Tuesday, July 31, 2012

Salt Lake to Get Some?

Monsoonal thunderstorms caused some flash flooding in southern and central Utah, southern Nevada, southeast California, and northwest Arizona yesterday.  The Salt Lake Tribune reports this morning that flooding damaged multiple homes near Fountain Green and the Wood Hollow Fire burn scar.

Source: Sanpete County Sheriff's Office
Overnight, monsoonal moisture spread northward and precipitable water increased over Salt Lake City as can be seen in the analysis loop below.

and in the GPS precipitable water observations from the Salt Lake City International Airport.

At issue is whether or not the high clouds presently in place will break up enough to enable sufficient surface heating to get things going.  Although rain would be appreciated by most of us, flash floods and debris flows are a concern if heavy rains fall over wildfire scars near Alpine, Saratoga Springs, and elsewhere.

A continued threat of showers, thunderstorms, and flash flooding lingers in portions of Nevada, southeast California, and western Arizona as well.  In fact, flooding in the Imperial Valley of California this morning forced the closure of I-8 and SR-98.

Monday, July 30, 2012

Desert Weather Excitement

As anticipated, things are starting to fire up this afternoon over the lower Colorado River Basin and environs.  Click to enlarge.

Flash flood warnings have been issued for five areas in CA, AZ, and UT thus far.  More to come I'm sure.

Partly Juicy with a Chance of Flash Floods

As anticipated (see previous post), an impressive slug of monsoon moisture drapes from the lower Colorado basin to southeastern Utah this morning, with precipitable water > 50 mm (2.5 inches) near Yuma, AZ and environs.

Check out the morning (1200 UTC) sounding from Flagstaff, AZ, which is saturated or nearly saturated from 700 to 300 mb.

Things are quiet now, but with daytime heating, slow-moving thunderstorms could erupt and produce some impressive gully washers in this area.  The NWS has a flash flood watch (area of green below) in place from noon today through this evening for an area from south of Lake Havasu to just south of Price, UT, including Zion National Park, Capital Reef National Park, Grand Staircase–Escalante National Monument, and the San Rafael Swell.

A hazardous weather outlook covers much of southern Nevada, southeast California, and northern and western Arizona where thunderstorms and isolated flash flooding is possible.

Of concern is flash flooding in dry washes and burn scars from recent wild fires.  This is not a day to be canyoneering.  There's several great videos of flash floods on the Colorado Plateau illustrating just how dangerous it can be during these floods.  Here's one by Nancy Schutt that illustrates the dramatic changes that occurred one day in Capital Reef's Grand Wash.  They were fortunate to be able to get to higher ground.

I've always wanted to storm chase on the Colorado Plateau on a day like this, viewing these types of floods from a safe place.  Alas, there is real work to do today.  

Sunday, July 29, 2012

The Southwest Monsoon Climate Transition

Climatologically, there is a remarkable climate transition that occurs between southeastern Arizona, which is strongly influenced by monsoon rains, and southwestern Arizona and southern California which are considerably drier.  This transition is clearly evident in the mean precipitation for the two months of July and August.  The mea precipitation for these two months varies from 2–9+ inches over southeastern Arizona (depending on elevation), but is less than an inch (or even half inch) in the valleys of southern California, with a amaximum of only about 2 inches on the highest peaks near Palm Springs.

Data Source: Oregon State University
PRISM Climate Group
Better yet, let's look at the mean precipitation for July and August at individual stations (valley locations) going east to west across southern Arizona and California:

Tucson: 4.57"
Organ Pipe Cactus National Monument, AZ: 3.16"
Yuma, AZ: 0.70"
Imperial, CA: .42"

Impressive.  Imperial and Yuma are lower, but the change in elevation plays a secondary role in the precipitation contrast, as can be inferred by the analysis in the image above.

There are, however, times when southwest Arizona and southern California can get in on the action.  Tomorrow may be one of them.  There is a strong easterly wave presently moving across northern Mexico and southern Arizona that will move over southwest Arizona and southern California tomorrow.  

This should bring a good chance of showers and thunderstorms to the lower Colorado River and Imperial Valleys, which are some of the hottest and driest places in the United States this time of year.  

The loop below shows the march of high precipitable water air into the Imperial Valley.  Precipitable water increases from about 15 mm over the Salton Sea at 1200 UTC this morning to over 50 mm tomorrow.  

