Advisories

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 EXTREME 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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