Tropical Storm Guillermo Discussion Number 5
NWS National Hurricane Center Miami FL EP072021
900 AM MDT Sun Jul 18 2021
Guillermo's structure has changed little this morning. Very cold
overshooting cloud tops associated with deep convection have been
observed near the center of the tropical storm during the past
couple of hours, however most of the convective activity is still
limited to bands extending to the east and south of the tropical
cyclone. Dvorak intensity estimates from TAFB and SAB continue to
support an intensity estimate of 45 kt. Slight strengthening is
anticipated over the next 24 to 36 hours while Guillermo moves over
fairly warm waters. The rate of strengthening will likely be limited
by moderate northwesterly shear (10-20 kt based on SHIPS
diagnostics) and the relatively large size of the system. After
that, Guillermo will move over progressively cooler waters and into
a drier more stable environment which should cause it to slowly
weaken through the middle of the week. The GFS and HWRF forecast
that Guillermo will maintain tropical characteristics through the
end of the week, and this is reflected in the NHC forecast.
However, it is also possible it will become a remnant low by the
end of the forecast period.
The low-level center of Guillermo is obscured by nearby convection,
but it appears that the tropical storm is still moving
west-northwestward, more or less right on the previous forecast
track. Consequently no changes of note were made to the official
track forecast. A mid-level ridge to the north of Guillermo will
steer the cyclone westward for the next several days, likely with a
slight increase in its forward speed. Around day 4 or 5, Guillermo
is expected to weaken sufficiently so that it will become steered
primarily by low-level flow, and a slight bend toward the
west-southwest is anticipated. Like the previous advisory, the NHC
forecast is very near but just barely slower than the latest
multi-model consensus.
FORECAST POSITIONS AND MAX WINDS
INIT 18/1500Z 17.9N 112.5W 45 KT 50 MPH
12H 19/0000Z 18.3N 114.2W 50 KT 60 MPH
24H 19/1200Z 18.6N 116.8W 55 KT 65 MPH
36H 20/0000Z 18.7N 119.6W 55 KT 65 MPH
48H 20/1200Z 18.7N 122.5W 50 KT 60 MPH
60H 21/0000Z 18.6N 125.5W 40 KT 45 MPH
72H 21/1200Z 18.4N 128.4W 35 KT 40 MPH
96H 22/1200Z 17.9N 133.4W 30 KT 35 MPH
120H 23/1200Z 17.5N 138.5W 30 KT 35 MPH
$$
Forecaster Zelinsky
NWS National Hurricane Center Miami FL EP072021
900 AM MDT Sun Jul 18 2021
Guillermo's structure has changed little this morning. Very cold
overshooting cloud tops associated with deep convection have been
observed near the center of the tropical storm during the past
couple of hours, however most of the convective activity is still
limited to bands extending to the east and south of the tropical
cyclone. Dvorak intensity estimates from TAFB and SAB continue to
support an intensity estimate of 45 kt. Slight strengthening is
anticipated over the next 24 to 36 hours while Guillermo moves over
fairly warm waters. The rate of strengthening will likely be limited
by moderate northwesterly shear (10-20 kt based on SHIPS
diagnostics) and the relatively large size of the system. After
that, Guillermo will move over progressively cooler waters and into
a drier more stable environment which should cause it to slowly
weaken through the middle of the week. The GFS and HWRF forecast
that Guillermo will maintain tropical characteristics through the
end of the week, and this is reflected in the NHC forecast.
However, it is also possible it will become a remnant low by the
end of the forecast period.
The low-level center of Guillermo is obscured by nearby convection,
but it appears that the tropical storm is still moving
west-northwestward, more or less right on the previous forecast
track. Consequently no changes of note were made to the official
track forecast. A mid-level ridge to the north of Guillermo will
steer the cyclone westward for the next several days, likely with a
slight increase in its forward speed. Around day 4 or 5, Guillermo
is expected to weaken sufficiently so that it will become steered
primarily by low-level flow, and a slight bend toward the
west-southwest is anticipated. Like the previous advisory, the NHC
forecast is very near but just barely slower than the latest
multi-model consensus.
FORECAST POSITIONS AND MAX WINDS
INIT 18/1500Z 17.9N 112.5W 45 KT 50 MPH
12H 19/0000Z 18.3N 114.2W 50 KT 60 MPH
24H 19/1200Z 18.6N 116.8W 55 KT 65 MPH
36H 20/0000Z 18.7N 119.6W 55 KT 65 MPH
48H 20/1200Z 18.7N 122.5W 50 KT 60 MPH
60H 21/0000Z 18.6N 125.5W 40 KT 45 MPH
72H 21/1200Z 18.4N 128.4W 35 KT 40 MPH
96H 22/1200Z 17.9N 133.4W 30 KT 35 MPH
120H 23/1200Z 17.5N 138.5W 30 KT 35 MPH
$$
Forecaster Zelinsky
