Thursday, July 20, 2017

One Streak Ends, Another Continues

At just before 1 AM MDT on 19 July, a weak thunderstorm moved over the Salt Lake City International Airport, producing .01" of rain.  The thunderstorm was isolated in nature, but was enough to produce measurable precipitation at the airport for the first time in 34 days.

So that streak, although not even close to record breaking, is over.  If my notes are right, the record at the Salt Lake City airport for consecutive days without measurable precipitation is 63 days and there have been 9 instances of 40 or more.  Of course, .01" isn't really much in July when it evaporates off in a few minutes.

Getting to record breaking streaks, our consecutive day streak with minimum temperatures above 70 continued through yesterday and now sits at 17.  The overnight low this morning was only 77 or 78 degrees, so that streak will go to 18 unless we can get some thunderstorm cooled air to drop things to below 70 this afternoon or evening.

Speaking of thunderstorms, we noted on Tuesday that a monsoon surge and associated thunderstorm activity would push right to the doorstep of Salt Lake County tomorrow afternoon and that's pretty much what happened.  Below is the precipitable water analysis (contours, a measure of how deep the water would be if you condensed out all of the water vapor in the atmosphere) for 0000 UTC (6 PM MDT) yesterday afternoon.  Note the sharp dropoff from central Utah to the northwest Utah border.

Some strong storms popped over Utah, Summit, and Wasatch Counties and did try to sneak into Salt Lake County, but for the most part, we missed out on the action.  Pity, although the cloud cover and cooler outflow was appreciated.

Some of that monsoon moisture remains in the area today, so there's still the hope of something popping and giving us some rain this afternoon or evening.  Keep your fingers crossed.

After that, we see a shift in the flow and drier air moving into northern Utah.  By Saturday afternoon, precipitable water values over northern Utah are less than 15 mm, greatly reducing the thunderstorm threat, which will likely consists of just isolated storms over the highest terrain (Uinta Mountains, you know who you are).

With drier air moving in, there is a chance that we might actually see a minimum temperature below 70 if not with a storm this afternoon (low chances) then sometime over the next few days.  Another reason to keep your fingers crossed!

Tuesday, July 18, 2017

Airport Ugly Streaks Continue

Hopes were dashed at the Professor Powder abode last night as storms over the Salt Lake Valley left us high and dry.

The storms moved over the Oquirrh Mountains around dinner time.

And they brought measurable rain to many sites in the Salt Lake Valley, including a few that reached 0.15 inches.  Imagine that!

However, we barely traced at my house and a scant trace was also all that was observed at the Salt Lake City International Airport.

Thus, two ugly streaks continue at the airport.  The first is the number of consecutive days with a minimum temperature at or above 70ºF.  We are now at 15, which is an all-time record.  Last night's minimum was 74, so it is likely we'll stretch the record at least another day.

The second ugly streak is consecutive days without measurable precipitation, which now sits at 34.  That's not a record, but it's still a long time without a decent shower.

The models have been suggesting that we might have a modest monsoon surge into northern Utah tomorrow.  However, they've been fickle on strength and northern extent.  This morning's NAM, for example, puts the higher moisture and shower activity right on the Salt Lake County doorstep by tomorrow afternoon.

Bottom line: Do frequent rain dances over the next 36 hours and hope for the best.

Monday, July 17, 2017

Why Is It So Warm at Night in Salt Lake City?

Some of you have asked me why the overnight minimum temperatures have been so high in Salt Lake City this summer.  In particular, it seems like the minimum temperatures are more above normal than the maximum temperatures.

To answer this question, let's take a look at the long-term trends in mean maximum and mean minimum temperature in Salt Lake City during the first half of July since 1874. As can be seen from the chart below, both exhibit a long term warming trend.  If you look carefully, however, you can see a surge in minimum temperature during the early 1900s, and abrupt drop in minimum temperature in 1928, and then another rapid increase in minimum temperature, at a rate faster than the increase in maximum temperature, beginning in the 1970s.

These changes are better illustrated if we plot the mean difference between the maximum and minimum temperature, which meteorologists call the diurnal temperature range (DTR).  Prior to 1928, you can see a gradual decline in the DTR, followed by an abrupt increase in 1928.  Then there is another decline beginning in the 1970s.

