Advisories

WDPN32 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (PEILOU) WARNING 
NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.0N 158.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 623 NM NORTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 26 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 13W LOOKING DECEPTIVELY STRONG, WITH AN EXPANDING
CENTRAL CONVECTION CANOPY. HOWEVER IN THE LOWER LEVELS, THE
EASTERLY CLOUD LINES HAVE WEAKENED SIGNIFICANTLY AND APPEAR TO BE
BARELY WRAPPING INTO THE CORE, IF AT ALL. THE 110710Z WSFM 89 GHZ
MICROWAVE IMAGE REVEALS THE CENTER IS OFFSET TO THE SOUTH OF THE
CENTRAL CONVECTION, INDICATIVE OF THE 15-20 KTS OF SOUTHERLY
VERTICAL WIND SHEAR (VWS). THE IMAGE ALSO REVEALS THE TRUE EXTENT
OF THE DEEP CONVECTION, WHICH IS CONFINED TO A SMALL PORTION OF THE
NORTHERN QUADRANT. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY
UNFAVORABLE ENVIRONMENT, CHARACTERIZED BY SEVERE MID-LEVEL DRY AIR
ENTRAINMENT AND POOR OUTFLOW ALOFT, OFFSET SLIGHTLY BY THE LOW TO
MODERATE VWS AND WARM (28-29 C) SEA SURFACE TEMPERATURES (SST). THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 30 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE DVORAK FIXES LISTED
BELOW, SUPPORTED BY AN EARLIER 110218Z AMSR2 WINDSPEED PRODUCT THAT
SHOWS MAXIMUM WIND SPEEDS OF 25-30 KTS OUTSIDE OF THE RAIN
CONTAMINATED REGIONS.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
SOUTHEAST, ENHANCED BY THE MONSOONAL FLOW ASSOCIATED WITH THE LARGE
GYRE CENTERED TO THE WEST.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 53 KTS AT 110740Z
   CIMSS AIDT: 44 KTS AT 110740Z
   CIMSS D-MINT: 55 KTS AT 110609Z
   CIMSS D-PRINT: 42 KTS AT 110740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 13W IS FORECAST TO CONTINUE SPEEDING TO THE
NORTHEAST WHILE IT REMAINS STEERED BY THE NORTHWESTERN PERIPHERY OF
THE STR TO THE SOUTHEAST, WITH THE STEERING GRADIENT ENHANCED BY
THE MONSOONAL FLOW SURROUNDING THE LARGE LOW-LEVEL GYRE CENTERED TO
THE WEST, PROPELLING PEILOU NORTHEASTWARD. REGARDING INTENSITY, 13W
IS FORECAST TO GRADUALLY WEAKEN DUE TO THE INCREASING VWS, THE
DECREASING SSTS, AND THE HIGH AMOUNTS OF DRY AIR ENTRAINING INTO
THE CORE. TD 13W IS EXPECTED TO OPEN INTO A TROUGH AND DISSIPATE AS
A TROPICAL CYCLONE NO LATER THAN TAU 36.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGHOUT THE FORECAST PERIOD, SUPPORTING THE JTWC TRACK
FORECAST WITH HIGH CONFIDENCE. LIKEWISE, THE RELIABLE INTENSITY
AIDS ARE IN STRONG AGREEMENT IN STEADY WEAKENING THROUGH
DISSIPATION AT TAU 36. AS A RESULT, THE JTWC INTENSITY FORECAST IS
ASSESSED WITH HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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