Tropical Storm Olaf Discussion Number 5
NWS National Hurricane Center Miami FL EP152021
300 PM MDT Wed Sep 08 2021
Olaf's appearance has remained steady today and the storm is
characterized by a large curved band that encompasses much of the
circulation. There is good outflow in all quadrants, indicative of a
low-shear environment. An earlier ASCAT pass sampled peak winds of
37 kt, and this data along with a blend of the latest Dvorak
T-numbers from TAFB and SAB indicate that the initial intensity is
around 40 kt.
The storm is forecast to remain over warm waters and in a moist
environment for the next 36 hours. Therefore, additional
strengthening is likely during that time period. In a couple of
days, the cyclone is forecast to begin moving over cooler waters,
and into a drier and a much more stable atmospheric environment.
This should result in rapid weakening, and Olaf is expected to
become a remnant low this weekend. The latest NHC intensity forecast
is little changed from the previous one, and continues to be in good
agreement with the IVCN intensity consensus aid. Although the NHC
forecast does not explicitly show Olaf becoming a hurricane, this
could still occur Thursday or Thursday night.
Olaf continues to move slowly northwestward, or 325/5 kt. A
mid-level ridge building over northern Mexico should help maintain
this heading for a couple of days with a gradual increase in forward
speed. By Friday night, Olaf is expected to turn west-northwestward
as it weakens, and by Saturday a westward motion is forecast when
the shallow cyclone is steered by the surrounding low-level flow.
The overall model guidance shifted slightly to the east through 48
hours, and thus the NHC track forecast was nudged in that direction
for that time frame. Because of this track shift, probabilities of
tropical storm and hurricane conditions have increased for southern
portions of Baja California Sur. Therefore, the government of
Mexico has issued a Hurricane Watch and a Tropical Storm Warning
for portions of this area. After 48 h, the guidance has shifted a
little to the south, and the NHC forecast was tweaked in that
direction as well.
Key Messages:
1. Olaf is forecast to strengthen to near hurricane intensity while
it passes to the southwest of the southern portion of Baja
California Sur Thursday and Friday. Tropical storm conditions are
expected and hurricane conditions are possible across that area
beginning late Thursday. Interests there should continue to monitor
the progress of Olaf.
2. Heavy rains associated with Tropical Storm Olaf are possible
across portions of far southern Baja California Sur Thursday through
Friday. This will pose a threat of flash flooding and mudslides.
FORECAST POSITIONS AND MAX WINDS
INIT 08/2100Z 19.4N 107.7W 40 KT 45 MPH
12H 09/0600Z 20.2N 108.3W 50 KT 60 MPH
24H 09/1800Z 21.2N 109.4W 60 KT 70 MPH
36H 10/0600Z 22.3N 110.9W 60 KT 70 MPH
48H 10/1800Z 23.2N 112.5W 55 KT 65 MPH
60H 11/0600Z 23.5N 114.2W 45 KT 50 MPH
72H 11/1800Z 23.5N 115.5W 35 KT 40 MPH
96H 12/1800Z 23.1N 118.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 13/1800Z 22.4N 120.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Latto
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