Wasatch Weather Weenies

Tomorrow marks the first anniversary of the Wasatch Weather Weenies.   I'd like to thank all of you out there in the blogosphere for making the first year a success. We started as an invited only, password protected blog.  I wanted to be able to discuss weather and climate issues without a lot of political baloney (a problem these days when it comes to climate), but I was quickly inundated with requests for access and eventually realized that my fears were unwarranted. Readership has grown fairly steadily over the past year, with a slight dip during the summer when the U is in recess and interest in snow is admittedly low.  In September, we've had an average of about 140 pageviews per day.  That's far better than the attendance at my classes! Despite my innate interest in snow and winter weather, the six most popular posts have nothing to do with snow (what is wrong with you people out there!).  The Wasatch Weather Weenies first year top-10 is: Tou...

On Tuesday, I violated one of my cardinal rules by digging into the small-scale details of a medium-range forecast .  As usual, that has left egg on my face. Of concern at that time was the potential recurving of Hurricane Hilary into the southwest United States.  Ahead of Hilary, a surge of tropical moisture was expected into the lower Colorado River Basin. While that surge of moisture may yet materialize, Hilary has other ideas.  She kept moving westward and her core of moisture is now expected to continue in that direction. This is not to suggest that the weather in Utah won't get interesting the next few days.  It looks like it is going to be an exciting week.  Stay tuned.  

On September 3, the Boston Red Sox sat 9 games over the Tampa Bay Rays for the American League wildcard.  The FiveThirtyEight blog from the New York Times estimates that they had a 99.6% chance of making the post season on that day. Yesterday morning, they were tied with the Rays for the wildcard spot.  Later that night, the Rays trailed the Yankees 7–0 in the 8th inning .  The odds of a Rays win (also from FiveThirtyEight)?  0.3%.  As the Rays were chipping away at the lead, the Red Sox were beating the Orioles 3–2 in the 9th inning after a rain delay.  The odds of a 9th inning comeback by the Orioles?  2%.  But it's even worse than that.  The Orioles eventually were eventually down to their last strike.  Two outs and two strikes on the batter, Dan Johnson, who was hitting .108 for the season.  He had two strikes on him, and was 1–45.  The odds of the Rays making the playoffs were long indeed. So what happened? ...

Source: http://starwars.wikia.com/wiki/Yoda "I cannot teach him.  The boy has no patience." - Master Yoda The time has come to channel your inner Jedi and be patient as the anticipation of the upcoming ski season approaches. Although Master Yoda trained Jedi Knights for 800 years, I'm not quite that long in the tooth, but I have lived long enough in Utah to recognize that early snow is a blessing and a curse.  It helps us feed our primal urges, but often leads to nasty avalanche problems in subsequent weeks.  Utah Avalanche Center Director Bruce Tremper likes to say that thin snow is weak snow , but an important twist of this phrase is  early snow usually becomes weak snow .   Near the ground, the temperature of the snowpack is nearly always near freezing, but the snow surface can be much colder.  A thin snowpack has a larger temperature gradient than a deep snowpack since the temperature change is concentrated over a smaller distance. ...

I am violating one of my cardinal rules today by digging into the small-scale details of a medium-range forecast.  Given the large-scale uncertainty that exists at long lead times, this is always a dangerous thing to do, and could set me up for a real egg-on-my-face moment in a few days.  However, there's little of interest happening right now, so let's go off into what I call "dream-prog-land." Hurricane Hilary is presently churning away happily at category 3 in the eastern Pacific, with maximum sustained winds near 115 mph. The contours in the analysis above are of precipitable water and show that while there is a local maximum near Hilary, the entire eastern Pacific off the coast of southern and central Mexico is quite moist. The GFS forecast shows that in advance of Hilary, there is a very strong Gulf of California surge that taps into this area of high precipitable water and advects it northward into the lower Colorado River Basin. The GFS forecast ...

No, not her, this Hilary, a category three hurricane with sustained winds of about 125 miles per hour and one powerful eye.   The latest (0600 UTC) GFS forecasts Hillary to make a hard right turn, saunter up the Baja Peninsula, and then move into the southwest United States. Even if this track verifies, Hilary will weaken substantially before reaching the southwest United States, but that doesn't mean she won't pack a punch.  Of primary concern is the potential for heavy precipitation and related flash flooding.  The GFS brings abundant moisture into northern Baja by 132 hours, with the remnants of Hilary moving into southern Arizona by 150 hours.  This occurs as a mid-latitude trough moves onto the Pacific Coast, serving as the so-called "kicker trough" that initiates the eastward movement of Hillary. Whether Hilary has any impact on Utah will depend greatly on how the large-scale pattern plays out over the next several days, as well as how q...

