Eastern Derecho

More fires in Utah.  It never ends this year.  

Today, however, we'll take a quick look to the east.  Strong winds associated with a thunderstorm complex known as a derecho produced wind gusts up to 80 miles per hour, knocking out power for more than a million people in the DC area yesterday. 

Washington-Reagan airport had a wind gust to 70 mph. Check out the dramatic passage of the gust front just before 0300 UTC.

The power outages couldn't come at a worse time as the region is embroiled in a terrible heat wave and the loss of air conditioning is a concern for heat-related illness.  It hit 104ºF yesterday at Dulles Airport, setting a new maximum temperature record for June by 2 degrees.  Fortunately, it's running several degrees cooler today, although the heat is probably still a concern for vulnerable people.  

For more on the derecho and it's impacts, see this report from the Capitol Weather Gang.  

Views of Fires

Here are a couple of views of the smoke from fires in Utah yesterday.  The first is from the Moderate Resolution Imaging Spectrometer (MODIS) on board NASA's Terra satellite.  The smoke plume on the left is from the Clay Springs Fire, the one of the right is likely the Seeley Fire.  There may be smoke from the Wood Hollow fire between them.

The second is from a 737 just north of the Uinta Mountains.  The smoke over the Uintas may be of remote origin, as well as from the Pole Creek and Church Camp fires.  The cumulus cloud on the horizon near the center of the picture may be a pyrocumulus from the Seeley Fire.

Rain looks unlikely through about the 4th of July, then the models are hinting at perhaps some monsoon moisture sneaking in.  We'll have to see if that comes to fruition and if it just merely adds to the misery due to more lightning starts.

Flagstaff Fire

Amongst the many fires raging in the west today is the Flagstaff Fire near Boulder, CO.  This one is near-and-dear to many atmospheric scientists as it is immediately west of the National Center for Atmospheric Research's Mesa Laboratory and threatens the homes of some colleagues.  Below is a time lapse of the fire taken by jjagogo, a CNN iReporter.

The Mesa Lab is an iconic I.M. Pei designed building that was once featured in the Woody Allen movie Sleeper.  

The lab is closed today due to the fire, and major supercomputers and data storage that are used by atmospheric scientists around the world are presently offline.  This is a minor inconvenience, however, given the threats to homes and property near Boulder, Colorado, and elsewhere in the Southwest.    

Waldo Canyon Fire

Credit:  Jerilee Benett, The Colorado Springs Gazette 

The Waldo Canyon Fire raging in Colorado Springs currently represents the nation's #1 wildfire priority.  News reports suggest that more than 32,000 people have been evacuated.

The weather in Colorado yesterday couldn't have been much worse.  It was one of the hottest days ever observed along the Front Range.  Denver and Colorado Springs tied or set their all-time maximum temperature records.

Denver hit 105ºF, Colorado Springs 101ºF, and Pueblo 106ºF.  I don't believe the 106ºF in Pueblo was an all-time record, but it was the third consecutive day of 105ºF or higher, which is a record.  The relative humidity at Colorado Springs was as low as 6% at 2200 UTC (4 PM MDT).

Media reports near the fire suggests winds yesterday afternoon reached 65 mph.  Unfortunately, a power outage in a server room last night means we can't take a close look at observations near the fire, but radar imagery shows some marked changes late in the day.  The blue box in the loop below roughly identifies the area of the fire.  Radar returns emanating from this area are likely the result of ash from the fire.  Note how this trails off downstream, but shifts later in the loop with the passage of an outflow boundary, the leading edge of denser outflow from precipitation to the north.

At the Air Force Academy, winds ahead of this outlfow boundary were southeasterly, gusting to as high as 31 miles per hour.  With the passage of the outflow boundary, winds shifted to westerly and then northwesterly, with gusts to 31.

All-in-all, a terrible situation.  Dry fuels, high shifting winds, low relative humidity, and a fire moving into the urban-wildland interface.  Colorado Springs Fire Chief Rich Brown described it as a "firestorm of epic proportions."  Today probably won't be quite as hot and dry, but conditions will still be difficult.  There is also a chance of afternoon showers and thunderstorms, which could produce strong wind gusts.  Let's hope that they get wetting rains instead.

