Wasatch Weather Weenies

Source: Joint Typhoon Warning Center That's super typhoon Jelewat, which presently has maximum sustained winds of 135 mph, with gusts to 165 mph.  The maximum significant wave height is 48 feet.  That will get your attention. The current track forecast has it turning clockwise, brushing by Taiwan and then moving across Okinawa.  Little wonder why the US Navy and Pacific Air Forces are so concerned about typhoons. Source: Joint Typhoon Warning Center I've been looking at the long-range forecasts produced by the GFS and after undergoing what is known as extratropical transition, the remnants of Jelewat move over Nome, Alaska by October 4th.  The weak low center over western Alaska in the image below is it. It is pretty common for tropical cyclone remnants to move across the North Pacific and undergo reintensification (a process known as extratropical transition ).  Many move into the high latitudes.  What role do these events play in the clima...

As we approach the cool-season, life in the midlatitudes is starting to get interesting.  Today we have an example of an explosively deepening cyclone  or bomb over the Gulf of Alaska.  Watch in the loop below how the cyclone deepens from a central pressure of about 1002 mb to less than 960 mb 24 hours. 1200 UTC 25 Sep – 1200 UTC 26 Sep IR imagery and GFS sea level pressure analysis The term "bomb" was used in the classic paper by Sanders and Gyakum (1980), which used that label for extratropical cyclones with a central pressure that falls at least 24 mb in 24 hours. Title and abstract of the seminal paper by Sanders and Gyakum (1980) Sanders and Gyakum (1980) showed that bombs in the Northern Hemisphere are most common over oceanic areas, especially along the Gulf Stream in the Atlantic and and from along the Kuroshio Current to the Gulf of Alaska over the Pacific Ocean.  Their analysis was based on a small sample, but more recent climatologies reflec...

Source: Alta.com That's more like it.  Today you can believe your eyes.

Source: Alta.com I'm not so sure.  I can't find snow in photos from other cameras (e.g., Snowbird Hidden Peak), I can't see it when I look at Lone Peak from my office, and the temperature at the top of the Collins lift has gotten no lower than 39ºF, which is quite marginal for snow to stick.  Rumor has it that the Sugarloaf camera image often suggests there's snow on the ground.  What do you think?

University of Utah Atmospheric Sciences Professor Dr. Thomas Reichler We interrupt today's blissfully cool and cloudy weather for a quick plug of a recent paper by University of Utah Atmospheric Sciences Professor Dr. Thomas Reichler, Atmospheric Sciences graduate student Junsu Kim, and two colleagues at other institutions, Elisa Manzina and Jürgen Kröger. The paper, which was published yesterday in Nature Geoscience and is available here (possibly paywalled for those outside the U or without a subscription to Nature), explores a possible link between the stratosphere and Atlantic climate variability. To learn more, see the paper or this press release from the University of Utah .

A high-amplitude upper-level ridge remains parked over western North America, but as shown in yesterday afternoon's 0000 UTC 23 Sep 500-mb height analysis, there is a potential fly in the ointment for Utah weather. Source: NOAA/ESRL The fly is the weak closed low that is sitting over the coast of Washington, which results from a weather feature that meteorologists call a coherent tropopause disturbance , or CTD.  A CTD is a localized cyclonic vortex, which is associated with counterclockwise rotation in the Northern Hemisphere and is strongest at the tropopause.  The tropopause separates the stratosphere from the troposphere. Source: NASA The CTD and closed low move into Nevada by tomorrow morning [1200 UTC (0600 MDT) 24 September]. A different perspective at this time is provided below by a 3-D colored representation of the tropopause, with cool colors indicating a lower tropopause and warm colors indicating a higher tropopause.  Note how the tropopause ...

In the previous post, we discussed how the summer sea-ice extent is declining in the Arctic.  This sea-ice decline is simultaneously a result of and a contributor to enhanced warming of the Arctic relative to other regions, which is sometimes referred to as Arctic Amplification.  Arctic Amplification is produced by increased greenhouse gas concentrations combined with feedbacks such as increased absorption of solar radiation due to declining snow and ice cover. An area of growing scientific interest concerns the implications of Arctic Amplification for midlatitude weather.  More rapid warming of the Arctic compared to the lower latitudes leads to a decrease in the average temperature contrast in the midlatitudes.  The strength of the upper-level flow is proportional to this temperature contrast.  Therefore, one would expect upper-level flow to weaken (on average) in response to Arctic Amplification.   Recently, Francis and Vavrus (2012) proposed that th...

This is the worst kept secret in science as you have probably read about it in the past week in the news or earlier on this blog, but records for the arctic sea ice minimum extent were smashed this summer.  The National Snow and Ice Data Center suggests that a minimum of 3.41 million square kilometers was reached on September 16, breaking the old record set on September 18, 2007 of 4.17 million square kilometers.   Source: NSIDC The image below provides a comparison of the sea ice extent on September 16 (white) with the median extent on that day from 1979–2000 and helps illustrate just how much sea-ice loss there has been during summer in recent years. Source: NSIDC Many sea-ice extent records begin with the satellite record in 1979.  Efforts have been made, however, to use proxy data to extend a sea ice record into the more distant past.  For example, recent work by Kinard et al. (2011) suggests that the recent decline may be unprecedented in at least th...

