Advisories

WDPN33 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KOGUMA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.9N 167.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 256 NM NORTH OF KWAJALEIN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TS 27W HAS STEADILY INTENSIFIED WHILE TRACKING NORTHWESTWARD OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS DEEP CONVECTION ISOLATED TO THE WESTERN PORTION OF A
LOW-LEVEL CIRCULATION CENTER THAT HAS BEEN PARTIALLY-EXPOSED BY
PERSISTENT, NEARLY UNIDIRECTIONAL EASTERLY FLOW ALOFT. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON ANIMATED MSI AND
A 052202Z METOP-SGA1 89 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY
OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A CONSENSUS
OF THE AUTOMATED CIMSS INTENSITY ESTIMATES LISTED BELOW, SLIGHTLY
ABOVE THE MULTI-AGENCY DVORAK FIX CONSENSUS OF APPROXIMATELY 40 
KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE AND PARTIAL 052305Z METOP-C
ASCAT PASS SHOWING THE WESTERN PERIPHERY OF THE CIRCULATION

CURRENT STEERING MECHANISM: BUILDING SUBTROPICAL RIDGE (STR)
EXTENSION TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS ADT: 51 KTS AT 052350Z
   CIMSS AIDT: 41 KTS AT 052350Z
   CIMSS D-MINT: 46 KTS AT 052256Z
   CIMSS D-PRINT: 36 KTS AT 052350Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS 27W WILL CONTINUE TO TURN TOWARD A
GENERALLY WEST-NORTHWESTWARD TRAJECTORY OVER THE NEXT 24 HOURS AS
AN EXTENSION OF SUBTROPICAL RIDGING TO THE NORTHEAST BUILDS ON THE
POLEWARD SIDE OF THE SYSTEM. THIS SUBTROPICAL RIDGE IS EXPECTED TO
REMAIN THE PRIMARY STEERING MECHANISM THROUGHOUT THE 120-HOUR
FORECAST PERIOD. BY TAU 96, TS 27W SHOULD PUSH A BIT POLEWARD AS IT
BEGINS TO ROUND THE SOUTHWESTERN EDGE OF THE STEERING RIDGE. SLOW
BUT STEADY INTENSIFICATION IS ANTICIPATED OVER THE NEXT 36 HOURS AS
MODERATE UPPER-LEVEL OUTFLOW AND PASSAGE OVER VERY WARM WATER VIE
WITH PERSISTENT EASTERLY VERTICAL WIND SHEAR. AFTER TAU 36,
DECREASING VERTICAL WIND SHEAR AND IMPROVING OUTFLOW - FIRST
EQUATORWARD AND LATER POLEWARD - WILL SUPPORT A HIGHER RATE OF
INTENSIFICATION THROUGH TAU 96.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT REGARDING THE OVERALL FORECAST SCENARIO. HOWEVER, VORTEX
TRACKERS FROM PHYSICAL AND AI-BASED MODELS ARE SPREAD NEARLY EVENLY
WITHIN AN ENVELOPE THAT STEADILY EXPANDS TO A 480 NM CROSS-TRACK
SPREAD BY TAU 120, WITH NAVGEM BRACKETING THE NORTHERN SIDE AND
NCEP AI-BASED MODELS BRACKETING THE SOUTHERN SIDE OF THE ENVELOPE.
GIVEN THE SMALL SIZE OF THE SYSTEM, TRACK ORIENTATION IS DEPENDENT
PRIMARILY ON EVOLUTION OF THE STEERING RIDGE, WHICH IS DEPICTED
SLIGHTLY DIFFERENTLY IN EACH MODEL SOLUTION. NOTABLY, ALONG TRACK
SPEEDS ARE CONSISTENT AMONG ALL MODELS ASIDE FROM THE
FASTER-TRACKING EGRR AND AFUM. THE CURRENT TRACK FORECAST LIES NEAR
THE CENTER OF ALL GUIDANCE, SPLITTING THE DIFFERENCE BETWEEN THE
PHYSICAL AND AI-BASED MODEL CONSENSUSES AND CONSISTENT WITH THE
PREVIOUS FORECAST. GIVEN NOTED SPREAD AMONG SOLUTIONS, ADDITIONAL
ADJUSTMENTS TO THE TRACK ORIENTATION ARE LIKELY IN SUBSEQUENT
FORECASTS. CONSENSUS INTENSITY FORECAST GUIDANCE INDICATES STEADY
INTENSIFICATION THROUGH AT LEAST TAU 72, WHILE GOOGLE DEEPMIND
INDICATES A SLOWER RATE THROUGH TAU 48 FOLLOWED BY RAPID
INTENSIFICATION THEREAFTER. ENVIRONMENTAL CONDITIONS FAVOR STEADY
INTENSIFICATION OVERALL, BUT WITH EASTERLY VERTICAL WIND SHEAR
EXPECTED TO PERSIST THROUGH TAU 36 THE RATE OF INTENSIFICATION IS
HELD BELOW THE INTENSITY CONSENSUS THROUGH TAU 36 AND CATCHES UP TO
THE PRIMARY MODEL GROUPING THEREAFTER. 

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