WDPN33 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (HAIKUI) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.7N 124.4E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 215 NM SOUTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER A 12 HOUR PERIOD WHERE DEVELOPMENT WAS ARRESTED, TYPHOON (TY)
10W (HAIKUI) LOOKS TO HAVE DETERMINED TO RAPIDLY ORGANIZE AND
INTENSIFY. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS STRONG CONVECTION FIRING OFF ALONG THE SOUTHERN PERIPHERY,
REMINISCENT OF EARLIER PERIODS OF CONVECTIVE BLOOMING. EARLY
INDICATIONS ARE THAT THIS TIME AROUND, THE SHEAR HAS LESSENED, AND
THIS SHOULD ALLOW FOR THE CONVECTION TO BEGIN WRAPPING UPSHEAR AND
ULTIMATELY SURROUND THE INNER-CORE. THE MOST RECENT MICROWAVE
IMAGERY FROM 021004Z, SHOWED A STRONG EYEWALL ALONG THE ENTIRETY OF
THE SOUTHERN SIDE OF THE SYSTEM, BUT A VERY WEAK, EYEWALL TO THE
NORTH AND NORTHWEST. ANIMATED RADAR DATA SHOWS A SIMILAR PATTERN,
WITH A ROBUST SOUTHERN EYEWALL WITH A WEAK EYEWALL TO THE NORTHWEST. 
THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
JAPANESE RADAR DATA AND POSITION FIXES. REANALYSIS OF EARLIER 
INTENSITY DATA RESULTED IN A DOWNGRADE OF THE SYSTEM TO 80 KNOTS, AND 
THE CURRENT INTENSITY REMAINS SET AT THIS LEVEL BASED ON THE AVERAGE 
OF THE AGENCY CURRENT INTENSITY ESTIMATES, THOUGH IT IS
ACKNOWLEDGED THAT THIS IS STILL WELL ABOVE ALL OF THE OBJECTIVE
ESTIMATES. SHEAR IS LOWER NOW THAN 12 HOURS AGO AND IS NO LONGER A
SIGNIFICANT INHIBITOR. THE PRESENCE OF VERY DRY AIR INFLOWING FROM
THE NORTH, AS INDICATED IN THE 0000Z ISHIKAGIJIMA SOUNDING, IS
LIKELY THE GUILTY CULPRIT. THE MESOSCALE AND GLOBAL MODELS HOWEVER,
INDICATE THAT THE ATMOSPHERE WILL MOISTEN SIGNIFICANTLY AS THE
SYSTEM APPROACHES TAIWAN AND THE 1200Z SOUNDING SUGGESTS THIS MAY
BE OCCURRING, WITH THE WEDGE OF DRY AIR SEEN AT 0000Z NOW
COMPLETELY GONE. THE OVERALL ENVIRONMENT IS FAVORABLE FOR
INTENSIFICATION, SAVE FOR THE DRY AIR TO THE NORTH.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 67 KTS AT 021107Z
   CIMSS ADT: 63 KTS AT 021130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR TO THE NORTH. 

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: BASED ON THE LATEST RADAR ANIMATION, IT
APPEARS THAT TY 10W IS TRACKING ALMOST DUE WEST, ALONG THE SOUTHERN
SIDE OF THE STEERING RIDGE TO THE NORTH. SOME WOBBLES EITHER SIDE
OF THE FORECAST TRACK ARE EXPECTED, BUT OVERALL THE SYSTEM SHOULD
TRACK WEST-NORTHWEST THROUGH THE NEXT 12 TO 18 HOURS. LANDFALL
ALONG THE SOUTHWEST COAST OF TAIWAN, NEAR TAITUNG, IS FORECAST NEAR
TAU 18. AFTER LANDFALL, THE LOW LEVEL CENTER (LLC) WILL LIKELY TURN
SHARPLY SOUTHWESTWARD DUE TO TERRAIN EFFECTS, THEN CROSS BACK INTO
THE SOUTHERN PORTION OF THE TAIWAN STRAIT AROUND TAU 30. HOW MUCH
THE TRACK DEVIATES TO THE SOUTHWEST IS HIGHLY DEPENDENT ON THE
EXACT LANDFALL LOCATION AND APPROACH ANGLE AND THUS IS NOT CAPTURED
