Saturday, May 2, 2009

Winter (sort of ) in May



Looking at the weather maps, I had a sense of deja vu....is this January? In fact, the maps didn't look like January in January. This winter has generally been colder than normal with a major ridge of high pressure in the eastern Pacific and a cold trough over the Northwest. Rare has been the classic situation with strong, wet southwest flow heading into the west coast. But now it is here.
Yesterday was glorious buttoday some frontal bands are moving up from the SW. Take a look at the satellite and radar imagery...the band is clear...with relatively intense rain now falling over Puget Sound as it makes its way north.

The remainder of the week continues this trend...look at the upper level flow maps for the next several days (shown below). The lines are parallel to the winds and the closer they are the stronger the winds. Strong westerly and southwesterly flow that will bring a series of weather systems and rain into the area. In fact, a pretty strong low is forecast to cross northern Vancouver Island late Monday (see map).

So if we didn't get classic winter in December or January...at least we will get it in May. Something to be thankful for. I guess.

PS: Want to see the cooling power of evaporation--take a look at this plot of temperature, humidity and other parameters at UW today. As the rain started in earnest around 6 PM (o100 GMT/UTC), the RH jumped up (due to evaporation of falling rain) and the temperatures plummeted. As the air saturated (RH near 100%), the cooling ceased.

PSS: Due to the warm weather my vegetable seeds have germinated...soil temps are now in the low fifties. The cloudy weather will prevent any real cold...so delicate plants should be ok.

7 comments:

andycottle said...

I`ve been looking at the models as well for early-mid next week, and so far, it appears that the GFS models may give some blustery conditions to parts of the WA coast as a roughly 985mb low passes to our NW and over Vancouver Island. But on the other hand, NAM models keep it much weaker and near 1000mb and just south of Western WA. So there are differences in the models, but we`ll see what happens.

mainstreeter said...

rainy on the east side of the state now, but was (nice) earlier with temps in the 60's and some clearing.

richard583 said...

".....PSS: Due to the warm weather my vegetable seeds have germinated...soil temps are now in the low fifties. The cloudy weather will prevent any real cold...so delicate plants should be ok."

.... This, with more immediately (appreciable or otherwise), .. the moon's present phase.

Fred said...

Cliff-

Care to comment on the differences between upcoming forecast and a "classic" pineapple express?
I checked the river forecasts. Rising levels but keeping below flood stage. Wouldn't there be a potential for a lot of sustained snow melt with this forecast?

-Fred

Julia said...

The rain yesterday afternoon (at least in Shoreline) was interesting - not just heavy but huge drops. I'm assuming this is the warm-air uplift phenomenon I've seen discussed.

Dude Diligence said...

Healthy wind last night behind the rain. Lost power here in Edmonds around 9 pm for about a half hour or so.

Keeping one's head above water said...

i have the weather channel icon on my google home page. It sasys we are have a severe weather alert here. are they fearmongering or are we in for some severe weather? Oh, btw you would be proud of the chehalis school district: my daughter is only in 9th grade and is 2 years ahead in her grade for math. SHe will be in pre calculus in 1oth grade and done with the eniter math curriculum in 11th.