Addendum 10:35 AM MDT:

Below is yesterday afternoon's MODIS image of the fire plume and pyrocumulus.

Summer Reading

Looking for some summer reading?  Given the active fire season, there are some excellent books on western wildfires and the dangers of wildland firefighting.  Here are three that I recommend.  

I frequently pass the scars created on Storm King Mountain by the South Canyon Fire, which killed 14 firefighters.  It has been an emotional experience ever since I read John Maclean's Fire on the Mountain.  Reading these three books will give you new appreciation for those who put their lives on the line fighting wildland fires, as well as fire weather and physics.  

A Remarkable Photo

Source: ksl.com

The above is a remarkable photo of the Wood Hollow Fire from the ksl.com web site.  Unfortunately, it is unattributed so I can't provide proper credit.  Kudos to the photographer.

The cauliflower-like lower cloud is known as a pyrocumulus and is generated by the intense updraft produced by strong heating in the fire.  It is likely composed of smoke, ash, and cloud droplets.  The latter form as the air rises and cools, with water vapor released by the burning of fuels that contain water also contributing to the water budget.  In some cases, pyrocumulus can produce lightning and thunder.

The pyrocumulous is topped by a more fibrous pileus cloud.  Pileus clouds are similar in appearance to lenticular clouds that form from the interaction of flow with mountains and hills (sometimes called wave clouds).  The pileus cloud, however, forms when an intense updraft forces a layer aloft upward.  They can be produced by convective clouds, volcanic eruptions, and thermonuclear explosions (fortunately, these are banned today, but you can see examples in historical footage).

Pileus cloud during eruption of Sarychev Peak in July 2009.
Source: NASA/JPL and Wikipedia Commons.

A "Nearly" Rainless June?

Source: http://environment.nationalgeographic.com/

It's looking increasingly likely that we will not record measurable precipitation at the Salt Lake City Airport this month, if we get through today.

Thus far in June, only a trace of precipitation has been reported (on the 2nd and 5th).  The last measurable precipitation (.01 inches) fell on May 27th.

Today, however, we have the slightest chance that a rogue, isolated thunderstorm will somehow find a way to put down measurable precipitation at the airport, but it is a long shot.   Precipitable water has increased over the past 24 hours and is now nearly 2 cm.

And the dewpoint just hit 41ºF, a welcome change from the obscenely low values of the past couple of days.

Isolated storms generated by this weak surge of monsoon moisture will probably produce gusty winds and perhaps a bit of lightning, but the odds of measurable rain at the airport are low.  Looking out further, the latest GFS forecasts suggests we will remain in dry southwesterly flow for the rest of the month.  A bit of monsoonal moisture pushes into southeast Utah from time to time (e.g., below), but fails to make it to Salt Lake City.

So, barring a rogue isolated thunderstorm today or a surprise shift in the forecast, we're going to make it through the month without measurable precipitation.

Agent 99 Has Arrived

As one of our reader's commented on the previous post, it is unbelievably dry today.  I don't know what the record dew-point depression (the difference between the air temperature and dew point) is at the Salt Lake City Airport, but at 4 PM this afternoon it was 100.4ºF with a dewpoint of 1.4ºF.  Well chief, that gives us an Agent 99 dewpoint depression and a 2% relative humidity.

Some industrious soul needs to process the hourly weather records and see how common a 99ºF dewpoint depression is at KSLC.  My guess is it is extremely rare.  I know that in June, the average afternoon (6 PM) dewpoint is 42ºF, but have never looked at the extremes.

Western Fires

Smoke from the Dump Fire in Utah county is less obvious in today's MODIS image.  Compare the one below in which smoke is barely evident to the one from the previous post.  Squint and you might be able to make out the fire scar just west of the northern part of Utah Lake (click to enlarge).

A heroic effort by firefighters kept the fire out of residential areas yesterday.  They must have thrown everything at it but the kitchen sink.  It may also be fortunate that there are no heavy fuels in the lower elevations near the homes and that the fire was moving downhill.

Conditions at the Eagle Mountain are fairly similar to yesterday, but perhaps a touch drier.  It is currently 95ºF with a dewpoint of 9ºF, for a relative humidity of a remarkably low 4%.  Winds are currently southwesterly at 21 miles per hour gusting to 29.

