Friday, October 24, 2014

Strong Winds on Saturday Night

You can expect a fairly strong blow tomorrow evening over much of western Washington as a fairly strong low center moves up the coast and crosses over western Washington.

First, the latest satellite picture. You can see the swirl of clouds associated with the low due west of northern California.  Clouds extend northeastward from the low (in an occluded or bent-back warm front).  Nice pic.


Let's look at the latest UW WRF forecast (solid lines are isobars, lines of constant pressure).  We start for the forecast at 2 AM Saturday morning.  Strong low, with a central pressure at 985 hPa (millibar).  Strong, but nothing like the great storms like the Columbus Day Story (around 955 hPa)!


 By 2 PM Saturday, the low reaches the SW Washington Coast.  Big pressure gradient and associated winds along the Oregon coast.  The low has filled a bit (987 hPa).

 By 11 PM, the low moved across the Olympics and reached southern BC.
Big pressure gradients over western Washington...it will be windy then....gusts to 30-40 mph are quite possible.


There is another wind threat that will be more localized.  As the warm front moves northward tonight, you can expect accelerating winds along the western slopes of the Cascades from Enumclaw to North Bend.  Gusts to 40 mph are probable.

Here are the forecast gusts at 5 AM Saturday morning.  You can see what I mean about strong winds along the western slopes.


At 10 AM Saturday morning, the low is off the central Oregon coast and huge winds are found along the Oregon coast.  Winds OVER 70 knots.   If you are on the Oregon coast, either get away or get prepared...these will be severe conditions if the forecast model is correct.



As the low moves northward across out region late tomorrow afternoon/evening winds will accelerate...here is the strong at 5 PM.   Gusty wind pushing up the Sound and VERY strong along the central and southern WA coast (to 50 kts).


Six hours later, as the low moves north of us, the winds will remain strong in the Sound, but will get very powerful (50 kts plus) in the Strait as air accelerates eastward in the gap.


And yes, plenty of rain.  Here are the totals for the next 48h.

Very wet along the coast and in the north Cascades 2-5 inches).  We are experiencing a very second half of October, with much of the region already way above the normal monthly totals...and we have a week left to run.


Keep in mind that although this is a very recent model forecast, there is still some uncertainty with this event.   One source of additional uncertainty is that the weather satellite information feed was discontinued for 1-2 days to the National Weather Service modeling group.  The implications of this failure is not clear, but losing data over the ocean is a problem for us.

Another potential storm on Tuesday..but that will have to wait until another blog.

Thursday, October 23, 2014

Longview Tornado Ravages Dumpster

An EF-1 (86-110 mph) tornado hit Longview, Washington around 12:50 PM today (Thursday) in the unstable air that followed the recent atmospheric river.

This tornado did some minor damage to buildings and power lines but seemed to take particular vengeance on dumpsters.    Amazingly, the tornado pushed one dumpster all the way down the street.  I don't think I have ever seen a dumpster pushed down a street any further by a tornado...and I am interested in that kind of thing.    Here is the proof.




You can see the small, but intense, convective cell associated with this fearful weather phenomenon (I indicated the echo with a yellow highlight).  A far stronger line had just passed through Portland.



According to the National Weather Service, the tornado was on the ground for 1.3 miles and left a damage swath 200 ft wide.

It is a well known in the meteorological community that tornadoes are attracted to mobile homes and dumpsters.  (see pictures)   We are not sure why this is true, but there is ongoing research.



Recently, someone made a dumpster into a mobile home  (see picture).  I can imagine the attraction this will have for tornadoes.



Finally, with the recent Anderson Island waterspout, I am getting many inquiries over whether the recent rash of tornadoes/waterspouts are caused or "consistent with" global warning.  You can imagine the answer.






Wednesday, October 22, 2014

Heavy Rainfall, Eclipse Weather, and Possible Saturday Windstorm

Today we had an active atmospheric river over western Washington and Oregon, producing some impressive one-day totals.  Take a look at the total precipitation for the 24-h period ending 8 PM on Wednesday (see image).  Some locations (such as near the SE side of the Olympics) have reached over 4 inches, while 2-4 inches was widespread over terrain.  Only portions of eastern Washington received less than .05 inches.


The 24-h rainfall amounts from Seattle Rainwatch, based on the Camano Is. radar, shows a huge contrast in western Washington, ranging from 2-3 inches in the southern Sound to roughly half that north of Everett.
An infrared satellite picture at 1 PM his afternoon shows the plume of moisture extending into our region, and lots of unstable air behind it over the Pacific, which will be moving in tomorrow.


The partial solar eclipse

A partial eclipse of the sun will occur tomorrow (Thursday) afternoon starting at 1:36 PM and ending at 4:20 PM here in Seattle.  Will it be clear enough for you to see it?


Here is the UW WRF model's cloud forecast for 3 PM.  Best place to go for a chance for clear skies?  The eastern slopes of the Cascades.


And finally, I and others have been watching the potential storm on Saturday.  The solutions have shifted a bit, but right now it looks like we will have a decent blow on Saturday night, but not an historic windstorm.

On Saturday at 11 AM, the pressure forecast shows a strong, but elongated low off the Washington/Oregon coast.  Elongated is not good...you want a compact, concentrated storm.  But there are large pressure gradients along the northern CA and southern Oregon coasts--40-60 mph gusts are possible
 By 2 AM on Sunday the low has passed into southern BC and a large pressure gradient is over western Washington.  Expect wind and some power outages, particularly since leaves are on the trees.  Still plenty of uncertainty with this storm, so will watch it carefully.

Monday, October 20, 2014

Heavy Rain Coming and Windstorm Threat

An atmospheric river, a warm current of large amounts of water vapor, will be approaching our region starting later tomorrow (Tuesday), but it will be coming from a less frequent direction:  the west.  And the result will be the heaviest rainfall to strike our region since last winter.

