Despite my grumblings about frustrating forecasting of hit-and-miss convection, it's been a pretty good May in the Salt Lake Valley. Any time you can make it until late May with predominantly green foothills you have to be happy.
That's about to change.
Tomorrow marks the first day of meteorological summer, which covers June, July, and August (sorry astronomers, your seasonal definitions based on solstices and equinoxes are LAME and not used by meteorologists).
Not only is tomorrow the first day of summer, but it also will mark a warmup that marks entry into the hottest stretch of weather that we've had all year. As can be seen in the water vapor image and GFS analysis for 1200 UTC this morning, a high amplitude ridge lurks along the Pacific coast and is moving slowly eastward.
Although we've seen some days in the 80s this year, and a max of 88 on May 14, it looks like we will eclipse 90 later in the week and see a sustained stretch of summer-like temperatures.
For those of you looking for late season turns, you'd better get on it ASAP. We'll probably see a loss of 2 inches of snowpack water equivalent a day with a warm pattern like this.
Oh the humanity!
Tuesday, May 31, 2016
Monday, May 30, 2016
Frary Peak Splendor
Frary Peak, high point on Antelope Island |
I probably missed the green grass and wildflower peak by two weeks, but it was still colorful on north aspects, which the trail frequents as it moves southward along the Frary Peak ridgeline.
The summit is hidden for most of the hike, until you are within about a half mile.
On the trip I saw bison (on the plains in the distance) and these fellas, which I think are big horn sheep.
Summit view of America's great inland sea (i.e., the Great Salt Lake), with the Stansbury Mountains and Deseret Peak in the distance. For those of you looking for something to do next weekend, the Twin Couloirs looked quite inviting from here.
Looking southeast toward the central Wasatch, showing what a formidable barrier they pose for northwesterly flow. Pretty much nothing in the way until you hit the east bench.
Looking north toward Buffalo Point, Fremont Island, and the Bear River Bay.
As Yogi Berra said, "you can observe a lot just by watching." With relatively weak flow over northern Utah this morning, convective initiation occurred preferentially over the high terrain of the Wasatch, Oquirrh, and Stansbury ranges. Note how the clouds are training off the the east (left), consistent with the large-sale northwesterly flow.
On the descent, a nice view of the northern Wasatch Front with Willard and Ben Lomond Peaks in the center.
Such a shame that the snow has gone so fast this year.
Sunday, May 29, 2016
Lightning Safety Lessons
I need to pick on myself today for poor lightning safety practices. Much like avalanche accidents, human factors often come to play in lightning accidents.
As I was heading out for a quick mountain bike, a cell was popping over the Oquirrhs. It wasn't much to be concerned with at the time, but I made a mental note to keep an eye on it. Plus, I needed to be somewhere later and had to get my ride in.
The climb from the valley to the ridge was uneventful, other than running into this not-so-friendly fellow.
I know little about snakes, but I come across one about once a month in the warm season. Usually they are gopher snakes. I'm not sure what this one was. It was fairly non-aggressive and wasn't rattling, but a close look at the tail suggested it may have been a rattlesnake that had lost the rattle. I watched him slither into the grass and kept my distance.
Getting back to lightning safety, I didn't hear any thunder on the climb, but on the summit, although the main cell was in the distance, it was clear that the anvil had overspread me.
Anvils are capable of producing lightning, so being somewhat removed from the main cell is no guarantee of safety. As I rode along the trail at elevation, I heard thunder, which was a tell-tale sign that I should have turned around earlier.
I made it home safely and a quick look at lightningmaps.org showed now cloud-to-ground strikes anywhere near my ride. However, a post-ride assessment show it would have been best to wait.
As I was heading out for a quick mountain bike, a cell was popping over the Oquirrhs. It wasn't much to be concerned with at the time, but I made a mental note to keep an eye on it. Plus, I needed to be somewhere later and had to get my ride in.
The climb from the valley to the ridge was uneventful, other than running into this not-so-friendly fellow.
I know little about snakes, but I come across one about once a month in the warm season. Usually they are gopher snakes. I'm not sure what this one was. It was fairly non-aggressive and wasn't rattling, but a close look at the tail suggested it may have been a rattlesnake that had lost the rattle. I watched him slither into the grass and kept my distance.
Getting back to lightning safety, I didn't hear any thunder on the climb, but on the summit, although the main cell was in the distance, it was clear that the anvil had overspread me.
