Wednesday, May 25, 2016

Steven's Pass Melt Out

On Saturday, Steven's Pass had its "melt out", which is defined as the first day of the summer when less than two inches of snow water equivalent (SWE) was left on the ground.


It was the 8th earliest melt out in the last 36 years.  The average melt-out date the last 35 year is June 2, so it is about 1.5 weeks early.   Folks care about the melt out date because it is an integrated measure of the depth of the snow pack and the degree of spring warmth, and both of those are expected to be influenced by global warming.  Increased levels of CO2 should result in warming that will result in less build up of mountain snowpack in the winter and a quicker melting in the spring of what snow does accumulate.

Last year (2015) was a profound example of warming causing a reduction in snowpack and a very early melt off date (the earliest on record!).    Some folks are saying that there is trend towards poorer snowpacks and earlier melt-outs, and that that this is an indication that we are already experienced human-caused global warming.   But is it true?

Mark Albright, past Washington State climatologist, has plotted up the Steven's Pass melt-dates from 1981-2015 (see below).  The annual melt-out dates are shown by the blue dots, the mean over the period by the horizontal gray line, and the 5-year running mean by the purple line.   There is no evidence of a long-term trend for earlier melt-out dates.  In fact, just the opposite....melt out dates are trending later (which implies cooling or greater snowpacks or both).  Last year (2015) was an outlier, although two other years came close.

So there doesn't appear to be any global warming signal producing earlier snow melt offs in our region.
To drive this point home further, here are the mean melt-out dates for recent decades (again, thanks to Mark Albright).  It appears that the melt-out dates are getting progressively later, just the OPPOSITE of what we would expect global warming would do.

1980s: 30 May
1990s: 1 June
2000s: 2 June
2010s: 4 June (thru 2016)

This small delay in the melt out is consistent with other independent measures of snow content in the Cascades, such as the April 1 snowpack amount, also show little trend.
One or two bad years are not an indicator of a long-term trend and the evidence, as shown above, suggests minimal decadal trends of snow in the Cascades.

Monday, May 23, 2016

Most Weather-Related Wildland Firefigher Deaths Can Be Prevented: Here's How.

Last summer three wildland firefighers died near Twisp, Washington as wind reversed during the afternoon.

In 2013, nineteen firefighters died near Yarnell, Arizona as the gust front emanating from some thunderstorms caused the fire they were working to explode.


Between 1910 and 2014, 1096 wildland firefighters died while they were fulfilling their missions, and a significant number of these tragedies were weather related.

And as I will describe below, most weather-related wildfire deaths can be avoided if fire agencies are willing to apply current generation observing and forecasting technologies, while enhancing critically needed personnel.


As someone who specializes in local weather in the western U.S., regional weather prediction, and the effects of terrain on regional flow patterns, I have always been interested in the weather associated with major wildland fires.   Looking at major recent fires associated with firefighter deaths (such as Yarnell and recent Twisp fires), I have concluded that each was associated with a sudden wind shift and that these wind changes were easily foreseeable by someone possessing meteorological knowledge and state-of-the-art observational resources (click on the links for these two fires to see my blog analysis).

The Yarnell fire deaths were associated with the outflow boundary of cooler air emanating from thunderstorms to the northeast, something evident from weather radar imagery and regional surface observations.  The Twisp disaster was connected with a windshift, associated with cooler air moving across the Casacades, that was predicted by regional weather prediction models and was evident in real time from surface observations.

The convection and gust front associate with the Yarnell Tragedy was evident in weather radar imagery

Recently, I listened to an excellent presentation on "tragedy fires" at the Northwest Weather Workshop that was given by Andy Haner, an experienced National Weather Service meteorologist specializing in wildfire prediction.  In his talk, he went through five fatal fires--Yarnell (2013), Twisp (2015), Thirty Mile (2001), Frog Fire (2015), Beaver Fire (2014)--and found that four of them were associated with clearly predictable weather phenomena.  He had not worked up the Thirty Mile Fire (he is a relatively young man), but I had--it was the same story:  a trained meteorologist could have easily seen the threat coming.  Furthermore, many of the deaths occurred for relatively new and small fires, fires for which no incident meteorologist had been assigned (Incident Meteorologists (IMETs) are forecasters specially trained to work during severe wildfire outbreaks).