The 22 May Joplin tornado killed 160 people, the most people killed by a single tornado in the United States. Source: Army Corps of Engineers The NWS recently issued a report on the tornado , and there is also a nice article on Andrew Revkin's Dot Earth blog .  Have a look.  Preventing such large losses of life is more than just a meteorological challenge.  Societal, economic, and engineering factors are important contributors and need to be addressed for society to become more weather and climate resilient.

Not a cloud in the sky, but there are some decent radar returns in the Ogden area. Might these be birds?  If so, what species? Even the more diffuse clear-air returns in the south part of the domain above are impressive by northern Utah standards.

The temperature evolution at the Pony Express Marker site in the Rush Valley this past week is quite remarkable.  Note how the diurnal cycle amplitude has generally increased through the period.   This morning, the minimum temperature was 27F, the coldest this week, and as of 3:15 PM they are sitting at 84F the warmest this week.  That's a daily temperature range of 57F, and we might still squeeze a couple of degrees out of it!

Based on the National Snow and Ice Data Center analysis, it appears we have passed the sea-ice extent minimum for the 2011 calendar year, as the extent has increased over the past several days. This year's minimum was just slightly higher than the record minimum for the satellite era, which was set in 2007.  Nevertheless, model estimates of total sea-ice volume from the Polar Science Center at the University of Washington, show this was a record low year when the total ice volume is considered (the analysis below removes the monthly mean, which helps take out the seasonal cycle). If you are wondering how this compares with the pre-satellite era, there is a discussion of longer records of ice coverage in the IPCC fourth assessment report .  They concluded that there was a "clear indication of sustained decline in arctic ice extent since about the early 1970s, especially in summer" as can be seen in the time series of northern hemisphere sea-ice extent for Septem...

Yesterday provided a few examples of mixing (or lack thereof) in a stable atmosphere.  First, let's have a look at the morning sounding from Salt Lake City, which showed a shallow surface-based inversion below 850 mb, surmounted by a stable layer that extended to about 775 mb, or 1 km above the valley floor.  In both of these layers, one would expect limited vertical transport and mixing.   Indeed that morning there was copious evidence of this limited vertical transport and mixing.  First, there was a structural fire at about 9:30 am near Cottonwood Heights that produced a fascinating smoke plume with a zig-zagged or perhaps spiraled layered pattern (click to enlarge). Photo: Sebastian Hoch The layering of the smoke provides visual evidence confirming the atmospheric stability in the lower km of the atmosphere.  Meteorologists call such flows with limited mixing between the layers, laminar . The real mystery here, however, is explaining the zig...

As mentioned yesterday , we are in a pattern that lends itself to the development of strong cold pool, especially in topographic basins.  The Peter Sinks are the king of all Utah cold spots, but the Rush Valley is a close second and, more importantly, is well instrumented. The Rush Valley is poorly named as it is really a closed hydrologic basin located south of Tooele and East of Provo. Map Background Source: ACME Mapper It is surrounded by a jumbled mess mountain ranges including the Stansbury and Onaqui Mountains to the west, the Sheeprock and Tintic Mountains to the south, the Oquirrh Mountains and Thorpe Hills to the east, and South mountain to the north.  Much of the valley floor is below 5100 feet, but the low point is at Rush Lake, just south of the Stockton Gap, at about 4960 feet.  The topography surrounding the Rush Valley has two major weaknesses.  One at what I call Stockton Gap (~5120 ft), the other at Five Mile Pass (~5300 ft).  Between th...

The high-amplitude ridge is settling in over Utah and we are in for several days of clear, dry weather with large daily temperature ranges. Large diurnal temperature ranges will be observed during this period, especially in basins, closed topographic depressions with no drainage outlet.  Such basins include the Rush Valley south of Tooele (which is misleadingly named and is really a basin) and the meteorological king of the diurnal temperature range, the Peter Sinks of the Bear River Mountains east of Logan. We'll have a look at the Rush Valley tomorrow, but let's talk about the Peter Sinks today.  The Peter Sinks are a series of limestone sinkholes known for remarkably cold temperatures.  As described by wikipedia , the lowest temperature ever recorded in Utah -69.3F, was measured in the Peter Sinks on 1 Feb 1985. The Peter Sinks aren't much to look at.  They aren't even very deep.  They are modest depressions, but do feature a pronounced vegetation inver...

I was quite pleased to see a dusting of the white stuff on the American Fork Twin this afternoon. It won't last, but the deep powder days will get here eventually.

