Thursday, 03 September 2009
4:00 update: Interesting and surprising. Env. Can still has precipitation in their 3:30 forecast for Monday:
Monday: Cloudy with 60 percent chance of showers. Low 11. High 23.
even though both their latest global and ensemble models do not show it. Hmmmm. Unless the precip reappears on tonight's run of the model, I don't expect that precip to be there on tomorrow's forecast.
The next few days will be a continuation of the past few days, sunny and warm (relative to normals, which is 22 for highs and 12 C for lows). The question mark is for Labour Day monday, wouldn't you know it. After predicting sun, sun, sun, Env. Can. is all of a sudden calling for cloudy conditions and possibly rain. Hmm, waddupwiddat?
I had a look at the 6Z run of the GFS this morning and it was in agreement with the Canadian but the 12Z run has backed away, at least with the precip. Essentially what is happening over the course of the weekend is that the current high pressure system is moving off to the east, giving our region a warmer and moister (is that a word?) southerly flow of air on its backend. The next high pressure system coming down from northern Canada has a cooler and dryer front end. Where these air masses interact, there could be some condensation of moisture from the southern air. Until today, this wringing out of the air was happening south of us, but last night's model run of the Canadian and GFS snuck it north. This morning's GFS has moved it south of us again, and a preliminary look at the 12Z Canadian looks like it has moved the precip south again as well. So you will likely see a change in the Env. Canada's forecast for Ottawa on Monday to dryer conditions again.