GFS Surface wind, sea level pressure, and precipitable water
analysis and forecast from 1200 UTC 29 Jul – 0000 UTC 31 Jul 2012.
Gully washers are a real possibility.  Wish I could be there.  

Friday, July 27, 2012

More on Snow and Ice

While we are on the subject of snow and ice (see previous post), it seems a good time to take a look to the Arctic.  On 23 July, the National Snow and Ice Data Center (NSIDC) reported that the Arctic sea ice extent was 7.32 million square kilometers, slightly lower than the record low for the day set last year (7.22 million square kilometers) and far below the 1979–2000 average (1979 is the start of the satellite record).

Source: NSIDC
Source: NSIDC
Arctic sea-ice extent typically reaches a minimum in September, and the lowest extent in the satellite record occurred during 2007.  As can be seen in the graph above, we are presently neck-and-neck with 2007.  Whether or not we break the 2007 record will depend on the meteorology over the next few weeks.   For further information, see the NSIDC's Arctic Sea Ice News & Analysis.

Thursday, July 26, 2012

Hitting the Reset Button

With a bad snow year and a warm spring and summer, we are essentially hitting the reset button with regards to snow in the Wasatch Mountains.  The Wasatch are not a glaciated range, but usually there are some areas patches of snow that linger at higher elevations into late summer (or longer), or even persist until the next winter (i.e., last year), but not this year.

Yesterday evening we did some hiking in Albion Basin.  Snow typically lingers in Gunsight well into summer, but this year, it is entirely snow free.

Not much in the Castle either, except right at the top of the Castle Apron.

The view from Hidden Peak suggests snow is quite limited on the American Fork Twin as well.

Source: snowbird.com
I don't know how often this occurs, but I suspect we will see a complete elimination of all snow in the Wasatch Mountains this year, including the so-called Timp Glacier.  I haven't been up there this year (send me a recent photo if you have one and we'll post it up), but it was largely snow free in 2003.

Source: summitpost.org
Those hoping to do Turns All Year in Utah had better get out on August 1st to make whatever turns they can and then hope for a storm in September.

Wednesday, July 25, 2012

A Monsoon Break for Northwest Utah?

Overnight, somewhat drier air has moved into northwest Utah, as shown by the loop of 700-mb wind and integrated precipitable water below.

Integrated precipitable water is the depth of water that you would have if you condensed all the water vapor in the atmosphere.  Higher values (warmer colors above) indicate more integrated water vapor, lower values (cooler colors above) indicate less.

Integrated precipitable water can be calculated using data from upper-air soundings (i.e., weather balloons), but those are only launched twice a day and frequently contain biases that can be quite large.

Alternatively, we can measure and track changes in integrated precipitable water using ground-based GPS receivers.  This is because the time it takes for a GPS signal to travel from the satellite to the receiver is partly a function of the atmospheric water vapor content.  Clever wizards (a.k.a. scientists) figured out how to use the signal delay to infer the integrated water vapor.

Based on these GPS measurements, we can examine trends in integrated precipitable water at the Salt Lake City airport.  Note how the integrated precipitable water peaked yesterday at almost 3.5 cm, but now sits at just under 2.5 cm, consistent with the analysis above.

Partly because of the decline in integrated precipitable water, I suspect we'll see less widespread convective activity in northwest Utah this afternoon.  The odds of a thunderstorm aren't zero, however, as we may see a few isolated thunderstorms pop up.  Nevertheless, we'll call this a monsoon "break" given the expected reduction in thunderstorm coverage.

Tuesday, July 24, 2012

Meteorological Pioneers

It is Pioneer Day in Utah, a state holiday providing yet another opportunity to play with fireworks and spark wildfires.  Let's be careful out there!

The Wasatch Weather Weenies will celebrate by working, banking "comp time" for a future powder day, and remembering two of our pioneers.

The first is Horace-Benedict de Saussure (1740–1799) who was a Professor of Philosophy in Geneva Academy (Switzerland), the second person to climb Mt. Blanc, and the first person to establish a temporary mountain meteorology station.

