Hurricane GUILLERMO Forecast Discussion
WTPZ44 KNHC 311444
HURRICANE GUILLERMO DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015
800 AM PDT FRI JUL 31 2015
The satellite presentation has improved during the past several
hours. The eye, however, is not completely closed on microwave
imagery at this time. There are several cyclonically curved
convective bands around the center, and the outflow is symmetric.
Both objective and subjective Dvorak numbers have continued to
increase, and the average of these numbers leads to an initial
intensity of 80 kt.
The current environment of low shear and warm ocean is quite
favorable for Guillermo to intensity further, and the NHC forecast
brings the winds up to 100 kt in about 24 hours. This forecast is a
little bit higher than the SHIPS guidance, but follows the
upward trend of the consensus. Beyond two days, the hurricane will
encounter a less favorable shear environment as Guillermo approaches
the prevailing upper-level westerlies. By the end of the forecast
period, when Guillermo is expected to be nearing the Hawaiian
Islands, the cyclone should have weakened to a tropical storm.
The hurricane is racing west-northwestward or 285 degrees at about
15 kt. The cyclone will likely continue on this track and speed for
the next day or two while embedded within a layer of deep easterlies
to the south of the subtropical ridge. After 48 hours, the hurricane
is expected to slow down as it approaches the southwestern edge of
the subtropical ridge. By then, the presence of weaker steering
currents makes the track forecast uncertain, and even more uncertain
as the cyclone approaches the Hawaiian islands in about five days.
The NHC forecast is consistent with the solution provided by global
models. The forecast is also near the consensus, but heavily
weighted on the GFS and ECMWF models.
FORECAST POSITIONS AND MAX WINDS
INIT 31/1500Z 12.4N 132.7W 80 KT 90 MPH
12H 01/0000Z 13.0N 134.9W 90 KT 105 MPH
24H 01/1200Z 13.6N 137.8W 100 KT 115 MPH
36H 02/0000Z 14.3N 140.4W 100 KT 115 MPH
48H 02/1200Z 15.0N 142.4W 90 KT 105 MPH
72H 03/1200Z 16.3N 145.4W 70 KT 80 MPH
96H 04/1200Z 17.5N 148.3W 60 KT 70 MPH
120H 05/1200Z 18.5N 152.0W 50 KT 60 MPH