A Look At The WRF Forecasts

Edited to add: Re earlier post on new building for the LTRR there's a nice photo collage of their open house at                      http://uanews.org/photos/laboratory-treering-research-debuts-new-home

This morning the global models have come into sync as the storm event develops for the Southwest. The GFS and ECMWF have been jumping around for the last 4 days on the evolution of this system - sometimes progressive sometimes slow; sometimes a large closed low and sometimes a sheared, positive-tilted trough. Both models now forecast the system through Arizona more quickly and indicate a positive tilt with time as the main vorticity maximum moves out toward the Plains. The uncertainty has been due to events in the central Pacific. A very intense surface low is developing just south of the Aleutian Islands and having downstream impacts. I just checked the GFS forecasts for the Pacific and the model appears to have gotten this system accurately in its 12-hour forecast.

This morning I have looked at Atmo's early WRF-GFS forecasts. The graphic above is from the 5.4 km grid and shows forecast radar echoes valid at 8 am on Friday morning (March 8th). The model forecasts three substantial bands of showers in the Southwest at that time. The high-resolution grid for Arizona at the same time (below) indicates that the leading band of showers will be crossing eastern Pima County at 8 am.

The surface forecast for the metro area at 5 pm on Friday is above. The front has already moved well east of the Tucson area and conditions here are windy, wet, and cold (relative to the warmth prior to this storm).

The model does not yet forecast out through Saturday. The total precipitation forecasts through midnight on Friday night (high-resolution forecast above and 5.4 km forecast below) indicate an event that produces widespread precipitation across the state, with best amounts over higher elevations. The quicker movement of this system will be better for the Tucson Festival of Books, but Saturday morning will likely still present a weather challenge for attenders and exhibitors!