How can we explain these DTR characteristics?  Let's begin with the abrupt increase in DTR in 1928.  It is my understanding that this is when the official Salt Lake City observing site shifted from downtown Salt Lake City (near the present Vivint Smart Home Arena) to the airport.  Thus, the rapid increase in DTR reflects this change, with the airport featuring a larger DTR because of its lower elevation (favoring lower minimum and higher maximum temperatures) and rural character.

The decline prior to 1928 is interesting and I suspect is an urban heat island effect related to the development of downtown Salt Lake City, which was quite extensive by 1920.

Salt Lake City in 1920.  Source:, Utah State Historical Society
The time series since 1928 is more difficult to explain and really requires more careful investigation.  The period prior to the 1970s saw little change in the DTR, but it has dropped significantly since then.  Potential contributors to these trends include the following.

1. Urban Heat Island. There has been dramatic growth of the population of Salt Lake City, Salt Lake County, and the Wasatch Front in recent decades.  For example, the population of Salt Lake County has grown from under 200,000 in 1928 to over 1,000,000 today.

This has undoubtably had a significant impact on local and regional temperatures, although we lack precise knowledge of this impact.  Typically urban heat islands have a stronger influence on minimum temperatures than maximum temperatures (although both increase), leading to a reduction in DTR.

2. Site Characteristics at the Airport. Temperatures are also strongly dependent on the land surface characteristics and the precise location of the instruments at any given observing site.  The Salt Lake City International Airport is dramatically different today than it was several decades ago.  In addition, the location of the observing site at the airport may have changed.  Even small changes in location can make a difference (ask any golfer or hiker who walks around in an open area on a clear morning).

3. Instrumentation Bias.  Over the years, the instruments used by the NWS have changed and this too can affect long-term trends.  The DTR decrease since the 1970s is, however, more than 5ºF and likely can't be fully explained by bias.

4. Global Warming.  A decrease in the DTR and a more rapid increase in minimum temperatures than maximum temperatures are consistent with an enhanced greenhouse effect and expectations of global warming.

5. Regional Climate Change and Variability.  Characteristics of the trends since 1928 might also be influenced by regional climate change and variability, such as variations in large-scale circulations, including the North American Monsoon.

All of these factors may play some role, although their relative importance is unclear and to my knowledge unquantified.  In addition, explaining shorter-term trends, such as why trends in the DTR shifted so abruptly in 1970 is also difficult.  The 1970s did mark a significant shift in trends in global temperatures, and it is also possible that growth along the Wasatch Front and/or near the airport reached a "critical mass" around that time.  Careful investigation is needed by people who are smarter than me.

Sunday, July 16, 2017

Ridiculously Hot First Half of July

The first 15 days of July are in the bag and it has been ridiculously hot in Salt Lake City.  The average temperature for those 15 days was a whopping 86.6ºF, 2.3ºF warmer than the first half of July 2002.

Source: NOAA Regional Climate Centers
Such a temperature, if it were to hold throughout July, would also easily set the all-time monthly record.


Saturday, July 15, 2017

Uinta Misadventures

As many of you already know, the Uinta Mountains are often another world weather wise compared to the Wasatch Front.

Indeed that was the case today as our hike turned into a quagmire thanks to thunderstorms that fired up near the Uinta crest.

I knew there was a chance we'd get caught out, so our plan for the day was to hike the Highline Trail to either Rocky Sea Pass or Naturalist Basin, hopefully being down in the trees if anything sparked.    Ideally, we would have had a crack of dawn start, but it's hard to get the teenager out of bed, so we hit the trail mid morning.

After a quick approach, we approachedNaturalist Basin, but heard a few rumbles to the east.  Not a good sign.

Eventually it was clear the time had come to turn around, so we headed back down.  That's when things really fell apart.  First heavy rain turned the trail into a quagmire.

And then the pea size hail started.  Although not large, the some of the larger stones stung pretty good.

The hail began to cover the ground.  Unfortunately, my camera battery was dead today, and my cell phone crapped out after the photo below, so that I couldn't take any photos after the trail was buried deeply in the stuff.

It was really hard to believe it when we got to Park City and there was barely a cloud in the sky!  Goes-16 imagery for 2032 UTC shows the contrast well.

