942  
WTPZ44 KNHC 012041  
TCDEP4  
 
HURRICANE GUILLERMO DISCUSSION NUMBER 12  
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015  
200 PM PDT SAT AUG 01 2015  
 
THE CLOUD PATTERN HAS BEGUN TO DETERIORATE, BUT IT IS ORGANIZED  
ENOUGH TO KEEP THE SAME DVORAK T-NUMBERS WITH AN INITIAL INTENSITY  
OF 90 KT. GUILLERMO IS HEADING TOWARD A SHEAR ENVIRONMENT, AND ON  
THIS BASIS, THE NHC FORECAST CALLS FOR A GRADUAL WEAKENING. BY THE  
TIME GUILLERMO APPROACHES THE HAWAIIAN ISLANDS, THE UPPER-LEVEL  
WINDS ARE FORECAST TO BE EVEN MORE UNFAVORABLE, AND BY THEN,  
GUILLERMO IS EXPECTED TO HAVE WEAKENED TO A TROPICAL STORM. THE NHC  
FORECAST CONTINUES TO BE VERY CLOSE TO THE INTENSITY CONSENSUS MODEL  
ICON.  
 
GUILLERMO IS MOVING TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT 12  
KT. THE HURRICANE IS ALREADY LOCATED ON THE SOUTHWESTERN EDGE OF  
THE SUBTROPICAL RIDGE, AND THERE IS A LARGE WEAKNESS IN THE RIDGE TO  
ITS NORTHWEST. THIS PATTERN SHOULD FORCE THE CYCLONE TO SLOW DOWN  
EVEN FURTHER AND TURN MORE TO THE WEST-NORTHWEST OR NORTHWEST. THE  
MOST RELIABLE TRACK MODELS ARE NOW IN BETTER AGREEMENT, AND THE  
MULTI-MODEL CONSENSUS BRINGS GUILLERMO JUST NORTH OR VERY NEAR  
THE HAWAIIAN ISLANDS. THE NHC FORECAST FOLLOWS THE CONSENSUS AND IS  
VERY SIMILAR TO THE PREVIOUS ONE.  
 
DUE TO UNCERTAINTIES IN LONGER-RANGE TRACK PREDICTIONS, IT IS  
IMPORTANT FOR USERS NOT TO FOCUS ON THE EXACT TRACK FORECASTS AT 96  
AND 120 HOURS. GIVEN THE LARGE SPREAD OF THE MODELS BEYOND 72  
HOURS IN THIS CASE, THE FORECAST UNCERTAINTY IS PARTICULARLY HIGH AT  
THOSE TIME PERIODS.  
 
SINCE GUILLERMO IS NOW MOVING INTO THE CENTRAL PACIFIC, FUTURE  
INFORMATION WILL BE PROVIDED BY THE CENTRAL PACIFIC HURRICANE  
CENTER AT HONOLULU, HAWAII.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 01/2100Z 13.8N 140.1W 90 KT 105 MPH  
12H 02/0600Z 14.3N 141.8W 85 KT 100 MPH  
24H 02/1800Z 15.1N 143.8W 75 KT 85 MPH  
36H 03/0600Z 15.9N 145.4W 65 KT 75 MPH  
48H 03/1800Z 16.7N 146.7W 60 KT 70 MPH  
72H 04/1800Z 18.2N 149.5W 55 KT 65 MPH  
96H 05/1800Z 19.7N 152.4W 50 KT 60 MPH  
120H 06/1800Z 21.0N 155.5W 40 KT 45 MPH  
 

 
FORECASTER AVILA  
 
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