Advisories

WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 044//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.1N 139.1E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 158 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 30W
(IN-FA) WITH A STEADILY IMPROVING CONVECTIVE STRUCTURE AND SIGNS OF
A REDEVELOPING EYE. CLOUD TOPS HAVE CONTINUED TO COOL OVER THE PAST
6 HOURS AND THE CONVECTIVE BANDING HAS BECOME MORE DEFINED,
PARTICULARLY ALONG THE EASTERN SEMICIRCLE. A 030300Z AMSR3 37 GHZ
MICROWAVE IMAGE REVEALED A LARGE MICROWAVE EYE FEATURE WITH A
WEAKNESS IN THE NORTHWESTERN QUADRANT. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED MSI ALONG WITH
EXTRAPOLATION FROM THE AMSR3 MICROWAVE IMAGE. THE INITIAL INTENSITY
OF 70 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE HIGHER
END OF THE AGENCY DVORAK FIXES AND CIMSS INTENSITY ESTIMATES LISTED
BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 30W IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW
ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA
SURFACE TEMPERATURES OFFSET BY DRY AIR ENTRAINMENT FROM THE WEST.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT WITH A
DEEP-LAYER STR TO THE EAST AND ANOTHER DEEP-LAYER STR TO THE WEST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   CIMSS SATCON: 61 KTS AT 030412Z
   CIMSS ADT: 37 KTS AT 030600Z
   CIMSS AIDT: 61 KTS AT 030600Z
   CIMSS D-MINT: 62 KTS AT 030412Z
   CIMSS D-PRINT: 63 KTS AT 030600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 30W IS FORECAST TO TRACK SLOWLY
NORTHWESTWARD, ALONG THE WESTERN PERIPHERY OF THE STR TO THE EAST
THROUGH TAU 12. THE STR TO THE WEST, WHICH IS CENTERED NEAR TAIWAN,
WILL REMAIN IN PLACE THROUGH TAU 12, KEEPING THE SPEED OF ADVANCE
BELOW 5 KTS. AFTER TAU 12, AN INCOMING TROUGH WILL BREAK DOWN THE
WESTERN RIDGE, ALLOWING FOR THE EASTERN RIDGE TO BECOME THE PRIMARY
STEERING MECHANISM. THIS WILL CAUSE 30W TO ACCELERATE
NORTHEASTWARD, AROUND THE NORTHWESTERN EXTENT OF THE STR,
THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. IN TERMS OF
INTENSITY, 30W IS FORECAST TO SLIGHTLY REINTENSIFY OVER THE NEXT
12-24 HOURS IN RESPONSE TO THE ROBUST POLEWARD OUTFLOW AND LOW
VERTICAL WIND SHEAR. BY TAU 36, WESTERLY SHEAR WILL BEGIN TO
INCREASE, PUTTING AN END TO THE REDEVELOPMENT. 30W WILL THEN CROSS
THE 26 C SST ISOTHERM AROUND TAU 48, FURTHER AIDING IN WEAKENING
THE SYSTEM. HOWEVER, THE EXCEPTIONAL POLEWARD OUTFLOW CHANNEL AND
BAROCLINIC FORCING IS FORECAST TO ALLOW 30W TO MAINTAIN
TYPHOON-INTENSITY THROUGHOUT THE TRANSITION INTO AN EXTRATROPICAL
CYCLONE. EXTRATROPICAL TRANSITION IS FORECAST TO BEGIN AT TAU 60
WITH COMPLETION AROUND TAU 72, AS THE VORTEX BECOMES EMBEDDED IN
THE STRONG MID-LATITUDE WESTERLIES WITH AN EXPANSIVE WIND FIELD.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT IN THE
CROSS-TRACK DIRECTION WITH A CROSS-TRACK SPREAD OF JUST 50 NM AT
TAU 48 AND 160 NM AT TAU 72. NAVGEM IS THE SOLE EAST-OF-TRACK AND
SLOW OUTLIER THIS MODEL RUN. THERE CONTINUES TO BE A CONSIDERABLE
AMOUNT OF ALONG-TRACK SPREAD THOUGH, ESPECIALLY FROM TAU 60 ONWARD.
THE PHYSICS-BASED MODELS REMAIN THE SLOWER GROUPING WHILE THE
AI-BASED MODELS ARE FASTER AROUND THE RIDGE. THE JTWC TRACK
FORECAST IS PLACED NEAR THE MODIFIED CONSENSUS (REMOVING NAVGEM)
THROUGH TAU 48, AND THEN HEDGED CLOSER TO THE AI CONSENSUS THROUGH
TAU 72 WITH OVERALL MEDIUM CONFIDENCE. INTENSITY GUIDANCE GENERALLY
AGREES ON INTENSIFICATION THROUGH TAU 24-36 FOLLOWED BY WEAKENING
THROUGH TAU 48 AND THEN STEADY THROUGH TAU 72. COAMPS-TC IS THE
MOST AGGRESSIVE MODEL THIS RUN, SUGGESTING A PEAK INTENSITY OF 90
KTS AT TAU 24. THE JTWC INTENSITY FORECAST FOLLOWS THE MULTI-MODEL
CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH MEDIUM CONFIDENCE.

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