Anvils are capable of producing lightning, so being somewhat removed from the main cell is no guarantee of safety. As I rode along the trail at elevation, I heard thunder, which was a tell-tale sign that I should have turned around earlier.
I made it home safely and a quick look at lightningmaps.org showed now cloud-to-ground strikes anywhere near my ride. However, a post-ride assessment show it would have been best to wait.
Saturday, May 28, 2016
Frustrating Forecasting
Developing thunderstorm over the Oquirrh Mountains yesterday morning |
It does look like we'll be getting a drying out and a warming up early next week. Probably by next Wednesday I'll be wishing for a return of the unsettled weather!
Thursday, May 26, 2016
What Is the PDO?
Anyone who follows seasonal predictions, including those critical to Wasatch Weather Weenies like snowfall, is immediately confronted with an acronym stew of climate indices such as ENSO, PNA, AO, NAO, PDO, IPO, QDO, MJO, etc.
Driving mechanisms
This post is concerned with the PDO, or Pacific Decadal Oscillation, because I receive many questions and comments regarding its use for seasonal snowfall outlooks over western North America.
What is the PDO?
If we skip over the gory statistical details, the PDO is simply the dominant pattern of sea-surface temperature (SST) variability in the North Pacific. The positive (a.k.a. warm) phase of the PDO features a horseshoe of relatively warm (compared to climatology) SSTs along the west coast of North America and the eastern subtropical North Pacific with relatively cool SSTs over the midlatitude western and central Pacific.
PDO Positive Phase. Source: Wikipedia. |
During the "cool" or negative phase, the pattern is reversed.
Discovery
By the mid 1990s, scientists recognized that an abrupt, widespread change in the climate of the North Pacific Basin occurred in the late 1970s. They were also identifying shifts in ecological indicators, such as production levels of Pacific salmon, that occurred on time scales of about a decade.
Steven Hare, a fisheries scientist at the University of Washington, first used the term Pacific Decadal Oscillation in 1996. Subsequently, Nate Mantua, an atmospheric scientist at the University of Washington and an avid fisherman, led the seminal paper identifying the main characteristics of the PDO and its relationship to salmon production in 1997.
Discovery
By the mid 1990s, scientists recognized that an abrupt, widespread change in the climate of the North Pacific Basin occurred in the late 1970s. They were also identifying shifts in ecological indicators, such as production levels of Pacific salmon, that occurred on time scales of about a decade.
Steven Hare, a fisheries scientist at the University of Washington, first used the term Pacific Decadal Oscillation in 1996. Subsequently, Nate Mantua, an atmospheric scientist at the University of Washington and an avid fisherman, led the seminal paper identifying the main characteristics of the PDO and its relationship to salmon production in 1997.
Mantua et al. (1997) |
Nate's contributions in this area are evidence of the Anthony Doerr quote that "there is a connection between thinking and fishing mostly because you spend a lot of time up to your waist in water without a whole lot to keep your mind busy."
Driving mechanisms
The PDO was identified statistically and is not a single phenomenon. Research over the past 25 years shows that the PDO reflects the combined influence of several atmospheric and oceanic processes operating at differing time scales. One is ENSO, the El Nino/Southern Oscillation, with El Nino and La Nina reflecting the warm and cold phases of ENSO, respectively. The relationship between the PDO and ENSO is apparent in the illustration above, which in addition to showing the North Pacific SST pattern associated with the PDO positive phase, also shows a tongue of anomalously warm water in the tropical Pacific consistent with El Nino, the warm phase of ENSO. ENSO contributes to the PDO by influencing the mid-latitude atmospheric circulation over the North Pacific. Other mechanisms affecting the PDO include interactions between the Aleutian Low and the North Pacific Ocean, a phenomenon known as "reemergence" in which ocean temperature anomalies from the prior cool season persist at depth in the ocean and reemerge the next cool season, and other aspects of ocean dynamics in the north Pacific. Yeah, there's a lot going on, as illustrated by the "summary" view below.
The key point is that the fluctuations in North Pacific SST that we call the PDO are a reflection of a several processes operating in the atmosphere and ocean.
Source: Newman et al. (2016) |
Implications for climate variability and prediction
The fact that the PDO is a reflection of many processes has a number of implications for climate variability and prediction. For one, correlation with the PDO does not necessarily imply causality. For example, a relationship between the PDO and snowfall in a given region could reflect an alternate forcing mechanism, such as ENSO, rather than the PDO. Assigning causal linkages to the PDO should be done very cautiously. For two, combining the PDO with other modes of climate variability like ENSO to try and improve predictions for any given season partly represents a form of "double counting" since the two are intrinsically linked. Whether or not this ultimately degrades the usefulness of seasonal predictions is unclear, but one needs to be cautious. Like an onion, the more you peel it, the more it stinks.