The Salt Lake Tribune reports that the winds have slowed the "counterattack" on the fire and have extended the evacuation order for about 600 homes.

Meanwhile, serious fires are raging elsewhere in the west.  The Weber Fire near Mancos, CO has forced evacuations and has generated a plume that is readily apparent in today's MODIS imagery.

And, while the High Park fire continues to burn west of Fort Collins (now up to a size of almost 70,000 acres), an additional fire broke out in that area today and burned at least 10 homes near Estes Park.  The plume from this fire is also readily apparent in MODIS imagery.

Remarkably, it is still only June.  What will happen when lightning activity increases over the southwest?  It could be a very long summer.  

Dump Fire Weather Update

Modis imagery captured the smoke from the Dump Fire fairly well this afternoon.  Fire-weather conditions are unfortunately very difficult.  Temperatures at valley level are in the 90s with strong winds at some locations.

The MesoWest site near Eagle Mountain is presently 94ºF with a relative humidity of 8% and winds gusting to 30 miles per hour.

Things aren't going to change much until late in the day when the sun finally begins to set, although it probably won't be a quiescent night given the large-scale flow.  Fire weather conditions will improve, but be difficult compared to the nighttime climatology.  Further, this pattern will dominate through the weekend.  It will be hot, dry and windy with southwesterly large-scale flow.  Perhaps there will be a slight increase in dewpoint and a few cumulus on Sunday (with a slight risk of thunderstorms that will almost surely be dry, but that's about it.

All in all a terrible situation.  Let's hope the firefighters can somehow keep the fire at bay.  It's going to be a very difficult task.

Smoke on the Utah Lake Water

We all came out to Montreux,

On the Lake Geneva shoreline.

To make records with a mobile,

We didn't have much time.

But Frank Zappa and the Mothers,

Were at the best place around,

But some stupid with a flare gun,

Burned the place to the ground.

Smoke on the water, a fire in the sky. 

- Deep Purple's Smoke on the Water

Yup, it has happened again.  Another fire sparked by target shooting west of Utah Lake.  As Einstein said, insanity is doing the same thing over and over again and expecting a different result. 

The aptly named "Dump Fire" was sparked yesterday afternoon.  The National Interagency Fire Center  (NIFC) situation report this morning puts it at 600 acres, with 20% containment.  Fortunately, no structures have been lost thus far, although the Salt Lake Tribune update this morning suggests that attention will need to be given to protect commercial and residential properties today.  Given the large-scale southwesterly flow, there is a subtle campfire-like smell around the University of Utah campus with smoke filtering through Point of the Mountain.  

Wildfire conditions today are going to be difficult.  Very difficult.  Our nocturnal inversion is just beginning to burn off and winds at many locations are on the increase, although some sites near the fire remain light.  I suspect it is already blowing on the mountain.

The GFS forecast for this afternoon shows a developing trough off the Pacific Coast with dry southwesterly flow over Utah. 

This means hot, dry, windy (and gusty) conditions in and around the fire.  Yesterday, the Pioneer Crossing MesoWest site near Saratoga Springs had a high of 92ºF, a minimum relative humidity of 10%, and a maximum wind gust of 18 miles per hour.  

Today will be hotter, windier, and just as dry.  Let's hope that despite these difficult conditions, the fire can be quickly and safely contained.

Update: 10:25 AM MDT

Photo below of the Dump Fire was taken at 9:45 this morning by blog reader Jim Edman from Lehi.

Photo Credit: Jim Edman

Lone Peak is now fully obscured.  This is quickly becoming a very serious fire given the southwest winds.  KSL reports that a mandatory evacuation has been ordered for homes near the fire.  

Utah to Flirt with Monsoon Moisture

Following up on the previous post, the latest GFS model forecast suggests that Utah will see it's first surge of monsoon moisture this summer on Sunday.  The precipitable water and 700-mb wind loop below shows the moisture penetrating into southeastern Utah late Saturday and then spreading through most of the central and eastern portions of the state on Sunday.

