Tropical Storm RAMMASUN Advisory 15 Ιουλ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (RAMMASUN) WARNING NR 18//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 09W (RAMMASUN), LOCATED APPROXIMATELY 362 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 13
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY (EIR) SHOWS TY 09W HAS, FOR THE MOST PART, MAINTAINED ITS
DEGREE OF WRAP AND CONVECTIVE PATTERN WITH A SLIGHT DEEPENING IN THE
CENTRAL CONVECTION EVEN AS THE EYE HAS BECOME CLOUD-FILLED. THE
INITIAL POSITION IS BASED ON THE EIR ANIMATION WITH FAIR CONFIDENCE.
THE INITIAL INTENSITY IS BASED ON CONGRUENT DVORAK ESTIMATES FROM
PGTW AND RJTD. UPPER LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT
AS VIGOROUS EQUATORWARD AND WESTWARD OUTFLOW CONTINUE WHILE VERTICAL
WIND SHEAR ARE AT LOW (05 TO 10 KNOT) LEVELS. TY 09W REMAINS ON A
GENERALLY WESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 09W IS FORECAST TO TRACK ON A MORE WEST-NORTHWESTWARD
TRAJECTORY AS A TRANSITORY MID-LATITUDE TROUGH WEAKENS THE STEERING
STR. IT IS EXPECTED TO MAKE LANDFALL JUST NORTH OF SORSOGON,
PHILIPPINES, SHORTLY AFTER TAU 12. THE FAVORABLE UPPER LEVEL
ENVIRONMENT AND CONDUCIVE SEA SURFACE TEMPERATURES (SST) WILL ALLOW
FOR FURTHER INTENSIFICATION THROUGH THE NEXT 12 HOURS BEFORE THE
SYSTEM BEGINS TO INTERACT WITH LAND. AFTERWARDS, AS THE SYSTEM DRAGS
ACROSS SOUTHERN LUZON AND INTO MANILA, IT WILL WEAKEN DUE TO
FRICTIONAL EFFECTS BUT WILL RE-EMERGE IN THE SOUTH CHINA SEA JUST
NORTH OF SUBIC BAY SHORTLY AFTER TAU 36 AS A STRONG TROPICAL STORM.
WARM SST IN THE SOUTH CHINA SEA PLUS CONTINUED FAVORABLE UPPER LEVEL
CONDITIONS WILL FAVOR RAPID RE-INTENSIFICATION, PEAKING AT 90 KNOTS
BY TAU 72.
   C. IN THE EXTENDED TAUS, TYPHOON RAMMASUN IS FORECAST TO CONTINUE
NORTHWESTWARD ACROSS THE SOUTH CHINA SEA MAKING A SECONDARY LANDFALL
OVER NORTHERN HAINAN BEFORE TAU 96. IT WILL THEN CROSS THE GULF OF
TONKIN AND MAKE A FINAL LANDFALL OVER NORTHERN VIETNAM NEAR HANOI.
LAND INTERACTION WILL PRIMARILY CAUSE ITS WEAKENING; HOWEVER,
RAMMASUN WILL MAINTAIN A SOLID 85-KNOT TYPHOON INTENSITY BEFORE ITS
FINAL LANDFALL. DUE TO THE OVERALL GOOD AGREEMENT IN THE MODELS,
THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK. HOWEVER, THERE IS
STILL SOME UNCERTAINTY IN THE EXTENDED INTENSITY FORECAST DUE TO THE
EXTENT OF THE WEAKENING ANTICIPATED WITH THE LAND INTERACTION IN THE
MID FORECAST.//
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