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 482 
 WTPA44 PHFO 041504
 TCDCP4
 
 TROPICAL STORM GUILLERMO DISCUSSION NUMBER  23
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP092015
 500 AM HST TUE AUG 04 2015
  
 THE LATEST INFRARED SATELLITE PRESENTATION OF GUILLERMO HAS 
 DEGRADED IN APPEARANCE SINCE THE LAST ADVISORY...WITH WARMING CLOUD 
 TOPS AND A REDUCTION IN THE THUNDERSTORM ACTIVITY. THE LATEST 
 UW-CIMSS VERTICAL WIND SHEAR ANALYSIS INDICATES 25 KNOTS OF SHEAR 
 FROM 270 DEGREES...AND THIS IS LIKELY RESPONSIBLE FOR THE DEEP 
 CONVECTION HAVING DIFFICULTY MAINTAINING ITSELF NEAR THE LOW LEVEL 
 CIRCULATION CENTER OF GUILLERMO. DESPITE THE VERTICAL WIND SHEAR 
 PRESENT OVER THE SYSTEM...DVORAK CLASSIFICATIONS FROM PHFO AND JTWC 
 CONTINUE TO INDICATE T NUMBERS OF 3.5 OR 55 KNOTS...AND 3.0 OR 45 
 KNOTS FROM SAB. ADVANCED DVORAK TECHNIQUE (ADT) ALSO INDICATES A T 
 NUMBER OF 3.6 OR 57 KNOTS AS OF 04/1300Z. THE FINAL DECISION ON THE 
 INITIAL INTENSITY WAS ONCE AGAIN BASED ON DATA FROM THE U.S. 53RD 
 WEATHER RECONNAISSANCE AIRCRAFT WHICH SAMPLED THE INNER CORE OF 
 GUILLERMO EARLIER THIS MORNING. THE AIRCRAFT FOUND MAX FLIGHT LEVEL 
 WINDS OF 73 KNOTS...25 NM EAST OF THE CENTER OF CIRCULATION. 
 ADJUSTING THE FLIGHT LEVEL WINDS FROM THE 850 MB FLIGHT
 LEVEL...YIELDS SURFACE WINDS OF 58 KNOTS. ADDITIONALLY...SFMR DATA
 FROM THE AIRCRAFT INDICATED SURFACE WINDS OF AROUND 60 KNOTS IN THE
 NE AND NW QUADRANTS OF THE STORM. AS A RESULT...THE INITIAL
 INTENSITY OF GUILLERMO WAS KEPT JUST BELOW HURRICANE STRENGTH AT 60 
 KNOTS...UTILIZING A BLEND OF THE FLIGHT LEVEL AND SFMR WINDS FROM 
 THE AIRCRAFT. 
 
 THE INITIAL POSITION OF THE SYSTEM WAS BASED ON SATELLITE 
 EXTRAPOLATION FROM EARLIER CENTER FIX POSITIONS FROM THE 
 RECONNAISSANCE AIRCRAFT...WITH AN INITIAL MOTION TOWARD THE 
 NORTHWEST...OR 320 DEGREES AT 10 KNOTS. THE LATEST MODEL GUIDANCE 
 CHANGED VERY LITTLE FROM THE PREVIOUS ADVISORY PACKAGE...LIKELY 
 RESULTING FROM BETTER INITIALIZATION OF THE MOTION OF THE SYSTEM. 
 THE MOTION OF GUILLERMO APPEARS TO BE DRIVEN LARGELY BY THE
 STRENGTH OF THE VERTICAL WIND SHEAR AS WELL AS A WEAKNESS IN THE
 MID-UPPER LEVEL RIDGE WHICH EXTENDS FROM GUILLERMO OFF TO THE
 NORTHWEST TO A LOCATION NEAR 30N157W. THE WEAKNESS IN THE RIDGE IN
 COMBINATION WITH THE DEEP LAYER FLOW IS KEEPING GUILLERMO ON A TRACK
 OFF TO THE NORTHWEST AT THE CURRENT TIME. AS A RESULT...THE OFFICIAL
 FORECAST FOLLOWS A DIRECTION ON THE NORTH SIDE OF THE GUIDANCE
 ENVELOPE THROUGH 24 HOURS WHICH ASSUMES MAINTENANCE OF DEEP
 CONVECTION AND INTERACTION WITH THE WEAKNESS IN THE MID-UPPER LEVEL
 RIDGE. BEYOND 24 HOURS AS WESTERLY WIND SHEAR IS FORECAST TO
 INCREASE SIGNIFICANTLY OVER THE SYSTEM...CONVECTION SHOULD BECOME 
 INCREASINGLY SHALLOW...AND THE OFFICIAL FORECAST SHOWS A SHIFT
 TOWARD THE WEST-NORTHWEST WHICH IS VERY CLOSE TO THE GFS AND TVCN
 TRACKS AND SLIGHTLY TO THE NORTH OF THE PREVIOUS OFFICIAL FORECAST.
 ON THIS TRACK...THE CLOSEST APPROACH OF GUILLERMO REMAINS WELL TO
 THE NORTHEAST OF ALL THE HAWAIIAN ISLANDS. THE TROPICAL STORM WATCH
 FOR THE BIG ISLAND AND MAUI COUNTY WAS MAINTAINED WITH THIS
 ADVISORY PACKAGE...BUT IF THE MOTION OF THE SYSTEM CONTINUES...THE
 WATCHES MAY BE CANCELLED LATER TODAY.
 
