WDPN34 PGTW 111500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 136.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 203 NM NORTH-NORTHWEST OF YAP
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TS 27W
AS CONTINUING TO SLOWLY CONSOLIDATE OVER THE LAST SIX HOURS, WITH
FORMATIVE CONVECTIVE BANDING WRAPPING CYCLONICALLY AROUND THE
NORTHERN AND WESTERN QUADRANTS, SIGNIFYING INCREMENTAL
INTENSIFICATION. ALTHOUGH INTENSIFICATION HAS BEEN OBSERVED FROM JUST 
A FEW HOURS AGO, THE ANIMATED WATER VAPOR LOOP CONTINUES TO SHOW WEAK
POLEWARD OUTFLOW ALOFT, LIMITING 27W TO SLOW AND STEADY
INTENSIFICATION. AROUND THE PERIPHERY OF THE SYSTEM, DRY AIR IS
EVIDENT AS MUCH OF THE SOUTHEAST QUADRANT REMAINS CONVECTION FREE
WITH SLOW-MOVING LOW-LEVEL CYCLONICALLY ROTATING CLOUD LINES. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON AN
110909Z 91 GHZ MICROWAVE IMAGE SHOWING LOW-LEVEL CLOUD LINES
LOOSELY WRAPPING INTO THE ASSESSED LOW-LEVEL CIRCULATION CENTER
(LLCC), OBSCURED BY FRAGMENTED CENTRAL AND SPORADIC CONVECTION. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
SUBJECTIVE AGENCY ESTIMATES LISTED BELOW AND CIMSS OBJECTIVE
ESTIMATES RANGING BETWEEN 35 KTS AND 43 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST AND
EXTENDING WESTWARD.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 43 KTS AT 111330Z
   CIMSS AIDT: 37 KTS AT 111330Z
   CIMSS D-PRINT: 35 KTS AT 111330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-31 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TROPICAL STORM 27W IS FORECASTED TO CONTINUE
TO TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE
TO THE NORTH THROUGH THE FIRST 72 HOURS OF THE FORECAST PERIOD.
FOLLOWING TAU 72, 27W BEGINS THE NORTHWARD TRACK OVER LUZON AND INTO
THE LUZON STRAIT, ROUNDING THE SUBTROPICAL RIDGE AXIS JUST
SOUTHEAST OF TAIWAN BY TAU 120. AFTER TAU 96, THE SYSTEM WILL BEGIN
ITS NORTHEAST TRACK INTO TAU 120 ALONG THE WEST-NORTHWEST PERIPHERY
OF THE STR. WITH REGARD TO INTENSITY, TS 27W IS FORECASTED TO
STEADILY INTENSIFY TO 105 KTS BY TAU 72 AS THE ENVIRONMENT REMAINS
LARGELY CONDUCIVE, WITH LOW VERTICAL WIND SHEAR (VWS) OF 19 KTS OR
LESS, WARM SEA SURFACE TEMPERATURES RANGING FROM 29 C TO 30 C, AND
AN UPPER-LEVEL POINT SOURCE PROVIDING OUTFLOW ALOFT. AFTER TAU 72,
DRY AIR ENTRAINMENT IS EXPECTED TO BEGIN ERODING THE SYSTEM FROM
THE WEST, WRAPPING CYCLONICALLY INTO THE SOUTHERN QUADRANT AND INTO
THE VERTICAL STRUCTURE THEREAFTER. ALONG WITH THE AFOREMENTIONED
DRY AIR, WESTERLY VWS INCREASES SUBSTANTIALLY AFTER TAU 72 WITH A
MAGNITUDE OF 25 KTS OR GREATER INTO TAU 120, FURTHER ERODING THE
SYSTEMS STRUCTURE. BY TAU 120, 45 KTS INTENSITIES ARE EXPECTED AS
TS 27W CONTINUES ITS WEAKENING PHASE WITH COOLER SEA SURFACE 
TEMPERATURES NEAR LATITUDE 20 N IN CLOSE PROXIMITY TO TAIWAN.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY TIGHT
AGREEMENT WITH A CONTINUED AND NARROW CROSS-TRACK SPREAD OF JUST 67
NM BY TAU 48. AFTER TAU 48, TRACK GUIDANCE DIVERGES AS TS 27W
CONTINUES THE AFOREMENTIONED ANTICYCLONIC TRACK AROUND THE STR,
INCREASING TO 212 NM AT TAU 96. AFTER TAU 96, THE TRACK GUIDANCE
CONFIDENCE LESSENS FURTHER WITH A BIFURCATION IN SOLUTIONS DUE TO
VARYING INFLUENCES FROM THE EQUATORWARD EXTENDING MID-LATITUDE
WESTERLIES AS TS 27W NEARS LUZON. WITH THAT BEING SAID, THE JTWC
TRACK CONFIDENCE IS HIGH THROUGH THE FIRST 72 HOURS, DECREASING
THEREAFTER INTO TAU 120. THE JTWC INTENSITY GUIDANCE IS IN TIGHT
AGREEMENT THAT INTENSIFICATION IS FORECASTED INTO TAU 72 WITH
CONDUCIVE ENVIRONMENTAL PARAMETERS. AFTER TAU 72, AN INITIAL
WEAKENING PHASE IS EXPECTED INTO THE END OF THE FORECAST PERIOD AS
TS 27W PROGRESSES THROUGH THE LUZON STRAIT AND JUST EAST OF TAIWAN,
LENDING MEDIUM CONFIDENCE TO THE JTWC INTENSITY FORECAST BETWEEN
TAU 72 AND TAU 120. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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