Thursday, July 13, 2017

Thank You for Smoking, 2017

If you haven't seen Thank You for Smoking, watch it some day as it is a great satirical comedy.  The main character, Nick Naylor, is a lobbyist for Big Tobacco who does a hell of a job spreading disinformation about the linkages between smoking and lung cancer.  The sad thing of course is that this really did happen, delaying improvements in public and individual health for Americans.

Fast forward to 2017.  Nick Naylor is now Scott Pruitt, Administrator of the Environmental Protection Agency.  Pruitt wants scientists to debate climate on TV, and "red team, blue team" exercises to evaluate climate science.

These proposed debates and exercises have nothing to do with science.  They have one objective, and that is to create doubt in the minds of Americans about the quality of climate science and the threat posed by global warming.  Doubt is his product, just as doubt was the product for the cigarette industry.

I have been around long enough to remember when there was legitimate, spirited scientific debate about the rate and causes of global warming.  As changes in temperature, sea level, snow, and ice became clear and evident over the past few decades, I've also seen all sorts of "alternative hypotheses" developed to explain global warming, from cosmic rays to solar changes.  None of these alternatives has ever survived rigorous testing.  Not only do they fail to explain the unusual intensity of recent warming, but they are also unable to explain patterns of warming, both geographically and from the lower troposphere to the stratosphere.  A preponderance of evidence from thousands of scientific publications supports the view that recent global warming is happening, that the rate of warming is unusual, and that it is caused by human activities, especially the buildup of greenhouse gases in the atmosphere from fossil fuel combustion and deforestation.

There are of course important uncertainties about the rate of warming, the rate and magnitude of sea level rise, changes to runoff and water resources, and regional climate change.  These are issues being explored by scientists from many fields.  There are also misleading news articles and political framing of climate science from both the right and left extremes.  Finally, spirited discussion and debate about the actions that we might take for climate mitigation and adaptation is quite justifiable. However, every major scientific organization, including the National Academy of Sciences, American Meteorological Society, American Physical Society, and American Chemical Society accepts that the Earth's climate is changing and that this warming is caused largely by human activity. As stated by the American Geophysical Union, "the Earth's climate is...changing at rates and in patterns that are not natural and are best explained by...human activity."

Nothing Nick Naylor says is going to change that.

Tuesday, July 11, 2017

Was Yesterday Really Cooler?

Chances are you thought that yesterday afternoon was comparatively pleasant compared to the previous several afternoons.  However, was yesterday really cooler than the previous several days?

Well, it depends.  If we're talking maximum temperature, it was cooler.  Yesterday's maximum temperature was 96ºF, the lowest maximum temperature since July 1st when we reached only 94ºF.  However, if we're talking minimum temperature, it was warmer.  Yesterday's minimum temperature was 79ºF, the highest minimum of the past 10 days.

Source: NOAA Regional Climate Centers
With a low of 79ºF and a high of 96ºF, yesterday's mean temperature was 87.5ºF, rating as the fourth highest of the month behind the 5th (90.5ºF), 8th (90.5ºF), and the 9th (88.5ºF).  So, from this perspective too, yesterday was pretty warm.  

You can blame all of this on the cloud cover, which acts to reduce the diurnal range of temperature, or the difference between the minimum and maximum temperatures.   Further, thanks to the cloud cover and higher humidities, swamp coolers were a bit less effective than we've seen thus far this summer.  

The lowest temperature to which air can be cooled by evaporation is known as the wet-bulb temperature.  Plotted below is the temperature and wet-bulb temperature at the Salt Lake City International Airport over the last 14 days.  Both exhibit daily ups and downs, reaching a maximum typically during the day and a minimum at night, although the wet-bulb is more damped. Yesterday, however, the wet-bulb temperature was nearly flatlined and remained near 65ºF overnight.  That's the highest sustained value we've seen probably all summer, although I haven't gone back through June to confirm this.  

Some people have asked me if this is the start of the monsoon.  That is a difficult question to answer.  "Monsoon" is often used to describe a seasonal reversal in the wind that is accompanied by rain.  In northern Mexico, for example, the flow during summer typically shifts from westerly to easterly, with a pronounced increase in precipitation.  For example, over Mexico, the climatological flow at 500 mb (about 18,000 feet) is westerly in May, but shifts to easterly in July.

Source: Douglas et al. (1993)
Source: Douglas et al. (1993)
This results in a very pronounced rainy season over northwest Mexico and portions of Arizona and New Mexico.