For those who are really interested in gory details about the PDO, a review article by Matt Newman and colleagues entitled The Pacific Decadal Oscillation, Revisited, is about to appear in the Journal of Climate. It's paywalled, but freely available in early release mode to those of you from campus or who have a subscription for American Meteorological Society journals.
Correction: The Pacific Decadal Oscillation, Revisited, is public access, so anyone can have a look. Thanks to the authors (or their funding agencies!) for making that happen.
Correction: The Pacific Decadal Oscillation, Revisited, is public access, so anyone can have a look. Thanks to the authors (or their funding agencies!) for making that happen.
Tuesday, May 24, 2016
The Central Wasatch Need Better Transit and a Better Fee Plan
It's a bluebird powder day a few years in the future and you're heading out for a backcountry tour. You haven't picked a destination yet, so you bring your Mill Creek Pass in case you tour in Mill Creek, your interagency access pass in case you go to Cardiff Fork, your UDOT Snowpark Pass in case you tour Butler Fork, and your Town of Alta Snowpark in case you decide to up-and-over from Alta to Big Cottonwood.
You pick up your buddies, decide to tour Wills Hill due to the high avalanche hazard, and decide to park at one of the Park-n-Rides at the bottom of Big Cottonwood. Unfortunately, you got a late start and the lots are full. You decide your best bet is to drive.
Double unfortunately, it's total gridlock at the bottom of the canyon. That used to be a thing in Little Cottonwood, but now it's a thing in Big Cottonwood too.
So, you inch up Big Cottonwood, but when you get to the Solitude Lot, not only is it $10 to park (that's not covered by your fee plans either), but the lot is full. You'd park on the road, but that's impossible. Cars stretch as far as the eye can see.
All of these fee programs, but none of them have addressed the most critical issue in the canyons: Improving the accessibility, frequency, and reliability of mass transit.
These were my thoughts when I picked up the Salt Lake Tribune this morning and learned that the US Forest Service is considering implementing a fee program in Big and Little Cottonwood Canyon.
To be sure, I'm not opposed to fees. I buy a National Parks and Interagency Access Pass every year. For me, the proposed US Forest Service fees in the Cottonwoods would not be an additional financial burden (although I am sensitive to how such a program might reduce recreation access for other groups and individuals).
No, what concerns me is the potential for piecemeal implementation of these and other fees while having little impact on the real challenges facing the central Wasatch. The US Forest Service desires to improve parking lots, picnic areas, and trails. While a laudable goal, it is the automobile that is despoiling public recreation in the Wasatch. It's difficult to imagine that the proposed $6 three-day or $45 annual fee is going to do anything about that, especially since there is no public transit in the Cottonwoods during the hiking season.
What is needed is a real transportation plan, a strategy to fund it, and a unified, non-balkanized fee program to broadly support recreation infrastructure in the central Wasatch. Yes, I know I live in a dream world, but this is what I want, as opposed to a litany of fee programs that fail to address the 800 pound gorilla in the zoo.
You pick up your buddies, decide to tour Wills Hill due to the high avalanche hazard, and decide to park at one of the Park-n-Rides at the bottom of Big Cottonwood. Unfortunately, you got a late start and the lots are full. You decide your best bet is to drive.
Double unfortunately, it's total gridlock at the bottom of the canyon. That used to be a thing in Little Cottonwood, but now it's a thing in Big Cottonwood too.
So, you inch up Big Cottonwood, but when you get to the Solitude Lot, not only is it $10 to park (that's not covered by your fee plans either), but the lot is full. You'd park on the road, but that's impossible. Cars stretch as far as the eye can see.
All of these fee programs, but none of them have addressed the most critical issue in the canyons: Improving the accessibility, frequency, and reliability of mass transit.
These were my thoughts when I picked up the Salt Lake Tribune this morning and learned that the US Forest Service is considering implementing a fee program in Big and Little Cottonwood Canyon.
To be sure, I'm not opposed to fees. I buy a National Parks and Interagency Access Pass every year. For me, the proposed US Forest Service fees in the Cottonwoods would not be an additional financial burden (although I am sensitive to how such a program might reduce recreation access for other groups and individuals).