Considering the seriousness of this issue, I conferred with some very experienced fire weather researchers in the Forest Service (who preferred anonymity).  They agreed with my and Haner's analysis:  virtually all the major wildland firefighters deaths could have been prevented with better information and guidance using current observations and forecasting technology.

Disturbingly, official reports on these wildland firefighter deaths do not consider or provide superficial coverage of this crucial issue (for example, the initial Twisp report is here).  Very disappointing.


So based on my analysis of several fires and discussions with a number of fire weather experts, let me describe how we could end most wildland firefighter deaths.

(1)  ALL wildland firefighting efforts should have supported by trained meteorologists that are continuously watching the situation.  Importantly, this includes even small or emerging fires (since they are involved in many of the deaths).  This does not require one meteorologists per fire, since a meteorologist can watch over several in an area (think of the meteorologists being similar to flight controllers that supervise several flights at a time).  These meteorologists would be responsible to provide guidance, forecasts, and warnings to fire crews.

(2)  All wildland firefighting crews will have continuous and uninterruptable communications to the meteorologists.   This means that every crew must have satellite phones before they go to a fire.

Weather observation and prediction technology has greatly improved during the past decades, allowing meteorologists to provide radically better support for wildland firefighters.  For example, we have large number of  surface weather observations throughout the U.S., including remote areas.  To illustrate, here is map that shows the latest wind observations over the Washington State (and there are much more available than is shown here).


Weather radar imagery are providing constant coverage over much of the western U.S. (although there are some gaps).  In those areas, high-resolution satellite imagery is available.

New weather prediction technology is now available, such as the High Resolution Rapid Refresh (HRRR) forecasting systems that uses all available observations to create high resolution analyses and short-term forecasts each hour (see below)


And there are many more observing and forecasting resources that I have not mentioned.  Simply put, modern meteorologists have an extraordinary set of tools to determine what the weather is doing now and what it will be doing in the future, even in relatively remote areas.    Importantly, there is no reason that sudden windshifts, the source of many of the wildfire tragedies, can not be diagnosed and forecast.

The deaths of brave young men and women can be greatly reduced if trained meteorologists with the proper tools are assigned to all fires.  With modest resources, such meteorological support could quickly become a reality.   

And there is one more thing, and it is perhaps controversial.   Firefighting teams should never risk their lives to save isolated homes or buildings.   Most of regional forests are meant to burn and have burned for millennia.   Homes and buildings don't belong there and it should be understood by all that the buildings are expendable and will not be protected.  They are not worth risking human lives.

Not worth a human life.

Saturday, May 21, 2016

A significant precipitation event from the "wrong" direction

As predicted, a deep trough has formed over the West Coast, bringing cooler temperatures and precipitation.   The atmosphere has reconfigured itself during the past week, as the pesky ridge of high pressure, which brought warmth and aridity to our region, has moved to the west.

As shown by the latest (Saturday AM) infrared satellite image (see below, with my annotations), an upper low center is found over eastern Oregon, with substantial moisture rotating around it into our region.    There is a substantial EASTERLY (form the east) component of the winds and that produces upslope precipitation on the normally dry easterly slopes of the Cascades.  Eastern WA is also getting rain.


How much so far?   Here is the 24h totals ending 9 AM Saturday over central Washington.  Impressive amounts (over an inch in some locations) over the eastern slopes, will many locations wetted by more the .5 inches.  Good rain over northeast Washington.


A band of precipitation is now circling into western Washington (see radar).   My garden will be happy.


Normally dry, eastern Oregon has done very well from this event, with some eastern Cascade locations getting over 1.5 inches.


The latest WRF model forecast for the next 24 h (ending 5 AM Sunday), brings lots of rain to the central and southern Cascades, with relatively dry conditions along the coast.