Monthly rainfall at selected sites. Source: Adams and Comrie (1997)
From the standpoint that we have had and will continue to have an upper-level ridge centered in the four-corners area and easterly large-scale easterly flow over Mexico and portions of the American Southwest, we are already "in" the monsoon.  Such a circulation is quite consistent with the North American Monsoon.  However, in such a pattern, moisture transport into northern Utah is quite fickle.  Really, northern Utah is in the monsoon surge region, meaning we need some help from a well positioned upper-level high and/or troughs in the easterlies to the south and westerlies to the north to draw in abundant monsoon moisture to give us wide spread showers and thunderstorms.  We really haven't had those key ingredients come together yet.  Thus, we've had some scattered thunderstorms, but nothing to truly soak the region and cool us down.

Monday, July 10, 2017

Evolution of the western "Death Ridge"

The loop below shows very nicely the evolution of the western "Death Ridge" from 1200 UTC (0600 MDT) Saturday 8 July through 1200 UTC (0600 MDT) Saturday 15 July.  The evolution is subtle, but there is some weakening early this week (hence the slight drop in maximum temperatures), followed by a Lazarus like return to dominate the circulation over the western US by next weekend.

At this point, I rate the odds that this July will go down as the hottest on record in Salt Lake as better than 50/50.  That is admittedly a risky forecast to make with three weeks left in the month, but we are off to a hell of a start.  Through the first 9 days of July, the average temperature for the month was 86.5ºF.  If that were to hold for the entire month, we would beat 2014 by a full 2.4ºF.

Source: NOAA Regional Climate Centers
At this point, I hope that either the models are wrong or we break the record.  If we must suffer, we may as well get bragging rights.

Sunday, July 9, 2017

Day Six and Summer Three of Oppressive Heat

The National Weather Service reports this afternoon that we've hit 100ºF this afternoon, marking the sixth straight day with temperatures reaching 100 or greater.

If you are keeping score at home, the highs are 102, 105, 102, 103, 104 and at least 100 today.  Three of those tied or broke record highs for the day.

I thought about backpacking this weekend, but the temperatures were simply too high, even in the Uintas.  I did hike up Snowbird today, and it was probably the most uncomfortable trek to the tram that I can remember.  It was not only hot, but there was also little wind, even on the ridge.

The snowpack has taken a beating the past couple of weeks.  For as much snow as there was in the Wasatch in late May, there's really not much left.

June through August is supposed to be hot, but this is not normal.  Over the past three years the period from 1 June through 8 July has been exceptionally warm at the Salt Lake City International Airport, rating as the 3 hottest such periods on record.  The summer so far this year is actually a shade behind the previous two years, although the difference is just 0.2ºF.

A very slight cool down is on tap for tomorrow, possibly breaking our streak of triple digit highs, but the extended range forecast remains pessimistic for any significant relief for northern Utah.  We got some thunderstorms in the Salt Lake Valley last night, and there's always the hope of such storms popping up or a monsoon surge sneaking in, but by and large, the forecast simply looks hot and uncomfortable.

Once again, for your entertainment purposes I provide below the 10-day forecast from the weather channel.


Friday, July 7, 2017

The Start of a Blistering July

With three days of 100+ in the bag, including a 105, it's no surprise that the first 6 days of July have been blistering and rate as the warmest first 6 days of July on record, with an average temperature of 85.4ºF.

Source: NOAA Regional Climate Centers
This is a family blog, so I won't say it, but you can utter or scream your favorite expletive here.

There's really no relief in site.  The NWS calls for triple digit high temperatures at the airport through Sunday.  Monday they drop the high to 97, but lets see if that pans out and really, that's still above average.

The overall pattern over the next 10 days ain't great.  There's always the hope of a summertime thunderstorm, and a weak trough is expected to approach on Monday, but that's about it.  The 180 hour GEFS forecasts below scare the hell out of me, with most going for a high amplitude ridge that is configured in a way that we'll see blistering conditions right through the end of the month.

Bottom line: This could get ugly.

Wednesday, July 5, 2017

Air Quality Woes

Last night's fireworks displays caused some notable declines in air quality around the region.  At Neil Armstrong Academy in West Valley City there there was a rapid rise in PM2.5 concentrations just prior to 10 PM, coinciding with increases in individual and public fireworks displays, reaching a brief peak at a remarkably high 180 ug/m3.

