Wednesday, September 20, 2017

More September Snows?

Looks like a beautiful sunrise up in the Wasatch this morning, with a dusting of snow covering the mid and upper elevations.

Source: Snowbird
More September snow is in the way, although this is a fairly tricky forecast because the front that will drive our next round of precipitation is expected to slow and pivot as it moves into northwest Utah.

This results in challenges in both the timing and amount of precipitation expected.  This does, however, look to be an event that will produce some additional mid- and upper-elevation snowfall.

Most members of our downscaled SREF product are generating 0.4 to 0.8 inches of water equivalent for the event, with a mean of just over a half inch.  Note that there are contrasts in timing with some members getting things started Thursday afternoon, others later Thursday or Thursday night.
By and large, this looks to be a "dust on dirt" event, with perhaps 2-5 inches of snow for a storm total at Alta.  If that comes through, it would be our biggest storm of the season so far, good for tourism promotion, but otherwise a nuisance for hiking and other fall persuits.  There's a chance of more, but the odds of more than say 8" are low.  Bottom line: My skis remain in the rack.  

Sunday, September 17, 2017

September Snows

Friday's storm brought a bit of the white stuff to the upper-elevations of the Wasatch Range, providing a boost to the morale of skiers and a nice contrast to the comparatively green grassy slopes remaining in early September.

By and large, the pattern over the next several days is more October like than September like.  First, we have a quick moving trough that gives us a brush-by late Monday and Tuesday.  This isn't a very deep trough and it's a close call on the placement of precipitation, but it could bring some light snow accumulations to the high elevations.

Then we have a deeper trough with the attendant cold front currently progged to push through Thursday morning.  This one is far enough out that we should be cautious about reading into details too much, but its a cold system for September (-4ÂșC at 700 mb/10,000 ft) and has some potential to give us a better coating than Friday's storm.

Then, the main upper-level trough and deep cold pocket swing through for next weekend.  Temperatures definitely more like mid October than mid September.

It's been a long time since we had a stretch of weather where things were biased on the cold side of average.  Enjoy!

Saturday, September 16, 2017

Snowbird's Hidden Peak Cam Is Awesome

Snowbird has done a complete upgrade of their web site and perhaps their web cams because they seem so much better than they were a couple of months ago.  The Hidden Peak Cam is amazing.  You can't do it justice with a screengrab, but this morning's is below showing the dusting of snow, but also the abrupt transition of visibility when one gets to the top of what I think is the smoke layer that moved in with the latest cold surge.

Source: Snowbird
This is a meteorological preference, but I'd like to see a time stamp on these images, but I suspect they don't want to spoil them.  There is an indication of how old the images are on the web site.

BTW, it is a bit convoluted how to find the full size images on Snowbird's web site.  The direct link is here.  High frequency animations would also be appreciated (hint hint).

Thursday, September 14, 2017

The Echo Chambers Are Giving Me a Headache

To all the pundits and activists out there acting like you are experts on extreme weather, hurricanes, and climate change, I have only one thing to say.


This is a remarkably complex and difficult subject and you people are running around acting like you have it all figured out.  And there's plenty of room for a beatdown of people on both the right and left of this issue.  Gosh, the articles I am reading and discussions I am seeing are so absolutely horrific and they are setting weather and climate science back decades.

To those on the left who are conflating weather and climate, take a deep breath and let the scientists do their work and figure this out.  Don't lose sight of the fact that the IPCC issued a comprehensive report on extreme weather and climate change in 2012 entitled "Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation."  Here's what they had to say:
"The uncertainties in the historical tropical cyclone records, the incomplete understanding of the physical mechanisms linking tropical cyclone metrics to climate change, and the degree of tropical cyclone variability provide only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences."
"Attribution of single extreme events to anthropogenic climate change is challenging."
And this from the most recent IPCC assessment report, released in 2013.  See in particular the row for "Increases in intense tropical cyclone activity."
Source: IPCC AR5 Summary for Policy Makers
And for those of you on the right who have a smile on your face because of the above comments, wipe it off now.  Note that those statements pertain to cyclone activity.  We know that storm surge associated with tropical cyclones is worsening and will continue to worsen because of sea level rise.  And just because we can't say with confidence that global warming is having a detectable influence on tropical cyclones right now doesn't mean that (i) change isn't happening or (ii) that we won't see a clear trend in the future.  There are good reasons why we expect to see tropical cyclones become more intense and increase in destructive potential with global warming.  Finally, there are also good reasons to expect tropical cyclone precipitation rates to increase as well.  So quit hiding behind the natural variability and we've had storms like this before narrative as if that means we have nothing to worry about.

