####018003583####
WTPZ44 KNHC 030244

TCDEP4

 

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