WDPN32 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W (BOLAVEN) WARNING NR 13//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 16W (BOLAVEN), LOCATED APPROXIMATELY 580 NM 
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 05 
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY SHOWS THAT A VERY LARGE CENTRAL DENSE OVERCAST PERSISTS OVER 
THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 230039Z AMSU-B 89 GHZ 
MICROWAVE IMAGE REVEALS THAT THE MAJORITY OF DEEP CONVECTION IS 
CONFINED TO THE SOUTHERN AND EASTERN SECTORS OF THE TY. THE CURRENT 
POSITION IS BASED ON THE AMSU-B IMAGE WITH GOOD CONFIDENCE. THE 
CURRENT INTENSITY IS BASED ON THE HIGHER RANGE OF DVORAK ESTIMATES 
BETWEEN 77 TO 90 KNOTS. UPPER-LEVEL ANALYSIS INDICATES THAT TY 16W 
IS APPROXIMATELY TWO DEGREES WEST OF THE NORTHWESTERN PACIFIC 
EXTENSION OF THE SUBTROPICAL RIDGE (STR) AXIS WITH THE CENTER 
ANCHORED EAST OF JAPAN. THE ORIENTATION OF THIS AMPLIFIED STR AXIS 
IS NORTHEAST-SOUTHWEST AND TY 16W IS CURRENTLY STEERING ALONG ITS 
SOUTHERN PERIPHERY. ALTHOUGH A SELF-INDUCED MESO-ANTICYCLONE STILLS 
EXISTS OVER THE LLCC, TROPICAL UPPER-TROPOSPHERIC TROUGHING TO THE 
NORTH IS CAUSING STRONG (30 KNOTS) NORTHERLY VERTICAL WIND SHEAR 
(VWS) AND CONVERGENT PRESSURE ON THIS SIDE, AS NOTICED IN THE AMSU-B 
IMAGE. EQUATORWARD OUTFLOW REMAINS ROBUST DUE TO SPEED DIVERGENCE 
AND VWS IS WEAKER (05-10 KNOTS) OVER THE SOUTHEASTERN PORTION OF THE 
LLCC.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. AS THE MID-LATITUDE TROUGH PROPAGATES OUT OF THE REGION WELL 
NORTHEAST OF JAPAN, THE STEERING STR WILL REGAIN ZONAL ORIENTATION 
AND STEER TY 16W NORTHWESTWARD ALONG ITS SOUTHERN PERIPHERY. 
CONTINUED INTENSIFICATION IS EXPECTED AS SEA SURFACE TEMPERATURES 
AND OCEAN HEAT CONTENT REMAIN FAVORABLE ALONG WITH THE STRONG 
EQUATORWARD OUTFLOW. THE ONLY MECHANISM HOLDING BACK INTENSIFICATION 
IS A LACK OF POLEWARD OUTFLOW. TY 16W IS A VERY LARGE SYSTEM THAT 
SHOULD BE ABLE TO MODIFY THE STEERING RIDGE DUE TO INCREASED BETA-
EFFECT PROPAGATION IN RELATION TO ITS SIZE. THE PEAK INTENSITY 
SHOULD OCCUR BEFORE LANDFALL OVER OKINAWA AND IMPACT THE ISLAND AS A 
VERY INTENSE TYPHOON. ADDITIONALLY, BY TAU 72 ANOTHER TRANSITORY MID-
LATITUDE TROUGH WILL BE PROPAGATING EASTWARDS FROM EASTERN CHINA. 
THIS TROUGH WILL AID IN THE EROSION OF THE STR'S WESTERN FLANK AND 
ALLOW TY 16W TO TRACK MORE POLEWARD.
   C. IN THE EXTENDED FORECAST TY BOLAVEN SHOULD TRACK NORTH-
NORTHWESTWARD INTO THE WEAKNESS CAUSED BY THE PREVIOUSLY MENTIONED 
TROUGH. TRACK SPEEDS WILL ACCELERATE DURING THIS TIME AND INTENSITY 
WILL BE ON THE DECLINE AS OCEAN PARAMETERS BECOME LESS FAVORABLE. 
HOWEVER, AN INCREASE OF POLEWARD OUTFLOW SHOULD BE ABLE TO SLIGHTLY 
OFFSET THE COOLER OCEAN TEMPERATURES AND ALLOW TY 16W TO MAINTAIN 
TYPHOON STRENGTH INTO THE SOUTHERN YELLOW SEA. ADDITIONALLY, VWS 
SHOULD INCREASE AS THE SYSTEM EMBEDS FURTHER INTO THE TROUGH AND 
UPPER-LEVEL WESTERLIES. OBJECTIVE AID GUIDANCE IS IN EXCELLENT 
AGREEMENT UP TO OKINAWA. AFTER THIS POINT THE GUIDANCE SPREAD 
INCREASES DUE TO VARIOUS DEPICTIONS OF TROUGH INTERACTION AND SYSTEM 
STRENGTH. DURING THIS TIME THE ECMWF WAS FAVORED AS IT WAS IN CLOSE 
AGREEMENT WITH THE MODEL CONSENSUS. THERE REMAINS HIGH CONFIDENCE IN 
THE TRACK FORECAST DUE TO THE TIGHT ENVELOPE OF GUIDANCE.//
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