Tropical Storm ISELLE Forecast Discussion
WTPZ44 KNHC 010848
TROPICAL STORM ISELLE DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092014
200 AM PDT FRI AUG 01 2014
Iselle is continuing on an intensification trend with very deep
convection in a central dense overcast feature. A recent AMSU
microwave pass also suggests that the inner core has become better
defined, with perhaps a partial eyewall in the eastern semicircle.
The initial wind speed is raised to 50 kt based on an ASCAT-B pass
from 0507 UTC.
Environmental conditions appear conducive for further strengthening
over the next couple of days with light-to-moderate northeasterly
shear and warm water. Although the SHIPS-RI index has decreased
somewhat from the last cycle, rapid intensification remains a
possibility, especially given the recent development of inner core
features. The NHC forecast is raised from the previous one, on the
higher side of the guidance envelope close to the SHIPS and FSSE
models. After 48 hours, Iselle should be moving into a more stable
environment near cooler SSTs. Thus, a gradual weakening is
forecast, near or slightly above the intensity consensus.
Iselle continues to move to the west-northwest while it remains to
the south of the subtropical ridge. Global models are in excellent
agreement on this general track for the next 3 days while the ridge
persists. After that time, the track uncertainty greatly increases
due to a trough digging into the eastern Pacific, near or east of
the forecast longitude of Iselle. With many varying solutions from
the global models, it makes sense to stay close to the track
consensus, which generally moves Iselle westward at long range.
Since this consensus is near the last NHC prediction, the new
forecast is basically unchanged from 6 hours ago.
FORECAST POSITIONS AND MAX WINDS
INIT 01/0900Z 13.5N 124.6W 50 KT 60 MPH
12H 01/1800Z 14.1N 125.9W 60 KT 70 MPH
24H 02/0600Z 14.8N 127.6W 70 KT 80 MPH
36H 02/1800Z 15.3N 129.4W 75 KT 85 MPH
48H 03/0600Z 15.8N 131.3W 75 KT 85 MPH
72H 04/0600Z 16.5N 134.8W 70 KT 80 MPH
96H 05/0600Z 16.8N 137.5W 60 KT 70 MPH
120H 06/0600Z 17.0N 140.5W 50 KT 60 MPH