Big Blow

Severe thunderstorms in Utah produced a 78 mile per hour guest along I-80 near the Cedar Mountains and a 72 mph gust at Wendover.

We even had some rain in the Salt Lake Valley.  What a relief!

Summer Won't Quit

It has been a remarkable August.  Check out the daily temperatures at the Salt Lake City International Airport.  There has been only two days with a minimum temperature below average (Aug 3 and 4, when the minimum temperatures were 65ºF and 64ºF, respectively, compared to an average of 66ºF).

There has also been only one day with a maximum temperature below average (91ºF on Aug 11, compared to an average of 92ºF).  Add in only 0.01 inches of rain, and you have one hot dusty month.

Thusfar, the minimum temperature for today is 71ºF, but there is cloud cover and some isolated sprinkles.    The clouds and showers are associated with a weak monsoon surge, which has brought moisture into northern Utah from the lower Colorado River Basin.

During August, the monsoon has largely been a bust for northern Utah.  Monsoon surges have been fairly weak and not very productive.  This is another one that falls into that category.  Showers and thunderstorms will be around, but it will take some good luck for one to bring a cooling deluge to your area.  Let's hope it happens.

The Isaac Deluge

Hurricane Isaac is moving very slowly through Louisiana, extending what is surely a long period of suffering for residents of New Orleans, the Mississippi Delta, and environs.

Source: MesoWest

The New Orleans International Airport saw about a 12 hour period overnight with sustained winds of 35 mph and gusts in excess of 55 mph, reaching up to 70 mph at times. 

Source: MesoWest

Yeah, that's not hurricane force, but it isn't pleasant either, especially given the heavy rain and potential for flooding.

The Hydrologic Prediction Center forecast calls for over 10 inches of rain to fall across much of southeast Louisiana through Monday.  That's in addition to what fell prior to this morning, and much of it will come over the next 24 hours, although there will be rain at times even after Isaac moves inland.

Source: HPC

To put that into perspective, the average annual precipitation at the Salt Lake City Airport is 15.7".  There will be places in Louisiana that probably will get that much this week.  The New Orleans International Airport reports 6.20 inches of rain since noon yesterday.

Tropical Cyclone Isaac: The Long View

1800 UTC 17 Aug – 1800 UTC 27 Aug 2012 IR satellite imagery and
GFS sea level pressure and 700-mb wind analyses

Tropical Cyclone Isaac (classified @ 1200 MDT 27 Aug as a tropical storm with peak sustained winds of 65 knots but expected to strengthen) has already disrupted the Republican National Convention and is now headed for the Gulf Coast.

As shown in the loop below (click to enlarge), Isaac formed within a tropical wave that originated over Africa and moved across the tropical Atlantic Ocean.  Not all tropical waves develop into tropical cyclones and you can see two examples trailing Isaac.  Better understanding the mechanisms that contribute to tropical wave development or non-development is an area of active research in the atmospheric sciences, including efforts by Prof. Ed Zipser and his students here at the University of Utah.  Of course, the issue now concerns the position and intensity of Isaac at landfall, as well as impacts ranging from storm surge to precipitation-induced flooding.

Sea Ice Record Broken

Realclimate.org reports this morning, based on data from the National Snow and Ice Data Center, that we are now in record territory for minimum Arctic sea-ice extent.  

Source: realclimate.org

With a couple of weeks until the mean climatological minimum in sea-ice extent, it looks like 2012 will set quite a standard.  

Pitter Patter

I awoke this morning to pitter patter on the roof.  I figured it was a dream, but noticed drops on the car and discovered that a remarkable 0.01 inches of rain fell at the Salt Lake City Airport just after 7 am.

So much for another summer month with no measurable rain.  The rogue shower gets us again.  If only we could get a real deluge.

Tantalizingly Close

It is that time of year to start looking to the west and northwest for our first blast of cooler Pacific air in weeks (er, months this year).  The latest GFS forecast puts us tantalizingly close to cooler air, with a trough on our doorstep in a few days.

Yeah, it's a weak trough and fading fast as it comes in, but the GFS has a shallow layer of slightly cooler air slide into northern Utah on Thursday.

GFS 850-mb temperature and wind forecast valid 30 Aug 2012

That's not much to get excited about, especially since it will probably be accompanied by Idaho smoke, but think good thoughts.  Markedly colder air is just to the north!  I'm not optimistic it will get here based on the latest model runs, but what do we have to lose?

