Advisories

WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.9N 131.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 263 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 22W (KROVANH) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH CONVECTIVE BANDING WRAPPING AROUND THE WESTERN
AND SOUTHERN PERIPHERIES. A 021137Z METOP-B ASCAT PASS REVEALED
THAT THE CORE OF THE CIRCULATION REMAINS SLIGHTLY STRETCHED IN THE
EAST-WEST DIRECTION. THE ASCAT PASS MISSED MOST OF THE EASTERN
SEMICIRCLE, BUT SHOWED WINDS WITHIN THE WESTERN SEMICIRCLE ARE
AROUND 25-30 KTS. HOWEVER, AN EARLIER 020922Z RCM-3 SAR PASS CAUGHT
THE NORTHEASTERN QUADRANT AND SHOWED A SWATH OF 35 KNOT WINDS WITH
A VMAX RIGHT AROUND 38 KTS. AS A RESULT, THE INITIAL 34 KNOT WIND
RADII ARE NOW ONLY CONFINED TO THE NORTHEASTERN QUADRANT. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED ASCAT PASS. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAR DATA WHICH IS
SUPPORTED BY THE AGENCY DVORAK AND CIMSS INTENSITY ESTIMATES LISTED
BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 22W IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK EQUATORWARD OUTFLOW
ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, DRY AIR, AND WARM (28-29
C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 38 KTS AT 021140Z
   CIMSS ADT: 33 KTS AT 021140Z
   CIMSS AIDT: 36 KTS AT 021140Z
   CIMSS D-MINT: 32 KTS AT 020920Z
   CIMSS D-PRINT: 34 KTS AT 021140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE 34 KNOT WIND RADII HAVE BEEN
SIGNIFICANTLY ALTERED COMPARED TO THE PREVIOUS FORECAST TO MORE
ACCURATELY MATCH THE STORM MOTION 

FORECAST DISCUSSION: TS 22W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH
TAU 36. NEAR TAU 36, 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 FROM TAU 36 TO TAU 60. SOME
KEEP THE SYSTEM QUASISTATIONARY, SOME TAKE AN EASTWARD TURN, AND
OTHERS TAKE A WESTWARD TURN. HOWEVER, THERE HAS BECOME A BIT MORE
AGREEMENT ON A SOUTHWARD TRACK FROM TAU 60 TO 96.  THERE IS NOW A
CLEAR LACK OF MODELS SHOWING A RECURVE SCENARIO. AS IT STANDS, THE 
JTWC TRACK FORECAST CALLS FOR A SLOW SOUTHWARD TURN FROM TAU 36 TO TAU 
96 FOLLOWED BY AN EASTWARD TURN THROUGH TAU120. ACCOMPANYING THE 
UNCERTAINTY IN THE TRACK IS AN EXTREME UNCERTAINTY IN THE 34-KNOT WIND 
RADII, WHERE MODELS VARY SIGNIFICANTLY ON THE SYMMETRY AND EXTENT OF 
GALE-FORCE WINDS. THIS FORECAST NOW HAS THE 34-KNOT WIND RADII 
SHIFTING TO THE WESTERN SIDE OF THE CIRCULATION AFTER IT MAKES THE 
SOUTHWARD TURN, WHICH APPEARS MORE REALISTIC WHEN ACCOUNTING FOR THE 
STORM MOTION. 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 130 NM
WITH THE ECMWF NOW BEING THE WESTERNMOST MODEL AND THE JGSM
REMAINING THE EASTERNMOST MODEL. AFTER TAU 36, MODELS BEGIN TO
DIVERGE IN NEARLY EVERY DIRECTION. THE ECMWF AND EC-AIFS TAKE THE
WIDEST TURN OUT TO THE WEST BEFORE MAKING THE COUNTERCLOCKWISE
LOOP. THE GFS AND GEFS HAVE STARTED TO BECOME IN BETTER AGREEMENT,
SHOWING A SHARP SOUTHWARD TURN SIMILAR TO THE EXPERIMENTAL GOOGLE
DEEPMIND ENSEMBLE MEAN. THE JTWC TRACK FORECAST IS PLACED NEAR THE
CONSENSUS THROUGH TAU 36 AND THEN CLOSER TO THE GOOGLE DEEPMIND
THROUGH TAU 120 WITH LOW CONFIDENCE. INTENSITY GUIDANCE GENERALLY
AGREES ON A GRADUAL INCREASE TO A PEAK AT 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//
NNNN