No, what concerns me is the potential for piecemeal implementation of these and other fees while having little impact on the real challenges facing the central Wasatch. The US Forest Service desires to improve parking lots, picnic areas, and trails. While a laudable goal, it is the automobile that is despoiling public recreation in the Wasatch. It's difficult to imagine that the proposed $6 three-day or $45 annual fee is going to do anything about that, especially since there is no public transit in the Cottonwoods during the hiking season.
What is needed is a real transportation plan, a strategy to fund it, and a unified, non-balkanized fee program to broadly support recreation infrastructure in the central Wasatch. Yes, I know I live in a dream world, but this is what I want, as opposed to a litany of fee programs that fail to address the 800 pound gorilla in the zoo.
Monday, May 23, 2016
The Great Melt Is Underway
Anyone who has read the news won't be surprised to learn that it has been an exceptionally hot northern hemisphere cold season (November to April, hereafter just cold season) globally, especially in the Arctic. Let's have a quick look at the numbers. Because I'm being lazy, I'm going to mix two global temperature data sets, one produced by the NASA Goddard Institute for Space Studies (NASA-GISS) and the other produced by the National Centers for Environmental Information (NCEI). Neither of their web sites produced everything I want, but I can get it if I mix and match.
Let's begin with the global temperature anomalies for November to April, which show the past cold season really was quite remarkable, running more than 1ºC (2ºF) above the 20th century average. The tremendous surge during this period is largely a result of long-term global warming combined with El Nino.
The plot below shows the distribution of temperature anomalies for this period (relative now to the 1951–1980 average), illustrating the large positive anomalies in the tropics and most of the northern hemisphere, especially the arctic. In contrast, the higher latitudes of the southern hemisphere were closer to the 1951-1980 average or in some cases below it.
Another way to look at this is to average the temperature anomalies around a latitude circle (called a "zonal average) and then plot them from the south to north pole (left to right below). This shows the near-average temperatures in the high latitudes of the southern hemisphere and the extreme warmth in the high latitudes of the northern hemisphere.
The tendency for the Arctic to warm faster than the global average temperature and exhibit larger positive temperature anomlies is called Arctic amplification. It is driven by several factors, but feedbacks related to the decline in Arctic sea ice is dominant.
And, speaking of sea ice, the Arctic sea-ice extent is currently running well below prior seasons in the satellite record. Perhaps a record minimum will be reached in September.
Let's begin with the global temperature anomalies for November to April, which show the past cold season really was quite remarkable, running more than 1ºC (2ºF) above the 20th century average. The tremendous surge during this period is largely a result of long-term global warming combined with El Nino.
Source: NCEI |
Source: NASA-GISS |
Source: NASA-GISS |
And, speaking of sea ice, the Arctic sea-ice extent is currently running well below prior seasons in the satellite record. Perhaps a record minimum will be reached in September.
Source: NSIDC |
Although we may see a temporary decline in global temperature anomalies from their El Nino fueled highs this past cold season, the global warming train has left the station and is accelerating. The great melt is underway.
Saturday, May 21, 2016
Overnight Deluge
A slow moving precipitation band brought significant rain to the Wasatch Front late last night and early this morning, especially north of Salt Lake City. Radar imagery below shows the strong returns over the northern Wasatch and lowlands upstream (northern most red rectangle).
As of 9:30, Snowbasin-Middle Bowl recorded 0.81" of water equivalent since 4 AM. And yes, some of that precipitation has fallen as snow on the upper mountain.
Ogden airport picked up a half inch, which is a good dousing for the lawns and gardens.
Further south, the central Wasatch (southern rectangle) were late to get in on the action. Alta-Collins has had only .12" of water equivalent since 3 AM, although temperatures are now down to 30ºF, putting that site above the melting layer for now, and they may get a couple more hours of snow. A little something for the diehards.
Meanwhile, in the Salt Lake Valley, the U is up to .27", which should be enough to keep my sprinklers off for another week, which is good because I just discovered that I have some work to do to get some of mine working.
As of 9:30, Snowbasin-Middle Bowl recorded 0.81" of water equivalent since 4 AM. And yes, some of that precipitation has fallen as snow on the upper mountain.
Ogden airport picked up a half inch, which is a good dousing for the lawns and gardens.
Further south, the central Wasatch (southern rectangle) were late to get in on the action. Alta-Collins has had only .12" of water equivalent since 3 AM, although temperatures are now down to 30ºF, putting that site above the melting layer for now, and they may get a couple more hours of snow. A little something for the diehards.
