Advisories

WDPN31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (KROVANH) 
WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.4N 129.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 109 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: EASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS FLARING
CONVECTION AROUND THE PERIPHERY OF AN ELONGATED, POORLY DEFINED
LOW-LEVEL CIRCULATION CENTER (LLCC), WITH THE RESULTING CIRRUS
COMPLETELY OBSCURING THE LOW-LEVEL FEATURES. ANIMATED WATER VAPOR
IMAGERY REVEALS THAT THE POLEWARD OUTFLOW CHANNEL HAS BECOME LESS
POTENT OVER THE LAST SIX HOURS, WHILE A SIGNIFICANT WEDGE OF DRY
AIR REMAINS OVER THE EAST CHINA SEA. THE INITIAL POSITION IS PLACED
WITH LOW CONFIDENCE BASED ON THE ASSESSED CENTER OF ROTATION OF 
CONVECTION IN THE ANIMATED EIR AS THERE HAS BEEN A COMPLETE LACK OF
SCATTEROMETER AND MICROWAVE IMAGERY OVER THE PAST SIX HOURS. IT'S
POSSIBLE THAT THE POORLY DEFINED LLCC SEEN PREVIOUSLY IS REORGANIZING 
AGAIN SOMEWHERE WITHIN THE OBSCURING MASS OF CONVECTION. THE INITIAL 
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 
BLEND OF THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY 
ESTIMATES, LEANING SLIGHTLY ON THE LOWER END BASED ON THE LACK OF 
COHERENT STRUCTURE IN THE SATELLITE IMAGERY. THE ENVIRONMENT IS 
CHARACTERIZED AS MARGINAL FOR FURTHER DEVELOPMENT DUE TO LOW-MODERATE 
VERTICAL WIND SHEAR (VWS), WEAKENING OUTFLOW ALOFT, AND CONTINUED DRY 
AIR ENTRAINMENT, DESPITE WARM SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE NORTHERN PERIPHERY OF A NEAR
EQUATORIAL RIDGE (NER) POSITIONED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 43 KTS AT 051741Z
   CIMSS ADT: 35 KTS AT 051810Z
   CIMSS AIDT: 33 KTS AT 051810Z
   CIMSS D-MINT: 34 KTS AT 051743Z
   CIMSS D-PRINT: 27 KTS AT 051810Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 22W HAS TRANSITED 
GENERALLY EASTWARD BETWEEN OKINAWA AND MINAMI DAITOJIMA OVER THE PAST 
6 HOURS UNDER THE STEERING INFLUENCE OF THE NER TO THE SOUTH. THE 
FORECAST TRACK IS ACCELERATED WHEN COMPARED TO THE PREVIOUS FORECAST 
DUE TO THE ANALYZED 051800Z POSITION, ALTHOUGH THERE IS UNCERTAINTY IN 
THE CENTER POSITION AS PREVIOUSLY DISCUSSED. THE SYSTEM IS FORECAST TO 
TRACK EAST-NORTHEASTWARD THROUGH TAU 24, THEN TURN POLEWARD AS IT 
TRACKS ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) 
POSITIONED SOUTHEAST OF JAPAN. A NORTHEASTWARD TURN IS EXPECTED TO 
BEGIN AROUND TAU 72 AS 22W APPROACHES THE RIDGE AXIS. THE SYSTEM MAY 
HAVE A BRIEF OPPORTUNITY TO INTENSIFY TO 35 KTS IN THE SHORT TERM IF 
THE RECENT BOUT OF CONVECTION CAN MANAGE TO PERSIST AND ENABLE THE 
LLCC TO CONSOLIDATE, WHICH IS REFLECTED IN THE INTENSITY FORECAST. 
AFTER TAU 12, PERSISTENT LOW-MODERATE VWS AND CONTINUED DRY AIR 
ENTRAINMENT PRECLUDE ANY FURTHER INTENSIFICATION THROUGH THE REMAINDER 
OF THE FORECAST PERIOD. BETWEEN TAU 72-96 THE CIRCULATION WILL LIKELY 
BECOME EXTREMELY STRETCHED AS IT INTERACTS WITH THE HOSTILE UPPER-
LEVEL WINDS. AS A RESULT, 22W IS FORECAST TO DISSIPATE OVER WATER BY 
TAU 96 WITH A SHALLOW AND ELONGATED VORTEX.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT 
THROUGH TAU 60 WITH A CROSS-TRACK SPREAD OF 100 NM FOLLOWING THE 
POLEWARD TURN. AFTER TAU 60, SOME TRACKERS BEGIN TO LOSE THE VORTEX 
WHILE THOSE THAT MAINTAIN THE VORTEX TEND TO ACCELERATE NORTHEASTWARD. 
THE JTWC TRACK FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH TAU 
60, THEN CLOSER TO THE GUIDANCE THAT FAVORS THE DISSIPATION SCENARIO. 
THERE IS UNCERTAINTY ABOUT THE VORTEX INITIAL POSITION THAT PROPAGATES 
UNCERTAINTY THROUGH THE TRACK FORECAST. ALL INTENSITY GUIDANCE REMAINS 
BELOW 35 KTS AFTER THE BRIEF SPIKE AT TAU 12 AND THE JTWC INTENSITY 
FORECAST FOLLOWS CLOSE TO THE CONSENSUS MEAN THROUGH TAU 60, THEN OFF-
RAMPS IN ANTICIPATION OF DISSIPATION DUE TO THE EXPECTED UNFAVORABLE
ENVIRONMENT.

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