WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (YAGI) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

 SUMMARY:
   INITIAL POSITION: 20.3N 109.0E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 179 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 12W (YAGI) PASSED OVER THE NORTHERN PORTION OF HAINAN,
WITH THE EYE PASSING DIRECTLY OVER THE CITY OF HAIKOU, CHINA AT
061200Z. IN THE PAST SIX HOURS, THE SYSTEM HAS NOW PICKED UP SPEED
AND MOVED INTO THE OPEN WATERS OF THE GULF OF TONKIN. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A RAPID
REORGANIZATION, PARTICULARLY OVER THE SOUTHERN HEMISPHERE OF THE
SYSTEM, WITH CONVECTION RAPIDLY REDEVELOPING OFF THE NORTHWEST
COAST OF HAINAN. CLOUD TOP TEMPERATURES IN THE HOT TOWERS ARE
REACHING -90C IN SOME LOCATIONS, INDICATING THE SYSTEM IS ALREADY
TAKING ADVANTAGE OF THE VERY WARM (32C), VERY HIGH OHC (120 KJ PER
CM2 OR HIGHER) WATERS. ANIMATED RADAR IMAGERY SUGGESTS THE INNER
EYEWALL REMAINED INTACT DURING PASSAGE OVER HAINAN AND HAS BEGUN TO
STRENGTHEN OVER THE GULF OF TONKIN. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON RADAR FIX DATA, AND THE
CONGRUENCE OF ALL AGENCY FIX POSITIONS. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, HEDGED HIGHER THAN THE BULK OF THE
AGENCY CURRENT INTENSITY ESTIMATES, TOWARDS THE SATELLITE CONSENSUS
(SATCON) AND CIMSS DRPINT ESTIMATE OF 100 KNOTS. THE ENVIRONMENT
REMAINS VERY FAVORABLE, WITH VERY WARM SSTS, VERY HIGH OHC, LOW
VWS, AND RADIAL OUTFLOW ALOFT.
 
INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYERS
SUBTROPICAL RIDGE (STR) TO THE NORTH.
 
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 107 KTS AT 061800Z
   CIMSS ADT: 97 KTS AT 061800Z
   CIMSS DPRINT: 100 KTS AT 061800Z
 
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
 
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 12W HAS PICKED UP SPEED AFTER LEAVING
HAINAN ISLAND, NOW ESTIMATED TO BE MOVING AT ABOUT 12 KNOTS. THERE
IS NO HINT OF ANY REAL SLOWDOWN IN THE FUTURE, AS THE STEERING
RIDGE OVER CHINA REMAINS STRONG. HENCE, LANDFALL NEAR HAIPHONG,
VIETNAM IS ANTICIPATED WITHIN THE NEXT 12 HOURS. AFTER MAKING
LANDFALL, THE SYSTEM WILL CROSS NORTH OF HANOI, EVENTUALLY ENDING
UP IN THE FAR NORTHERN REACHES OF LAOS BY THE END OF THE FORECAST
PERIOD. IN LIGHT OF THE VERY FAVORABLE ENVIRONMENTAL CONDITIONS,
THE SYSTEM IS EXPECTED TO INTENSIFY OVER THE NEXT 6 TO 12 HOURS
PRIOR TO LANDFALL IN VIETNAM. THE ONLY LIMITING FACTOR WILL BE THE
SHORT AMOUNT OF TIME OVER WATER AND THE FORWARD TRACK SPEED, WHICH
WILL SOMEWHAT LIMIT THE INFLUENCE OF THE VERY HIGH OHC WATERS. EVEN
STILL, THE SYSTEM IS EXPECTED TO INTENSIFY TO AT LEAST 115 KNOTS,
POTENTIALLY SLIGHTLY HIGHER, WITHIN THE NEXT SIX HOURS OR SO,
BEFORE SLAMMING INTO THE VIETNAMESE COASTLINE. THE ONCE ASHORE THE
SYSTEM WILL BE SLOW TO WEAKEN AT FIRST DUE TO PASSAGE OVER THE RED
RIVER DELTA REGION BUT WILL RAPIDLY WEAKEN AFTER THE FIRST FEW
HOURS OVER LAND. FULL DISSIPATION OVER THE FAR NORTHERN PORTION OF
LAOS IS EXPECTED BY TAU 48.

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY TIGHT AGREEMENT, WITH
LITTLE IN THE WAY OF CROSS- OR ALONG-TRACK SPREAD, LENDING HIGH
CONFIDENCE TO THE JTWC TRACK FORECAST. INTENSITY GUIDANCE IS FOR
THE MOST PART INDICATING A WEAKENING TREND FROM THE START OF THE
FORECAST. HOWEVER, THE RIDE RAPID INTENSIFICATION AID, AS WELL AS
THE HAFS-A AND HWRF INTERPOLATED MESOSCALE MODELS ARE INDICATING
INTENSIFICATION, WITH RIDE REACHING 125 KNOTS WHILE THE HAFS-A AND
HWRF SHOWING A PEAK OF 115 KNOTS. THE NON-INTERPOLATED 1200Z HAFS-A
AND HWRF SHOW A PEAK INTENSITY OF 130-135 KNOTS, PROVIDING
ADDITIONAL SUPPORT FOR A SHORT PERIOD OF RI IN THE GULF OF TONKIN.
THE JTWC FOLLOWS THE INTERPOLATED HWRF TO 115 KNOTS, THEN RAPIDLY
WEAKENS THE SYSTEM THEREAFTER IN PHASE WITH THE CONSENSUS MEAN.
CONFIDENCE IN THE INTENSITY FORECAST IS MEDIUM.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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