Records Will Fall

The Guardian reports this morning that a new sea-ice minimum should be set in the next few days.  This is consistent with the National Snow and Ice Data Center (NSIDC) analysis of sea-ice extent below, which is current through 22 August.

Rain for Me, Not for You

We were treated to a reinvigorating rainstorm last night in Steamboat Springs.  I stood outside on a few occasions and let the raindrops fall lightly on my face while breathing in the cool, damp air.  What an experience after not seeing rain for weeks.  We were able to enjoy a great view of undercast in the Yampa Valley from our condo this morning.

Making last night sweeter was the announcement that our friend and colleague at the U, Prof. Dave Whiteman, received this year's award in Mountain Meteorology from the American Meteorological Society.

Dave Whiteman (holding plaque) with his current staff and students.
Photo: John Horel

Dave is not only a great scientist, but also an outstanding mentor and friend to all who know him.  Congrats Dave!

Getting back to Salt Lake, it's looking increasingly likely that we might go the entire month of August without measurable rain at the Salt Lake Airport.  Perhaps we'll get lucky and get a stray thunderstorm the next few days, but the odds are low.  June was also a rainless month.  What a summer.  Winter can't come soon enough.

Seasonal Forecast Insanity

We've reached the time of year where speculation runs rampant about what kind of winter we will have.  Don't buy into the hype.  If El Nino develops as currently predicted, it might skew the odds a bit for above average snow in the Southwest and below average in then Northwest.  This is reflected in the Climate Prediction Center outlook for Sep–Nov.

 Beyond that it's anyone's guess, as summarized nicely in this Powder Magazine graphic.

Presumably by "a lot or a little" they mean relative to climatology.  Another perspective is provided by this T-shirt, which I spotted last winter at Alf's Restaurant.

For northern Utah, I feel pretty comfortable saying that I have no idea if it is going to be an above average or below average winter, but I'll take my chances in the Cottonwoods compared to anywhere else in the contiguous US.

Weather Weenies Road Trip

Steamboat's Storm Peak from Thunderhead Peak

A large contingent from the University of Utah is in Steamboat Springs this week for the 2012 American Meteorological Society Mountain Meteorology Conference.  We're stacked deep in three condos and a few hotel rooms.  A few of us arrived early yesterday and did some hiking around the ski area.  Although it doesn't look too bad in the picture above, it was taken at sunset looking away from the sun.  In reality, the smoke is here and only marginally better than it is in Salt Lake.

We just heard a talk from one of Steamboat's managers boasting about their abundant powder and how in a good season they get about 350" at 9200 feet.  Most of the Wasatch Weather Weenies, powder snobs that we are, got a chuckle out of that.  

Changing Colors?

If you didn't know any better, a hike or bike up City Creek Canyon this weekend might fool you into thinking it's fall.  Quite a bit of the scrub oak has changed colors, giving an autumnal feel despite the apocalyptic warmth and smoke.

I don't have any scientific evidence to back this up, but I don't think the colors are due to the changing seasons given that it is only mid August.  My guess it is is due to the drought and the combination of a lack of precipitation and high temperatures.  Perhaps an ecologist out there can comment.

Living Vicariously Through Others

It has been a hot summer in Utah, and brutally hot in other portions of the country.  A cold-frontal passage would be so refreshing.  Unfortunately, the best we can do for now is to live vicariously through others, namely those in eastern Montana and the northern high plains.  They've actually just had a bonafide cold-frontal passage.  Check it out.  Cool air in the contiguous United States!  What a concept.

And look at this.  Minimum temperatures this morning as low as 35ºF.

Wouldn't that feel good?  Imagine throwing open the windows and letting that airmass pour in.  Close your eyes and visualize!

Utah's Wasatch Range Book Signing Event

There will be a book signing party for Utah's Wasatch Range: Four Season Refuge on August 20th at 7:30 pm at Simply Amish of Salt Lake (Furniture Store), 2892 Highland Drive, Salt Lake City, UT.  The book features photographs by Howie Garber and essays about the Wasatch Mountains by Mayor Ralph Becker, Congressman Jim Matheson, Peter Metcalf, Gale Dick, Andrew McLean, and many others.  I have an essay on Wasatch snow and climate change.  Many of these authors will be at the book signing party, which is open to the public.

