973
WTPA44 PHFO 171451
TCDCP4
TROPICAL STORM PEWA DISCUSSION NUMBER 5
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP012013
500 AM HST SAT AUG 17 2013
THE DEEP CONVECTION NEAR THE CORE OF PEWA...PRONOUNCED /PEH-VAH/...
HAS BEEN PULSING OVERNIGHT. THE RAINBAND STRUCTURE THAT HAD BEEN
WEST OF THE CENTRAL DEEP CONVECTION HAS FADED...BUT THE UPPER LEVEL
OUTFLOW PATTERN APPEARS TO BE IMPROVING. THE SATELLITE FIX AGENCIES
AT PHFO...JTWC AND SAB ALL SHOWED THE CURRENT INTENSITY IS 3.5.
THERE WAS ALSO AN ASCAT PASS AT 0936Z WHICH SHOWED A FEW WINDS NEAR
45 KT. WITH THE IMPROVED APPEARANCE IN SATELLITE IMAGERY...THE
SUBJECTIVE DVORAK INTENSITY AND THE ASCAT DATA...WE HAVE ESTIMATED
THE INITIAL INTENSITY HAS INCREASED TO NEAR 50 KT.
THERE IS STILL SOME DOUBT ABOUT THE LOCATION OF THE CLOUD SYSTEM
CENTER AS OPPOSED TO THE LOW-LEVEL CIRCULATION CENTER /LLCC/ BASED
ON AN ASCAT PASS FROM 0936Z. THE RECENT MICROWAVE PASSES ALSO HAVE
NOT BEEN VERY USEFUL IN LOCATING THE LLCC. SO THERE IS UNCERTAINTY
IN THE EXACT LOCATION OF THE CENTER OF PEWA TONIGHT. THE CURRENT
MOTION IS 290/11 SINCE PEWA IS BEING STEERED BY THE DEEP LAYER FLOW
AROUND HIGH PRESSURE LOCATED FAR NORTH OF THE AREA. THE FORECAST
MODELS SHOW THIS HIGH PRESSURE WILL BUILD WESTWARD...WHICH IS
EXPECTED TO KEEP PEWA ON A GENERAL WEST NORTHWEST TRACK INTO EARLY
NEXT WEEK. THE LATEST CONSENSUS OF THE DYNAMICAL MODELS HAS SHIFTED
NORTHWARD...AND THE CURRENT FORECAST HAS BEEN NUDGED SLIGHTLY TO THE
RIGHT OF THE PREVIOUS TRACK TO MORE CLOSELY FOLLOW THIS GUIDANCE.
THE INTENSITY FORECAST CONTINUES TO REMAIN VERY CHALLENGING.
ENVIRONMENTAL CONDITIONS APPEAR TO BE CONDUCIVE FOR FURTHER
INTENSIFICATION OF PEWA DURING THE NEXT 36 TO 48 HOURS. THE FORECAST
TRACK IS OVER WARM SSTS OF AT LEAST 28C AND THE VERTICAL WIND SHEAR
IS EXPECTED TO REMAIN RELATIVELY LOW. THE FORECAST PATH IS ALSO OVER
GREATER OCEANIC HEAT CONTENT VALUES. HOWEVER...PEWA MAY EVENTUALLY
BE IMPACTED BY THE CIRCULATION AROUND AN UPPER LEVEL LOW CURRENTLY
NEAR 21N 174E. THE LATEST INTENSITY FORECAST ASSUMES PEWA CAN
INTENSIFY TO A TYPHOON IN THE NORTHWEST PACIFIC OCEAN WITHIN THE
NEXT 36 TO 72 HOURS. AFTER THAT IS ASSUMED THAT THE INFLUENCE OF THE
UPPER LEVEL LOW WILL KEEP IT FROM INTENSIFYING FURTHER DURING DAYS 4
AND 5. NOTE THAT THE INITIAL WIND RADII WERE ADJUSTED BASED ON THE
LATEST ASCAT PASS.
FINALLY...THE CENTER OF PEWA IS FORECAST TO CROSS THE INTERNATIONAL
DATE LINE INTO THE AREA OF RESPONSIBILITY OF RSMC TOKYO LATER THIS
WEEKEND. BASED ON THE LATEST TRACK...PEWA MAY MAKE THIS CROSSING
AROUND 18/0600Z...BUT IT IS TOO EARLY TO MAKE THIS DETERMINATION
YET.
FORECAST POSITIONS AND MAX WINDS
INIT 17/1500Z 10.7N 177.3W 50 KT 60 MPH
12H 18/0000Z 11.4N 179.0W 55 KT 65 MPH
24H 18/1200Z 12.4N 179.0E 60 KT 70 MPH
36H 19/0000Z 13.7N 176.9E 65 KT 75 MPH
48H 19/1200Z 14.9N 174.7E 70 KT 80 MPH
72H 20/1200Z 17.5N 170.0E 70 KT 80 MPH
96H 21/1200Z 20.5N 165.5E 70 KT 80 MPH
120H 22/1200Z 23.0N 161.0E 70 KT 80 MPH
$$
FORECASTER HOUSTON
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