The past few weeks have been drier than usual on the West Coast, and based on the latest forecasts, February will almost certainly be below normal for the western US. After an unusually wet fall and early winter.
In this blog, I want to provide some perspective on this dry month and take a look at some updated models running through the rest of February.
This graph of rainfall anomaly over the past two weeks shows the problem: below-normal rainfall from the Bay Area through Washington State, with some locations 1.5 to 4 inches below normal. inches. The SeaTac only received 0.21 inches this month, 1.12 inches lower than usual.
February is an interesting month for rainfall in the area, something that is shown by the graph of February precipitation at SeaTac over the past 70 years (see below).
HUGE variations from about 9 inches to about a third of an inch! The wide variation from year to year, with the mean number (3.76 inches) being the result of average extremes in both directions. There are some wet years, with a total of about 8 inches, and many years with only about 2 inches in the rain gauge. It shows you that you have to take the average values with a large amount of salt.
Why is there such a difference?
Some years are affected by one or more rivers with a soggy atmosphere, while others are not. Like this year.
So dry February is nothing new…or unusual…a fact you need to keep in mind. And this month is associated with an extremely persistent high-pressure band offshore.
Look forward
It did rain this morning…. a few drizzle from the low clouds… but that’s insignificant.
The weekend will be completely dry, but on Monday a weak system will pass, followed by a few more the following week. Check out the forecast for total precipitation through 4pm next Thursday across the region (see below).
There is nothing I would write home about. Probably a few tenths of an inch above the western lowlands. A little more in the mountains.
Central Europe’s cumulative rainfall at SEATAC through Sunday, February 20 is around 0.6 inches, with more rain to come next weekend. Enough to get us out of record dry territory.
But the big question is that by the last week of the month, with both Europe and the US patterns going back to near-normal rainfall regimes for the region, which could see SeaTac hitting monthly totals. about 2 inches, joining the bulk of dry precipitation. year shown in the figure above.
The good news is that even with the recent dry spell, the region’s total water volume for the year (as of October 1st) is above normal, and reservoirs are generally well above normal. The year-round chart for SeaTac below shows the story…..still WAY above normal after fall (dark green indicates above normal). So enjoy dry conditions and the coming sun: you earned if by all means last fall.