Gullywashers?  Nope.  This is a modest increase in moisture, so we will mainly see an increase in afternoon cumulus clouds and thunderstorm risk, especially over the mountains.  Dry lightning is a possibility, which is not great for wildfires.

The surge is short lived in Salt Lake, as the forecast presently calls for drier air to move back into the northern part of the state by Tuesday.

A Southwestern "Dryline"

A pattern change the next couple of days will result in substantial contrast in weather across the southwest United States.  A deep mid-latitude trough is developing off the Pacific Coast, while a ridge intensifies over the south-central United States.  This will lead to a confluent flow pattern over Utah and Arizona with significantly different airmass origins for the two states through Saturday morning.  A confluent flow pattern is one in which two different airstreams are brought together.

Most of Utah will be in the southwesterly flow ahead of the mid-latitude trough, resulting in hot, dry, windy conditions Thursday and Friday.  It's pretty much a worse-case scenario for fire-weather conditions, so let's be careful out there.

GFS 700-mb wind vectors and precipitable water (cool and warm colors
indicate low and high values, respectively)

In contrast, southern and eastern Arizona will be strongly influenced by easterly and southeasterly flow on the upstream side of the developing ridge.  While it is quite dry there today, moisture will be on the increase over the next few days, leading to an increasing thunderstorm threat.  They will need to worry about lightning in addition to accidental fire.

As can be seen at the end of the loop, this leads to a strong contrast in precipitable water between the two regions.  Precipitable water (a.k.a. integrated water vapor) is the depth of water one would have if all the water vapor in the atmosphere rained out.   By Saturday morning, values are less than 5 mm over central Utah, but more than 20 mm in portions of southern Arizona.  

Thus, the southwest will have it's own "dryline" separating relatively moist and dry air on Saturday.

Yesterday's Dust Sources

Some of you may have noticed some dust (and maybe smoke) in the air over northern Utah yesterday evening.

Visible satellite loops show that this dust originated from the Carson Sink, a dry lakebed in western Nevada (large red box below).  It was a big day for dust emissions from the salt playas of the Great Basin yesterday there were also dust plumes from the Honey Lake dry lake bed in northern California, Smoke Creek Desert in northern Nevada and the Gabbs Valley area of central Nevada.

There's also a fire in the Schell Creek Range east of Ely, although it seemed to be a minor producer of aerosols (small particles) compared to the salt playas yesterday.

Beating the Heat

Source: Ellie Buzbee, Auburn University

Looking to cool off?  Salt Lakers have a couple of options.  One is to head up into the Wasatch or Uinta Mountains to higher elevations and cooler air.  The other is to spend a night in one of northern Utah's low elevation basins or sinkholes where nighttime temperatures drop like a rock to ridiculously low values.

For example, check out the rush Valley south of Tooele and west of Utah Lake.  Overnight, temperatures bottomed out as low as 48ºF at the Faust MesoWest site along the valley floor compared to 60s in the Salt Lake Valley.

Minimum temperature since Midnight, 18 Jun 2012

The Rush Valley is famous amongst meteorologists for it's low minimum temperatures.  Of course, the cold air that forms in the valley is very shallow.  Note how minimum temperatures on the benches around the valley are much warmer.  For example, it only bottomed out at 66ºF on the bench along the southwest flake of the Oquirrh Mountains.

In addition, while it is cold at night, it is very hot during the day along the valley floor.  Faust dropped to 48ºF, but it had a high of 95ºF yesterday.

So, if you want to cool off in the Rush Valley, you need to be a nocturnal animal.

The Spring Drought: A Harbinger for the Future?

It's another scorcher out there today.  Everything is parched and today I'm running the soaker hoses to give my drought tolerant plants just a hint of water.

Spring is a critical season for water the Salt Lake Valley.  On average, May, April, and May are the three wettest months of the year, as shown by the blue bars in the graph below.

Climatological and 2011-12 water year precipitation at the Salt Lake
International Airport.  Source: NWS and Western Region Climate Center

This year, we reached just above average in April, but March and May were way below average.  Average precipitation for March through May is is 5.63 inches, but this year we got 3.61 inches, 64% of average.  June is a transitional month climatologically, with the first part of the month sometimes bringing a few storms.  The monthly average precipitation is .98 inches, but this year we've gotten only a trace.