Meanwhile, in the Salt Lake Valley, the U is up to .27", which should be enough to keep my sprinklers off for another week, which is good because I just discovered that I have some work to do to get some of mine working.
Friday, May 20, 2016
Another Blow Is Coming
It was an eventful day yesterday with a power outage on campus in the morning, storms in the late afternoon (northern Wasatch Front) and evening (Salt Lake Valley), and more power outages overnight. The Salt Lake Tribune reports that 85,000 people lost power overnight after a "cascade of outages" struck numerous areas of the Wasatch Front an Tooele. If high winds were indeed the cause, chalk this one up to cheapness. Bury those electrical lines and we wouldn't be as vulnerable to these events.
Turning from commentary to weather, I mentioned in Wednesday's post that the cold front would tease us Thursday afternoon and then retreat back to the north and the west and that's exactly what has happened. Check out how the frontal precipitation band pushes into northern Utah, doesn't like what it finds (insert your favorite colorful reason why here), and then decides to tuck tail and move back to the north and west.
You don't see that every day and it is a result of the digging trough along the Pacific coast, which has resulted in a backing (counterclockwise turning) and intensification of the flow over the western interior. So far, that flow intensification hasn't been felt on the ground in most of the Salt Lake Valley. There are, however, hints that things are going to change as the day progresses. Note, for example, the 40 knot flow at Stockton Bar and 30 knot flow at Dugway in the MesoWest plot below.
Those are areas where the cold pool from last night's storm has mixed out. That cold pool is currently preventing the strong flow from aloft from mixing to the surface in the Salt Lake Valley and some other lowland locations. Indeed, the morning sounding shows a deep cold pool, but it is topped by strong flow, suggesting that we'll see a rapid increase in wind speed once that cold pool has been eroded.
And, the NAM forecast for 0000 UTC (6 PM MDT) this afternoon shows a band of 700-mb flow of 40-50 knots extending from southwest Utah over the Salt Lake Valley. Another blow is coming.
So, if you are looking at the limp flags this morning and are wondering if the high-wind warning issued by the NWS for western Utah and the Salt Lake Valley is going to verify, have no fear.
Soon those winds will be here and they may be bringing dust with them.
Turning from commentary to weather, I mentioned in Wednesday's post that the cold front would tease us Thursday afternoon and then retreat back to the north and the west and that's exactly what has happened. Check out how the frontal precipitation band pushes into northern Utah, doesn't like what it finds (insert your favorite colorful reason why here), and then decides to tuck tail and move back to the north and west.
You don't see that every day and it is a result of the digging trough along the Pacific coast, which has resulted in a backing (counterclockwise turning) and intensification of the flow over the western interior. So far, that flow intensification hasn't been felt on the ground in most of the Salt Lake Valley. There are, however, hints that things are going to change as the day progresses. Note, for example, the 40 knot flow at Stockton Bar and 30 knot flow at Dugway in the MesoWest plot below.
Those are areas where the cold pool from last night's storm has mixed out. That cold pool is currently preventing the strong flow from aloft from mixing to the surface in the Salt Lake Valley and some other lowland locations. Indeed, the morning sounding shows a deep cold pool, but it is topped by strong flow, suggesting that we'll see a rapid increase in wind speed once that cold pool has been eroded.
And, the NAM forecast for 0000 UTC (6 PM MDT) this afternoon shows a band of 700-mb flow of 40-50 knots extending from southwest Utah over the Salt Lake Valley. Another blow is coming.
So, if you are looking at the limp flags this morning and are wondering if the high-wind warning issued by the NWS for western Utah and the Salt Lake Valley is going to verify, have no fear.
Soon those winds will be here and they may be bringing dust with them.
Thursday, May 19, 2016
A Little "Love" from the Storm Prediction Center
The Storm Prediction Center is giving northern Utah a little love, putting us in the marginal risk category for severe thunderstorms for today and tonight.
The impetus for this is the expected late-day increase in thunderstorms near and along the cold front, combined with a deep boundary layer and strong low-level flow that could allow some storms to organize and produce strong to severe wind gusts and hail. These storm-environment characteristics show up fairly well in the NAM sounding for 2300 UTC (5 PM MDT) this afternoon.
A marginal risk means that these severe storms would be limited in organization and longevity, or low in coverage and marginal in intensity. Thus, not everyone will see a severe storm, but you should keep an eye on the weather.