There are a lot of folks worried about heat and drought this summer and potential impacts such as wildfires and poor harvests.     This event is very positive as has been the reconfiguration of the atmospheric circulation.  Eastern WA soil moistures are near normal and our reservoirs, such as those in the critical Yakima drainage are full and above normal (see below for yesterday...and that is before the today's rain).
El Nino is collapsing and the latest  NOAA CFSv2 seasonal forecast predicts wetter than normal conditions from June, July and August (spoiler alert:  the skill of these forecasts is not great).

However, with warm water still offshore, El Nino still be present, and other factors, the subseasonal forecast models are projecting warmer than normal conditions over our region this summer (see below).   Not crazy warm like last year, but .5-1 C warmer. Warm temperatures encourage evaporation and thus contribute to surface drying.

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SaveKPLU

If you are a listener of KPLU, please consider contributing to the effort to save the radio station.  They need 7 million dollars to succeed and they have now garnered 6.2 million.  Your pledge will be matched by generous other donors.     The savekplu website is here.

Thursday, May 19, 2016

Cherry Weather Worries

Eastern Washington State is one of the premier growing regions for sweet cherries in the world, possessing both good soils and climate.  But cherries have weather vulnerabilities that can cause severe loss of fruit.    One of them is frost during the budding season, but that has not been much of a problem during the past few years due to our unusually warm weather.


But there is another: rain just before harvest that can cause fruit to split.  Recently, unusually heavy rain hit California, halving their harvest.  Very bad.


Typically, the Washington State cherry harvest starts around June 1st.   But with unusually warm weather, the date will probably move up to May 23rd, according to what I have been reading in the Ag magazines.  Very soon.  


The problem is that with a trough of low pressure moving over us, significant rain is forecast during the next several days (see the WRF model 24h total ending 5 PM Saturday)... .5-1 inches over some of the cherry growing region over the eastern slopes of the Cascades.  Heavier amounts in some location.  This is very good for general moisture over eastern WA and  to keep the fire threat down.


According to the agricultural experts at WSU,  when cherries are close to harvest the pressure inside increases.  Rain, particularly when the weather is warm, can be absorbed through the outer surface of the cherry (called the cuticle),  sometimes leading to the bursting of the cherry.  Heavy thunderstorms during warm weather are particularly problematic.  Burst cherries may not look great, but are certainly valuable for many uses (juice, jam, etc.).  They are less valuable.


Growers have a number of approaches to deal with rain on cherries, including blowers and running helicopters over orchards.


The main rain threat is on Friday/Saturday as the upper low passes south of Washington and precipitation swings northward over eastern Washington, accompanied by easterly (upslope flow)--see upper level (500 hPa) map for Friday at 11 PM.

 Since we are very early in the cherry season, only a limited amount of the crop is vulnerable.   But orchardists and meteorologists will be watching the situation closely.   I certainly will--I love cherries and limited supply can cause the price to rise.

Tuesday, May 17, 2016

Troughzilla

Well, we had Ridgezilla, the intense area of high pressure that brought low snowpack and warm temperatures last year.  Or the persistent and powerful Godzilla El Nino.  But during the next week we will experience something different:  Troughzilla, an area of intense low pressure over the west coast that will make it cooler and wetter than normal at least through next week.


Let me show some upper level  (500 hPa, around 18,000 ft) forecast maps that document the  development of this beast.   Today was a fine day, with a modest ridge over us (see map for 5 PM today-Tuesday).   This is the last day of warmth for a while.

 By 5 PM Wednesday, a trough of low heights (or pressures) has developed over the eastern Gulf of Alaska.
 One day later (Thursday 5 PM), a very strong low center is centered over western Washington and a huge, powerful ridge over the central NE Pacific.

Friday afternoon?  Now it has grown and extended into California.


 On Saturday at 5 PM, the infernal beast is now over the entire West Coast.

As you can imagine, this pattern is not going to result in any heat waves, as illustrated by the latest forecast for Seattle from the Weather Channel. No more 70s or 80s for a while.   Temperatures at or even below normal.

Precipitation?   You bet.   For the next 72 hours, wet offshore and modest rain over our local terrain.


 The next 72 h (ending 5 AM Monday) is far wetter, with several inches over the mountains, lots of moisture over eastern Washington, and substantial rains over northern CA.

The atmosphere has shifted to a very different configuration, one we have not seen for a while.  Find a sweater and protect you tomatoes.

