System Over The Eastern pacific

First, a bit about the low temperatures this morning. Yesterday's WRF-GFS forecast for TUS was too warm. Winds became light and temperatures dropped lower than the model forecast of 56F. The airport and Atmo reported morning lows of 45F (here at house the low was 32F). However, DM AFB appears to have had a morning low of 56F, with stronger winds persisting there - only about 4-5 km separate DM and TUS. Another example of just how difficult forecasting the low temperatures can be here inside the Tucson city limits.

There is a fairly distinct upper-level cyclone spinning in the Eastern Pacific this morning. The 6 am MST water vapor image (above) indicates this feature is at about 30N and 140W. There is a considerable amount of PW with this system, as the 3 am blended analysis (below) shows - light blue indicates about 40 mm of PW.

This morning's NAM analysis of RH at 700 mb for 12 UTC (above) shows that the model has high RH in about the right place. But it is not obvious that the model has this system initialized well. The 48-hour forecast (below for 12 UTC Friday morning) indicates a fairly substantial area of high RH air at 700 mb coming ashore into the Southwest. After 48-hours the NAM lowers the RH and minors the system out. However, something to keep an eye on the next couple of days.