 THE INTENSITY FORECAST FOR GUILLERMO IS A BLEND OF ICON AND HWRF 
 INTENSITY GUIDANCE ALONG WITH WEIGHT GIVEN TO THE PREVIOUS OFFICIAL 
 FORECAST. THE GLOBAL MODELS ARE SHOWING THE POTENTIAL FOR SOME 
 SLIGHT STRENGTHENING THROUGH THIS EVENING...AS SHEAR REMAINS NEARLY 
 UNCHANGED. VERTICAL WIND SHEAR IS THEN FORECAST TO FURTHER 
 STRENGTHEN OVER THE SYSTEM TONIGHT...AND THIS SHOULD LEAD TO STEADY 
 WEAKENING OF GUILLERMO THROUGH THE REMAINDER OF THE FORECAST. GIVEN 
 THE FAVORABLE SEA SURFACE TEMPERATURES OF AROUND 82 DEGREES 
 FAHRENHEIT BASED ON MODIS DATA FROM YESTERDAY AFTERNOON...IT IS NOT 
 OUT OF THE QUESTION THAT GUILLERMO COULD BECOME A HURRICANE OVER
 THE NEXT 12 HOURS. THE OFFICIAL INTENSITY FORECAST WILL SHOW LITTLE 
 CHANGE IN STRENGTH HOWEVER OVER THE NEXT 12 HOURS...THEN SHOW SLOW 
 BUT STEADY WEAKENING THROUGH 120 HOURS. 
 
 ANOTHER RECONNAISSANCE AIRCRAFT MISSION INTO GUILLERMO IS SCHEDULED 
 FOR 18Z THIS MORNING. THE VALUABLE DATA TRANSMITTED IN REAL-TIME 
 FROM THESE MISSIONS WILL HELP US TO BETTER DETERMINE THE
 LOCATION...INTENSITY AND SIZE OF THE TROPICAL STORM...ALONG WITH
 ANY POTENTIAL IMPACTS TO THE HAWAIIAN ISLANDS.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  04/1500Z 19.7N 148.5W   60 KT  70 MPH
  12H  05/0000Z 20.4N 149.6W   60 KT  70 MPH
  24H  05/1200Z 21.4N 151.5W   50 KT  60 MPH
  36H  06/0000Z 22.4N 153.4W   45 KT  50 MPH
  48H  06/1200Z 23.1N 155.1W   40 KT  45 MPH
  72H  07/1200Z 25.0N 159.0W   35 KT  40 MPH
  96H  08/1200Z 26.5N 163.0W   30 KT  35 MPH
 120H  09/1200Z 28.0N 167.0W   25 KT  30 MPH
  
 $$
 FORECASTER JELSEMA/BIRCHARD
  
 
 
 
 
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