF WEAKENING THE SYSTEM WILL EXPERIENCE NEAR AFTER TAU
72 DUE TO INTERACTION WITH THE COLD POOL.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN
NNNN