Source: SPC |
A marginal risk means that these severe storms would be limited in organization and longevity, or low in coverage and marginal in intensity. Thus, not everyone will see a severe storm, but you should keep an eye on the weather.
Wednesday, May 18, 2016
Trouble Is Lurking in the North Pacific
Trouble is lurking this morning in the form of an upper-level trough that is presently over the northeast Pacific.
The latest model runs call for this trough to dig along the Pacific coast and be centered over southern Oregon by 6 PM MDT Friday.
The forecast for northern Utah on Thursday is a bit touch-and-go as the cold front ahead of the upper-level trough is expected to push into the northern part of the state. The latest NAM puts the surface front right at the Salt Lake City airport at 0300 UTC 20 May (9 PM MDT Friday), giving us a chance of some showers and thunderstorms late tomorrow and early tomorrow evening.
This is not a simple cold frontal passage, however. The models tease us with the front late tomorrow and tomorrow evening and then push it back to the north and west. As a result, during the day on Friday, we're forecast to be in strong southerly flow, which could mean a possible dust event Friday afternoon.
All in all, it looks more interesting than the boring weather we've had the past couple of days, but much depends on precisely how far south and east the front pushes late tomorrow. Keep an eye on the forecast. I'm hoping it pushes far enough south and east that we get some rain. I haven't even had to think about watering the lawn and gardens yet this year and would like to keep it that way for a while longer.
The latest model runs call for this trough to dig along the Pacific coast and be centered over southern Oregon by 6 PM MDT Friday.
The forecast for northern Utah on Thursday is a bit touch-and-go as the cold front ahead of the upper-level trough is expected to push into the northern part of the state. The latest NAM puts the surface front right at the Salt Lake City airport at 0300 UTC 20 May (9 PM MDT Friday), giving us a chance of some showers and thunderstorms late tomorrow and early tomorrow evening.
This is not a simple cold frontal passage, however. The models tease us with the front late tomorrow and tomorrow evening and then push it back to the north and west. As a result, during the day on Friday, we're forecast to be in strong southerly flow, which could mean a possible dust event Friday afternoon.
All in all, it looks more interesting than the boring weather we've had the past couple of days, but much depends on precisely how far south and east the front pushes late tomorrow. Keep an eye on the forecast. I'm hoping it pushes far enough south and east that we get some rain. I haven't even had to think about watering the lawn and gardens yet this year and would like to keep it that way for a while longer.
Tuesday, May 17, 2016
Quote of the Week
Source: The Onion |
"Pseudoscience is a societal mental disease too powerful to be fought in the public arena. The media — the public's main source of information — are more interested in what is popular than what is right. However, behind the relative protection of classroom walls, we have an opportunity to reach the future citizenry and thus a hope that our grandchildren and their children will not succumb to the irrationality that has afflicted our generation."– Sadri Hassani in the May 2016 Physics Today
Monday, May 16, 2016
Troughy
During the cool season the past few years, it seems like upper-level ridging has been an omnipresent feature over the western United States. That's not the case at present. Cooler air and upper-level troughing moved over Utah yesterday and the GFS forecast shows another one moving in right behind it.
We may get a break in the action between the troughs, especially if the second one opts to dig down the coast, but for the most part the pattern over the next several days looks springy, with some showers and thunderstorms scattered about. The NWS forecast summarizes this nicely.
No need to panic as there should be periods of dry weather in there with opportunities for outdoor activities, but keep an eye to the sky and adjust plans accordingly.
Meanwhile, on the east coast, check out the photo below from Caribou Maine this morning. They've had 3.5" of snow so far today, the most on record so late in the season.
Reports are up to 7" in the surrounding region.
Further evidence of the tortuous weather of the northeast US.
We may get a break in the action between the troughs, especially if the second one opts to dig down the coast, but for the most part the pattern over the next several days looks springy, with some showers and thunderstorms scattered about. The NWS forecast summarizes this nicely.
No need to panic as there should be periods of dry weather in there with opportunities for outdoor activities, but keep an eye to the sky and adjust plans accordingly.
Meanwhile, on the east coast, check out the photo below from Caribou Maine this morning. They've had 3.5" of snow so far today, the most on record so late in the season.
Source: NWS Caribou Forecast Office |
Further evidence of the tortuous weather of the northeast US.
Saturday, May 14, 2016
Hot, But Change Is Coming
Although it fell short of the daily record (89ºF in 2013), today's high of 88ºF was the highest of the calendar year so far. Temperatures were in the 80s beginning just before 11 PM, giving us a day more typical of late June than mid May.
More seasonable weather returns tomorrow. Hooray. I can live without the 80s for a while longer.
Source: MesoWest |
Thursday, May 12, 2016
GFS Improvements
Significant upgrades were made by the National Centers for Environmental Prediction (NCEP) to the Global Forecast System (GFS) yesterday. Perhaps the most significant is a shift from three-dimensional to four-dimensional hybrid ensemble-variational data assimilation. This, along with other changes to add or improve the assimilation of several satellite and aircraft datasets, should improve the initial analysis. A complete list of the gory details is available in Technical Implementation Notice 16-11.
In celebration, NOAA issued a slick announcement with some fancy visualization, including the loop below.
The meteorological world is waiting, however, to see if these upgrades make the GFS more competitive relative to the ECMWF Integrated Forecast System (IFS, typically called the ECMWF, EC, or Euro).
In the future, I'm hoping we will see some significant upgrades to the GFS cloud and precipitation parameterization, which clearly has problems over the mountainous western United States.
In celebration, NOAA issued a slick announcement with some fancy visualization, including the loop below.
The meteorological world is waiting, however, to see if these upgrades make the GFS more competitive relative to the ECMWF Integrated Forecast System (IFS, typically called the ECMWF, EC, or Euro).
In the future, I'm hoping we will see some significant upgrades to the GFS cloud and precipitation parameterization, which clearly has problems over the mountainous western United States.
Wednesday, May 11, 2016
A Green Monster?
Yesterday evening, the foothills were so green and the view so spectacular that I could hear Julie Andrews singing "the hills are alive with the sound of music" in my left ear.
Regularly spaced deluges have led to a remarkably lush carpet in many areas.
Regularly spaced deluges have led to a remarkably lush carpet in many areas.
But is all this grass a green monster lying in wait? Each year I see reports on what kind of fire season to expect. A recent report on Fox-13 called for an average fire season, but what does that mean?
Nothing.
We are living in a world where the baseline for fire is changing rapidly. Much of the arid west has and is experiencing rapid development, much of it in the wildland interface. Our vulnerability has never been higher.
Now add the rise in wildfire intensity, which has occurred for many reasons including past wildland management practices, invasive species, disease, and climate change. With regards to the latter, there is quite a bit of variability from year to year and periods of wet, cool weather, but the dice are increasingly loaded for warmer weather, which even if the rainfall is near average, leads to drier fuels because of increased evapotranspiration.
This new reality requires vigilance and preparation each and every year. It is best to expect the worst and hope for the best.
Nothing.
We are living in a world where the baseline for fire is changing rapidly. Much of the arid west has and is experiencing rapid development, much of it in the wildland interface. Our vulnerability has never been higher.
Now add the rise in wildfire intensity, which has occurred for many reasons including past wildland management practices, invasive species, disease, and climate change. With regards to the latter, there is quite a bit of variability from year to year and periods of wet, cool weather, but the dice are increasingly loaded for warmer weather, which even if the rainfall is near average, leads to drier fuels because of increased evapotranspiration.
This new reality requires vigilance and preparation each and every year. It is best to expect the worst and hope for the best.
Monday, May 9, 2016
Let's Build a Mountain and Make It Rain!
Source: Tinelot Wittermans via Wikipedia |
Weather modification is the term given to the alteration of weather by humans. It can be intentional (e.g., cloud seeding) or inadvertent (e.g., effects of aerosols and land-use changes on precipitation).
We are doing both today. Cloud seeding is intentional, but it really isn't really all that well understood how it works in nature and what the unintended consequences might be. Modification of local meteorology by cities, especially large ones, is inadvertent but has a robust and clear signal through the urban heat island and changes in precipitation patterns. Of course we are also running the ultimate inadvertent weather modification experiment by jacking up long-lived greenhouse gas concentrations and then seeing what happens.
The efficacy and ethics of weather modification has long been a point of debate in my field (see American Meteorological Society information statements Inadvertent Weather Modification and Planned Weather Modification through Cloud Seeding). The use of weather modification during warfare, something that the United States did in southeast Asia during the Vietnam war (e.g., Operation Popeye), has been banned by the United Nations.
Perhaps the UAE would be willing to negotiate with California for the Sierra Nevada. That would be a win for them and a win for Utah since the moisture flux into the Great Basin would be much higher if that high barrier wasn't upstream. Calling Kennecott?
Sunday, May 8, 2016
Efficient Spillover of Precipitation across Wasatch Range
A quick look at the radar loop this morning shows that the Salt Lake Valley will be seeing steady precipitation for most of the morning.
A closer look reveals that the broader-scale precipitation shield is moving southward as the echoes move from the northeast. This is a classic "wrap around" situation in which we receive precipitation being generated in the northeasterly flow behind the upper level low. Those cells are being generated well above crest level as the flow at mountaintop level shifted to southwesterly overnight.
Of one goes up a bit higher, however, to 500 mb (about 18,000 feet above sea level), one finds the magic northeasterlies and the layer where those cells are being generated.
One might wonder why with northeasterly flow we're not seeing downsloping and drying on the west side of the Wasatch Range. The answer is wind shear. The upper-level flow is northeasterly, but as can be seen in the Ogden Peak time series, the flow at crest level has a westerly component. Surface observations in the valleys show generally light, disorganized flow. Thus, there really is no downslope and we're seeing efficient spillover of precipitation across the Wasatch Range.
The rain will help keep the foothills green going and the sprinklers off for a while longer and is certainly appreciated.
A closer look reveals that the broader-scale precipitation shield is moving southward as the echoes move from the northeast. This is a classic "wrap around" situation in which we receive precipitation being generated in the northeasterly flow behind the upper level low. Those cells are being generated well above crest level as the flow at mountaintop level shifted to southwesterly overnight.
Of one goes up a bit higher, however, to 500 mb (about 18,000 feet above sea level), one finds the magic northeasterlies and the layer where those cells are being generated.
One might wonder why with northeasterly flow we're not seeing downsloping and drying on the west side of the Wasatch Range. The answer is wind shear. The upper-level flow is northeasterly, but as can be seen in the Ogden Peak time series, the flow at crest level has a westerly component. Surface observations in the valleys show generally light, disorganized flow. Thus, there really is no downslope and we're seeing efficient spillover of precipitation across the Wasatch Range.
The rain will help keep the foothills green going and the sprinklers off for a while longer and is certainly appreciated.
Friday, May 6, 2016
Graduation Rumblings
Although the University of Utah general commencement was last night, most college convocations are today, ensuring that campus is bustling with activity. The morning dawned, however, with thunderstorms and rain on campus, which surely sent a shiver down the spine of Deans, Administrators, and campus planners.
Radar imagery at 1333 UTC (7:33 AM MDT) showed stronger returns just west of the Wasatch spine east of campus, with two cells further west, including one over campus.
These storms were moving northward and as I write this at 7:50 AM MDT, rain has stopped.
Graduation day was always stressful for me back in the day. We used to have our college reception outdoors, and the dean would always want to know if he needed a tent and would call me for a forecast starting days in advance.
Today, we have a new building and enough room to hold the reception indoors, so I'm off the hook. Nevertheless, nobody likes rain and thunder on campus for graduation.
Despite the early action, I don't think today will be a washout. Showers and thunderstorms will be scattered today, so lets just hope the activity is well timed to allow for dry walks around campus. If thunder roars, head indoors.
Thunderstorm over the University of Utah campus around 7:05 AM MDT this morning. |
These storms were moving northward and as I write this at 7:50 AM MDT, rain has stopped.
Graduation day was always stressful for me back in the day. We used to have our college reception outdoors, and the dean would always want to know if he needed a tent and would call me for a forecast starting days in advance.
Today, we have a new building and enough room to hold the reception indoors, so I'm off the hook. Nevertheless, nobody likes rain and thunder on campus for graduation.
Despite the early action, I don't think today will be a washout. Showers and thunderstorms will be scattered today, so lets just hope the activity is well timed to allow for dry walks around campus. If thunder roars, head indoors.
Thursday, May 5, 2016
Ah, Spring!
There's no better time of year to take advantage of the close proximity of the Avenues foothills than spring. The hills are green, the mountains are white, and the views simply spectacular. Yesterday was especially nice with sunny skies and a high of 82ºF.
We're fortunate to have wilderness and the BST at the offing, but development continues below protected areas. Below is a new McMansion going in just east of Ensign Peak. I'm no geologist, but I'm not sure this is the best place to build a house given the rocks and boulders that have calved off the cliffs above. Society exists by geologic consent, subject to change without notice.
It always amazes me how much aspect affects the ecology in Utah. As arid as the south aspects are, it's pretty lush still on north aspects. Last week the flowers were in bloom here too, but they are past peak now.
Graduation celebrations and ceremonies here at the U are today and tomorrow. Congrats to the class of 2016.
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