Advisories

WDPN31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15E (NOLO) WARNING NR 066//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.3N 164.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 388 NM SOUTH-SOUTHEAST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
DEGRADED VORTEX STRUCTURE, CHARACTERIZED BY A COLLAPSING AND
INCREASINGLY ASYMMETRIC CENTRAL DENSE OVERCAST (CDO). THE INNER CORE
OF THE CDO REMAINS REMARKABLY RESILIENT; HOWEVER, IT EXHBITS
PRONOUNCED ZONAL ELONGATION IN RESPONSE TO PERSISTENT EASTERLY 
VERTICAL WIND SHEAR (VWS). THE LATEST HIGH-RESOLUTION MICROWAVE PASS, 
A 061918Z WSF-M COLOR-ENHANCED IMAGE, REVEALED THE LAST SATELLITE 
EVIDENCE OF AN UPPER-LEVEL EYE SIGNATURE COINCIDENT WITH THE 
INITIATION OF VERTICAL VORTEX DECOUPLING. THE INITIAL POSITION IS 
ASSESSED WITH LOW CONFIDENCE, DERIVED FROM AN EXTENDED DOWNSTREAM 
EXTRAPOLATION OF EARLIER MICROWAVE FIXES. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE, ALIGNED WITH THE SUBJECTIVE AND 
OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW. ENVIRONMENTAL 
CONDITIONS ARE UNFAVORABLE FOR TROPICAL DEVELOPMENT, DOMINATED BY 
STRONG AND PERSISTENT EASTERLY SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   PHFO: T4.5 - 77 KTS
   CIMSS SATCON: 78 KTS AT 062100Z
   CIMSS ADT: 69 KTS AT 062330Z
   CIMSS AIDT: 86 KTS AT 062330Z
   CIMSS D-MINT: 77 KTS AT 062239Z
   CIMSS D-PRINT: 72 KTS AT 070030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TYPHOON (TY) 15E (NOLO) CONTINUES TO TRANSLATE
WESTWARD AT A HIGH VELOCITY ALONG THE STEEP PRESSURE GRADIENT ON THE
EQUATORWARD SIDE OF THE EXPANSIVE STR CENTERED TO THE NORTH. 15E WILL
CONTINUE TRACKING WEST-NORTHWESTWARD THROUGH TAU 36, DECELERATING 
AFTER TAU 24 AS IT TRANSITS INTO THE WEAKENED STEERING GRADIENT ALONG 
THE SOUTHWESTERN PERIPHERY OF THE STR. THE CYCLONE WILL SLOW TO 
APPROXIMATELY 7 KNOTS BY TAU 60 AS IT APPROACHES THE RIDGE AXIS. THE 
SYSTEM IS FORECAST TO INTERSECT THE RIDGE AXIS BY TAU 72, THEREAFTER 
EXECUTING RECURVATURE AND ACCELERATING NORTHEASTWARD BY THE LATER 
FORECAST TAUS. REGARDING INTENSITY: PERSISTENT NORTHEASTERLY VWS WILL 
WORK TO WEAKEN 15E FOR THE NEXT 24 TO 36 HOURS. AS THE SYSTEM 
APPROACHES THE RIDGE AXIS, SHEAR IS FORECAST TO RELAX SLIGHTLY, 
FACILITATING A BRIEF PERIOD OF STABILIZATION OR MODEST RE-
INTENSIFICATION AS 15E COUPLES WITH THE OUTFLOW INTO A POLAR JET MAX 
TRANSITING TO THE NORTH. POST-TAU 72, HOWEVER, ACCELERATING SHEAR 
COMPILED WITH A SHARP DECREASE IN SSTS WILL DRIVE RAPID DECAY THROUGH 
THE REMAINDER OF THE FORECAST. THERE REMAINS A SIGNIFICANT AMOUNT OF 
UNCERTAINTY IN THE TRACK FORECAST, CRITICALLY MODULATED BY BINARY 
INTERACTION WITH TS 27W, CURRENTLY POSITIONED APPROXIMATELY 650 NM 
SOUTH-SOUTHWEST OF 15E. THE SEPARATION DISTANCE IS PROJECTED TO HOVER 
NEAR 600 NM THROUGHOUT THE FORECAST PERIOD. THE PRIMARY DYNAMICAL 
DIVERGENCE CENTERS ON THE LONGITUDE OF THE RECURVATURE POINT, WHICH 
IS A DIRECT FUNCTION OF THE COUPLING MAGNITUDE WITH TS 27W. THE ECMWF 
AND GFS DYNAMICAL SUITES DELAY RECURVATURE, EXTENDING THE WESTWARD 
TRACK COMPONENT SIGNIFICANTLY. CONVERSELY, AI-ML SOLUTIONS PROJECT 
MINIMAL BINARY COUPLING AS 15E OUTRACES TS 27W, PROMOTING AN EARLIER 
POLEWARD RECURVATURE ROUTE SITUATED FARTHER EAST. THE JTWC FORECAST 
STRONGLY FAVORS THE PROGRESSIVE AI-ML SCENARIO.


MODEL DISCUSSION: TRACK GUIDANCE DEPICTS SIGNIFICANT UNCERTAINTY,
EXHIBITING PRONOUNCED CROSS-TRACK DISPERSION. AS 15E APPROACHES THE 
RIDGE AXIS AT TAU 72, THE GUIDANCE PACKAGE IS FANNED ACROSS A 400 NM 
ENVELOPE, WITH THE AI CONSENSUS (AICN) AND EC-AIFS RESIDING ON THE 
EASTERN (INNER) PERIPHERY OF THE RECURVATURE PATH, WHILE THE 
DETERMINISTIC ECMWF AND ECEPS MEAN DEFINE THE WESTERN (OUTER) FLANK. 
THROUGH TAU 120, CROSS-TRACK ANOMALIES NARROW SLIGHTLY, ALTHOUGH 
ALONG-TRACK TRANSLATION SPEED BIAS BECOMES THE PREVALENT UNCERTAINTY 
DRIVER, STRETCHING TO OVER 500 NM BETWEEN THE FAST GFS AND THE SLOW 
MULTI-MODEL CONSENSUS MEAN. THE AI-ML RECURVATURE TRACKS ARE 
CLUSTERED ON THE EASTERN PERIPHERY OF THE ENVELOPE, MEDIAN TO THE 
ACCELERATING ALONG-TRACK OUTLIERS. THE ECMWF AND GFS EXCURSION 
REMAINS SOUTH-SOUTHWEST OF THE GROUP THROUGH TAU 120. THE JTWC TRACK 
IS POSITIONED NEAR THE GOOGLE DEEPMIND TRACKER WITH LOW CONFIDENCE. 
INTENSITY GUIDANCE IS IN GOOD AGREEMENT, WITH THE ENTIRE MODEL SUITE
PROJECTING AN INITIAL DECAY PHASE THROUGH TAU 24, A TEMPORARY 
STRUCTURAL STABILIZATION THROUGH TAU 48, AND ACCELERATED DECAY POST-
TAU 72.

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