I'm on the road and have missed out on the smoke in the Salt Lake Valley, but I assure you it is far worse in other areas. Check out this MODIS image of the central Idaho Mountains from yesterday. The valleys are choked with smoke.  There may be a bit of fog in there as well, but for the most part, its smoke. Stable cold pools that form in these valleys at night prevent the vertical transport and mixing of the smoke until late in the day this time of year.  This is very similar to what happens in Salt Lake during an inversion.  As a result, the smoke remains trapped in the valleys.   One can really see just how strong these nocturnal cold pools are by looking at the weather the past few days at Stanley, Idaho.  Yesterday they observed a high of 75ºF, but that was preceded by a morning minimum temperature of 26ºF.  It got down that low again last night.   A few years ago I was on a camping trip in the Sawtooths in September an...

Source: Loveland Ski Area Source: Unknown Portions of the Colorado Rockies got a dusting of snow yesterday (Monday) morning as a weak front traversed the region. Fall is the one time of year when Colorado can sometimes get the goods over Utah.  Owing to altitude and the somewhat colder, continental climate, they often see more early season snow than the Wasatch.  In addition, the snowpack hasn't decomposed yet into nasty avalanche-prone depth hoar, as it usually does during the Colorado winter.   Have no fear.  We always catch up eventually.  

I can sum up the forecast for the next 10+ days in one word.  Dry.  An upper-level ridge is going to be parked over the western United States, with our only hope of any precipitation being the possibility of a closed low swinging underneath it and tapping into a last gasp of monsoon moisture. We had a weak upper-level trough brush by last night.  That trough is presently moving across the upper midwest and eastern Rockies, with nothing upstream except a high amplitude ridge.   IR satellite imagery and 500-mb geopotential height analysis for 1200 UTC 17 September 2012. The medium range ensembles show nothing but ridging from now until the end of time (that's an exaggeration as they only go out 384 hours in the future, but that is the end of time as far as they are concerned).  Here are a few snippets at forecast hours 120 (valid 0000 UTC Sep 22), 240 (valid 0000 UTC 27 Sep), and 384 (valid 0000 UTC 3 Oct). Source: Penn State E-Wall All of the...

If you want to see huge swings between maximum and minimum temperatures, September is probably your month.  There's still a decent amount of incoming solar radiation during the day, the soils are dry so much of this energy goes into heating rather than evaporation and transpiration, and the nights are moderately long. This enables us all to enjoy warm days and cool nights, but where is the difference between the minimum and maximum temperatures, which meteorologists call the diurnal temperature range, the largest in northern Utah? The best place to look are in basins that are either fully enclosed or only allow cold air to leak out through very constricted channels.  One such place is the Rush Valley, which is located southwest of Salt Lake City and the Oquirrh Mountains. Overnight minimum temperatures on 16 Sep 2012.  Ignore misleading caption at upper left! Despite its name, the Rush Valley is really an enclosed basin.  Passes to the north to the Tooele V...

It's that time of year where in the morning there are some remarkable contrasts in surface temperature due to topographic and land surface contrasts. Nowhere is this more apparent than in Utah's West Desert.  Check out the observations from 1347 UTC (0747 MDT) this morning.  It was an incredible 55ºF over the salt playa along I-80, but as cold as 38ºF over the sagebrush region of Dugway Proving Ground to the southeast. Zooming into the Dugway Proving Ground you can really see the intensity of the inversions that formed overnight.  Temperatures on the valley floor (~1310 m) range from 38–52ºF.  On the summit of Camel Back Mountain (just below the center of the image, 1547 m), it was 65ºF. This variability is related to the formation of nocturnal cold pools due to radiational cooling at night.  The coldest temperatures are often found in those low elevation areas where the flow is weakest as the lack of turbulence and mixing enables the radiational ene...

W hy are a tornado and a BYU divorce similar?  You know someone is going to lose a house trailer. - BYUsucks.net Why doesn't BYU have an atmospheric sciences program? It requires math beyond counting on your fingers and toes. Go Utes!

Addendum @ 1150 AM: It's a few hours after writing about the unbelievable airmass in place over northern Utah and it appears that smoke has moved in yet again!  Will it ever end?  Try and enjoy anyway.... ----------------------- The weather doesn't get much better than yesterday and today.  Yesterday at the U we saw a maximum temperature of 73ºF, with an overnight minimum of 57ºF.  Dewpoints are in the teens to low 20s. The morning temperature at the Salt Lake Airport appears to have dipped to 50ºF.  The last day we saw a temperature that low was June 11th, three months ago.  Open up the windows and feel the chill! It appears that the incredible weather will be with us for quite a while.  Nearly all the models keep the jet to our north and east and a ridge over the western United States for at least the next week, as illustrated by the 144 hour ensemble mean 500-mb height forecast by the GEFS, which is valid for 0000 UTC Sep 19. It...

