Advisories

WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15E (NOLO) WARNING NR 064//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.4N 169.1E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 391 NM NORTH-NORTHEAST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTED THE
SUDDEN AND DRAMATIC COLLAPSE OF TYPHOON (TY) 15E'S CENTRAL EYE JUST
A FEW HOURS AGO. ADDITIONALLY, THE POLEWARD OUTFLOW CHANNEL IS
COMPLETELY SUPPRESSED BY THE MODERATE TO HIGH (20-25 KTS) NORTHERLY
VERTICAL WIND SHEAR (VWS). THE EQUATORWARD OUTFLOW CHANNEL REMAINS
AVAILABLE, BUT INCREASINGLY WEAK. THE 061015Z ASCAT DATA REVEALS
A TIGHT INNER CORE WITH AN ASYMMETRIC WIND FIELD. A THIN BAND OF
STORM- AND TYPHOON-FORCE WINDS IS PRESENT ALONG THE SOUTHWESTERN
SEMICIRCLE, CONTRASTED BY THE EXPANSIVE RANGE OF ELEVATED WINDS
WITHIN THE NORTHEAST SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS A
MARGINALLY UNFAVORABLE ENVIRONMENT, CHARACTERIZED BY MODERATE TO
HIGH VWS, SIGNIFICANT DRY AIR ENTRAINMENT, MARGINAL (0-20 KJ PER CM
SQUARED) OCEAN HEAT CONTENT (OHC), AND POOR OUTFLOW, OFFSET
SLIGHTLY BY WARM (27-28 C) SEA SURFACE TEMPERATURES (SST). THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
COLLAPSED EYE IN ANIMATED EIR AND EXTRAPOLATION FROM THE 061015Z
ASCAT DATA. THE INITIAL INTENSITY OF 100 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND THE CIMSS
AUTOMATED INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: ADJUSTED WIND RADII USING THE 061015Z
ASCAT DATA

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   PHFO: T5.0 - 90 KTS
   CIMSS ADT: 97 KTS AT 061200Z
   CIMSS AIDT: 95 KTS AT 061200Z
   CIMSS D-PRINT: 90 KTS AT 061200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TY 15E (NOLO) IS FORECAST TO CONTINUE TRACKING
WESTWARD TO WEST-NORTHWESTWARD WHILE IT REMAINS ON THE EQUATORWARD
PERIPHERY OF THE STR CENTERED TO THE NORTHEAST. BEGINNING AROUND
TAU 48, 15E WILL TURN POLEWARD INTO A WEAK STEERING ENVIRONMENT
CREATED BY A BREAK BETWEEN THE ROBUST STEERING STR AND A BUILDING
LOW- TO MID-LEVEL RIDGE CENTERED OVER JAPAN. DURING THIS PERIOD,
15E IS FORECAST TO SLOW ITS TRANSLATIONAL SPEED. ULTIMATELY, 15E IS
FORECAST TO DRIFT POLEWARD AND RECURVE ABOUT THE STEERING RIDGE
THROUGH THE REMAINDER OF THE FORECAST PERIOD. TRANSITION INTO AN 
EXTRATROPICAL CYCLONE WILL BEGIN NO LATER THAN TAU 120.
REGARDING INTENSITY, 15E IS FORECAST TO STEADILY WEAKEN THROUGH TAU
36-48 AS THE ENVIRONMENT REMAINS MARGINALLY UNFAVORABLE. BY ABOUT
TAU 48, VWS IS EXPECTED TO ABATE SLIGHTLY, CONCURRENT WITH THE
POLEWARD OUTFLOW CHANNEL STRENGTHENING AS THE STORM ENTERS THE
WEAKNESS BETWEEN RIDGES. AS A RESULT, 15E IS ANTICIPATED TO
REINTENSIFY SLIGHTLY BETWEEN TAU 60-72. AFTER TAU 72, VWS IS
EXPECTED TO INCREASE, STIFLING THE POLEWARD OUTFLOW CHANNEL AND
FORCING EXCESSIVE AMOUNTS OF DRY AIR INTO THE CORE. THE
ENVIRONMENT WILL CONTINUE TO DETERIORATE AS NOLO TRACKS POLEWARD,
ALONG WITH THE WEAK OUTFLOW, VWS, AND DRY AIR, IT IS EXPECTED TO
CROSS THE 26C ISOTHERM AROUND TAU 96. BETWEEN TAU 96-120, 15E IS
FORECAST TO BEGIN INTERACTION WITH THE UPPER-LEVEL WESTERLIES AND
ENTER THE BAROCLINIC ZONE, THUS BEGINNING EXTRATROPICAL
TRANSITION.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 24, AT WHICH POINT THE CROSS-TRACK SPREAD
BEGINS TO INCREASE. THE SPREAD GETS PARTICULARLY LARGE AROUND TAU
48, AS MODELS DISAGREE ON THE TIMING AND SPEED OF THE POLEWARD
TURN. THE DISAGREEMENT CONTINUES TO GET EXACERBATED THROUGH THE
REMAINDER OF THE FORECAST PERIOD, ULTIMATELY RESULTING IN A
CROSS-TRACK SPREAD OF 900 NM AT TAU 120 BETWEEN THE WESTERN-MOST
MEMBER (ECMWF) AND THE EASTERN-MOST MEMBER (GSM). THE ALONG-TRACK
SPREAD ALSO INCREASES OVER THE COURSE OF THE FORECAST, THOUGH NOT
NEARLY AS DRAMATICALLY AS THE CROSS-TRACK SPREAD. THE JTWC TRACK
FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS, THE GFS SOLUTION,
AND THE EXPERIMENTAL GOOGLE DEEPMIND WITH MEDIUM CONFIDENCE FROM
TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120. RELIABLE INTENSITY
AIDS ARE IN AGREEMENT ON GENERAL INTENSITY TRENDS, BUT NOT
EXACT INTENSITY. ALL MODELS DEPICT A STEADY WEAKENING TREND THROUGH
TAU 36-48 FOLLOWED BY A SLIGHT REINTENSIFICATION BETWEEN TAU 60-72,
THEN A FINAL WEAKENING TREND. THE JTWC INTENSITY FORECAST IS IN
CLOSE AGREEMENT WITH THE MULTI-MODEL CONSENSUS WITH MEDIUM
CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120. 

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