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Tropical Storm Pilar Discussion Number  22
NWS National Hurricane Center Miami FL       EP192023
1000 PM CDT Thu Nov 02 2023
 
On regular geostationary satellite imagery, Pilar's structure is not 
that impressive, with pulsing deep convection near the center and a 
continued lack of banding features. However, an earlier AMSR-2 
microwave pass at 2003 UTC and a more recent 2231 UTC GPM pass show 
the cyclone's low-level structure is more formidable, with a cyan 
ring evident on the 37-GHz channel. However, the 89-GHz channel 
shows the deeper convection is displaced northeast of the center, 
possibly a result of moderate westerly vertical wind shear due to 
the brisk Gulf of Tehuantepec gap-wind flow Pilar is embedded in.  
While subjective Dvorak estimates remains on the lower side, at 
T3.0/45 kt from TAFB, and T2.5/35 kt form SAB, the initial intensity 
will remain 50 kt this advisory, out of respect for the earlier 
scatterometer data. The maximum winds on Pilar's north side are 
likely a result of Pilar's cyclonic vortex superimposed on the 
larger gap-wind flow in the area.
 
This same flow appears to have caused Pilar to accelerate today, and 
its estimated motion is currently rapid to the west-southwest at 
250/19 kt. A continued west-southwestward motion with a gradual 
slowdown is expected for the next day or so as the small cyclone is 
steered by the low-level gap winds in addition to a mid-level ridge 
draped along to its northwest. Farther upstream, an upper-level 
trough is forecast to dig into the Baja California Peninsula, which 
will ultimately erode the ridging at the same time Pilar leaves the 
influence of the gap wind flow, allowing for a turn westward and 
west-northwestward by the end of the forecast. The track aids this 
evening have shifted faster and a bit farther south, influenced some 
by the initial position assisted by the microwave data. The NHC 
track forecast is a blend of the prior interpolated track with the 
consensus aids.
 
As earlier stated, the environmental conditions do not appear all 
that favorable for Pilar, as the gap winds the storm is embedded in 
also contribute to moderate westerly vertical wind shear. The shear 
direction is important, because that could result in Pilar importing 
dry air upstream as seen in the GOES-18 water vapor imagery. In 
addition, the cyclone is quite small, potentially making it more 
susceptible than usual to less favorable environmental conditions. 
Thus, the NHC intensity forecast continues to slow little change in 
intensity or very gradual weakening, despite the storm moving over 
warmer sea-surface temperatures. The latest NHC intensity forecast 
favors a blend of the HAFS-A/B hurricane-dynamical guidance and IVCN 
consensus aid. By early next week, even stronger vertical wind shear 
will lead to a faster rate of weakening, and it's possible Pilar 
could become a remnant low or dissipate by the end of the forecast 
period.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0300Z 10.7N  99.2W   50 KT  60 MPH
 12H  03/1200Z 10.0N 101.8W   50 KT  60 MPH
 24H  04/0000Z  9.7N 105.0W   45 KT  50 MPH
 36H  04/1200Z  9.6N 108.0W   45 KT  50 MPH
 48H  05/0000Z  9.8N 110.6W   45 KT  50 MPH
 60H  05/1200Z 10.1N 112.7W   45 KT  50 MPH
 72H  06/0000Z 10.8N 114.5W   40 KT  45 MPH
 96H  07/0000Z 11.8N 116.7W   35 KT  40 MPH
120H  08/0000Z 13.6N 118.8W   30 KT  35 MPH
 
$$
Forecaster Papin
 
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