Dear WeatherCat west coast of the
USofA weather watchers,
We are having an unusual atmospheric river event today. This morning water vapor images showed a plume of moisture (precipitable water values near 1.50") from northern California back to the subtropics. Recent GFS/NAM forecasts have indicated strong integrated water vapor transport (IVT) values approaching 800-1,000 kg/m/s today. Yet there has been only moderate rainfall. The high pressure ridge over Southern California was slower to retreat then predicted and that dried the air under the river and also narrowed the path it would traverse.
Even so we had a decent rain event this morning and are expecting more rain tonight. The peak rainfall rate was 1.52"/hr (38.6mm/hr) and the total rain received was 0.41" (10.4mm) thus far. We might come close to doubling that overnight.
The other oddity is the temperatures. It has been close to 60˚ F (15.5˚ C) all day. That is extremely warm for late November. This is also due to the combination of moist tropical air on top of the Southwestern Ridge.
I'm not complaining but it is very unusual weather. I can't recall anything quite like this.
Cheers, Edouard