Super Moisture Plume Headed for the Northwest.

Many of you will need umbrellas during the next week.   And perhaps a lightning rod.  

The cause? 

A dramatic plume of moisture will be heading into the Northwest from the south.  

Southwest Monsoon moisture will be entering our region, and our chances of breaking any dry spell records are dimming fast.

The latest water vapor satellite image shows the impressive moisture plume over the Southwest---and it is heading our way.


Let me start by showing you the latest precipitation forecasts from the UW WRF model.  For the 72 hours ending 5 PM Tuesday, the interior gets wetted down well, with some favored locations enjoying over an inch of rain.  This precipitation is from the plume of moisture from the southwest U.S.  


But our wet bounty is not over: during the next 48 h the first Pacific disturbance of the season moves in from the west and provides precipitation for western Washington and southwest BC. This system is a bit earlier than normal (normally the first wet system occurs during the third or fourth week of August), but no one is going to complain.


Now back to the superplume of moisture coming up into our region.  

Below is the forecast total moisture in the atmosphere predicted by the European Center model for Sunday evening. Known as precipitable water, it represents the depth of water that would occur if all water vapor was condensed out of the atmosphere.  The colors represent the percent of normal.  Blue is high (over 160% of normal, gray is VERY high (over 250% of normal).  Lots of moisture moving northward east of the Cascade crest.


How unusual is this moisture plume?  The predicted values over eastern WA and southern BC on Monday morning will be up to FIVE standard deviations from normal for that date (see image below, dark gray).  A standard decision is a measure of deviation from the mean.  Five standard deviations indicate essentially unprecedented conditions over the past several decades.

So we will go from extreme heat to extreme moisture in a little over a month!

This moist air will be relatively unstable, which means a good chance of thunderstorms east of the Cascade crest.   The simulated infrared satellite image on Saturday night suggests a number of storms in eastern Oregon (see below).  Thunderstorms can bring needed rain, but they can also start wildfires.


With the lack of thunderstorms and wind, wildfire activity has actually declined in recent days.  So this situation will be one to watch carefully.

Reminder:  new podcast tomorrow morning.  Perhaps it is time to talk about Northwest thunderstorms!


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