Friday, August 27, 2021

Ida And Nora

Thunderstorm over the Catalinas yesterday afternoon about 3:00 pm MST.

Tropical Storm Ida (NHC outlook above) is forecast to hit western Cuba today as a hurricane and then to threaten southern Louisiana as a moderate hurricane by Monday night. The 1530 UTC visible satellite image below shows Ida, as well as Tropical Storm Nora off the southwest coast of Mexico.

The NHC outlook for Nora (below) currently forecasts the storm to become a hurricane and track right up the GoC. This track results in a pressure gradient pointing south, down the GoC - thus, strong moisture advection into southern Arizona may be delayed until the remnants of the storm arrive. This a much more difficult situation to accurately forecast than when storms move southwest of Baja.

Also of interest is Hurricane Nora of 1997 - this storm crossed Baja and came into southwestern Arizona, but produced no rain here in the Tucson (ended up being called NO Rain At all)! 

There were afternoon storms yesterday, as per plot of detected CG flashes - above for 24 hours ending at about 2:00 am this early morning (from Atmo and Vaisala). Eight stations in the ALERT network had more than 0.04" as per map below for 24 hours ending at 8:00 am this morning.

This morning's sounding for TUS/TWC (above) has a deep residual BL as well as CAPE above about 650 mb. The light and variable wind profile has no real steering winds. Storms on the mountains could end up drifting toward lower elevations.

Precipitation forecasts from the WRF runs at Atmo are: above from 12z WRF-RR this morning showing rainfall forecast through 5:00 am tomorrow morning, and below from 00z WRF-GFS showing model's forecast of rain amounts through 5:00 am September 1st. So there continues to be some chance of a bit more rain across Tucson region before the end of August.

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