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Tropical Storm Olaf Discussion Number  12
NWS National Hurricane Center Miami FL       EP152021
900 AM MDT Fri Sep 10 2021
 
The satellite presentation of Olaf has significantly degraded over 
the past several hours after the center moved across the southern 
portion of Baja California Sur overnight. The system's organized 
convection has collapsed, and infrared satellite imagery indicates 
cloud top temperatures are rapidly warming near the estimated center 
position. The initial intensity is lowered to 60 kt for this 
advisory, which now makes Olaf a tropical storm. This estimate may 
still be generous, but limited surface observations and radar data 
make it difficult to confidently assess the intensity. Hopefully, 
scatterometer data this afternoon will provide more insight into 
changes in Olaf's surface wind field. 
 
The tropical storm has slowed down a bit since last night, and its 
estimated motion is northwest (310 degrees) at 9 kt. Recent 
microwave imagery suggests the center of Olaf is just offshore the 
southwestern coast of Baja California Sur, and the cyclone is likely 
to move roughly parallel to the coast today. Then, a strong 
mid-level high pressure ridge centered over the southern Rockies is 
expected to build westward to the north of Olaf. This ridge should 
turn Olaf toward the west by tonight, and then toward the southwest 
through early next week. The official NHC track forecast has been 
adjusted to the south of the previous forecast once again, in 
agreement with the latest multi-model consensus aids.
 
Olaf is likely to continue rapidly weakening during the next couple 
of days. In the short-term, its proximity to the mountainous terrain 
of the Baja California peninsula will disrupt its ability to sustain 
organized convection. As Olaf moves away from land, the cyclone will 
encounter decreasing sea-surface temperatures and very dry mid-level 
air, which should expedite its transition into a post-tropical 
cyclone. In fact, the latest GFS and ECMWF model simulated satellite 
imagery show Olaf becoming completely devoid of convection within 
the next 24-36 h. The latest NHC intensity forecast shows more rapid 
weakening than the previous one, primarily based on recent satellite 
trends and the lower initial intensity. The official forecast 
remains below the HCCA and IVCN consensus aids, which are inflated 
by the SHIPS and LGEM models that fail to weaken Olaf during the 
next 24 h.
 
 
Key Messages:
 
1.  Olaf is forecast to move along the southwestern coast of the 
Baja California peninsula today, with tropical storm conditions 
continuing over southern portions of Baja California Sur through 
this evening.  These winds should diminish tonight as Olaf continues 
weakening and turns westward away from land.
 
2.  Heavy rains associated with Olaf are expected across portions of 
southern Baja California Sur through today. This will pose a threat 
of significant and life-threatening flash flooding and mudslides.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 24.1N 111.3W   60 KT  70 MPH
 12H  11/0000Z 24.5N 112.4W   50 KT  60 MPH
 24H  11/1200Z 24.6N 113.6W   40 KT  45 MPH
 36H  12/0000Z 24.3N 114.7W   35 KT  40 MPH...POST-TROPICAL
 48H  12/1200Z 23.4N 115.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  13/0000Z 22.4N 117.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  13/1200Z 21.6N 118.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  14/1200Z 20.7N 121.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  15/1200Z 20.0N 123.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Reinhart
 
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