Monday, October 12, 2009

TS Patricia Moving Slowly Northward

Tropical Storm Patricia (see IR image from 12 UTC above) is located south of the tip of Baja and is moving slowly north-northwestward. The combined influences of Patricia and the negatively-tilted trough off California have produced a long fetch of southerly to south-southwesterly winds from the south end of Baja northward into southern Arizona. There is a strong gradient in precipitable water (see the PW time series at atmo home page), ranging from half an inch along the southern Arizona border to over 2 inches at Navajoa, Sonora. Strong morning convection is underway about half way up the Gulf of California, and a low-level cumulus field is moving northward into southern Arizona. So, there are some indications that the current moisture plume, below 500 mb, from the subtropics may affect southeastern Arizona. The morning NAM model runs indicate the deeper moisture will just clip the southeast corner of Arizona and impact mostly New Mexico; however, the NAM also forecasts a strong southerly flow at 850 mb from the GoC into southern Arizona persisting for next 24 to 36 hours. So, something to keep an eye on to the south.

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