Source: MesoWest

Elevated levels above about 40 ug/m3 persisted through about 3 AM, after which they declined to much lower levels.

Sith mostly sunny skies and hot temperatures kicking photochemistry into overdrive, ozone concentrations over the past five afternoon at Hawthorne Elementary have peaked at levels considered unhealthy for sensitive groups.

Source: DAQ
Today and the next three days are expected to be no different.
Source: DAQ
Unlike high wintertime PM2.5, which is typically confined to the Salt Lake Valley, the nearby Wasatch Mountains are probably no safe haven from the high ozone as they are also enveloped in the urban airmass and might even observe higher ozone concentrations than the city (this is common in forested areas adjacent to urban areas due to a variety of factors that perhaps we can discuss in the future).

Probably the best thing you can do for cleaner air this week is to simply avoid running outdoor gas-driven power equipment like lawnmowers and leaf blowers.  My lawn needs cutting, but I'll probably hold off on mowing until we get a good wind blowing in the valley again.

Monday, July 3, 2017

Entering the Dog Days of Summer

I love the four seasons, but July in Salt Lake City is a four letter word.  There are probably worst places to spend July, such as central Florida or southern Arizona, but in my view, as a resident of northern Utah, July is my least favorite month.

And, with June in the rear view, the forecasts show that the first half of July is clearly is out to get us this year.  We are looking down the gun barrel of a period characterized by little synoptic variability and just the hope of perhaps a sneak of moisture from time to time to give us a shower or thunderstorm.  To show the lack of variability, below are the 60, 120, and 180 hour forecasts from the GFS showing a ridge centered over the four corners, a ridge centered over the four corners, and a ridge centered over the four corners, respectively.  It's a forecast that is redundantly redundant.

Nor surprisingly, the time-height section for 0-180 hours shows a freezing level that shows little variability, rising only slightly from about 575 to 550 mb (time increases to the left) and very little change in the overall environment from day to day.

If you want variety, about all you can hope for is that the ridge shifts enough or there's a weak wave passing in just the right way to send a bit of moisture our way.  I'm no fan of 10-day icon based forecasts, but what the hell, here's today's from the Weather Channel.

Iceland, how I miss thee...

Friday, June 30, 2017

Combustible Fourth of July Weekend Forecast

With the Fourth of July next Tuesday, we have a holiday weekend on tap.  My forecast for the weekend can be summarized in one word.  Combustible.

The Brian Head fire gets everyone's attention, but both lightning- and human-sparked fires have been quick to flare up across the state.  Despite a good snow season, fire danger is rated as moderate to high across northern Utah and very high to extreme across southern Utah.

Source: USFS Wild Fire Assessment System
Precipitation has been scant across the state for several weeks, with 50% or less of average falling across much of the state over the past 60 days.

Source: NOAA/NWS
The past 60 days have also been unusually warm.  For example, the period from 29 April through 29 June is the 2nd warmest on record at the Salt Lake City International Airport (ignore the first year in the graph below as it contains several missing days).

Source: NOAA Regional Climate Centers
This has led to tinderbox conditions across most of Utah, with energy release component indexes, a measure of how hot a fire could burn, remarkably high across southern Utah and well above median across most of the rest of the state.  

Now, lets turn to the forecast.  After a refreshing night last night, we're moving into nuclear summer for the weekend.  Forecast highs for the Salt Lake International Airport are in the mid to high 90s.

Source: NWS
St. George?  Triple digits.

Source: NWS
Basically, we are in the Venn diagram overlap region of dangerous fire conditions, hot weather, and a fireworks laden holiday.  If you are wondering, information on fireworks restrictions for Salt Lake County is available here and for the state here.   

Wednesday, June 28, 2017

GOES-16 Rocks!

GOES-16, previously called GOES-R, is a remarkable next-generation satellite that was launched in November.  Although not "official" yet, it has been providing remarkable imagery for several months.
GOES is short for Geostationary Operational Environmental Satellite.  Geostationary means that the satellite is in an orbit in which it remains over the same point on the equator, allowing it to repeatedly sample roughly one half of the Earth at all times.  GOES-16 offers several major advances over previous US geostationary satellites including higher spatial resolution (0.5 km for the 0.64 um visible channel, 1 km for other visible channels, and 2 km for longer wavelength channels), which equates to approximately four times as many pixels, more frequent images (every 5 minutes over the continental US and as often as 30-60 seconds over selected regions), and 16 spectral "bands."  Previous GOES satellites sampled only 5 spectral bands.  The increased number of bands will allow for a remarkable advance in the quality of the imagery and the detection of critical weather and environmental phenomenon.

