733  
WTPZ44 KNHC 010258  
TCDEP4  
 
HURRICANE GUILLERMO DISCUSSION NUMBER 9  
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015  
800 PM PDT FRI JUL 31 2015  
 
BOTH MICROWAVE AND CONVENTIONAL SATELLITE IMAGERY INDICATE THAT  
GUILLERMO HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST  
SEVERAL HOURS. IN FACT, THE SATELLITE PRESENTATION APPEARS TO HAVE  
DETERIORATED SINCE EARLIER TODAY WITH MICROWAVE DATA SHOWING THE  
NORTHWESTERN PORTION OF THE EYEWALL ERODING. SATELLITE INTENSITY  
ESTIMATES FROM TAFB AND SAB AND THE LATEST OBJECTIVE INTENSITY  
ESTIMATE FROM UW-CIMSS ADT SUGGEST THAT INITIAL INTENSITY REMAINS 90  
KT.  
 
GUILLERMO CONTINUES TO MOVE RAPIDLY TO THE WEST-NORTHWEST, WITH AN  
INITIAL MOTION ESTIMATE OF 285/18 KT. LITTLE CHANGE TO THIS MOTION  
IS EXPECTED FOR THE NEXT 24 HOURS, WITH THE CYCLONE REMAINING TO THE  
SOUTH OF A MID-LEVEL SUBTROPICAL RIDGE. BEYOND 24 HOURS TO AROUND  
72 HOURS, A DEEPENING MID- TO UPPER-LEVEL TROUGH OVER THE CENTRAL  
PACIFIC IS FORECAST TO CREATE A BREAK IN THE SUBTROPICAL RIDGE,  
WHICH SHOULD CAUSE THE TROPICAL CYCLONE TO SLOW DOWN AND TURN MORE  
TOWARD THE NORTHWEST. THE SPREAD IN THE GUIDANCE SUITE INCREASES  
BEYOND 72 HOURS, BUT MOST OF THE MODELS MAINTAIN A GENERAL  
WEST-NORTHWESTWARD MOTION. THE NEW FORECAST TRACK IS BASICALLY AN  
UPDATE OF THE PREVIOUS TRACK THROUGH 72 HOURS, AND IS THEN NUDGED  
SLIGHTLY TO THE RIGHT OR NORTH OF THE PREVIOUS TRACK TOWARD THE  
MULTI-MODEL CONSENSUS THEREAFTER.  
 
THE INTENSITY FORECAST HAS BECOME SOMEWHAT PROBLEMATIC. THE REASON  
FOR THE RECENT ARRESTED DEVELOPMENT IS UNCLEAR, ALTHOUGH IT MIGHT BE  
RELATED TO DRY AIR ENTRAINMENT INTO THE NORTHWESTERN QUADRANT OF THE  
CYCLONE. HOWEVER, THERE IS STILL THE OPPORTUNITY FOR GUILLERMO TO  
STRENGTHEN A BIT MORE DURING THE NEXT 12 TO 24 HOURS, WHILE THE  
SYSTEM REMAINS WITHIN A LOW-SHEAR ENVIRONMENT AND OVER WARM SEA  
SURFACE TEMPERATURES. THE NEW INTENSITY FORECAST IS ADJUSTED  
SLIGHTLY DOWNWARD TO 95 KT AT THE 12- AND 24-HOUR FORECAST TIMES.  
THEREAFTER, THE CYCLONE IS FORECAST TO MOVE INTO AN UPPER-LEVEL  
DEFORMATION ZONE BETWEEN SUBTROPICAL RIDGES TO THE EAST AND WEST,  
WHICH IS A LESS FAVORABLE ENVIRONMENT. ALSO, SEA SURFACE  
TEMPERATURES GRADUALLY COOL ALONG THE FORECAST TRACK. WE HAVE  
FOLLOWED THE PREVIOUS FORECAST TREND OF GRADUAL WEAKENING, WHICH IS  
IN GOOD AGREEMENT WITH THE LATEST SHIPS/LGEM AND IVCN CONSENSUS  
GUIDANCE. WHEN GUILLERMO APPROACHES THE HAWAIIAN ISLANDS, IT IS  
EXPECTED TO ENCOUNTER INCREASING WESTERLY SHEAR, AND THE NEW  
INTENSITY FORECAST FOLLOWS THE PREVIOUS FORECAST IN WEAKENING  
GUILLERMO TO TROPICAL STORM STRENGTH.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 01/0300Z 13.2N 136.1W 90 KT 105 MPH  
12H 01/1200Z 13.7N 138.5W 95 KT 110 MPH  
24H 02/0000Z 14.3N 141.1W 95 KT 110 MPH  
36H 02/1200Z 15.0N 143.2W 90 KT 105 MPH  
48H 03/0000Z 15.8N 145.0W 80 KT 90 MPH  
72H 04/0000Z 17.0N 147.5W 65 KT 75 MPH  
96H 05/0000Z 19.0N 150.5W 60 KT 70 MPH  
120H 06/0000Z 20.5N 153.5W 50 KT 60 MPH  
 

 
FORECASTER BEVEN/JACOBSON  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab TPC Page Main Text Page