The water cycle is affected not only by precipitation, but also evaporation and transpiration by plants, which we refer to collectively as evapotranspiration.  Evapotranspiration is influenced by a number of factors (sun, wind, etc.), but one of the most important is temperature.  All else being equal, higher temperatures mean greater evapotranspiration rates and faster drying of the soils.  At the Salt Lake City International Airport, March was 5.4ºF above average, April 3.4ºF above average, May 1.7ºF above average.  Although we've had a couple of cold spells, June is running just above average thus far too.  Thus, the soils this spring are drying more quickly.

Climate model precipitation projections for the middle 21st century vary over northern Utah, but most call for May and June to be a bit drier than they were in the later half of the 20th century.

Source: Thomas Reichler, University of Utah

That being said, the difference relative to climatology is fairly small compared to current year-to-year variations in precipitation, so I'm not ready to hang my hat on a prediction of less precipitation in the coming decades.  I am, however, confident that we will see more frequent springs with higher temperatures and more rapid drying of the soils in the coming decades, as we have this year.   This will likely yield increased demand for residential irrigation, assuming current landscaping practices continue.

For more discussion, see section 5 of our climate report to former Gov. Jon Hutsman Jr.'s Blue Ribbon Advisory Council on Climate Change.

Friday's Political Reading

There's an interesting article in The Atlantic by Jonathan Adler, a professor at Case Western, that discusses a possible approach to combating climate change.  I've always been of the opinion that innovation is essential to lowering the cost of low-carbon energy and gradually reducing our reliance on fossil fuels.  Adler lays out a series of policies to do this, including federal support of prizes that encourage the development of low-carbon technology, reducing red-tape and other barriers to the development of alternative energy, migration to a revenue-neutral carbon tax (i.e., a carbon-tax that is offset by tax reductions in other areas), and finally, adaptation.

Take a look and see if the article is compelling from your perspective.  

US Open Weather

"The coldest winter I ever saw was the summer I spent in San Francisco"

- Attributed to Mark Twain, but source unverified

This year's U.S. Open is being held this weekend at The Olympic Club in San Francisco.  The Olympic Club sits just inland from the Pacific Coast and south of Lake Merced Park, as illustrated by the two Google Maps images below.

For the mountain meteorologist, San Francisco and the surrounding Bay Area has a great deal to offer.  Complex terrain, complex land surfaces, and land-sea contrasts create tons of fascinating microclimates.

During the summer, high pressure and low clouds are a semi-permanent feature off the California Coast, whereas low pressure dominates over the Central Valley and Great Basin.  Indeed, this is the case today.

This leads to large contrasts in surface weather from the Pacific Coast, which is inundated by cool marine air, and the Central Valley, which has a more continental summertime climate.  For example, maximum temperatures yesterday increased from the 50s along much of the Pacific Coast to as high as 101ºF at one MesoWest site in Sacramento.

The Point Reyes Lighthouse on the top of Point Reyes National Seashore (left side of the image above) is figuratively one of the coldest places I've ever been.  It experiences strong northwesterly flow for most of the summer with temperatures in the 50s.  It is a major shock to the system in July!  San Francisco often features large (~10ºF) variations in temperature depending on location.

The only MesoWest site near the Olympic Club is a citizen weather observer station (K16BSW) about 2 miles to the north.   Over the past five days, temperatures even in the afternoon have been in the 60s, whereas morning temperatures have been near 50.  Winds have been predominantly southerly, although there was a period of stronger northwesterly flow late yesterday with gusts over 20 miles per hour.

The weather during the US Open will be strongly affected by the battle between marine and continental airmasses.  When the marine air dominates, cold, cloudy, windy conditions prevail.  When it doesn't, it's still cool, but cloud cover is less prevalent and temperatures can be a few degrees warmer.

For the first round today, the marine airmass will continue to dominate.  It will be a cool, cloudy start this morning.  However the forecast models call for low pressure to develop over southern California on Friday.

Over northern California, this should yield large-scale offshore flow and, for the Olympic Club, improving weather during the day on Friday that should persist through at least Saturday.  The players should be quite happy with this shift as it will probably be less cloudy and warmer than one would expect based on climatology.