The Climate Prediction Center (CPC) has issued an El Nino Watch as conditions are favorable for the development of a weak El Nino this fall. In August, sea-surface temperatures were weakly above average across much of the equatorial Pacific Ocean (for example, see the so-called Nino3.4 region, which lies between 90–150ºW and 5ºS–5ºN), although the far eastern equatorial Pacific saw some areas of below average sea-surface temperature. The development of above average sea-surface temperatures in the central and eastern equatorial Pacific is a hallmark of El Nino.  Nevertheless, the departures from average are small and atmospheric conditions in the tropics are not yet consistent with El Nino.  Convection remains primarily in the western equatorial Pacific (it typically shifts eastward during El Nino), and the easterly trade winds were near average (they typically weaken during El Nino). For these reasons, the CPC classified August as ENSO-neutral (meaning no clear EL Ni...

A few of our readers sent me photos of the Timp snowfield.  The first, from Carolyn Stwertka, was taken on July 29th and shows some skiers giving their skis a good stone grind. There are easier ways to add texture to your bases! The second was taken on Sunday by Beth Blattenberger and shows a few snow patches remain. The long range forecasts call for ridging and warm weather to return.  In other words, there's more melt to come.  Can the Timp Snowfield hold on?

Like Maverik and Goose in Top Gun, meteorologists feel the need for speed. The political conventions are over and predictably, both major-party candidates talked a good game about innovation, education, and the economy.  Well, I have something that either of them could do to immediately help in these areas: Infuse the National Centers for Environmental Prediction with the funding needed to put the United States back on top again in numerical weather prediction (NWP). NWP involves the use of mathematic models of the atmosphere and other Earth-system components to predict the weather (this is why meteorologists call them models).  First envisioned by Vilhelm Bjerknes, a Norwegian physicist and meteorologist in the early 20th century, NWP became a reality in 1950 when a group formed by John von Neuman and led by Jule Charney produced the first one-day forecast on ENIAC, the first electronic computer (see Platzman 1979 for a historical review). From left to right, Har...

In late July I speculated that we might lose all snow in the Wasatch Mountains this year .  A poor snow year followed up by a hot spring and summer is a recipe for snowpack oblivion. As we approach the end of the melt season, all that remains is a few patches of snow clinging to the high north aspects.  Yesterday, all that was left on the American Fork Twin were three narrow patches of snow that are probably doomed. Looking for turns?  How about this patch at the base of the northeast face of White Baldy. It might just survive the summer.  Chances are, this patch is probably neve (compacted, granular snow) from the great winter of 2010–11.  If I remember correctly, there was also a large avalanche on the northeast face of White Baldy that year that probably collected in this area.  I'm still waiting for someone to send me a recent photo of the Timpanogos snowfield. 

" The problem with weather is that our knowledge of its initial conditions is highly imperfect " -Nate Silver The Weatherman Is Not a Moron is an excerpt published in yesterday's New York Times from a forthcoming book by Nate Silver entitled "The Signal and the Noise: Why So Many Predictions Fail – But Some Don't."  I nearly bought a copy of the book in advance last week, but I was worried it was going to be a boring treatise of digital signal processing, but that is clearly not the case.  The Weather Is Not a Moron is a pretty good read and provides insights into how uncertainty impacts weather forecasting.  Hopefully the book delves into ensemble weather forecasting and efforts by meteorologists in the past two decades to quantify uncertainty, as that has become a critically important component of our profession.   The author covers numerical weather prediction in the excerpt, and how forecasters deal with uncertainty, but never states ...

Yesterday provided a great example of why it is important to remain vigilant as a forecaster and keep an eye on the most subtle weather features. The flow was fairly weak yesterday, but inspection of the 700-mb winds in the Rapid Refresh analysis showed a weak trough draped across northern Utah and central Nevada with a tongue of higher precipitable water air extending from southern Nevada into western Utah.  This moisture tongue became the locus for the development of convective rain showers yesterday afternoon, which proceeded to move across central Utah and produce a few showers as far north as Little Cottonwood Canyon. The moisture tongue was entirely unresolved by the conventional upper-air observing network, which provides observations only at Elko, Salt Lake, and Las Vegas.  The fact that the Rapid Refresh picked up on such a feature is a testament to the tremendous advance in numerical weather prediction and data assimilation that has occurred in recent ye...

The National Weather Service reports that this August was the hottest in the records at the Salt Lake City International Airport, and this summer (June–August) was the second hottest.  We obliterated the previous August record (1994) by 0.9ºF, while we just missed the summer record (2007) by only 0.1ºF. 1994 is now the third warmest year on record, although I think it carries on as the summer with the most 100 degree days (21).  This year we had 11. The heat was associated with an upper-level ridge that setup over the central United States and dominated the weather for most of the summer, as shown in the mean and anomaly 500-mb geopotential height analyses below. In August, this ridge was located a bit west of its mean position for the summer, which contributed to the anomalously high temperatures. Note also that the ridge had a positive  negative tilt, meaning the ridge axis was aligned from southeast to northwest.  This pattern helped keep...