Next to a good mid-winter storm cycle, there's nothing better in Utah than a high-amplitude ridge in September, and Mother Nature is about to deliver.  Check out the GEFS ensemble-mean forecast for the coming week. That is one monster ridge, and it should lead to a period of "severe-clear" bone-dry weather for northern Utah.  We should see some large diurnal temperature ranges, especially in noted nighttime cold spots like Rush Valley and the Peter Sinks.  Looking for something geeky to do?  Head to the Peter Sinks on Wednesday or Thursday and ride your mountain bike from the rim to the basin floor first thing in the morning.  I did this during the Peter Sinks experiment, described by Clements et al. (2003) , and froze my butt off as the temperature fell from something like the 40s on the rim to the teens at the bottom. And, I should add that I'm still savoring the Ute beatdown of BYU last night...

It is not uncommon to see convection, sometimes in the form of cells, other times in the form of bands, initiating downstream of the Great Salt Lake in westerly flow.  At issue is if the lake plays any role at all in initiating these bands, if they are a reflection of orographic lift, or whether it is pure happenstance that the convection triggers downstream of the lake. Case in point was this morning when there was some fairly strong convection downstream of the Great Salt Lake near Ogden. An hour or two later, I took this photo looking north toward Ogden from the Bonneville Shoreline Trail, showing a wimpy cloud band extending eastward into an apparent orographic cloud over the Wasatch Range. What are the roles of the lake, orographic, and large-scale processes in a case like this?  I think these westerly flow cases are amongst the most perplexing we have in northern Utah. BTW, the view to the west was simply spectacular and largely cloud free, although that c...

IR satellite imagery, sea level pressure (contours), dynamic tropopause (color fill), and 925-mb winds The loop above illustrates several key large-scale atmospheric processes that are important for weather prediction.  In fact, I could probably give an entire exam for synoptic-dynamic meteorology from this loop alone.  Can you more advanced Wasatch Weather Weenies identify them?

Source: utahutes.cstv.com Today is going to be a very interesting weather day, but with the Holy War tomorrow, I can't help but take a few cheap shots at that so-called university down the road. Now I have a number of friends and colleagues at BYU, and they have even had my back scientifically .  But, for the next 48-hours, we will simply refer to those at BYU as down south scum . Being that this is a weather and snow blog, and that the Holy War inevitably involves debate about which school is superior, I now announce the official Wasach Weather Weenies Top-10 reasons why the University of Utah is better than BYU: 10. We have the Great Salt Lake effect, they have the Utah Lake effect 9. We chase hurricanes, they chase honor-code violators 8. We have Alta-Snowbird, they have Sundance 7. The Cottonwoods get blower-pow in northwesterly flow, Timpanogos gets nothing 6. The Utah ski team has 10 NCAA championships and 63 individual national champions,  BYU races divisi...

Photo: Josh Wurman, Center for Severe Weather Research University of Utah students who are interested in learning more about winter storms and getting hands on experience with polarimetric radar are invited to attend a meeting at 2PM today (Friday 16 Sep) in 711 WBB .  As announced earlier this month , the famed Doppler on Wheels research radar will be deployed to the University of Utah from about 21 Oct – 21 Nov and available for student-directed research projects.  At today's meeting, we will be identifying some key phenomena and research issues to examine, and forming teams for developing deployment strategies, including siting and scanning sequences.

Recent work has shown that the Intermountain West is a fertile breeding ground for strong cold fronts, many of which develop over eastern Nevada and northwest Utah (e.g., Shafer and Steenburgh 2008 ; Steenburgh et al. 2009 ).  In particular, Shafer and Steenburgh (2008) show that the number of strong cold frontal passages, defined based on a temperature fall of at least 7ºC and pressure rise of 3 mb in 2–3 h in conjunction with a 700-mb temperature gradient of at least 6ºC/500 km, increases as from the Pacific Coast to Salt Lake City where there is a local maximum. Total number of strong cold-frontal passages 1979–2003 ( Shafer and Steenburgh 2008 ). There's a minimum at Wendover, but some weird stuff happens there (meteorological and other) because of the mountains to the immediate north and northwest. However, climate is what you expect and weather is what you get.  Some fronts that move across the Intermountain West do not intensify. For example, the NAM model pre...

The upper-level trough sliding across the southwest United States has organized the monsoonal clouds and precipitation over the past two days, with a nice comma cloud developing over southern Utah. Beneath the comma cloud is a weak, somewhat organized rain band with a few embedded convective cells. We often think of monsoon precipitation as airmass convection, but large-scale systems can be important.  This is especially true in September when midlatitude troughs interact with monsoon moisture.