A Dry Five Days, With Welcome Warming, Thanks To Omega

Get out your sunglasses and put away your umbrella--the next five days should be bright and dry here in western Washington.

Who can you thank for this meteorological bounty?  The greek letter omega.


The total precipitation for the five days ending Friday at 11 PM from the European Center model is, well, zero over most of western Washington.
 Bizarrely,  all the precipitation will be going into normally much drier California!  Here is the California precipitation total for the same period.  Wow.  Much of California, particularly in the mountains, will get several inches.  While we are dry.

This extreme difference in precipitation and the persistence of the pattern this week is due to a highly persistent "locking" of the atmosphere called an "omega block."  To illustrate, here are the forecast upper level (500 hPa) heights (like pressure)  for Tuesday evening.  The solid lines are the heights and the colors represent anomalies from normal (blue is lower--a trough, orange is higher than normal--a ridge).


There is a ridge, with two adjacent troughs/lows to the SE and SW.    Doesn't it look like the Greek letter "omega"? (see below)
This omega configuration is very, very stable and can stick around for days (or even longer).  The Northwest is immediately downstream (east) of the ridge of high pressure/heights, thus we will have dry skies and warming temperatures.

Those poor folks in California are downstream of the low/trough, bringing them unseasonably cool temperatures and lots of rain.

Because of the ridge, temperatures will progressively warm during the week.  Here are the temperature forecasts from the European Center model for this week in Seattle.  Temperatures first rise into the fifties and then to 65F on Friday.  Can you imagine how good that will feel?


After getting through a March that was cooler than a  normal January, we deserve this.  For California, the cool/wet weather is good news--filling the reservoirs, upping the snowpack, and delaying the inevitable fires.

Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more