You can purchase the book at http://www.utahswasatchrange.com and get a preview at http://utahswasatchrangehowiegarberphotography.com/bookpreview/book.html.

I had an opportunity to read the essays and enjoy Howie's photos this weekend.  The essays have a strong preservationist vibe and the book will appeal to anyone who feels a deep connection with the Wasatch Mountains.

Uncharted Territory

Arctic sea-ice extent is presently the lowest on this day in the satellite era (yellow line below), which begins in 1979.

Source: http://arctic.atmos.uiuc.edu/cryosphere/arctic.sea.ice.interactive.html

Time will tell if we will set a record for the warm-season minimum, which usually occurs in September.

For more information, check out the National Snow & Ice Center's Arctic Sea Ice News & Analysis web page.

Is The Answer Blowin' in the Wind?

Brazos Wind Farm, Texas.  Source: Wikipedia Commons.

Wind power in the United States exploded in the past few years, with capacity doubling since 2008.

Source: Wikipedia Commons

It was a boom time and jobs were plentiful.  According to the American Wind Energy Association, there are about 400 companies generating wind turbine components and about 75,000 jobs in the wind industry.   I have a number of friends who migrated to wind power jobs during this period.  For meteorologists and fluid dynamicists, opportunities existed in wind prospecting, farm design, turbine design, forecasting, you name it.

However, as can be seen in the graph above, installed new capacity peaked in 2009 and The Guardian reports today that while total US wind power capacity eclipsed 50 Gigawatts this year, layoffs are occurring throughout the sector because of a possible expiration of a wind power production tax credit at the end of 2012.

Extension of the wind power production tax credit is presently under consideration by Congress and it has become a subject of considerable political debate as it falls in the crosshairs of energy policy, tax policy, alternative energy subsidies, deficit concerns, etc. (see articles here and here).  The resulting industry uncertainty is stalling investment, delaying projects, and leading to layoffs.  Is this a short-term blip or a more serious long-term stalling of an industry attempting to produce 20% of the US power supply by 2030?  The answer my friends isn't blowin' in the wind, but in the smoke-filled rooms of Washington.

The Great Smokies

The Salt Lake Valley is smoke filled this morning.  The photo below shows the faint outline of the Wasatch Mountains above the SSB building on the University of Utah campus.

Yesterday afternoons MODIS image suggests that smoke from multiple sources in California and Nevada may be contributing.  The red areas designate active fires.

Source: NASA

The local Faust fire southwest of Dugway and Pinyon Fire in Camp Williams could also be contributors.  These seem to be the only major local fires noted on utahfireinfo.gov this morning.

Gust Front with Lake Stink

A nice gust front moved through the northern Salt Lake Valley this evening, bringing with it gusty winds and the infamous "lake stink."  The gust front marked the leading edge of outflow from thunderstorms to our immediate northwest.

Gust fronts are usually accompanied by a sharp drop in temperature and increase in wind speed (and/or wind shift).  Winds gusted to 44 miles per hour at the Spaghetti Bowl with the passage this evening.

Thunderstorm outflow is an example of a gravity current in which cold, dense air spreads and displaces warmer, less dense air.  There is usually a pronounced nose at the leading edge of the gravity current.

Source: http://www.aircraftpilots.com

You could see this structure this evening (other than the breaking waves at the top of the gravity current) as there was quite a bit of dust (and some "lake stink") in the thunderstorm outflow (flowing from right to left, opposite the image above).  Click to enlarge the image below.

Gravity currents are common in all sorts of "geophysical fluids", including the powder avalanche.  The classic textbook on the subject is Gravity Currents by John Simpson.

The Life, Death, and Resurrection of Ernesto

Life can can be complicated for tropical cyclones crossing through central America and southern Mexico.  Death is almost certain, but some, like Lazarus, can rise from the dead.

The latest to attempt to discover the afterlife is tropical cyclone Ernesto, which moved steadily across the Caribbean Sea and briefly attained hurricane status prior to making landfall on the Yucatan Peninsula.

Wind history of tropical cyclone Ernesto.  Source: NHC.

Ernesto then moved across southern Mexico, but its weak circulation and convective cloud cluster are beginning to move out over the eastern Pacific Ocean.

The National Hurricane Center presently gives Ernesto a 60% chance of reforming as a Pacific tropical cyclone during the next 48 hours.