Sunday, May 15, 2016

Heavy Rain and Potential Flooding (And a Warning about Parking)

I knew it was dangerous to do a blog on arid conditions on Friday the 13th.

Yesterday, a low pressure center to our southeast rotated moist, easterly flow into our region with substantial upslope precipitation leading to National Weather Service flood watches along the eastern slopes of the southern WA Cascades and over the Blue Mountains of NW Oregon (see figure below).

Here are the 24 h precipitation totals for southern WA.  Some locations near the Cascade crest received more than an inch, with many locations along the eastern slopes wetted by a half-inch.


With the system centered to the south, Oregon got even more rain, with some locations in the coastal mountains getting more than an inch.

Eastern slope rivers are surging from the combination of rainfall and snowmelt.  The critical Yakima river reservoirs are near capacity and still rising (blue line below).  Yakima agriculture should have plenty of water this summer.


As noted earlier, the cause of this wet bounty on the Cascade eastern slopes and Oregon has been a  low center positioned ever southern Idaho.  The 850 hPa (5000 ft) map below shows this feature clearly (wind barbs and temperatures at the level are also shown).


The slow-moving low will continue precipitation over eastern WA and Oregon for the next 24-h, as shown by the latest WRF model forecast below.  Go north, if you want drier weather.


This week is going to be interesting.   First, a weak ridge will develop over us, providing temporary improvement.  But then  a HUGEridge develops over the Pacific and a very deep low forms over our region (see upper level map for Friday at 8 AM).  WOW.


This a cool, wet pattern for us.  To show this, here is the 72h precipitation total ending 5AM Saturday.   Even California gets a piece of this.   You can expect the wildfire danger to be greatly reduced and all current fires should be controlled.   

One negative about rain--it is not good for maturing cherry crops.  California's harvest was radically reduced by recent, unseasonable rain.  I hope the same doesn't happen with WA cherries, which I love.
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Public Service Announcement: WARNING TO HIKERS ON CHUCKANUT DRIVE south of Bellingham.

If you are hiking near the trailhead of the wonderful Oyster Dome hike on Chuckanut Drive (SR 11), be VERY careful.  The State Patrol and their towing company buddies are towing lots of cars.  So be very careful if you park there.


Friday, May 13, 2016

Arid Spring

I have been doing a lot of gardening the past week, and I am startled by how dry the soil is.



What is particularly surprising is the aridity of the soil following the wettest winter in Northwest history.  The lack of rain was accompanied by very warm temperatures (April was the warmest on record at several western WA location, which has led to an earlier start of the fire season, with several wildfires west of the Cascades.  The picture below shows a fire in Snohomish County.



So what happened?  Let's start by looking at the percentage of normal precipitation for the past two weeks (below). Western WA and Oregon are very dry, with some locations at less than 5% of normal.

But percentages can be deceiving--here is the departure of observed precipitation from normal for the same period.  Less scary....but you will notice that some areas of western Washington are down a bit over two inches.  Much better situation east of the Cascades and over California/Nevada.

What about the entire spring?  Here are similar figures for the last 60 days.   For the percent of normal precipitation, much of the Northwest is well below normal--some locations 25-50% of normal.

Departure of accumulated precipitation?  2-6 inches in western Washington, 0-2 inches in eastern WA.  

So why have we been so dry and warm here in western Washington?   The key cause is persistent high pressure (ridging ) aloft.    Here is the difference from normal (anomaly) over the past 30 days for upper level  (500 hPa) heights (like pressure).  Above normal heights (yellow colors) over SW Canada and the northern portions of the Northwest).    Such ridging brings sinking air and dry/warm conditions.


This persistent pattern is rapidly evolving and next week an area of low pressure will move towards our coast.  The result will be clouds and rain.     Take a look at the latest 6-10 day precipitation forecast by the Climate Prediction Center.  Above normal precipitation over our region.  I suspect this will end the fire threat for a while.
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KPLU Event!

Meet an astronaut (and me) tomorrow (Saturday, May 14) at the Museum of Flight for a KPLU fundraiser (music at 6 PM) and presentation (7PM).  Information here: