Thursday, June 30, 2016

Record Heat Prospects and Mountain Hail Encounters

With 29 days in the bag for the month, the average temperature at Salt Lake City for this June is 77.3ºF, just 0.2ºF behind 2015 for the hottest of all-time.

Source: NOAA Regional Climate Centers
I've run some quick numbers using the last night's minimum temperature (74ºF) and the forecast maximum for the day (91ºF).  Those will bump this June up about .15ºF, which will put us very close to 2015 (and within the roundoff uncertainty of the monthly mean data I have access to, which is rounded off to the nearest tenth of a degree).  Much will depend on today's maximum and whether or not we get some dramatic cooling from precipitation to lower the minimum.  In either event, 2015 and 2016 will stand as back-to-back Junes of unusual warmth compared to past Junes in the historical record.

Meanwhile, here in the Northeast, yesterday was an "excursion" day at our conference, allowing us to get out into the Adirondack Mountains and climb Giant Mountain.  The day started out optimistically with partly cloudy skies.

The hike up Giant is short, about 2 3/4 miles, but involves about 3000 vertical feet of ascent up an extremely rugged Adirondack trail.

On the summit, we were treated to a nice view of the high peaks.

However, as we summited, we heard a low rumble of thunder and after a couple of minutes on top, it was clear we had to descend and descend fast.

After getting a few hundred vertical feet off the ridge, the skies opened up, initially with rain, but eventually with a deluge of pea-sized hail.

Here's a handful.

Steep Adirondack trails are nasty enough when dry, but even tricker when wet and covered with ball bearings of ice.  We also encountered quite a bit of "hail fog," a shallow fog mainly in the canopy layer due to cooling from melting ice.

Due to the retreat, our group photo was taken about half way down, after things dried out and the camera partially defogged.

Just another day of adventure with the Steenburgh group.

Monday, June 27, 2016

Race on for Hottest June

With four days left in the month, the race is now on for the hottest June on record.  The average temperature so far for this June puts us in 2nd place all time in Salt Lake City, 1.2ºF behind 2015.

Source: NOAA Regional Climate Centers
And the forecast calls for triple digit scorchers today and tomorrow and 90s for the last 2 days of the month with above-average minimum temperatures.

Source: NWS
It's gonna be close.  Although it's unclear which year will end up number one, it's clear we're going to go #1 and #2 for the past two Junes.  Yes, you have bragging rights.

Saturday, June 25, 2016

The View from Here

Looks like Salt Lake has gotten some much needed relief from the heat as I just pulled up the 2 PM MDT observation from the airport and it's only 77ºF with a dewpoint of 19ºF and winds from the northwest at 12 mph gusting to 18.  That must feel so good.

I'm currently in New York visiting family in advance of the American Meteorological Society Conference on Mountain Meteorology, which will be held in Burlington, Vermont next week.  Although we are warming up here and are expected to hit 90ºF tomorrow, it's been pleasant for my stay so far.

Today I did a hike up Snowy Mountain, which is not so snowy by Utah standards, but at 3899 ft, is the highest peak in the southern Adirondacks and requires about a 2000 vertical foot ascent.  Most of the trail is fairly easy, but the last several hundred vertical feet is your classic Adirondack knee breaker, basically a steep creek bed requiring the occasional "vegetable belay," especially on the descent.  A red trail marker on the tree center left confirms that this is the official route.

Many mountains in the Adirondacks still have old fire towers, which are no longer in use, but are greatly appreciated to provide a full 360º perspective given the dense trees on many summits.  When i was a kid, they still had rangers manning many of these towers looking for fires, and it was always a thrill to finish a climb with a visit.  That always seemed like the ultimate job to me, but fortunately I chose a different career path since we do it all with satellites and other tech these days.

From Snowy Mountain you can see the Adirondack "high peaks", a region encapsulating 46 peaks that were once thought to all exceed 4000 feet, although modern surveys reveal a few of these fall short.  I bagged a large number of these peaks with my Dad, but ultimately gave up the quest when I moved west.  No regrets.  The handful we had left required long misadventures with limited views.

The area around Snowy Mountain ain't Manhattan.  It's pretty unspoiled everywhere you look.  Indian Lake, pictured below, has always been one of my favorite large Adirondack lakes.  There are a few homes and camps, but it's fairly undeveloped and the forest is largely impenetrable.

It's good to be back "in the green."

Thursday, June 23, 2016

It's a Two Horse Race for Hottest June

Here are two ways to look at the temperature for June so far.  In the first, we compare the mean temperature for June 1–22 to similar periods in the past.  This year stands as the hottest such period on record, 0.1ºF warmer than June 1–22, 1918.

Source: NOAA Regional Climate Centers
In the second, we compare the mean temperature for June 1–22 to that of prior Junes (i.e., June 1-30).  The mean temperature for June so far would rate as the 2nd warmest on record, behind only last June.
Source: NOAA Regional Climate Centers
Although there's a cool down on tap for Friday and Saturday, we look to rebound again for the remainder of the month.  It looks like a two horse race for hottest June on record between 2015 and 2016.  My money is on the latter.

Tuesday, June 21, 2016

Heat Waves Are Going to Get Worse

Here are a few temperature "highlights" from yesterday:

  • The Salt Lake City Airport hit 100ºF, the first triple digit reading of the summer.  Was it a record?  Nope.  June 20, 1936 hit 101ºF.  
  • The Salt Lake City Airport also set a record high minimum for the day of 77ºF, trouncing the old record of 69ºF set in 2003
  • Alta hit 79ºF, breaking the old record for the day of 75ºF set in 2007
  • Numerous daily record maximum and high minimum temperatures were set in SoCal, including:
    •  122ºF in Palm Springs, which was 1ºF off their all-time record (123ºF) and also equates to 50.0ºC, precisely half way between freezing and boiling. 
    • 111ºF at Bob Hope Airport (Burbank), tying their June record
    • 125ºF in Needles, setting a new record for June and tying their all-time high (set in 1925 and 2005)
    • 126ºF in Death Valley, a record for the day
People often ask me if such heat waves are what we will be facing with global warming. This heat wave is not the future.  The future is worse.

We are still in the early stages of global warming.  Natural climate variability remains a major driver of extreme events like this (although global warming does tip the scales a bit).  When one looks at projections for the future under a "high-emissions" scenario, things don't get really ugly until the middle to late 21st century.  Gurshunov et al. (2013) provide an illustration of this for the most recent Southwest Climate Change Assessment Report.  They define heat waves as days when the maximum or minimum temperature exceeds that of the hottest 5% of summer days or nights (May–September) in the 1971–2000 climatology.   The heat wave index is the cumulative total number of degrees above the hottest 5% temperature threshold on these heat wave days. 

As shown in the graph below, for either maximum or minimum temperature, a clear long-term upward trend in maximum temperature heat waves over the U.S. Southwest has yet to be clearly detected (brown dashed and solid lines, with the latter representing the 5-year running mean), but there is some upward trend in minimum temperature heat waves.  

Source: Gurshunov et al. (2013)
 Heat waves are, however, projected to increase at an accelerating rate during the 21st century (black lines), with the climb for minimum temperature heat waves stronger than that of maximum temperature heat waves.  Studies examining southern California suggest that today's 100-year event becomes a 10-year (or shorter) event in the latter half of the 21st century.  Minimum temperatures are expected to climb faster than maximum temperature (consistent with the larger heat-wave index above), so the character of heat waves will also change, with less nighttime cooling.  

The graphs above are based on a high-emissions scenario in which we remain welded to fossil fuels for future energy demands.  Heat waves are going to get worse, but how much worse ultimately depends on the energy choices we make today and in the coming decades. 

Monday, June 20, 2016

Hot and Cold in SoCal

Although Arizona got some attention in the lead up to the current southeast heatwave, SoCal felt the heat yesterday too.
Source: Penn State
The temperature contrasts along the coast can be quite remarkable in patterns like this.  This morning at about 10 AM PDT, it was 98ºF at USC and 79ºF in Inglewood.  Out at Oxnard, with a decent onshore flow, it's a cool 69ºF.  Location, location, location.

Source: MesoWest
But perhaps the most remarkable temperature goes to Avalon Catalina Airport on Santa Catalina Island.  The airport is 1578 ft above sea level and above the marine layer.  The 11 am temperature was a whopping 101ºF.  Check out their temperature trace over the last 5 days.  Simply nasty.

Source: MesoWest
In case you are wondering, the average high at Avalon Catalina Airport in June is 67.6ºF.

Sunday, June 19, 2016

Box Elder on Father's Day

I often joke that there's no reason to go to Utah County, but really there's one, and that is the opportunity to hike (or ski) some truly spectacular peaks.  In fact, a credible argument can be made that the peaks of Utah County are more spectacular and beautiful than those of the central or northern Wasatch as they tend to be more isolated, have huge prominence, and have spectacular geology and ecology.

Today we hiked Box Elder Peak from Granite Flat Campground via the north ridge route.  The entire hike is spectacular, although much of the approach is south facing and hot.  Making it more tolerable are the tremendous views of huge ski lines that require full commitment.

Although it is only mid June, the hike is nearly entirely snow free.  The patch below was the largest we crossed on the north ridge and it was about 20 feet long.

Although steep, the north ridge has no real technical concerns, other than this highly intimidating class 2 Hilary Step that of course could be avoided to the left.

Nearing the summit.

View of Mt. Timpanogos from the summit.  Still quite a bit of snow on the primary hiking routes.  Willing to bet the Timp Snowfield will be DOA again this year.

Panorama of the divide with Little Cottonwood.

Father and son shot.

If you are sick of the crowds in the Cottonwoods, here's another reason to tag Box Elder.  Although it was very busy in American Fork Canyon, we saw exactly 2 people on the 10.5 mile hike.  Two people!  

In case you are wondering, the max temperature today in Phoenix was 118ºF., unless they had a spike after 5 PM.  Looks like the overnight low was 85ºF.  Yes, I know.  It's a dry heat...

Friday, June 17, 2016

June 2016 Looks To Be Salt Lake's Hottest on Record

I've been hoping we would avoid extreme heat next week in northern Utah, but the latest model runs are not optimistic.

Below is the 0600 GFS forecast of 500-mb heights from this 1200 UTC this morning through 0000 UTC 22 June (1800 MDT Tuesday).  Pretty much a worst-case scneario for us as the ridge over central North America builds westward across the U.S. Southwest and then northward into the Intermountain West.  

The forecast for Tuesday afternoon shows a core of 700-mb temperatures at or above 20ºC across southern Utah, with Salt Lake City around 18ºC.  

GFS 500-mb height and 700-mb temperature forecast valid 0000 UTC 22 June (1800 MDT Tuesday)
Such temperatures would be a record for that date and time (based on the Salt Lake City area upper-air sounding record) and near the all-time record for the month of June of 19.0ºC.

Source: SPC
Based on what I'm seeing in the extended model forecasts, I think we have a solid shot at the hottest June on record at Salt Lake City.  Although temperatures have been a bit more reasonable for the last several days, the average temperature for the first 16 days of June ranks as the 5th warmest compared to the average temperatures for all of June in the past.  

Source: NOAA Regional Climate Centers
Average temperatures for previous Junes have the advantage of having data from the last two weeks of the month, which are climatologically warmer.  The models show predominantly above average or well above average temperatures for the next week (Sunday might be near average if we're lucky) and suggest that trend will continue through the end of the month, as illustrated by the Climate Prediction Center 8-14 day outlook.

Source: CPC
It could be worse.  You could be in Phoenix.  Here's a comparison of The Weather Channel's forecasts for the two cities.

And remember, there's still about 11 weeks of meteorological summer left...