For you mountain weather nuts out there, this process of decay and reformation can be influenced by the topography of southern Mexico, in much the same way that midlatitude cyclones are influenced by interaction with the Rocky Mountains, Alps, and other ranges.  

If Ernesto can pull of this resurrection, I believe he will be renamed as cyclones are typically named in order of formation in major oceanic basins.  Up next for the eastern North Pacific is Hector.

Unfortunately for Hector née Ernesto, resurrection here is not a path to immortality.  Eventually he will move over cooler Pacific waters and/or be torn apart by wind shear.

A Hot July for the US

The National Climatic Data Center reports that this July was the hottest in the instrumented record (1895–present) in the contiguous US, nudging 1936.  Mean July temperatures were more than 6ºF above the 1981–2010 average across much of the interior central United States.

Source: NCDC

In case you are wondering, the mean temperature was 77.56ºF, whereas in July 1936 it was 77.43ºF. Other years with exceptionally high July mean temperatures include 2011, 2006, 1934, and 1901.

Source: NCDC

Before his passing in 2007, Tom Potter, the former Director of the Western Region of the National Weather Service and Weather Coordinator for the 2002 Olympic Winter Games in Salt Lake told me about surviving the 1936 heat wave.  As he put it

"We lived in North Dakota, so it only got to '117ºF in the shade' on the hottest day in our small town. No one had air conditioning in those days, so we all went down in the cellar and my Dad rigged up a homemade evaporative cooler by training a small fan on a wet blanket hung across the cellar doorway. We all survived and so did everyone else among the town's population of 307."

Thanks to rapid advances in our ability to squeeze everything we can out of weather observations, we now have four-times-daily atmospheric analyses extending back to 1871.  These are provided by the 20th Century Reanalysis Project and enable us to compare July 1936 with July 2012, with the caveat that there are greater uncertainties, especially at upper levels, in the July 1936 analysis.

Perhaps not surprisingly, the upper-air pattern over the contiguous US is quite similar.  In July 1936, a broad, high amplitude, 500-mb ridge covered much of the contiguous US, with the Pacific Northwest and Northeast somewhat under the influence of troughing.

Source: NOAA/ESRL

A similar pattern occurred this July, although it could be argued that the pattern was somewhat less amplified along the US–Canada border where the ridge over central North America and flanking troughs were a bit weaker.  These minor differences might not lie outside the range of observational uncertainties in the July 1936 analysis.

Source: NOAA/ESRL

I think back to Tom Potter's comments to me about his experience in July 1936 and how difficult that month must have been for those who lived in the midwest.  It may not hold the official record, but given the technology at the time, it must have been one of the most miserable months in US history.

What a Waste

There are two temperatures that most meteorologists, at least those of us who still deal with English units for surface temperature, consider to be a total and complete waste: 0ºF and 99ºF.

Yesterday's high at the Salt Lake City airport was 99ºF.  What a waste!  For it to be that hot and uncomfortable without reaching 100ºF is seriously disappointing.  I think 99ºF is the worst temperature, but only by a hair over....

0ºF.  For it to be that cold without getting into negative numbers is also a waste.  If it's going to be cold, let's get some psyche points!

Of course, all of this would be remedied if we just switched to Celsius.

The Outdoor Stadium Hazardous Weather Conundrum

Lane Stadium, Virginia Tech, 27 August 2000.  Photo: Eric Brady,
The Roanoke Times

Lightning killed a spectator this weekend following the rain-shorened Sprint Cup Race and Pocono Speedway.  An article wondering if NASCAR should have done more to protect spectators appeared in Monday's USA Today.  

A large outdoor crowd and severe or hazardous weather is a bad combination.  Between the false confidence of "safety in numbers" and the desire not to leave a sporting or entertainment event that is exciting and cost good money, it's difficult to take the appropriate action in a timely manner when weather threatens.  I remember attending a concert at Deer Valley several years ago when there was lightning all around.  It was clearly a situation that demanded that the show be halted and spectators be told to head to their cars, but the show went on, fortunately without incident.  We stayed until the end, which was not a smart move.  

Some of the issues at play are summarized in Storms and Stadiums, an article by Bob Hanson that appeared in the winter 2005–06 UCAR quarterly.  While some large stadiums have prepared action plans for severe and hazardous weather, I suspect the majority of smaller stadiums have not.  Further, while competitors and entertainers can usually find suitable shelter quickly, a large outdoor crowd needs time to evacuate. 

