Thursday, December 18, 2014

Northwest Warmth Continues

We can't seem to shake the above-normal temperatures.  Here is the temperature anomaly for the last month.  Virtually the whole western U.S. is warmer than normal, with particularly anomalous conditions in southern Idaho and Montana.  

Looking over the past four weeks at Seattle and Yakima shows almost an identical story...except for the one cold-spell in late November/early December, the temperatures have been above normal, with low temperatures often falling to the average highs for the day (red lines are average highs, blue lines average lows)
The main cause of the warmth has been the unusual persistence of warm southerly and southwesterly flow, but the unusually warm water off our coast has not hurt (see graphic, which shows the sea surface temperature anomaly yesterday.  Red areas are considerable above normal).


A strong ridge will build over the region over the weekend (see upper level map for 10 AM on Monday).

And this kind of  flow brings warmth and moisture into us. Take a look at the total precipitation for the next 72 days.  5-10 inches over some locations in the coastal mountain and Cascades.  Northern CA will get a piece of this, which is very good.  But not good for our snowpack.

But some good news...colder air make get here by the 24th, so that the mountains may get a bit of snow by Christmas.

Tuesday, December 16, 2014

How the Grinch Stole Northwest's Christmas Snow

We are now getting close enough to the holiday season to make an unfortunate forecast:  there probably will not be enough snow for Cascade mountain skiing during this holiday season in WA and OR.   As we will see, a major grinch will be a strong atmospheric river that will develop next week.

We start with a very poor snowpack in place.  Here is the % of normal snow water equivalent (SWE) in the western U.S. mountains. The western Cascade slopes are now 15-20% of normal.  The Olympics are 23%.  A bit better in the north Cascades and the eastern slopes, but still considerably below normal. With the recent precipitation, the California Sierra are doing much better....a nice turn of luck for them!

The NW Avalanche Center summarized the snow situation (snow depths) at some major ski areas (see below).  Mount Baker is 9% of normal, White Pass has NO SNOW,  Crystal has 6%, and Stevens has 25%.  We are way worse off than last year, which was not a good year.  6 out of the 11 sites have ALL TIME RECORD minimum snow for Dec. 15th.



So we start off with a sparse snowpack.  Next week a major ridge of high pressure builds over the West Coast.   Here is temperature anomaly (difference from normal) for the NCEP ensemble mean at 850 mb (around 5000 ft) for Monday December 21st at 4 PM.   Warmer than normal (orange colors).


The Climate Prediction Center (CPC)'s 6-10 day forecast for December 22-26th continues the trend with warmer than normal in the west.




A major issue is that a major atmospheric river will form over the weekend.  Warm, moist, air with heavy rain over Northwest mountains.  Here is the vertically integrated water vapor content prediction for Saturday at 10 PM.  Very juicy (red and white indicates the highest values).  There will be more flooding...guaranteed...bad for snowpack.


What about snow this week?  Let me snow you the UW WRF model totals for the next two 72 hour blocks.   First, 72h hours, perhaps 3-6 inches in the WA Cascades.


Next 72 hour, up to a foot in the north Cascades, but not much south of Snoqualmie.  Much more in the mountains of SW BC.   Whistler will be in better shape,


The trouble is that we won't get that much snow this week and then that snow will be hit hard by the heavy rain and warm temperatures.  Sorry.

Sunday, December 14, 2014

The Oregon Coastal Radar Gap

It was 10:30 AM on Thursday morning and the forecast models predicted that a deep low center from a Pacific storm was moving up the Oregon coast.    For meteorologists, it was crucial to know exactly where the low was located, both to check the model forecasts and to improve upcoming model runs. The visible satellite image was not definitive, with an elongated trough and no clear circulation evident.   But the models were emphatic it was off the coast somewhere.  But where?


What did the National Weather Service weather radars show?

The new Langley Hill radar on the Washington Coast was too far north, since the low was probably off the southern/central Oregon Coast.  It did not show a circulation, since it was too distant.


The Portland radar, too far from the ocean and the lower beam blocked by the coastal mountains, showed practically nothing offshore.  We see this problem all the time--the Portland radar is not very useful for viewing coastal or offshore weather.


The Medford, Oregon radar, too far inland and too high (it is on top of Mt. Ashland at around 7500 ft) showed little offshore.   No help at all over the ocean.

Putting all the radars together in a composite, there is little evidence of the circulation around the low...or anything else off of Oregon.  Not good.

Four hours later, when the the low center was further north and in the range of the Langley radar, the swirling circulation around the low was evident.  But for critical hours we did not have a good fix on the low.


The problem?    A huge gap in radar coverage over the Oregon coast and coastal ocean west of Oregon.  Here is an official National Weather Service radar map that shows the problem.  As I mentioned in a previous blog, there is also a major gap in coverage on the eastern slopes of the Cascades,

Since storms often come from the southwest and west, that means a major metropolitan area (Portland) lacks proper (or any) radar coverage upstream.   And as illustrated with the storm this week, it hurts western Washington forecasting as well, but at a more extended time range.  The lack of radar coverage off of the Oregon coast is something that Portland TV meteorologist Mark Nelsen has been blogging about repeatedly.  He knows.