Thursday, June 16, 2016

Yesterday's Big Blow

Some impressive winds were reported around northern Utah yesterday and I think it's safe to say that they exceeded forecast expectations.  Peak gusts at valley locations reported to MesoWest include the following:

Sherwood Hills: 82 mph (0210 UTC/2010 MDT)
SR201 at I-80: 80 mph (0130 UTC/1930 MDT)
Syracuse: 76 mph (0120 UTC/1930 MDT)
Great Salt Lake Marina: 73 mph (0136 UTC/1936 MDT)

Many mountain sites, especially in the northern Wasatch, also reported strong gusts.

The setup for the event was very similar to many other strong southerly wind events in the spring.  With a developing surface trough extending from the southern Sierra Nevada across central Nevada and northern Utah.
RAP sea level pressure analysis, surface observations, and GOES IR satellite imagery at 0100 UTC 16 June 2016
In such situations, strong surface heating typically has two effects.  One is to contribute to the intensification of the surface trough and the associated low-level pressure gradient.  The other is to grow a deep surface-based mixed layer or what meteorologists sometimes call a convective boundary layer or CBL.  Thermals driven by intense heating penetrate upwards through the CBL, and these updrafts are utilized by gliders for lift.  The updrafts are just one side of the story, however, as the CBL also features areas of descending motion.  These updrafts and downdrafts transport and mix momentum through the CBL and lead to gusty surface winds.

During the spring, meteorologists commonly use the 700-mb flow to get some idea of the potential for strong winds under such conditions, but late yesterday, the 700-mb flow wasn't really all that impressive with modest southerly flow (30-35 knots) east of the trough over Utah.  In the spring, I've seen stronger flow than this produce less impressive winds than we saw yesterday.

RAP 700-mb geopotential height and winds and GOES IR satellite imagery at 0100 UTC 16 June 2016
Yesterday's CBL, however, was remarkably deep and so we were mixing momentum through a much deeper layer, tapping into stronger momentum air above 700 mb.  As shown in the afternoon (0000 UTC/1800 MDT) sounding from the Salt Lake City Airport, the CBL extended to almost 450 mb, or about 20,000 feet above sea level.  Winds between 700 and 500 mb peaked at about 50 knots, suggesting that the 700-mb analysis doesn't capture the strongest winds in the CBL and thus the potential for high gusts at the surface.

Source: SPC
On the other hand, even looking at that sounding in hindsight, I'm not sure if I would have gone for 80 mph valley gusts.  Nevertheless, I'll be making a mental note to pay closer attention to the CBL depth and the strength of flow throughout the CBL, especially for potential events in mid June when the surface heating is so strong.

Wednesday, June 15, 2016

Southwest Bakefest on Tap

Over the next several days, portions of the southwest U.S. will experience a warming trend leading to fry-an-egg-on-the-sidewalk conditions as a high amplitude ridge sets up over the region.  The 500-mb heights look to be about as high as they get, exceeding 6000 meters (6 km) near the center of the ridge.  For example, in the GFS forecast for 0000 UTC 20 June (6 PM MDT Sunday), 500-mb heights exceed 6000 meters at a few locations in Arizona, New Mexico, and Colorado.  Temperatures at 925-mb, roughly 750 meters above sea level, exceed 40ºC (104ºF) across most of Arizona (Note: this level is below ground for high-elevation regions, but illustrates the extreme heat for lower elevation portions of the state).

0600 UTC 15 June GFS 500-mb height and 925-mb temperature forecast valid 0000 UTC 20 June
The National Weather Service has issued an excessive heat watch for much of southern California and Arizona.
Source: NWS
Excessive heat in that part of the world means an event fit for neither man nor snake.  I pulled up the National Weather Service grid-point forecast for the Phoenix airport and forecast maximum temperatures climb from 103ºF today to 119ºF on Sunday.  In the extended (not shown), forecast highs are 119ªF on Monday and 117ºF on Tuesday.  The all-time record high in Phoenix is 122ºF, set on June 26th, 1990.  

