Advisories

WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0N 129.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 71 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) ASSOCIATED WITH
TROPICAL STORM (TS) 22W.  CONVECTION PERSISTS ONLY ALONG THE
SOUTHERN SEMICIRCLE DUE TO THE PRESENCE OF DRY AIR AND MODERATE
NORTHWESTERLY VERTICAL WIND SHEAR. THE UPPER-LEVEL OUTFLOW IS WEAK
AND PRIMARILY EQUATORWARD AS THE SYSTEM STRUGGLES TO COUNTERACT THE
EFFECTS OF SHEAR AND AN OVERHEAD TROUGH. THE ENVIRONMENT IS
MARGINAL, WITH TS 22W TRAVERSING WATERS WITH SEA SURFACE
TEMPERATURES (SST) OF 27-29 DEGREES CELSIUS AND EXPERIENCING 15-20
KTS OF VWS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE MSI. A 030003Z ASCAT-B PASS REVEALED AN EXTENSIVE AREA
OF 35-40 KT WINDS ALONG THE EASTERN PERIPHERY, WITH A BROAD CORE OF
LIGHT WINDS NEAR THE CENTER. AS THE CONVECTIVE STRUCTURE HAS NOT
APPRECIABLY CHANGED SINCE THAT OBSERVATION, THE INITIAL INTENSITY
HAS BEEN HELD AT 40 KTS WITH HIGH CONFIDENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE SOUTHEAST OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 42 KTS AT 030457Z
   CIMSS ADT: 35 KTS AT 030540Z
   CIMSS AIDT: 38 KTS AT 030540Z
   CIMSS D-MINT: 35 KTS AT 030458Z
   CIMSS D-PRINT: 36 KTS AT 030540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DRY AIR ON THE NORTH SIDE

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK FROM TAU 60 TO TAU
120 HAS SHIFTED WESTWARD BY 30-50 NM, NOW PLACING MOST OF OKINAWA
WITHIN THE NORTHEAST QUADRANT OF THE CIRCULATION FROM TAU 48 TO TAU
72.

FORECAST DISCUSSION: THE CENTER OF TS 22W HAS JOGGED SLIGHTLY
WEST-NORTHWESTWARD OVER THE PAST SIX HOURS. THE SYSTEM WILL RESUME
A GENERAL NORTHWESTWARD MOTION FOR THE NEXT 24 HOURS. A FAST-MOVING
TROUGH PASSING OVER THE KOREAN PENINSULA WILL ALLOW A RIDGE TO
BUILD OVER MAINLAND CHINA, INDUCING A NORTHEASTERLY SURGE OF COOL,
DRY AIR EXTENDING FROM THE SURFACE TO 500 MB. THIS DEVELOPMENT WILL
CAUSE TS 22W TO SLOW AND STALL BETWEEN TAU 24 AND TAU 36. AS THE
RIDGE EXTENDS SOUTHEASTWARD, THE CIRCULATION WILL REVERSE COURSE
AND TURN SOUTHEASTWARD. BY TAU 72, TS 22W WILL BE PICKED UP BY
DEEP-LAYER SOUTHWESTERLY FLOW ASSOCIATED WITH BROAD CYCLONIC
ROTATION DOMINATING THE REGION SOUTH OF HONSHU, TURNING EASTWARD
AND THEN NORTHEASTWARD. THE FORECAST DEPICTS A SLIGHT WEAKENING
TREND THROUGH TAU 24-36, FOLLOWED BY A NEAR-STEADY INTENSITY TREND
THROUGH TAU 120. ENVIRONMENTAL CONDITIONS WILL REMAIN SIMILAR UNTIL
THE SYSTEM STALLS AND ENCOUNTERS THE NORTHEASTERLY WIND SURGE NEAR
TAU 24. THIS SURGE WILL SLIGHTLY WEAKEN THE SYSTEM BY INTRODUCING
ADDITIONAL DRY AIR AND HIGHER VWS. AS TS 22W MOVES EQUATORWARD, THE
VWS WILL EASE, AND THE MOISTURE PROFILE WILL IMPROVE. HOWEVER, THE
BROAD CIRCULATION WILL REQUIRE TIME TO REORGANIZE, LIMITING THE
POTENTIAL FOR SIGNIFICANT REINTENSIFICATION. THE FORECAST 34-KT
WIND RADII DEPICT THE OUTER EXTENT OF GALE-FORCE WINDS. THROUGH TAU
60, SUCH WINDS WILL NOT EXTEND CONTINUOUSLY TO THE CENTER. DUE TO
THE BROAD NATURE OF THE CIRCULATION, THE 34-KT WINDS BEGIN
APPROXIMATELY 30-60 NM FROM THE CENTER.

MODEL DISCUSSION: SIGNIFICANT UNCERTAINTIES EXIST IN THE LONG-TERM
TRACK AND INTENSITY FORECAST DUE TO DIFFERENCES IN THE STRENGTH OF
THE RIDGE THAT WILL EXTEND SOUTHEASTWARD, THE ORIENTATION OF THE
SOUTHWESTERLY FLOW, AND POTENTIAL INTERACTION WITH THE DEVELOPING
TROPICAL DISTURBANCE 97W TO THE EAST. THESE UNCERTAINTIES ARE
REFLECTED IN THE INCREASING CROSS-TRACK SPREAD, WHICH EXPANDS FROM
150 NM AT TAU 60 TO 215 NM AT TAU 96 AND 300 NM AT TAU 120. TRACK
GUIDANCE HAS ALSO SHIFTED WESTWARD, NECESSITATING A CORRESPONDING
WESTWARD ADJUSTMENT TO THE JTWC FORECAST TRACK. AI-BASED MODELS
PREFER A SHARPER 180-DEGREE REVERSAL, WHILE THE DYNAMICAL MODELS
DEPICT A WIDER TURN. THEREFORE, THE JTWC FORECAST TRACK IS PLACED
NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 WITH MEDIUM
CONFIDENCE AND NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE THEREAFTER
WITH LOW CONFIDENCE. THE JTWC INTENSITY FORECAST IS SET NEAR GFS,
HAFS-A, AND THE EXPERIMENTAL GOOGLE DEEPMIND GUIDANCE WITH MEDIUM
CONFIDENCE IN THE NEAR TERM AND LOW CONFIDENCE THEREAFTER.

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