Tropical Storm RAI Advisory mar, 14-12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT)
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 5.2N 141.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 310 NM SOUTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CONSOLIDATING SYSTEM WITH IMPROVED CONVECTIVE BANDING WRAPPING INTO
A BROAD LOW-LEVEL CIRCULATION (LLC). ALTHOUGH THERE IS MEDIUM
CONFIDENCE IN THE INITIAL POSITION BASED ON THE MSI, A 130024Z
ASCAT-C IMAGE SHOWED A BROAD CIRCULATION WITH A VERY SHARP TROUGH
EXTENDING NORTHWARD. A 130430Z AMSR2 89GHZ MICROWAVE IMAGE SHOWED
FRAGMENTED BANDING OVER THE NORTH QUADRANT BUT ALSO SHOWED DEEP
CONVECTION ALONG THE TROUGH AXIS WITH A CURVED BAND DISPLACED
NORTH ALONG 7N. THE LLC IS EXPECTED TO CONSOLIDATE, HOWEVER, THERE
MAY BE SOME UNCERTAINTY AND JUMPS IN THE EXACT CENTER LOCATION AS
THE LOW-LEVEL FEATURES MERGE INTO A DISCRETE, WELL-DEFINED
LOW-LEVEL CIRCULATION CENTER. ENVIRONMENTAL ANALYSIS REVEALS
DIVERGENT EASTERLY FLOW OVER TOP OF THE SYSTEM, AIDING THE
CONVECTIVE ACTIVITY CURRENTLY BEING SEEN, THOUGH OVERALL OUTFLOW
REMAINS RELATIVELY WEAK AT PRESENT, BOTH POLEWARD AND EQUATORWARD.
SSTS ARE VERY WARM (29-30C) AND VWS IS LOW, LEADING TO AN OVERALL
FAVORABLE ENVIRONMENTAL ASSESSMENT.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 32 KTS AT 130419Z
   CIMSS ADT: 28 KTS AT 130540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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: TROPICAL DEPRESSION (TD) 28W IS EXPECTED TO
TRACK WEST-NORTHWESTWARD THROUGH THE DURATION OF THE FORECAST
PERIOD ALONG THE SOUTHERN SIDE OF AN EXTENSIVE STR ENTRENCHED TO
THE NORTH. TD 28W IS EXPECTED TO CROSS THROUGH THE SOUTHERN
PHILIPPINE ISLANDS AFTER TAU 72, AND ULTIMATELY EMERGE INTO THE
SULU SEA AND TRACK WEST OF PALAWAN BY TAU 120. OVER THE NEXT 12
HOURS, THE LLCC IS EXPECTED TO FURTHER CONSOLIDATE WHILE MOVING
UNDER THE DEEP CONVECTION, ESTABLISHING A WELL DEFINED CORE. THIS
WILL MARK THE START OF A PERIOD OF STEADY INTENSIFICATION TO A PEAK
OF 90 KNOTS BY TAU 72. AFTER TAU 72, TD 28W WILL WEAKEN AS IT
TRACKS ACROSS THE SOUTHERN PHILIPPINES BUT A SLIGHT
REINTENSIFICATION IS EXPECTED BY TAU 120 AS THE SYSTEM TRACKS INTO
THE SOUTH CHINA SEA AND POLEWARD OUTFLOW IMPROVES.
MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH IS THE
NORTHERN OUTLIER, NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT THROUGH TAU 120 WITH A 120-140NM SPREAD IN SOLUTIONS IN
THE EXTENDED PERIOD. THE 130000Z ECMWF ENSEMBLE (EPS), HOWEVER,
INDICATES A LARGER SPREAD OF SOLUTIONS RANGING FROM NORTHERN
MINDANAO TO SOUTHERN LUZON WITH A WIDER SPREAD OF SOLUTIONS IN THE
SOUTH CHINA SEA, ESPECIALLY AFTER TAU 120. MUCH OF THE SPREAD IN
THE EPS OVER THE PHILIPPINE ISLANDS IS LIKELY DUE TO POSITIONAL
UNCERTAINTY IN THE EARLY FORECAST PERIOD RELATED TO THE COMPLEX
NATURE OF THE LLC DISCUSSED IN THE SATELLITE ANALYSIS, INITIAL
POSITION AND INTENSITY DISCUSSION. IN GENERAL, RELIABLE INTENSITY
GUIDANCE SUPPORTS THE JTWC INTENSITY FORECAST THROUGH TAU 72 WITH
MEDIUM CONFIDENCE. AFTER TAU 72, THERE IS LOW CONFIDENCE IN THE
JTWC INTENSITY FORECAST WITH GREATER SPREAD DUE TO A NORTHEAST
SURGE EVENT EXPECTED TO BUILD INTO THE SOUTH CHINA SEA IN THE
EXTENDED PERIOD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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