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.
Posted by Cliff Mass at 7:06 PM