A nifty site for playing around with GOES-16 imagery and animation is the Cooperative Institute for Research in the Atmosphere's SLIDER.  You can access imagery from both GOES-16 and the comparably equipped Japanes Himawari-8 satellite on this site.

Below is the GeoColor image from 1817 UTC (1217 MDT) this afternoon (click to enlarge).  This is a truly spectacular product, leveraging the GOES-16 capabilities to provide remarkable images far beyond the old black and white imagery of the past.  I've highlighted a few features including the Brian Head fire smoke plume, standing water on the salt flats, and the lava flows in Craters of the Moon National Monument.

Everything points to GOES-16 being a revolutionary advance for weather prediction.  We will make extensive use of it in future posts.

Tuesday, June 27, 2017

Smoke for the Morning Commute and Antecedent Meteorology of Brian Head Fire

An addendum has been added to the end of this post concerning uncertainty about the source of the smoke or dust over the Salt Lake Valley this morning.  

A smoky sunrise in the Avenues
A weak trough passage last night has brought smoke into the Salt Lake Valley, along with a little lake stink.

As far as troughs go, this one was about as weak as it gets and barely put a dent in the near-surface flow.  The trough is, however, more easily seen in upper air (700mb, about crest level) analyses, with the pronounced wind shift moving across the Salt Lake Valley early this morning.

Thus, the smoke is not from the Brian Head fire, but more likely originates from one of the large incidents to our west and northwest over Nevada and Idaho.

Speaking of the Brian Head fire, lets take a few moments to talk a little bit about the meteorology leading up to the event, motivated in part by comments concerning yesterday's post.

Snowfall last winter was impressive in the Brian Head area, leading to an above-median peak snowpack.  However, the ensuing meteorology of the spring has led to very high to extreme fire danger over the region.  

To illustrate this, I've pulled data from two nearby SNOTELs at Midway Valley (9826 ft) and Webster Flat (9158 ft).  There are other SNOTELs in the area, but these had good data coverage and a long-term median.  

Both show a peak snowpack water equivalent well above median.  There are really two major snowpack peaks at each site, one in early March, the other in early April, although the primary maximum is in early March at Webster Flat and early April at Midway Valley.  

Source: CBRFC 

Although the snowpack at both sites was well above median, each site lost significant snowpack during the March heat wave that affected much of Utah and Colorado (dashing Spring Break powder skiing hopes).  Snowfall melt rates after mid April were also quite high.  As a result, the last day of measurable snowcover at Midway Valley was near median (late May) and at Webster Flat was about a week earlier than median.

Long-term observations from sites at high elevations around Bryan Head are somewhat scarce, but the time series from Bryce Canyon below shows that the period from March 10 to June 25th rated as the 2nd warmest on record since 1960.  

NOAA Regional Climate Centers
There are, however, some missing days at that site.  Alternatively, we could look at Cedar City, which is geographically closer, but also much lower.  There, temperatures for the period rate as the 16th warmest on record since 1949.  

Source: NOAA Regional Climate Centers
Finally, we can look at precipitation and see that over the last 90 days, precipitation in the region was 50-100% of average depending on what pixel you choose from Cedar City to Brian Head.

It has been especially dry over the past month or so.  There has been no measurable precipitation in Cedar City since May 16 or at Bryce Canyon since May 11.  

So, despite a fat snowpack in March and early April at upper elevations, snowmelt this spring was rapid, temperatures were above average, and precipitation was scant.  This has contributed to fire danger in the region that sits today over southwest Utah in the very high to extreme categories.  

Bottom line: Warm Dry Spring 1, Fat Snowpack 0.

Addendum at 9 AM MDT:

Spectacular GOES-16 imagery from CIRA leaves me scratching my head about the source of the smoke (or maybe dust) over the Salt Lake Valley this morning.

Addendum at 9:25 AM:

NWS suspects smoke source is fire near Snowville.