As a spectator, it is probably best to assume that you will not be given a clear and timely alert if severe or hazardous weather approaches and to consider taking appropriate individual action if warranted.  The challenge is overcoming that desire to remain in an exposed area when the game plays on and thousands of others are staying put.  

Uinta Weather

As anticipated, yesterday was a gorgeous day in the Uinta mountains with only a few shallow cumulus clouds evident along the Uinta crest as one looked east from the summit of Mount Watson.

As is often the case, the High Uintas served yesterday as the locus for cumulus cloud initiation.  The broad, gradual slopes of the Uinta Mountain "massif" is ideal for the generation of upslope flows during the day.  These upslope flows converge and cause rising motion near the Uinta crest, which contributes to the initiation of cumulus clouds, as shown schematically on yesterday's MODIS image below.

This is one reason why the Uintas are such a hotbed for thunderstorm activity in the summer, with the lightning danger further enhanced by the highly exposed nature of the topography.  There aren't many safe places to hide in the Uintas and lightning fatalities have occurred even in the "lower elevations" such as at campgrounds along the Mirror Lake Highway.

Of course, cumulus clouds and thunderstorms do occur off the Uinta crest.  Yesterday simply provided a very clean example in which slope flows dominate the processes leading to cloud initiation.

Uinta Dreams

Granddaddy Mountain, Uinta Mountains, June 2007

There's nothing like a trip to the cool climate of the Uinta Mountains during the dog days of summer.  Today or tomorrow are the days to do it.  The Uintas see frequent thunderstorms in the summer, but we have a remarkably dry airmass in place.  The GFS analysis shows precipitable water values less than 10 mm across northern Utah, which is quite low for this time of year.

At KSLC, current precipitable water values are the lowest they have been in at least a week.

Finally, this dry air should remain over the area on Saturday  The GFS calls for precipitable water (upper left hand panel) to remain near or below 12.5 mm (0.5 inches) through Saturday afternoon.

I've learned never to discount the chance of a thunderstorm in the Uintas during summer, but the odds for today and tomorrow are as low as they get.  I'll keep an eye to the sky just in case, but it looks like we're in for a couple of days where we won't be dodging bolts.  Scattered thunderstorms may be back in the Uintas on Sunday, however, as some moisture bleeds in from the south.

Drier Air

It's a desperate time here at the Wasatch Weather Weenies.  There's not much to talk about except waxing and waning of the monsoon system.  Even that hasn't been too exciting up here in Salt Lake, although it has been interesting to the south.

Drier air is moving into northern Utah this morning, as can be seen in the loop below and the precipitable water meteogram from the Salt Lake City International Airport.

1200 UTC 31 Jul – 1200 UTC 2 Aug WV imagery and
GFS precipitable water (contours) and 700-mb wind vectors

Source: NOAA/ESRL

Precipitable Water currently sits at a bit less than 2 cm and should drop further today as drier air moves in from the west and northwest.  This should yield a break in thunderstorm activity for northern Utah through Saturday.  Some action will remain, however, to the south.  I'd call this a monsoon break, except we never really got much action in the Salt Lake Valley with the last surge. 

Good Riddance To July

July is over and we can all be thankful for that.  It is my least favorite month even in a year where temperatures are near average, but this year was even worse.  It disappointed even further yesterday when thunderstorms popped up in the area, but left Salt Lake high and dry.

The last radar image of July 2012.  A few thunderstorms
around, but none over the Salt Lake Valley.

At the Salt Lake airport, the average high and low temperatures were 94.9ºF and 69.5ºF, respectively, which are 4.8ºF and 2.2ºF above the 1971–2000 averages.  We also saw 7 days with a maximum temperature of 100º or higher, including 103ºF on July 11 and 12.

The graph below from the National Weather Service summarizes July nicely.  In my view, the minimum temperatures are the big story.  A quick glance suggests only four days with a minimum temperature at or below the average.  That makes for uncomfortable weather.  Little wonder why my desire to sit out on the porch in the evening has been a bit lower this year.

Source: NWS

There were a couple of monsoon surges that knocked the maximum temperature down.  We can be grateful for that.

With July in the books, we can look forward to the Greatest Snow on Earth.  Soon we'll notice the sun setting earlier and cooler conditions in the evenings.  Based on past experience, there's probably about a 30% chance that those willing to hike will find some freshies within 3 months (i.e., by the end of October).  Hopefully my back will be ready to go by then.