WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.1N 132.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 323 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 22W (KROVANH) WITH A TIGHTENING LOW-LEVEL CIRCULATION CENTER
(LLCC) THAT BECAME EXPOSED RIGHT AROUND 020600Z. CONVECTIVE
ACTIVITY IS CONFINED TO THE WESTERN SEMICIRCLE WITH A CLEAR LACK OF
CONVECTION WITHIN THE EASTERN SEMICIRCLE. A 020703Z F18 SSMIS 91
GHZ MICROWAVE IMAGE REVEALED EXPOSED LOW-LEVEL CLOUD LINES TIGHTLY
WRAPPING INTO THE LLCC WITH A LOCALIZED BURST OF CONVECTION
DIRECTLY TO THE WEST OF THE CENTER. EARLIER SCATTEROMETER DATA FROM
AROUND 020330Z REVEALED A CONSOLIDATING AND SYMMETRIZING WIND FIELD
WITH 30-35 KNOT WINDS IN ALL QUADRANTS. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE BRIEFLY EXPOSED LLCC IN
ANIMATED MSI.  THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE AFOREMENTIONED SCATTEROMETER DATA
ALONG WITH THE AGENCY DVORAK AND CIMSS ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A SUBTROPICAL
RIDGE (STR) CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 020550Z
   CIMSS ADT: 33 KTS AT 020550Z
   CIMSS AIDT: 36 KTS AT 020550Z
   CIMSS D-MINT: 34 KTS AT 020431Z
   CIMSS D-PRINT: 30 KTS AT 020550Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT FROM THE SOUTH

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE SYSTEM IS NOW FORECAST TO MAKE A
COUNTERCLOCKWISE LOOP NORTHEAST OF OKINAWA, KEEPING THE SYSTEM
CLOSER TO THE ISLAND FOR A LONGER PERIOD.

FORECAST DISCUSSION: TS 22W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH
TAU 48. NEAR TAU 48, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN
FROM THE NORTH AND BREAK DOWN THE STEERING RIDGE. THIS WILL CAUSE
22W TO BE PLACED WITHIN A WEAK STEERING ENVIRONMENT WITH RIDGING
OVER EASTERN CHINA, RIDGING TO THE EAST, AND A NEAR EQUATORIAL
RIDGE TO THE SOUTH. ONCE THE SYSTEM ENTERS THIS WEAK STEERING
ENVIRONMENT, THE TRACK IS LIKELY TO BE ERRATIC. MODELS SHOW THE
VORTEX TAKING A VARIETY OF TRAJECTORIES AFTER TAU 48, WITH SOME
ROUNDING THE RIDGE, SOME KEEPING THE SYSTEM QUASISTATIONARY, AND
OTHERS TAKING A SHARP TURN TO THE SOUTH. THERE IS EXTEME
UNCERTAINTY AFTER TAU 48, BUT THE JTWC TRACK CALLS FOR A SLOW
SOUTHWARD TURN THROUGH TAU 96 FOLLOWED BY AN EASTWARD TURN THROUGH
TAU 120. THIS FORECAST TRACK IS A BIT DIFFERENT COMPARED TO THE
PREVIOUS FORECAST, NOW KEEPING THE SYSTEM CLOSER TO OKINAWA FOR A
LONGER PERIOD OF TIME. ACCOMPANYING THE UNCERTAINTY IN THE TRACK IS
AN EXTREME UNCERTAINTY IN THE 34-KNOT WIND RADII. MODELS VARY
SIGNIFICANTLY ON THE SYMMETRY AND EXTENT OF GALE-FORCE WINDS. IN
TERMS OF INTENSITY, 22W IS FORECAST TO GRADUALLY INTENSIFY THROUGH
TAU 48 TO A PEAK OF AROUND 45 KTS AS THE WIND FIELD CONTINUES TO
CONSOLIDATE AND SHEAR REMAINS LOW. THE SYSTEM MAY ALSO BE ABLE TO
TAP INTO A POLEWARD OUTFLOW CHANNEL ONCE THE UPPER-LEVEL TROUGH
OVER JAPAN SETS UP AROUND TAU 36. AFTER TAU 48, THE SYSTEM WILL BE
VERY SLOW MOVING, SO THE UPWELLING OF COOLER WATERS COULD BECOME A
FACTOR. ADDITIONALLY, SHEAR AND DRY AIR ARE EXPECTED TO INCREASE,
CAUSING 22W TO WEAKEN THROUGH TAU 120. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT
ONLY THROUGH TAU 36 WITH MODELS AGREEING ON A NORTHWESTWARD TRACK.
THE CROSS-TRACK SPREAD AT TAU 36 IS MEASURED TO BE ABOUT 120 NM
WITH THE EC-AIFS BEING THE WESTERNMOST MODEL AND THE JGSM BEING THE
EASTERNMOST MODEL. AFTER TAU 36, MODELS BEGIN TO DIVERGE IN NEARLY
EVERY DIRECTION. JGSM AND NAVGEM SHOW THE SYSTEM TRACKING
NORTHEASTWARD, ATTEMPTING TO ROUND THE RIDGE AXIS. THE ECMWF AND
EC-AIFS TAKE A TURN OUT TO THE NORTHWEST WITH A WIDE
COUNTERCLOCKWISE LOOP. THE EXPERIMENTAL GOOGLE DEEPMIND AND ECMWF
ENSEMBLE MEANS SHOWS A SHARP SOUTHWARD TURN, NEAR OKINAWA. THE JTWC
TRACK FORECAST IS PLACED NEAR THE CONSENSUS THROUGH TAU 36, THEN
CLOSER TO THE GOOGLE DEEPMIND THROUGH TAU 120 WITH VERY LOW
CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES ON A GRADUAL
INCREASE TO A PEAK AROUND TAU 48 FOLLOWED BY WEAKENING. PEAK
INTENSITIES RANGE FROM 40 TO 55 KTS WITH THE HAFS-A BEING THE MOST
AGGRESSIVE MODEL. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE
CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH LOW CONFIDENCE DUE TO
THE HIGH UNCERTAINTY IN THE TRACK.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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