WDPN31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9N 124.2E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 243 NM SOUTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
DESPITE A ROBUST EQUATORWARD OUTFLOW CHANNEL AND GOOD POLEWARD
OUTFLOW, TYPHOON (TY) 14W CONTINUES TO SLOWLY DEGRADE DUE TO
PERSISTENT NORTHEASTERLY MID-LEVEL VERTICAL WIND SHEAR (VWS) AND
DRY AIR ENTRAINMENT. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS A RAGGED CORE WITH DEEP CONVECTIVE BANDING
PRIMARILY OVER THE SOUTHERN SEMICIRCLE. HOWEVER, ANIMATED RADAR
IMAGERY REVEALS AN INTACT EYEWALL SURROUNDING A 40 NM ROUND EYE
WITH EXTENSIVE SPIRAL BANDING WRAPPING FROM THE WESTERN QUADRANT
INTO THE EASTERN QUADRANT. A 031715Z AMSR2 36 GHZ MICROWAVE IMAGE
INDICATES A SMALL, WELL-DEFINED MICROWAVE EYE FEATURE WITH SPARSE
AND FRAGMENTED BANDING OVER THE NORTHEASTERN QUADRANT DUE TO THE
NORTHEASTERLY VWS AND DRY AIR ENTRAINMENT. BASED ON THE PLETHORA OF
HIGH-RESOLUTION SATELLITE AND RADAR DATA, THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 90 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON DVORAK CURRENT INTENSITY
ESTIMATES OF 90 KNOTS FROM ALL AGENCIES AND THE LATEST UW-CIMSS
DMINT AND DPRINT OBJECTIVE ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE BUT BASED ON A RECENT
(030945Z) RCM3 SAR BULLSEYE IMAGE. 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
BUILDING TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 108 KTS AT 031709Z
   CIMSS ADT: 94 KTS AT 031730Z
   CIMSS AIDT: 92 KTS AT 031730Z
   DPRINT: 86 KTS AT 031800Z
   DMINT: 89 KTS AT 031715Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 14W IS BEGINNING TO SLOW AND GRADUALLY TURN
ONTO A MORE WESTWARD TRACK TOWARD SOUTHERN TAIWAN. ANIMATED RADAR
IMAGERY AFTER 031800Z SHOWS A WESTWARD TRAJECTORY. UPPER-AIR DATA
OVER THE EAST CHINA SEA AND NORTHERN TAIWAN ALSO PROVIDES EVIDENCE
THAT THE STR IS BUILDING TO THE NORTH AS THE MIDLATITUDE SHORTWAVE
TROUGH QUICKLY PROPAGATES EASTWARD (NOW SOUTH OF KYUSHU).
THEREFORE, TY 14W WILL CONTINUE TO TRACK WESTWARD WITH LANDFALL
OVER SOUTHERN TAIWAN NEAR TAU 36. MODERATE TO HIGH (20 TO 25 KNOTS)
VERTICAL WIND SHEAR WILL PERSIST, OFFSET BY STRONG VENTING, WHICH
WILL ALLOW THE SYSTEM TO MAINTAIN INTENSITY THROUGH TAU 12. AFTER
TAU 12, SIGNIFICANT WEAKENING IS ANTICIPATED AS 14W APPROACHES AND
TRACKS OVER TAIWAN. AFTER TAU 36, THE SYSTEM WILL CONTINUE TRACKING
WESTWARD TO WEST-SOUTHWESTWARD TOWARD HONG KONG WITH FURTHER
WEAKENING DUE TO INTERACTION WITH THE COOLER, MORE STABLE NORTHEAST
SURGE FLOW ENTRAINING INTO THE WESTERN SEMICIRCLE AND EVENTUALLY
FRICTIONAL EFFECTS ALONG THE SOUTHEAST COAST OF CHINA.   

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGH ABOUT TAU 48 WITH A 70 NM CROSS-TRACK SPREAD IN
THE CONSENSUS VORTEX TRACKERS. AFTER TAU 48, GUIDANCE DIVERGES WITH
INCREASING UNCERTAINTY IN THE EXACT TRACK ALTHOUGH THE BULK OF THE
TRACKERS INDICATE A SOUTHWESTWARD TURN AFTER TAU 72. THE JGSM AND
UEMN TRACKERS ARE THE NOTABLE OUTLIERS INDICATING RAPID WEAKENING
AND A HIGHLY UNREALISTIC NORTHEASTWARD TRACK INTO THE NORTHEAST
SURGE FLOW. PROBABILISTIC GUIDANCE FROM BOTH THE EPS AND GEFS
ENSEMBLES SHOWS THE VAST MAJORITY OF SOLUTIONS TRACKING
SOUTHWESTWARD. IF TY 14W TRACKS SOUTH OF TAIWAN AS INDICATED BY THE
MESOSCALE MODELS (COAMPS-TC AND HAFS-A), THERE IS SOME POTENTIAL
FOR THE SYSTEM TO MAINTAIN TYPHOON INTENSITY FOR A LONGER DURATION
AS IT MAY AVOID ANY DELETERIOUS EFFECTS FROM THE NORTHEAST SURGE
FLOW.    

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN