Event Postmortem

The latest weather event has moved eastward and turned into quite a rain-maker for the lower Mississippi Valley. See the early morning radar composite above, from the CoD weather page. I got several e-mails about the event here in southeastern Arizona, so here's a summary.


First, the NWS forecast for Tuesday night (Feb 9/10) was for 100% POPs. When I took a look at
things on Tuesday evening - around 6:30 pm - the NWS forecast looked to be right on track. The IR satellite image showed a huge area of cold cloud that seemed to be moving northward right up toward Tucson. The models were in agreement, forecasting rainfall everywhere in the southeast part of state with some nice amounts indicated by the model QPF. But the model(s) obviously didn't get the movement of the disturbance quite right and were just enough off on the eastward component to change us, locally, from a forecasted good event to an observed almost zip.


I put the radar precip up on the blog yesterday morning to illustrate what a bust the model forecasts were here, right around Tucson. So it goes! I saw some amounts off to Tucson's southeast over an inch yesterday morning - so it just illustrates how a very small model error can really impact us. The event that's just ended provides a huge contrast to the major event in late December that was forecast very consistently for days and illustrates that sometimes the nodels can lock accurately onto hemispheric forcing and be extremely reliable but at other times be fickle even at 12-hours.

As for precipitation yesterday as the system headed east - here at house we got 0.10" and about 65% of the Pima County ALERT gauges had measurable rainfall in last 24 hours. Amounts were mostly around a tenth of an inch or less, with a few spots receving about a quarter of an inch. Arivaca had 0.63", Nogales had 0.44" and Douglas had 0.61" and some RAWS data indicated over an inch amounts in the far southeast part of the state. The more significant part of the event stayed to the south and east of the Tucson Metro NWS forecast zone. And so we have to hope that the next two events coming in off the Pacific do better in getting rain on the ground.