Time to replenish our renowned water resources!  And a good reason to be glad you don't live in California.   And speaking of parched California, they are going to get a piece of the action.

Let's start by looking at the latest view from space, showing the amount of moisture in the atmosphere.  Reds and purples are large amounts, and not surprisingly such enhanced values tend to be in the tropics.   But a huge northward push of moisture is occurring in the central Pacific and a tendril of it is moving westward towards us.    It has our name on it.


Let me show you the forecast atmospheric moisture for 2 AM on Wednesday morning.  You can see the heavier moisture (blue and white) heading towards us.   And when that moisture is forced to rise by our regional terrain, there will be lots of precipitation.


How much?  Here is the forecast from the UW WRF model for the 72 hours ending 5 AM on Thursday.  Big values (more than 5 inches in the Olympics, North Cascades, and northern Oregon coastal mountains. An inch or two in the lowlands.   Rake the leaves from the drains near your house or apartment!


The next 72 hours?  Still wet, but less so.  1-5 inches over the region west of the Cascade crest.  One good thing:  northern California will get enough rain to begin to fill their thirsty reservoirs.


As with most atmospheric rivers, there will warm temperatures and strong, but not damaging, winds (30-40 mph on Tuesday night and Wednesday AM).  To illustrate here are the forecast temperatures, heights and winds near crest level (850 hPa, about 5500 ft) on Tuesday at 11 PM.  You see how packed those height lines are approaching the Oregon/WA coast....those are associated with strong SW flow.  Reds are warm air.



Let me make clear...this is NOT going to be a record event.  But it will be the wettest period since last winter.

Finally, a number of the modeling systems are predicting that a deep low pressure center will approach our coast on Saturday morning.  Here is the solution from the U.S. GFS model (the solid lines are isobars, lines of constant pressure) for 8 AM Saturday.   Huge pressure difference (gradient) along the southern Oregon coast...with big winds (50-75 mph).  The European Center model has the same low, but fuarther north and offshore.   It will take a few days for the solutions to stabilize...but this is worth watching.


The latest run is in...and it is getting more threatening for western Washington!   This is valid 5 AM Saturday.  Only a 108 hr forecast...close enough that you got to be concerned.  985 hPa low.  This would be a major windstorm folks.


Here is pressure and sustained winds (kts) for the same time.   Wow...serious winds along the coast.


And by 10 AM Saturday, the low moves north of Puget Sound after crossing the Olympics...the most threatening windstorm path.  I am going to COSTCO tomorrow to buy batteries.




Saturday, October 18, 2014

The Extraordinary Minimum Temperature Heat Wave in the Northwest

I have been watching Northwest weather for a long time and I have never seen anything like what we have experienced during the last month:  

An extended and intense minimum temperature heat wave.

Something amazing has been going on this fall, and for some reason the Ebola-crazed media hasn't picked up on it.   But that is why we have blogs.  Gardeners know something weird is happening. Vegetable plants are not dying.   Tomatoes are still ripening.

There are movies about this issue.

Here are the temperatures at Seattle-Tacoma Airport during the past 4 weeks, with the average high (red) and lows (blue) shown.   Only ONE day in that entire period has seen the temperature dropping to the average low.  For most days, our minimum temperatures have been 5-10 degrees above normal. Our minimum temperatures last night were close to the average maximum for the date!
UPDATE MONDAY MORNING:  Here is the latest 4 weeks.  Our low temperatures the last few days have been around the NORMAL HIGHS.  And yesterday broke the record daily high at Sea-Tac Airport.

And this is not Seattle alone, here is the same trace for Bellingham.  Same thing.  Bellingham cooled to 59F last night!
Or Quillayute on the coast.   Mega-warm.
A plot of the minimum temperature anomaly (difference from climatology) for the western U.S. over the past month shows that our regional is RED HOT, with minimum temperatures 6-8F above normal on average.

A close-up over Washington State shows some areas are 8-10F above normal.


And the latest NOAA Climate Prediction Center extended forecasts show no end in sight
to the warmth:


Now why is this happening?   This is an important  question because one can expect some folks in the media and advocacy groups to start saying this is a "sign" or "consistent with" global warming due to mankind's emissions of greenhouse gases.  There is no reason to think that is true.

There are two main reasons for the warmth and they are both associated with the anomalous atmospheric circulations we are having.

Reason #1:  a persistent area of low pressure over the eastern Pacific.  The figure below shows the sea level pressure anomaly (difference from normal) for the past month.   There is an area west of us with pressures well below normal.   Such anomalous low pressure is associated with stronger than normal southerly and southwesterly winds over us that blow in warmer than normal air.
Here are the wind anomalies near the surface for the same period...look closely you will see they are southerly over us. It all fits.

This is probably the major cause.   Then there is something else, something I have talked about in previous blog:  the warm water BLOB off the coast.

Below is the sea surface temperature anomaly map for the past week.  You see the orange and red colors off the coast that indicate temperatures 2-4F above normal?  The BLOB still lives.  So air passing over the eastern Pacific  is exposed to warmer than normal water.  Me like BLOB, BLOB is good.

As I noted earlier, the BLOB has little to do with global warming but was produced by anomalous high pressure over the Pacific last winter and year.

So our ridiculously warm temperatures this fall are being produced by an unusual combination of high pressure a year ago that produced the blob and low pressure this fall that is bringing up warm air from the south.

There is no reason to think that these circulation anomalies are caused by human greenhouse gas emissions.  And remember that the eastern U.S. has been colder than normal.

Well, time for me to go out to my garden to harvest some more red tomatoes.