WDIO31 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01B (MOCHA) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0N 90.0E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 392 NM SOUTH-SOUTHWEST OF CHITTAGONG
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE CORE OF TROPICAL CYCLONE (TC) 01B (MOCHA) HAS QUICKLY
CONSOLIDATED OVER THE PAST SOX HOURS, WITH A WELL DEFINED BUT
CLOUD-FILLED EYE FEATURE EMERGING BY THE 0600Z HOUR. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS VORTICAL HOT TOWERS
(VHTS) DEVELOPING TO THE SOUTHWEST OF THE CENTER, AND QUICKLY
WRAPPING UPSHEAR TO THE NORTH AND NORTHWEST SECTORS, AND SUPPORTING
EMERGENCE OF THE SMALL EYE FEATURE. ANIMATED WATER VAPOR IMAGERY
SUGGESTS THAT THE ATMOSPHERE TO THE NORTH HAS MOISTENED
SIGNIFICANTLY, ELIMINATING A WEDGE OF DRY MID-LEVEL AIR THAT WAS
PREVIOUSLY ENSCONCED TO THE NORTH OF THE CIRCULATION CENTER.
ADDITIONALLY, WATER VAPOR IMAGERY SHOWS STEADY IMPROVEMENT IN THE
POLEWARD OUTFLOW, AND THE SYSTEM IS NOW STARTING TO FEEL THE
EFFECTS OF ENHANCED POLEWARD OUTFLOW INTO THE STRONG JET MAX OVER
SOUTHERN CHINA. THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE DUE TO THE FACT THAT THE SYSTEM LIES IN THE
HIGH-FORESHORTENING REGION BETWEEN THE GEOSTATIONARY SATELLITES,
AND THERE HAS BEEN NO RECENT MICROWAVE IMAGERY TO RESOLVE THE
POSITION AMBIGUITY. THE SYSTEM HAS ALSO BEEN EXHIBITING A LARGE
WOBBLE IN THE MOTION VECTOR, WHICH HAS COMPLICATED THE POSITIONING.
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
BLEND OF AGENCY CURRENT INTENSITY ESTIMATES SUPPORTED BY THE
SATCON, ADT AND OPEN-AIIR OF 113 KNOTS. THE SYSTEM HAS PICKED UP
SPEED NOW THAT IT HAS ROUNDED THE RIDGE AXIS, MOVING OFF THE
NORTHEAST AT AROUND 10 KNOTS. CONDITIONS ARE FAVORABLE FOR FURTHER
INTENSIFICATION, WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS),
WARM (31-32C) SSTS AND STRONG POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTHERN PHILIPPINES. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 113 KTS AT 130405Z
   CIMSS ADT: 107 KTS AT 130630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 31-32 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 01B WILL CONTINUE TO ACCELERATE ON A STEADY
NORTHEASTWARD COURSE THROUGH THE FORECAST PERIOD, ALONG THE
NORTHWEST PERIPHERY OF THE DEEP STR TO THE EAST. LANDFALL IS
EXPECTED AT OR NEAR TAU 24 IN THE VICINITY OF SITTWE, MYANMAR. DUE
TO THE IMPROVING ENVIRONMENTAL CONDITIONS, INCLUDING DECREASING
VWS, IMPROVING POLEWARD OUTFLOW AND MOISTENING OF THE ATMOSPHERE IN
THE DOWN-TRACK DIRECTION, ADDITIONAL NEAR-TERM INTENSIFICATION IS
LIKELY. IF THE NASCENT EYE FEATURE CAN CONTINUE TO CLEAR-OUT, IT IS
POSSIBLE THE SYSTEM COULD REACH 130 KNOTS WITHIN THE NEXT 6-12
HOURS. HOWEVER, BY TAU 12 CONDITIONS BECOME SLIGHTLY LESS
FAVORABLE, WITH INCREASED SHEAR BEING THE PRIMARY FACTOR IN THE
ANTICIPATED WEAKENING TREND. THE SYSTEM IS EXPECTED TO WEAKEN
SLIGHTLY, TO 115 KNOTS, JUST PRIOR TO LANDFALL. IMMEDIATELY AFTER
LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN AS IT IS TORN APART BY
HIGH SHEAR AND TERRAIN INTERACTION, FULLY DISSIPATING BY TAU 48
OVER FAR NORTHERN MYANMAR. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
TIGHT AGREEMENT ON THE NORTHEASTWARD TRACK, WITH JUST 55 NM OF
SPREAD AT LANDFALL, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST
TRACK. INTENSITY GUIDANCE IS ALSO IN VERY TIGHT AGREEMENT, HOWEVER
THE JTWC FORECAST DEVIATES FROM THE GUIDANCE THROUGH TAU 12. ALL
MEMBERS OF THE INTENSITY CONSENSUS AGREE THAT THE SYSTEM WILL NOT
INTENSIFY FURTHER AND BEGIN TO WEAKEN THE SYSTEM FROM TAU 00, WITH
THE CONSENSUS MEAN INTENSITY AT LANDFALL OF 100 KNOTS. BASED ON
CURRENT INTENSITY TRENDS AND ENVIRONMENTAL ANALYSIS, THE JTWC
FORECAST DEVIATES FROM THE GUIDANCE, TAKING THE SYSTEM TO 125 KNOTS
WITH A POSSIBILITY OF A SLIGHTLY HIGHER PEAK, FOLLOWED BY WEAKENING
THROUGH LANDFALL. THE LANDFALL INTENSITY IS APPROXIMATELY 15 KNOTS
HIGHER THAN THE GUIDANCE WOULD SUGGEST. AFTER LANDFALL THE OFFICIAL
FORECAST REJOINS THE CONSENSUS. BASED ON THE DEVIATION FROM THE
GUIDANCE PACKAGE, CONFIDENCE IN THE JTWC FORECAST INTENSITY IS
MEDIUM. 

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