WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (KOINU) WARNING NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.2N 115.7E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 107 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 14W GENERALLY MAINTAINING A STEADY-STATE STRUCTURE CONSISTING
OF A COMPACT, SYMMETRICAL CIRCULATION WITH DEEP CONVECTION
SURROUNDING A WELL-DEFINED EYE. TY 14W REMAINS A SMALL SYSTEM AS IT
TRAVERSES WARM SEA SURFACE TEMPERATURES (29-30 DEGREES CELSIUS)
WITH LOW VERTICAL WIND SHEAR (0-5 KNOTS). THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE GIVEN THE WARM AND CLEAR EYE. THE
INITIAL INTENSITY REMAINS ASSESSED AT 100 KNOTS WITH MEDIUM
CONFIDENCE BASED ON A BLEND OF OBJECTIVE INTENSITY GUIDANCE AND
SUBJECTIVE DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 84 KTS AT 061753Z
   CIMSS ADT: 79 KTS AT 061730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE 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 14W IS FORECAST TO TRACK SLOWLY
WEST-SOUTHWESTWARD IN A FAIRLY WEAK STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE AXIS EXTENDING AROUND THE NORTHWESTERN PERIPHERY
OF THE SYSTEM. THE CURRENT WINDOW OF FAVORABLE ENVIRONMENTAL
CONDITIONS IS LIKELY TO MAINTAIN THE SYSTEM AS A TYPHOON THROUGH
THE NEXT DAY OR SO, BUT GRADUALLY WEAKENING IS FORECAST TO COMMENCE
DUE TO UPWELLING OF COOLER WATER AND THE INCREASE OF DRY AIR
ENTRAINMENT. BEYOND TAU 48, A TURN TOWARD THE SOUTHWEST AND AN
INCREASE IN FORWARD MOTION IS FORECAST AS THE SYSTEM IS DRIVEN
TOWARD HAINAN BY A SUBTROPICAL RIDGE BUILDING IN FROM THE
EAST-NORTHEAST. A FINAL LANDFALL OVER VIETNAM IS EXPECTED BY TAU
120.

MODEL DISCUSSION: THE GLOBAL MOEDELS ARE IN GOOD AGREEMENT WITH A
SLOW WESTWARD TRACK IN THE NEAR TERM, FOLLOWED BY AN ACCELERATION
TOWARD THE SOUTHWEST BEYOND TAU 48. TWO NOTABLE EXCEPTIONS ARE
NAVGEM AND GALWEM, WHICH SUGGEST A CURIOUS TURN TO THE NORTHWEST
TOWARD HONG KONG BEFORE RESUMING A SOUTHWESTWARD TRACK. THIS
SCENARIO IS DISCOUNTED GIVEN THE PRESENCE OF THE NARROW SUBTROPICAL
RIDGE AXIS TO THE NORTHWEST OF TY 14W. THE CROSS-TRACK SPREAD AT
TAU 72 IS 110 NM AND AT TAU 120 IS 250 NM, THUS LEADING TO A HIGH
CONFIDENCE IN THE NEAR-TERM TRACK FORECAST AND MEDIUM CONFIDENCE
THEREAFTER. THE INTENSITY GUIDANCE IS UNANIMOUS IN ITS STEADY
WEAKENING, SO THE OFFICIAL FORECAST FOLLOWS THE INTENSITY
CONSENSUS. THE INTENSITY FORECAST CONFIDENCE IS HIGH THROUGH TAU 72
AND MEDIUM THEREAFTER, DUE TO UNCERTAINTY ASSOCIATED WITH THE
TIMING OF THE POTENTIAL LAND INTERACTION WITH HAINAN ISLAND.

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