Source: Barry (1978)
As summarized by Barry (1978), de Saussure worked to explain why it was cold in mountain areas.  He developed a heliothermometer and was the first to show that solar radiation increased with altitude.   This showed that mountain areas were not cold because of a lack of solar radiation, but because
"they are surrounded by and chilled by air which is constantly cold.  This air is cold because it cannot be strongly heated, neither by the rays of the sun, due to its transparancy, nor by the surface of the earth due to distance separating them (de Suassure, 1779–96, Vol. 2, chap. 35, p. 932)."
De Saussure was a world traveler, and his observations of differing tree line heights in the Peruvian Cordillera and on Mt. Blanc led him to conclude that temperature, not air density, controlled vegetation growth at high altitudes.  Given his many accomplishments in meteorological instrumentation, mountain meteorology, and glacial studies, Barry (1978) christens him as "the first mountain meteorologist.

The second is Norbert Untersteiner (1926–2012), who I only recently learned passed away on March 14.

Source: Arctic Sea Ice Blog/
University of Washington Polar Science Center
Copyright Pending
I first met Norbert in 1989 when I joined the graduate program of the Department of Atmospheric Sciences at the University of Washington where he was department chair.  He was a kind and gentle man, who always asked about my ski adventures.  At the time, he was in his mid-60s and I, like so many clueless youth, simply assumed he must have been that age his whole life.  I knew he was a pioneer in sea-ice physics (see his remarkable professional accomplishments here and here), but beyond that was clueless.

Then, late in my graduate career, he decided to give us graduate students a glimpse or two into his youth, presenting a slide show on his 1954 trip a scientific member of an expedition deep into the Karkoram.  Prof. Mike Wallace has a great slide show describing Norbert here, that includes a slide that makes it obvious why Norbert was selected for the expedition.

Source: Mike Wallace, University of Washington
Norbert's work wasn't always in the mountains, but with a spirit like that, he earns recognition on this Pioneer Day.

Monday, July 23, 2012

The Care and Feeding of Utah Convection

With a strong ridge of high pressure centered over the central United States, the large scale pattern is presently ideal for the care and feeding of Utah convection (i.e., thunderstorms).  Even though the large scale flow over northern Utah is out of the southwest, it originates in the tropical and subtropical easterlies that are characteristic of the North American Monsoon.  

1200 UTC 21 Jul – 1200 UTC 23 Jul IR Satellite Image and
GFS 500-mb streamline analysis
As a a result, dewpoints are elevated and we're seeing some rumblers across the state.  In St. George, where some thunderstorms moved through overnight, several sites are presently reporting a dewpoint of 67ºF.  

But it's a dry heat, right?  Here at the U, things aren't quite so humid, but the dewpoint is still 53ºF.

For comparison, our average for this time of day in July is about 41ºF.  Those of you with swamp coolers will probably find their effectiveness is lower.  

With all this moisture in place, perhaps Thor, God of Thunder, will pay us a visit again tonight.

Saturday, July 21, 2012

Change at the British Open

Of the four golf majors, the British Open is most infamous for bad weather.  This year, however, the weather has been benign, and that continues today at Royal Lytham and St. Annes Golf Club.  Nevertheless, change is coming and the golfers will be facing dramatically different conditions tomorrow.

Royal Lytham and St. Annes is located on the eastern shore of the Irish Sea, just north of Liverpool (see A thumbtack below).

As shown by the GFS analysis for 0600 UTC this morning, high pressure is firmly in control today, as was the case for the first two rounds.

However, a strong surface cyclone will be tracking toward Iceland tomorrow, and southwesterly flow will be on the increase in the British Isles tomorrow.  The GFS forecast for 1200 UTC puts Royal Lytham and St. Annes ahead of an approaching cold front, but in strong southerly flow.

Winds will be increasing during the day and by noon will likely be gusting to near 30 miles per hour.  Those hoping to wind the Claret Jug are going to need to adapt to dramatically different conditions  (Adam Scott presently is up 3 strokes, but no lead will be safe tomorrow).  Unlike the first 3 rounds, it will be absolutely essential to keep the ball low and on the ground.  Those who can make that adjustment will minimize damage, which is probably going to be the key to winning tomorrow.

Friday, July 20, 2012

Year to Year Climate Variations

One of our graduate students send me a few images from MODIS showing the stark contrast in snowcover between last summer and this summer.  The difference in weather between the preceding winters and springs couldn't be much bigger.  Winter 2010/11 was one of the biggest snow years ever in the Wasatch Mountains and was followed by a remarkably cold spring.  Winter 2011/12 was fairly dry and was followed by a very warm spring.

