Monday, May 4, 2009
The Big Storm
Well, I don't want you to forgot about the big Seattle math decision this week described in the previous blog, but I HAVE to discuss the big storm moving in later today.
It is really extraordinarily intense for this time of the year...reminds me of a strong November to January event. Ironically, we didn't get many strong windstorm/rainstorm events during midwinter due to the anomalous pattern that help in place this year, with a ridging over the eastern Pacific and a cold trough over the Northwest.
Take a look at the two attached satellite photos...one is a visible and the other is a water vapor image (in this picture the satellite is describing the amounts of water vapor in the middle to upper troposphere). The signature of a developing strong storm ins unmistakable, with broad areas of deep cloud. The water vapor image show an area of dry air behind the low center (green indicates moisture, black is dry). The strong storms usually have a tongue of dry, descending air right behind the low center.
The computer models indicate the storm will rapidly intensify today, but I think it will be coming in a bit closer than forecast (comparing the simulations against the satellite pictures). The simulations shows the low crossing northern Vancouver island with a low pressure of around 980 millibars (see attached graphics). This track does not bring the primo winds into Puget Sound...no more than around 20-30 mph from Seattle south very late tonight and tomorrow am. (see wind speed graphic) As the low moves north of us in the early morning hours, the winds in the Strait of Georgia will increase...so from Whidbey Is northward it will rock, with wind gusting to 40- 50 mph. The WA coast will get similar wind speeds. However, if track is closer in, as it appears from the satellite pictures at noon, the winds may be greater. I wish we had the coastal radar!!!!
And did I mention the rain...we will get plenty of that. The rain will move into western Washington this afternoon and moderate rain will occur tonight. (see graphic of 24-hr rainfall ending 5 AM tomorrow). Many places in Puget Sound will receive .25 to .75 inches, and the mountains --particularly the SW side of the Olympics will gain 2-4 inches. A nice addition to top off those reservoirs for the summer!
As I mention in my book, late season storms do happen...and some of them have caused tragic deaths, when group hit the mountains in May without checking on the forecast. By the way, for those on the Olympic Peninsula, I will be giving a public talk in Port Townsend on Sunday at 1 PM (see info at right).
Posted by Cliff Mass at 11:56 AM