Tropical Storm RAI Advisory vie, 17-12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 28W (RAI) WARNING NR
014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 9.9N 126.0E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 407 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT,
12NM EYE THAT IS WEAKENING AS THE SYSTEM MAKES INITIAL LANDFALL ON
THE ISLAND OF SIARGAO, PHILIPPINES. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE IN THE VISIBLE AND
INFRARED IMAGERY AS WELL AS EXTRAPOLATION OF THE MICROWAVE EYE IN
THE 160503Z AMSR2 89GHZ IMAGE. THE INITIAL INTENSITY IS ASSESSED
WITH MODERATE CONFIDENCE AT 130 KNOTS, AND IS BASED LOWER THAN THE
ADVANCED DVORAK TECHNIQUE (ADT) OF T6.9-137KTS AND MULTIPLE AGENCY
FIXES. PGTW WAS ONLY ABLE TO PLACE A POSITION ONLY FIX DUE TO THE
CENTER BEING OVERLAND. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE
OVERALL, WITH VERY WARM SSTS, HIGH OHC, GOOD POLEWARD AND
EQUATORWARD OUTFLOW, BEING SLIGHTLY OFFSET BY MODERATE TO STRONG
EASTERLY VWS.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: NO CURRENT ESTIMATE
   RJTD: T7.0 - 140 KTS
   KNES: T7.0 - 140 KTS
   CIMSS ADT: 137 KTS AT 160540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: STY 28W IS FORECAST TO TRACK WEST-NORTHWEST
OVER MULTIPLE PHILIPPINE ISLANDS AND PALAWAN ISLAND THROUGH THE
NEXT 24-36 HOURS, BEFORE TURNING POLEWARD ALONG THE STR TO THE
NORTH THROUGH TAU 96 AND THEN TURN SHARPLY TO THE EAST BY TAU 120.
STY 28W REACHED PEAK INTENSITY JUST BEFORE LANDFALL AND WILL
CONTINUE TO DECREASE BEFORE IT EMERGES BACK OVER THE SOUTH CHINA
SEA. ONCE THE STORM CROSSES THROUGH THE PHILIPPINE ISLANDS, THE
DISRUPTION OF THE LOW LEVEL INFLOW COMBINED WITH INCREASED VWS WILL
CONTINUE TO WEAKEN THE SYSTEM. AFTER IT REACHES THE SOUTH CHINA SEA
AT 95 KNOTS, THE SYSTEM WILL BEGIN TO TAP INTO STRONGLY DIVERGENT
POLEWARD OUTFLOW, WHICH WILL OFFSET MODESTLY INCREASED SOUTHERLY
WIND SHEAR, TO A PEAK OF 105 KNOTS AT TAU 48. A NORTHEAST SURGE
WILL BEGIN TO INDUCE COLD AIR INTO THE SYSTEM ERODING THE SYSTEM
STRENGTH RAPIDLY AS IT MOVES INTO STRONGER VWS WHILE MOVING
NORTH-NORTHEAST LEADING TO RAPID WEAKENING THROUGH THE END OF THE
FORECAST.
MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN GOOD AGREEMENT THROUGH
TAU 72, WITH A SPREAD OF NEARLY 200NM AT TAU 72. SPREAD INCREASED TO
310NM BY TAU 120 BETWEEN THE NAVGEM ON THE RIGHT AND AFUM ON THE
LEFT OF THE GUIDANCE ENVELOPE. THE JTWC FORECAST REMAINS CONSISTENT
WITH THE PREVIOUS FORECAST AND CLOSELY TRACKS THE CONSENSUS MEAN
THROUGH TAU 48, THEN SLIGHTLY TO THE LEFT OF THEMEAN THROUGH TAU
120. INTENSITY GUIDANCE IS IN FAIR AGREEMENT AS WELL, WITH ALL
MEMBERS INDICATING IMMEDIATE WEAKENING FROM TAU 00 WITH HWRF
REMAINING THE MOST PESSIMISTIC, REDUCING THE SYSTEM DOWN TO 75 KNOTS
WITHIN 24 HOURS, WHILE COAMPS-TC REINVIGORATES THE SYSTEM TO A
SECOND PEAK OF 125 KNOTS IN THE SOUTH CHINA SEA. THE JTWC FORECAST
REMAINS 15 KNOTS ABOVE THE CONSENSUS MEAN, BUT LOWER THAN THE COAMPS-
TC THROUGH TAU 36, THEN SLIGHTLY BELOW THE COAMPS-TC BUT ABOVE THE
REMAINDER OF THE GUIDANCE THROUGH TAU 120. CONFIDENCE IN THE TRACK
REMAINS HIGH, THEN TRENDS TOWARDS MEDIUM IN THE LONG-RANGE, WHILE
CONFIDENCE IN THE INTENSITY IS MEDIUM, THEN TRENDS LOW IN THE LONG-
RANGE DUE TO UNCERTAINTIES SURROUNDING THE IMPACT OF THE LAND
INTERACTION.
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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