Sunday, December 21, 2014

Desperate Ski Resorts Taking Matters into Their Own Hands

I never thought it would come to this...but it has...PINEAPPLECIDE.

Northwest ski resorts are desperate to deal with their nemesis:  the Pineapple Express.

You know what I am talking about...the current of warm, moist air that brings warm temperatures and heavy rain to the West Coast.   The generic name for such features is atmospheric river, but in our region we call it a pineapple express since our atmospheric rivers generally have their roots near Hawaii (see graphic).

But during the last week, faced with potential closure over the profitable Christmas break, some Northwest ski operators have turned to severe and unprecedented measures to deal with the threat. Hearkening back to approaches more appropriate to shamans or voodoo witch-doctors, crazed representatives of various Northwest skiing organizations are shooting, decapitating, and sacrificing pineapples in a display of desperation rarely seen in our region.

Below is  a video of the carnage, one not appropriate for the squeamish or those under 18 years old.

Meteorologists generally oppose such interventions regarding unwanted meteorological phenomena, but with recent attempts idealized in popular movies (e.g., Sharknado I and II), one can hardly fault the Northwest ski industry for taking matters into their own hands.   I will be the last person to criticize them if they succeed in bring back bountiful snow to our mountains.

Anti-pineapple video games are starting to appear.

And even some foreign governments, concerned about Northwest production of apples, hops, and other food imports, are getting involved, although the measures they are calling for might not be effective.

Saturday, December 20, 2014

Seattle in the Rain Shadow

Central Puget Sound residents do not frequently think about living in a rain shadow, like their friends in Sequim and Port Townsend.      But more frequently that you might expect, Seattle IS in a rain shadow and this will happen later today.

Seattle, with roughly 37 inches a year in annual precipitation, is far drier than the Washington coast, even places away from any terrain. For example, Westport, on the central Washington coast, gets about 74 inches....about twice a much as Seattle. The Long Beach Peninsula gets 81 inches.

The Puget Sound rain shadow is so profound that Seattle gets less rain than Chicago, New York, Washington, D.C. or Miami.

Our rain shadow is most evident when the winds along the coast are westerly (from the west), because of their interactions with the Olympics.

When the winds are from the west, air rises on the western side of the Olympics (producing heavy rain) and descends on the eastern slopes (causing drying).

During the past few hours (Saturday AM), a warm front has passed through our area  (sorry skiers), bringin warm air and a shift to westerly flow.  To illustrate this, here is the forecast heights, winds, and temperatures (shaded) at 850 hPa (about 5000 ft) for 4 PM Saturday (today).  The wind are parallel to the height lines and the closer the lines are together, the stronger the winds.  What you see is very strong westerly flow surging into our area, with red colors indicate very warm air.   You can get strong Puget Sound rain shadow with such a pattern, as well as heavy rain on the western sides of the coastal mountains and the Cascades.

 This air is also very moist, something suggested by the 10 AM water vapor product from satellite data (see below).   We have an atmospheric river today, with a narrow streamer of moisture extending from the tropics into our region.
 Now the fun part.  Here is the predicted rainfall for the 24h ending tomorrow (Sunday) at 4 PM PST. Wow...heavy precipitation in the mountains (as much as 2-5 inches) but a very strong rain shadow from Seattle westward over the Kitsap.   Only a few hundredths of an inch in some places.

Here is a radar image around 6 PM for the Seattle area.  A beautiful example of rain shadowing east of the Olympics!

What I like about this flow direction is that Sequim is way wetter than Seattle.  What I don't like is that there will be a lot of warm rain falling on the limited snow in the Cascade.  Stevens Pass opened for limited skiing today, with a 17 inch base.  Baker opened as well.  Bring old skis.

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 Wyoming.

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.