The lack of a coastal radar is a particular problem today, since the National Weather Service forecast systems, like the new High Resolution Rapid Refresh (HRRR),  assimilates all U.S. radars before they make their forecasts.   That means that the radar information is used to describe the atmosphere, which greatly improves the forecasts.  I have noticed that the HRRR often gets offshore structures that are only described by the Langley radar.  Imagine if we had a similar radar on the Oregon coast!

As we learned with the acquisition from the Langley Hill radar near Hoquiam, the National Weather Service will not fix this problem without intense local lobbying.  I tried contacting the Oregon congressional delegation, but they were not interested in talking to someone from out of state. Oregon State residents, businesses, and organizations need to work together, in concert with their congressional representatives, to make the case for an Oregon coast coastal radar and to push for its acquisition.

Thursday, December 11, 2014

Storm Nowcast

8:30 PM  I don't know how long I will have connectivity:  my power is flickering, strong gusts are periodically buffeting the house, and I can hear large branches snapping close by.   Some flashes are visible on the horizon:  a sure sign of blowing transformer fuses.

The gusts are amazing....you can hear them several seconds before they hit-- a roaring sound that grows closer and then arrives with my house groaning and the swish of air passing buildings and trees.   Gusts are associated with the turbulent mixing of strong winds aloft down to the surface.

The latest Seattle City Light Windwatch wind map shows plenty of winds between 30 and 45 mph, and stronger winds have hit Sea-Tac, Olympia, and other locations.

6300 CityLight and 63000 Puget Sound Energy customers are out of power at this time...and folks we have not hit the peak of this yet.   The north-south pressure gradient in the Sound is still increasing.

One hour later (9:38 PM, 14,500  City Light customers and 79,000 Puget Sound Energy customers had lost power
...................
The winds are going to hit suddenly and hard during the next few hours if you are in Puget Sound country.

Strong winds reached Olympia and now Tacoma (6:30 PM), with gusts to 48 knots in Olympia last hour.

Strong winds are descending to the surface rapidly.  Here are the winds above Seattle-Tacoma, with the left most reports at 6 PM.  30 knot wind were only a few hundred meters above the surface at this point in time.

Puget Sound Energy outage maps tell the story...lights started going out very rapidly when the winds surged in.

The latest forecast from the NOAA/NWS High Resolution Rapid Refresh System suggests Seattle will feel the winds during the next hour (by 8 PM) and they will be strongest around 10 PM (here is the forecast gust map from HRRR).  50-60 knots over the water, and 30-40 knots over land.
 So get ready for an exciting few hours...it will hit like a wall of wind.  Cook your dinners now!

Feel free to leave comments about the winds if you want to share your observations.

Big Wind Tonight

The models are basically in agreement now on the track and intensity of the cyclone that is moving up our coast and the model evolution compares well with observations, so there is substantial confidence in the forecast I will describe.

The storm...I have seen better defined low centers.  The low center is in the middle of the swirl off of Oregon.

There will be a major blow tonight over western Washington that will certainly cause power outages for some of you.  This event should bring the strongest winds we have seen during the last year, but damage will be mitigated by our leafless trees and the fact that earlier windstorms have done considerable pruning of new growth and weak limbs.

Let me show you the latest sustained wind (not gusts) forecast every 3 hours of surface (10-m) winds and sea level pressure from the UW WRF run starting at 1 PM (2100 UTC).  The Oregon coast gets hit hard...something we have been saying for while.  The storm slowly weakens during the day, but there is plenty of punch left in it as it crosses the NE tip of the Olympic Peninsula

1 PM
4 PM
7 PM
10 PM

At Point Oxford (near Pt. Blanco) on the southern Oregon coast the winds are increasing rapidly, gusting to 60 knots (69 mph)--see below.  Pressure is rising, suggesting that the storm is moving away--which agrees with the models.

Now, let's turn to the UW Super-Hi resolution forecasts...1.33 km grid spacing--some of the best model resolution of any numerical weather prediction in the country (sponsored by the NW modeling consortium by the way).  Let me show you the gusts (in knots, remember 1 knot=1.15 mph).  Click on images to expand

At 4 PM, very strong winds along the Washington coast (gusting to 60-75 mph).  Long Beach Peninsula is hit hard.  Gust to 30-40 knots over Seattle.

 By 7 PM, coastal winds back off a bit as the low weakens and is about the cross Tatoosh Is.  Strengthening winds over Puget Sound and real bad from Whidbey to Victoria. 
 At 10 PM, a bit stronger over the north Coast and bad news north of the San Juans.  Very strong winds over northern Puget Sound as air surges northward  towards the retreating low.

Bottom Line:  Nearly everyone will experience gusts to 40-50 mph tonight and some more (coast, near the Sound, NW Washington)

I would not plan any ferry trips tonight and if you need to cross the Sound do it before dinner.  I suspect a few hundred thousand folks will lose power in our region, so be ready.

San Francisco Weather Wimpology

The "terrible" and "huge" storm has passed through San Francisco.  Here are the max winds during the past 24 h after the worst has occurred.  Away from the water their gusts hit 13 to 28 mph.  In the forties (mph) near the water and exposed peaks.  We had a lot worse around here yesterday, without a big storm!

 A very strong front went through San Francisco bringing heavy rain for a few hours, with a few tenths to a few inches depending on location.  Northwesteners would yawn at such amounts.

Some San Franciscans have gotten defensive about their weather wimpology:  check out their newspaper coverage.