Advisories

WDPN32 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 29W (CHAMPI) WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.9N 150.2E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 328 NM EAST-SOUTHEAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 29 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 29W (CHAMPI) ASSESSED TO HAVE BEGUN RAPID INTENSIFICATION
(RI) OVER THE PAST SIX HOURS AS IT ATTEMPTS TO FORM A PINHOLE EYE
WITHIN THE COMPACT CORE. CONVECTION REMAINS EXPANSIVE TO THE SOUTHWEST
WITH THE PERIPHERY OF THE CLOUD SYSTEM BEGINNING TO NEAR THE
MARIANAS, WHILE THE BANDING ON THE NORTHERN SEMICIRCLE CONTINUES
TO DEVELOP. ENVIRONMENTAL CONDITIONS ARE ASSESSED AS FAVORABLE WITH
WARM (29-30 C) SEA SURFACE TEMPERATURES, LOW TO MODERATE (15-20
KTS) VERTICAL WIND SHEAR (VWS), AND STRONG WESTWARD OUTFLOW ALOFT.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
DEVELOPING EYE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE, BASED ON A BLEND OF AGENCY DVORAK FIXES AND CIMSS
OBJECTIVE ESTIMATES AS RI CONTINUES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTH-NORTHEAST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.0 - 65 KTS
   CIMSS SATCON: 77 KTS AT 161540Z
   CIMSS ADT: 97 KTS AT 161800Z
   CIMSS AIDT: 78 KTS AT 161800Z
   CIMSS D-MINT: 82 KTS AT 161617Z
   CIMSS D-PRINT: 75 KTS AT 161930Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG WESTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DEVIATION FROM PREVIOUS FORECAST
INTENSITY TO DEPICT AN INCREASE OF 15 KTS BETWEEN TAUS 0 TO 48
BASED ON RI

FORECAST DISCUSSION: FORECAST DISCUSSION: TY 29W IS FORECAST TO
TRACK STEADILY WEST-NORTHWESTWARD FOR THE NEXT 48 HOURS UNDER THE 
STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTH-NORTHEAST. THE RIDGING WILL REORIENT AROUND TAU 48 DUE TO
THE PASSAGE OF A MID-LATITUDE TROUGH, CREATING A WEAKNESS IN THE
STEERING ENVIRONMENT, ALLOWING 29W TO TURN MORE NORTHWESTWARD.
HOWEVER, ANOTHER STR CENTERED OVER TAIWAN IS EXPECTED TO BUILD, 
RESULTING IN AN OVERALL NORTHWESTWARD TRACK FOR THE REMAINDER OF
THE FORECAST PERIOD. REGARDING INTENSITY, TY 29W IS FORECAST TO
CONTINUE RAPIDLY INTENSIFYING FOR THE NEXT 48 HOURS AS ENVIRONMENTAL
CONDITIONS IMPROVE, WITH VWS DROPPING BELOW 10 KTS BY TAU 48 AS WELL 
AS MOVE INTO AN AREA OF HIGHER (120-150 KJ PER CM SQUARED) OCEAN HEAT 
CONTENT. AN OVERALL PEAK OF 135 KTS IS EXPECTED BETWEEN TAUS 48 AND 
72, ALTHOUGH THERE REMAINS A POSSIBILITY FOR A HIGHER PEAK. THE TIME 
OF CPA TO GUAM REMAINS CONSISTENT, ALTHOUGH THE NEW INTENSITY FORECAST 
NOW INCLUDES TINIAN AND SAIPAN FURTHER WITHIN THE EXPECTED GALE-FORCE 
WINDS BETWEEN TAUS 12 TO 48 DURING THE PASSAGE OF 29W SOUTH OF THE 
ISLAND CHAIN.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT IN THE 
SHORT TERM, WITH A 45 NM CROSS TRACK SPREAD AT TAU 24 AS 29W CPAS 
GUAM. SPREAD EXPANDS TO 150 NM BY TAU 72 AS MODELS DIVERGE 
ON THE TIMING OF THE NORTHWESTWARD TURN AS THE STEERING RIDGE 
REORIENTS. BY TAU 120, CROSS-TRACK SPREAD IS 200 NM AND ALONG-TRACK 
SPREAD IS 150 NM. THE OFFICIAL JTWC FORECAST TRACK IS ASSESSED WITH 
HIGH CONFIDENCE OUT TO TAU 72 AND MEDIUM CONFIDENCE THEREAFTER, 
CLOSELY IN LINE WITH THE MULTI-MODEL AND AI CONSENSUS TRACKS 
THROUGHOUT. MODEL INTENSITY GUIDANCE IS IN STRONG AGREEMENT OF A 
PERIOD OF RI OUT TO TAU 48 WITH A MAJORITY OF RI AIDS POPULATING. THE 
PREDICTED PEAK INTENSITIES OF HAFS-A AND GOOGLE DEEPMIND CONTINUE TO
INCREASE, REACHING 160 KTS AND 140 KTS, RESPECTIVELY. THE OUTLIERS
OF GFS AND NAVGEM BASED COAMPS-TC AND DECAY SHIPS PORTRAY A MUCH
MORE GRADUAL INTENSIFICATION AND PEAK OF AROUND 110 KTS. WHILE
CONTINUED RI IS ASSESSED TO BE VERY LIKELY, THE OFFICIAL JTWC
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE FOR THE
REMAINDER OF THE FORECAST PERIOD BASED ON THE UNCERTAINTY OF THE
ULTIMATE PEAK INTENSITY OF THE SYSTEM, BUT PLACED IN GOOD
AGREEMENT WITH GOOGLE DEEPMIND, ABOVE THE MULTI-MODEL CONSENSUS TO 
ACCOUNT FOR THE EFFECT OF THE PREVIOUSLY MENTIONED OUTLIERS THAT DO 
NOT PREDICT RI.

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