The two images below were taken on 5 Jun 2011 and 7 Jun 2012, respectively.

And these two are from 27 Jun 2011 and 28 June 2012, respectively.

The contrast is remarkable, especially with regards to mid-elevation snow in mountainous areas in early June.  Imagine the difference for plants and animals in those areas.  Last June, we were ski touring in the Wasatch a few days after the top left image was taken and noticed that the rodents were tunneling out of the snow and looking for food.

Alta, UT, 11 Jun 2011
Their foraging season was extremely short.  This year, the pendulum has swung to the opposite extreme.

We are basically experiencing nearly the full range of current climate variability and extremes in a two year stretch.

Thursday, July 19, 2012

Quote of the Week

"But the forecast hasn't been right all week.  Nice job to have, huh?"
- Tiger Woods, commenting on the weather forecasts for the British Open

Once the British Open is over, perhaps Tiger could attend the London Olympics and critique the forecasts for us (see previous post).  

Weather and the 2012 London Olympics

Climate information and weather forecasts are critical for every Olympic Games, be it those in Salt Lake or those forthcoming in London from 27 July – 12 August.

The UK Met Office, the United Kingdom's version of our National Weather Service, is contributing to climate and weather support for London 2012.  They have a great web page that provides access to weather statistics and forecasts for Olympic venues.  

For example, those with deep pockets who are heading to the Games can get a quick glimpse climatology for London.

Source: UK Met Office
Curiously, the table above is nearly all based on mks units, except for wind speed, which is in mph.  In operations, US meteorologists typically use mks for everything except surface temperature, dewpoint, and wind (which is what I do for the blog most of the time).  Yes, we are weird.  Most scientists out there I'm sure are laughing.  

With many Olympic venues indoors, most of the weather concerns probably revolve around those few venues that are weather sensitive, mitigating and adapting to potential weather impacts on transportation, and addressing public safety in areas where people are congregating outdoors.  There are also some weather-related security issues, such as dealing with the atmospheric transport of an accidental or terrorist release of hazardous materials, which we all hope doesn't happen.  

London is well known for crappy weather, so perhaps the most humorous venue is the Horse Guards Parade in central London, which serves as host for the Olympic "beach" volleyball events.  

Source: BBC
It's not exactly SoCal and, depending on how the weather pans out, it could be quite uncomfortable.  Given that the pro beach volleyball tour used to visit Seattle, they will probably survive.   Then again, Seattle has better weather than London in July and August.  In fact, the UK Met Office web page for the beach volleyball venue says
"Beach volleyball is more commonly played in warmer, drier locations such as California and Hawaii. Players prefer dry conditions as rain can make the ball slippery and difficult to control. Athletes will also be hoping for still conditions as the wind could affect the accuracy of their passes."
Perhaps a spot of tea will be needed instead of Gatorade during some matches!

Wednesday, July 18, 2012

West To Be Tickled by Fabio

Try and contain your excitement.  The west is about to be tickled by Fabio.  Sorry ladies, we're not talking about the Italian model and actor (pictured above) that graced the cover of romance novels back in the day.  Nope, we're talking about the remnants of former tropical cyclone Fabio.

Fabio was once a hurricane but has weakened and is now classified as a post-tropical cyclone, a phrase used to describe a cyclone that has lost the characteristics of a tropical cyclone.  Fabio is presently moving northward off the Baja coast, with his "big hair" cirrus blowoff streaming over southern California.

1200 UTC 16 Jul – 1200 UTC 18 Jul 2012 IR Satellite loop with
GFS precipitable water (contours) and dynamic tropopause (color filled)
Tropical cyclone remnants are an important part of the North American monsoon system, especially for southern California.  Corbosiero et al. (2009) show that while only about 10% of all eastern North Pacific tropical cyclones bring rainfall to the southwest United States, they account for about 15–25% of the warm season (16 Jun–15 Oct) rainfall in southern California and northern Baja California.

Percentage of warm-season (16 Jun–15 Oct) precipitation
associated with eastern North Pacific tropical cyclones.
Source: Corbosiero et al. (2009).
The climatology is dominated by some major events, including the remnants of Hurricane Doreen (1977), which brought up to ~60 mm (2.36 inches) of precipitation to some locations in California and Nevada and about 95% of the warm-season total in some regions.