Source: Phoenix
This is still a relatively long lead time forecast, so there's some uncertainty in just how high it will go, but an oppressively hot situation looks quite likely.  Right now, northern Utah looks to be on the periphery of the worst temperatures, meaning temperatures above average this weekend (high 80s at the Salt Lake airport), but not at record levels.  After that, we'll have to see.  

Monday, June 13, 2016

Yesterday's Strong Storms

After doing a post yesterday on some of the subtleties of convection during the morning and early afternoon yesterday (see prior post The Unusual Distribution of Cumulus Clouds Today), Mother Nature decided to crank things up and give us some strong storms later in the day.

The afternoon sounding from the Salt Lake City International Airport sets the stage.  With daytime surface heating and abundant atmospheric and soil moisture, the surface-based convective available potential energy (CAPE, a theoretical measure of the amount of energy a parcel of air would have if lifted vertically) was 2277 J/kg, a remarkably high value for northern Utah.  Mixing out the shallow surface layer gives lower values, but this is a sounding consistent with deep convection and strong updrafts.

Source: SPC
And we got some strong storms, some of which were long lived.  Perhaps the most impressive was the cell that tracked from the West Desert, across I-80, over the Great Salt Lake, and eventually to Willard, following the green line below.

KMTX 0.5º Radar Reflectivity at 0046 UTC (1846 MDT) 12 June

KMTX 0.5º Radar Reflectivity at 0259 UTC (0859 MDT) 12 June

Intrepid University of Utah storm chaser Sara Bang tweeted the photo below showing golf-ball sized hail that she intercepted along I-80.

Based on the time of her tweet, the hail was likely produced by the storm in the radar images above, which eventually produced 1.5 inch diameter hail in Willard and Perry as it crossed I-15 near Willard Bay.

Source: NWS
I suspect that there will be some dents on vehicles in these areas.

The Salt Lake Valley got some hail as well, although the largest report I saw was dime sized.  The storm that produced the hail was well-developed, with the visual characteristics of a weak mesocyclone.  From my house in the Avenues, looking southwest toward the southern Oquirrhs, the storm featured a well-developed wall cloud, characterized by a locally low cloud base, and a precipitation shaft consistent with the forward-flank downdraft.

I'm no convective storm chaser, so feel free to comment on this interpretation.  The anvil trained off downstream and produced some mammatus over the University of Utah.

More storms are likely today.  Although the shear is less favorable for such strong storms, the CAPE looks to be high.  Keep an eye to the sky and an ear out for watches and warnings as discerning between thunderstorms and severe thunderstorms is notoriously difficult in our part of the world.

Sunday, June 12, 2016

The Unusual Distribution of Cumulus Clouds Today

As far as cumulus clouds go, to day was pretty unusual in the Wasatch.  Usually during the summer, we have a deep surface-based mixed layer driving thermals that produce clouds with bases well above mountain-top level.  Under such conditions, there's usually only one layer of cumulus clouds and cloud bases are at about the same elevation over the valley and mountains.

That wasn't the case today.  While on Mt. Raymond, we observed shallow cumulus clouds to the northeast in the area around the lower terrain north and east of Mill Creek Canyon.  Presumably this caused some overcast if you were in that area, or at least partly to mostly cloud skies, but for us, it was undercast.  Meanwhile, at higher elevations, a completely distinct layer of cumulus with higher cloud bases formed over the central Wasatch.

Here's another perspective a bit later, although by this time, the lower clouds wer beginning to burn off.

What made today unusual was the complex layering of the atmosphere over northern Utah.  At low levels, a relatively well mixed layer was found (layer 1 below), which, with a little surface heating, supported the lower level cumulus clouds that formed the lower-level cumulus clouds.  This layer was capped by a strong stable layer (layer 2 below), so these low-level cumulus clouds were confined to low elevations (at least in the morning - they may penetrate more deeply this afternoon).  This stable layer is also keeping a lid on the atmosphere over the Salt Lake Valley, leading to hazy conditions.  Above this layer was another well mixed layer (layer 3) that supported the higher cumulus that was forming over the high terrain of the central Wasatch.  

All of this made for great cloud watching from the higher peaks.