WDPN34 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) 
WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 138.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 168 NM NORTH OF YAP
   MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 27W WITH IMPROVING CONVECTIVE BANDING WRAPPING
CYCLONICALLY AROUND THE WESTERN AND SOUTHEASTERN QUADRANTS. FLARING
CONVECTION IS EVIDENT OVER THE LOW-LEVEL CIRCULATION CENTER AS THE
SYSTEM HAS CONTINUED TO CONSOLIDATE OVER THE LAST FEW HOURS. AROUND
THE PERIPHERY OF THE SYSTEM, OBSERVABLE LOW-LEVEL CLOUD LINES LAZILY 
ROTATE JUST OUTSIDE OF THE UPPER-LEVEL CIRRUS SHIELD, LENDING 
CONFIDENCE TO THE ASSESSMENT OF A WEAK TROPICAL STORM. UPPER-LEVEL 
OUTFLOW HAS BEEN OBSERVED TO BE WEAK ON THE ANIMATED WATER VAPOR 
LOOP, SHOWING MINIMAL EQUATORWARD FLOW IN THE EASTERN SEMICIRCLE. THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE 
AFOREMENTIONED ANIMATED EIR SATELLITE IMAGERY, SHOWING LOW-LEVEL 
CLOUD LINES WRAPPING INTO THE WESTERN QUADRANT OF THE SYSTEM INTO AN 
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL INTENSITY 
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND 
OBJECTIVE INTENSITY ESTIMATES LISTED BELOW, HOVERING AROUND 33-36 
KTS. THE ENVIRONMENT REMAINS CONDUCIVE FOR FURTHER INTENSIFICATION AS 
VERTICAL WIND SHEAR (VWS) REMAINS LESS THAN 20 KTS, SEA SURFACE 
TEMPERATURES RANGE BETWEEN 29 C AND 30 C, AND DRY AIR REMAINS OUTSIDE 
OF THE CENTRAL STRUCTURE.

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: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 110730Z
   CIMSS AIDT: 34 KTS AT 110730Z
   CIMSS D-MINT: 36 KTS AT 110643Z
   CIMSS D-PRINT: 35 KTS AT 110730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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: TROPICAL STORM 27W IS FORECASTED TO TRACK
ALONG THE SOUTHWESTERN AND WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE 
DIRECTLY TO THE NORTHEAST THROUGHOUT THE 120 FORECAST PERIOD. BETWEEN 
TAU 0 AND TAU 72, THE SYSTEM IS EXPECTED TO TRACK WEST-NORTHWEST. 
AFTER TAU 72, 27W WILL BEGIN ITS NORTHWARD APPROACH TO THE 
SUBTROPICAL RIDGE AXIS NEAR THE LUZON STRAIT. AFTER TAU 96, THE 
SYSTEM IS FORECASTED TO TRACK NORTHEASTWARD JUST EAST OF TAIWAN ALONG 
THE WESTERN REACH OF THE AFOREMENTIONED SUBTROPICAL RIDGE. WITH 
REGARD TO INTENSITY, TS 27W IS EXPECTED TO STEADILY INTENSIFY TO 105 
KTS BY TAU 72 JUST EAST OF LUZON AS THE ENVIRONMENT REMAINS CONDUCIVE
WITH LOW VERTICAL WIND SHEAR NEAR 15 KTS, WARM SEA SURFACE
TEMPERATURES RANGING BETWEEN 29 C AND 30 C, AND A SUPPORTIVE POINT
SOURCE IN THE UPPER-LEVELS AIDING IN ENHANCED OUTFLOW ALOFT. AFTER
TAU 72, DRY AIR WILL BEGIN ADDING PRESSURE TO THE SYSTEMS SOUTHERN
SEMICIRCLE, EVENTUALLY MAKING ITS WAY INTO THE ONCE MOIST INNER
CORE. BETWEEN TAU 72 AND TAU 120, DRY AIR ENTRAINMENT AND INCREASED
VERTICAL WIND SHEAR WILL FURTHER WEAKEN THE SYSTEMS INTENSITY,
DECREASING SURFACE WINDS TO 45 KTS BY TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
WITH A NARROW CROSS-TRACK SPREAD OF 70 NM BY TAU 72. THE ONLY
EXCEPTION OUTSIDE OF THE TRACK SPREAD IS NAVGEM, WHICH MAINTAINS A
TRACK SLIGHTLY NORTH OF THE JTWC CONSENSUS. AFTER TAU 72, TRACK
GUIDANCE BEGINS TO DIVERGE SIGNIFICANTLY IN CLOSE PROXIMITY TO
LUZON, INCREASING THE SPREAD TO 183 NM BY TAU 96. BETWEEN TAU 96
AND TAU 120, BIFURCATION IN NUMERICAL MODEL TRACK GUIDANCE IS
OBSERVED AS INFLUENCES FROM EQUATORWARD EXTENDING MID-LATITUDE
WESTERLIES ARE CAUSING A SIGNIFICANT DIVERGENCE IN TRACK SOLUTIONS,
INCREASING THE CROSS-TRACK SPREAD EVEN FURTHER. WITH THIS, TRACK
CONFIDENCE IS HIGH DURING THE FIRST 72 HOURS AND BECOMES LOW
BETWEEN TAU 72 AND TAU 120. THE JTWC INTENSITY GUIDANCE IS IN
MODERATE AGREEMENT THAT THE SYSTEM WILL INTENSIFY INTO TAU 72, THEN
BEGIN ITS WEAKENING PHASE THEREAFTER AS VWS INCREASES TO ABOVE 20
KTS AND DRY AIR ENTRAINS INTO THE SYSTEM NEAR THE EXPECTED
NORTHWARD TRACK IN CLOSE PROXIMITY TO THE SUBTROPICAL RIDGE AXIS.

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