EXPLICITLY IN THE FORECAST TRACK. REGARDLESS, ONCE THE SYSTEM MOVES
BACK OVER WATER, A WEST-NORTHWEST TRACK WILL RESUME AS THE SYSTEM
COMES UNDER THE STEERING INFLUENCE OF STR AGAIN AND IT MOVES AWAY
FROM THE INFLUENCE OF THE TERRAIN OF TAIWAN. A SECOND LANDFALL IS
FORECAST JUST PRIOR TO TAU 72 ALONG THE COAST OF SOUTHEASTERN
CHINA, IN THE SOUTHERN REACHES OF FUJIAN PROVINCE. AFTER LANDFALL,
THE SYSTEM WILL CONTINUE TO SLOWLY TRACK FURTHER INLAND THROUGH THE
REMAINDER OF THE FORECAST PERIOD. IN TERMS OF INTENSITY, WITH THE
RECENT SOUNDING FROM ISHIKAGIJIMA SHOWING A DISTINCT MOISTENING OF
THE ENVIRONMENT TO THE NORTH, THE STAGE IS SET FOR THE SYSTEM TO
INTENSIFY QUICKLY PRIOR TO LANDFALL. THE LIMITED TIME REMAINING
PRIOR TO LANDFALL (ABOUT 18 HOURS) WILL LIMIT THE PEAK INTENSITY
HOWEVER. THE PEAK OF 105-110 KNOTS IS MOST LIKELY TO OCCUR JUST
AFTER TAU 12, AND THUS IS NOT CAPTURED IN THE DISCRETE FORECAST
POINTS. AFTER LANDFALL, THE RUGGED TERRAIN OF TAIWAN WILL TEAR THE
SYSTEM APART, LEADING TO A SHARP AND RAPID WEAKENING. AT BEST, THE
SYSTEM WILL EMERGE BACK OVER WATER AS A MINIMAL TYPHOON. CONDITIONS
IN THE TAIWAN STRAIT WILL GENERALLY BE FAVORABLE, BUT THE LIMITED
TIME OVER WATER MEANS THAT THE INTENSITY WILL REMAIN STEADY OR JUST
SLIGHTLY INCREASE PRIOR TO THE SECOND LANDFALL. AFTER MOVING
ASHORE, THE SYSTEM WILL RAPIDLY WEAKEN AND POTENTIALLY DISSIPATE BY
THE END OF THE FORECAST. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD AGREEMENT THROUGH TAU 72, WITH THE ENVELOPE GRADUALLY
EXPANDING TO 260NM AS THE SYSTEM MOVES INTO EASTERN CHINA. THERE
ARE TWO DISTINCT TRAJECTORIES EVIDENT IN THE GUIDANCE, WITH THE
GALWEM, NAVGEM, UKMET, AND UKMET ENSEMBLE TRACKING THE SYSTEM OVER
CENTRAL TAIWAN THEN NORTHWEST INTO EASTERN CHINA. THE SECOND GROUP
CONSISTS OF THE GFS, ECMWF, HAFS-A, COAMPS-TC, AND THE ASSOCIATED
ENSEMBLES WHICH DEPICT A MORE SOUTHERLY TRACK CONSISTENT WITH THE
JTWC FORECAST TRACK. BASED ON ANALYSIS OF THE UPPER-LEVEL STEERING
PATTERN AND RECENT TRACK MOTION, THE MORE SOUTHERN TRACK CLUSTER IS
DEEMED MORE LIKELY. OF NOTE, THE GFS IS A LONE OUTLIER AFTER TAU
72, IN TAKING THE SYSTEM TO THE SOUTHWEST TO NEAR HONG KONG BY TAU
120. THE ECMWF ALSO STARTS TO DRIFT TO A MORE SOUTHERLY TRACK BUT
REMAINS OVER SOUTHEASTERN CHINA. INTENSITY GUIDANCE IS IN FAIRLY
GOOD AGREEMENT, THOUGH CONTRARY TO THE PREVIOUS RUN, NONE OF THE
RAPID INTENSIFICATION (RI) AIDS ARE TRIGGERING. OF NOTE, THE ECENS
INTENSITY PROBABILITY CHART DOES SHOW A 30 PERCENT PROBABILITY OF
RI, WHICH IS HIGHLY UNUSUAL. THE HAFS-A ALSO SHOWS A SPIKE IN
INTENSITY UP TO 110 KNOTS BY TAU 12, FOLLOWED BY A SHARP DROP-OFF
AFTER LANDFALL. THE JTWC FORECAST AT TAU 12 IS 100 KNOTS, BUT A
PEAK OF 110 KNOTS IS POSSIBLE SHORTLY AFTER TAU 12 AND PRIOR TO
LANDFALL BUT IS NOT CAPTURED IN THE FORECAST POINTS. THE JTWC
FORECAST LIES ABOVE THE GUIDANCE THROUGH THE REMAINDER OF THE
FORECAST. 

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