TC CHABA STEADILY INTENSIFYING; FINAL TC RICHARD, 1ST SOUTH HEMI TC

TROPICAL CYCLONE CHABA PROGNOSIS


WDPN32 PGTW 261500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON (TY) 16W (CHABA), CURRENTLY LOCATED 375 NM SOUTH OF
KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 05 KNOTS DURING 
THE PAST SIX HOURS. NEARLY ALL THE DEEP CENTRAL CONVECTION HAD 
DISSIPATED AROUND 0600Z, BUT IT HAS SINCE REBUILT OVER THE CENTER. A 
STRONG COLD SURGE CONTINUES TO ADVANCE A MODIFIED POLEWARD AIRMASS 
EQUATORWARD. THIS SURGE APPEARS TO HAVE HAD LITTLE IMPACT ON THE TY 
THUS FAR, DESPITE NORTHEASTERLIES BEGINNING TO WEAKLY FILTER IN 
BENEATH THE CENTRAL CONVECTION. DUAL EXHAUST MECHANISMS PERSIST AND 
ARE POSITIONED TO AID INTENSIFICATION. VERTICAL WIND SHEAR 
FLUCTUATES BETWEEN LOW AND MODERATE, WITH THE LOW LEVEL FLOW BEING 
NEARLY 180 DEGREES OUT OF PHASE WITH THE UPPER LEVEL SOUTH- 
WESTERLIES. A NARROW EXTENSION OF A DEEP LAYER STEERING RIDGE TO THE 
EAST HAS CONTINUED TO ADVANCE THE TY NORTHWEST. 
3. FORECAST REASONING.
   A. THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST PHILOSOPHY. 
HOWEVER, TRACK SPEEDS HAVE BEEN ALTERED, ESPECIALLY IN THE LATER 
TAUS, TO ACCOUNT FOR A SLOWER CONSENSUS AND A DELAYED TURN TO THE 
NORTH. 
   B. THE RIDGE EXTENSION WILL BEGIN TO ERODE OVER THE NEXT 06 TO 12 
HOURS AND WILL ALLOW THE TY TO TRACK MORE TOWARDS THE NORTH. 500 MB 
HEIGHT ANALYSIS INDICATES THAT THE RIDGE HAS ALREADY BEGUN TO 
RETREAT TO THE EAST. AS CHABA TRACKS POLEWARD ALONG THE FLATTENED 
WESTERN EXTENSION OF THE DEEP LAYER RIDGE, IT WILL CONTINUE TO 
INTENSIFY, BUT AT A SLOWER RATE. POLEWARD OUTFLOW WILL WEAKEN AS AN 
UPPER LEVEL TROUGH PULLS TO THE NORTHEAST INTO THE DEEP MID-
LATITUDES. IT REMAINS UNCERTAIN WHAT IMPACT THE COLD SURGE WILL HAVE 
ON THE INTENSITY FORECAST, BUT CURRENTLY THE SYSTEM REMAINS 
UNSCATHED. TOTAL PRECIPITABLE WATER PRODUCTS SHOW A WELL-ISOLATED 
SYSTEM THAT CONTINUES TO PULL IN AIR FROM THE DEEP TROPICS. AROUND 
TAU 48 THE TY WILL SIT JUST SOUTH OF OKINAWA NEAR 90 KNOTS. MODEL 
GUIDANCE THROUGH THE FIRST 2 DAYS SHOWS A GENERAL SLOW POLEWARD 
TREND. BECAUSE THE SYSTEM HAS YET TO TURN NORTH-NOTHWEST FROM 
NORTHWEST THE ENTIRE FORECAST TRACK HAS BEEN SHIFTED SLIGHTLY WEST 
OF THE PREVIOUS FORECAST. IN ADDITION, THE MODEL CONSENSUS HAS ALSO 
SHIFTED WEST.
   C. THE CYCLONE WILL BEGIN TO ACCELERATE AROUND TAU 72 AS IT 
ROUNDS THE RIDGE AXIS INTO THE MID-LATITUDES, AND WILL ALSO BEGIN TO 
WEAKEN UNDER INCREASED VERTICAL WIND SHEAR. EXTRATROPICAL TRANSITION 
WILL ALSO BEGIN SHORTLY THEREAFTER AS THE SYSTEM INTERACTS WITH A 
BAROCLINIC BOUNDARY RUNNING SOUTH OF JAPAN. THE CYCLONE WILL QUICKLY 
TRANSITION FROM TROPICAL TO EXTRATROPICAL BY TAU 120, JUST NORTH OF 
TOKYO. THE FORECAST HAS BEEN SHIFTED FURTHER INLAND OVER HONSHU TO 
ACCOUNT FOR A CONSENSUS THAT HAS WALKED WEST. GIVEN THE WESTERLIES 
ALOFT IT IS UNLIKELY THAT THE SYSTEM WILL ADVANCE ANY FARTHER WEST 
OVER JAPAN THAN ALREADY FORECAST, DESPITE THE GFDN SOLUTION THAT 
WANTS TO PULL THE SYSTEM INTO THE SEA OF JAPAN. GFS AND ECMWF, 
THOUGH SOMEWHAT FASTER THAN THE OFFICIAL FORECAST, RESOLVE FORECAST 
TRACKS THAT ARE CONSISTENT WITH A SYSTEM ENTERING THE MID-LATITUDES, 
AND HAVE THE CYCLONE ACCELERATING TO THE NORTHEAST AFTER SKIRTING 
HONSHU.//
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TROPICAL CYCLONE 01S