Source: Corbosiero et al. (2009)
The GFS projects that Fabio will bring a surge of high precipitable water air into southern California today and tomorrow, following a path just west of that of Doreen (1977). 

0600 UTC 18 Jul – 0000 UTC 20 Jul 2012 GFS sea level
pressure (contours) and precipitable water (shaded) forecast
However, the moisture and instability are fairly meager and will yield only a slight chance of showers and thunderstorms over southern California today and tonight.  Moisture from Fabio will eventually stream through Nevada, but this will only yield a slight chance of showers and thunderstorms.   

Fabio may be a model, but meteorologically, he's a tease.   

Tuesday, July 17, 2012

News Bits and Bytes

Some interesting coverage of weather and climate issues in the media the past couple of days.

First, from FOX13, this story on the impacts of yesterday's thunderstorms at Lagoon Amusement Park.

Of concern is the lack of discussion about safety measures taken for lightning and microburst winds.  Hopefully that was an accidental omission.  They certainly were a concern given the close proximity of strong convective cells late yesterday.

Second is this article by Judy Fahys in the Salt Lake Tribune,

Source: Salt Lake Tribune.  Photo by Kim Raff, Article by Judy
Fays.  Click here to access.  
which highlights efforts by Brian McInerney of the National Weather Service who is working with other federal agencies to evaluate hazards in burned-out areas of Utah.  All Utahns can be thankful that Brian is on the job as he is extremely capable and dedicated.  Many people see the National Weather Service as simply producing forecasts like those done by the Weather Channel and other broadcast media groups, but there is far more going on behind the scenes (Disclosure: A portion of my research funding is provided by the National Weather Service).

Finally, there is an article in the Guardian discussing an experiment in New Mexico to evaluate the possibility of combatting global warming by injecting sulfate aerosols into the stratosphere.

Source: The Guardian.  Photo from Gallo Images/Getty Images.
Article by Martin Lukacs.  Click here to access.
We've inadvertently modified the climate with greenhouse gas emission.  Is planned geoengineering a reasonable response?  What are the policy, societal, weather, and climate implications?  This is an emerging geopolitical issue that will likely become more significant in the coming decades.

Monday, July 16, 2012

Batten Down the Hatches

The National Weather Service has issued a Severe Thunderstorm Warning for Salt Lake County and Northwest Utah County until 6 PM.

The radar loop below shows numerous intense convective cells spreading into Salt Lake County.  Be smart.  Seek shelter.  I'll be delaying my bike ride home and working late.

Climate "Cycles" and Utah

Dr. Robert Gillies is the State Climatologist for Utah and appeared on KSL's Sunday Edition this past weekend to discuss climate change.  You can link to the video here.  Skip the NBC report at the beginning and go to Rob's discussion, which starts at about 2:50.

Rob does a nice job responding to reviewer comments and the question about weather simply being cyclical.  Questions at the weather–climate interface are difficult to answer.  Weather does not equal climate.  Heat waves and cold waves are part of the natural system.  But the statistics of heat and cold waves are changing.  Warm days and nights are becoming more common, cold days and nights less common.  Rob deals with this issue with the following response:
"...One has to realize that here in the west, our climate is highly variable so, for example, last year was cold and wet and now we have see-sawed to very warm and dry and that's part of the natural variability.  What you've got to look at is how trends occur over time, say since the 1950s or even earlier than that.  So when people say this is cyclical, yes it is, that is part of climate, but now we have very distinct evidence from NASA and NOAA and from many other agencies around the world that are showing that the mean temperature of the planet has increased and it has increased quite dramatically."
What Rob is describing is clearly evident if we look at the state average spring (March to May) temperature from 1895-2012.  I have picked these three months as warmth this spring contributed to the drought conditions that presently exist in the state.

Utah mean spring temperature (Source: NCDC)
The first thing to notice is that this spring was about 3ºF warmer than the long-term 20th century average.  That being said, there were springs in the early 20th century (1934 and 1910) that were warmer.   In other words, the temperatures experienced in Utah this spring were within the range of natural variability even many decades ago.

Note, however, how the frequency of warm springs has increased in the past few decades.  Springs with temperatures above the long-term 20th century average are far more frequent.

So, indeed there are cycles.  However, there is a clear shift in the frequency of the temperature variability toward higher values.

Perhaps we will take a look at 1934 in a future post.