261500Z POSITION NEAR 11.3S 86.3E.
TROPICAL CYCLONE (TC) 01S (ONE), LOCATED APPROXIMATELY 850 NM EAST-
SOUTHEAST OF DIEGO GARCIA, HAS TRACKED SOUTHWARD AT 07 KNOTS OVER 
THE PAST SIX HOURS. THIS IS THE FIRST SYSTEM OF THE 2011 SOUTHERN 
HEMISPHERE TROPICAL CYCLONE SEASON. VERTICAL WIND SHEAR (VWS) HAS 
RELAXED OVER THE SYSTEM AND HAS ALLOWED FOR DEEP CONVECTION TO BUILD 
BACK OVER THE CENTER, ELEVATING DVORAK ESTIMATES FROM PGTW AND FMEE 
TO A T2.5 OR 35 KNOTS. A 260407Z ASCAT PASS ALSO SUGGESTS THE LLCC 
HAS STRENGTHENED TO 35 KNOTS. IN ADDITION, A 261112Z SSMI 37H 
MICROWAVE IMAGE SHOWS PRONOUNCED LOW LEVEL BANDING WRAPPING INTO A 
DISTINCT LLCC. CURRENTLY THE CYCLONE IS VENTING TO THE WEST AND 
SOUTHEAST AHEAD OF A LONGWAVE UPPER LEVEL TROUGH. THIS TROUGH ALSO 
APPEARS RESPONSIBLE FOR BOUTS OF ELEVATED VWS. LESS THAN SIX HOURS 
AGO THE LLCC HAD BEEN FULLY EXPOSED TO THE EAST OF THE DEEP 
CONVECTION. SLOW INTENSIFICATION IS ANTICIPATED OVER THE NEXT FEW 
DAYS AS VWS GRADUALLY EASES WITH THE PASSAGE OF THE TROUGH 
DOWNSTREAM. THE SYSTEM WILL CONTINUE TO TRACK ALONG THE NORTHERN 
PERIPHERY OF A LOW TO MID-LEVEL STEERING RIDGE TO THE SOUTH, THEN 
TRANSFER TO ANOTHER STEERING RIDGE FURTHER TO THE WEST AS THE MID-
LEVEL REFLECTION OF THE TROUGH PASSES AROUND TAU 48. VWS IS AGAIN 
EXPECTED TO ELEVATE NEAR DAY 4 AND WILL SLOWLY WEAKEN THE SYSTEM. 
SEA SURFACE TEMPERATURES REMAIN FAVORABLE THROUGHOUT THE FORECAST 
AND BEGIN TO TAPER NEAR 20S. THIS WARNING SUPERSEDES AND CANCELS REF 
A, NAVMARFCSTCEN 252251Z OCT 10 TROPICAL CYCLONE FORMATION ALERT 
(WTXS21 PGTW 252300)MAXIMUM SIGNIFICANT WAVE HEIGHT AT 261200Z IS 9 
FEET. NEXT WARNINGS AT 270300Z AND 271500Z.//
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TROPICAL CYCLONE RICHARD


261500Z POSITION NEAR 20.0N 92.9W.  135NM WNW OF CAMPECHE, MEXICO. 
12FT SEAS: NONE. THIS IS THE FINAL WARNING ISSUED BY NAVMARFCSTCEN.//
BT
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