For those of you interested in a scientific summary of these issues, see Global Warming and Hurricanes on the GFDL web site.  

Ask and You Shall Receive

I know I should be talking about the changes underway in Utah's weather, but I'm still suffering from a case of Irma-itis, amongst other maladies.   So, instead, I want to address some questions being asked by our readers about Irma's track shift.

I am neither a theoretician, nor a hurricane expert, so let me just come out and say it.  I don't understand hurricane dynamics well enough to answer these questions in what I consider a satisfying way.

On the other hand, sometimes it's not worth thinking too much about these things.

The ability to for numerical weather prediction systems (hereafter computer models) to predict the shift in Irma's track reflects the culmination of decades of research not just in atmospheric sciences, but also computer science, remote sensing, and other fields.

A human, even with all the incredible observations we have today, could never have anticipated that shift with such precision days in advance without computer models.  The problem with the way that humans think is that we have to simplify and categorize things.  We need to take shortcuts.  We rely on analogs to past events.  We tend to think linearly, whereas the atmosphere is nonlinear and doesn't always behave in straightforward ways.

In contrast, computer models are not constrained by excessive simplifications, past analogs, or linear thinking. They solve a set of equations based on the conservation of momentum, conservation of mass, conservation of energy, and ideal gas law.  In other words, the laws of physics, and those laws are a beautiful thing.  

Of course, since we are doing this on a computer, some approximations are needed.  In addition, we are limited by computer time and this means we can't directly simulate every physical process.   Nevertheless, a model based on the laws of physics can do things we might not anticipate as humans.  It can predict events that have never happened before.  It does not rely on simplistic, linear thinking, like most humans do.

Our computer modeling capabilities have improved steadily and dramatically since they were first developed circa 1950.  First, we have made huge advances in how we create "initial conditions" for these models, through the development of improved observing systems (especially satellite based) and new techniques for bringing all of that data together into an analysis.  We have been able to add more detail to the simulation (called "resolution"), resulting in the improved simulation of physical processes that influence hurricane intensity and track.  We have developed ensemble modeling systems that produce many forecasts to try to account for the chaotic nature of the atmosphere so that we recognize the uncertainties in the forecast.

So, where does this leave us?  The bottom line is this.  Computer models today largely show us the way.  Yes, there are some phenomenon we struggle with mightily (snowfall in the Wasatch for example) and you can bet there will be a future hurricane that is not as well forecast as Harvey or Irma.  However, no human can integrate the laws of physics in their head.  Meteorologists aren't spending a lot of time on "why," but instead the "what", as in what are the possibilities, what are the hazards and impacts, what are the uncertainties.  Then there is the issue of communicating all of this complexity to the public and decision makers.  It's an end to end process that is imperfect, but the good news, it's getting better and I think there is every reason to be very optimistic that it will get even better in the future.  

Tuesday, September 12, 2017

More Not So Deep Thoughts on Irma Plus Utah Weather

I'm still feeling frisky this morning about several issues, so the not so deep thoughts continue.

Anderson Cooper is clueless
With Irma still threatening the southeast, I continue to scan the news coverage and find appalling statements.  Anderson Cooper has been especially effective at getting under the nerves of this meteorologist.

Last night, while interviewing the Mayor of Jacksonville, which was hit with severe flooding yesterday, he made the dumbfounding statement that "clearly people were caught off guard."  No Anderson, people in mandatory evacuation zones were not caught off guard. 

Social media and other communications challenges
It's been clear in the snippets that I've caught of Anderson that he really likes the caught off guard/surprise narrative.  This is very common amongst reporters because people love that angle.  It makes the story more interesting.

Anderson has frequently brought up the "westward shift" of Irma and how it surprised people.  As a meteorologist, I find this to be grating as well, but in contrast to saying people in mandatory evacuation zones were caught off guard, this has some merit, depending on where you get your weather information from.

Official forecasts from the National Hurricane Center were very cautious not to endorse a specific storm track up either the east or west coast of Florida at long lead time.  They also issued hurricane and storm surge warnings on both coasts, as well as the south coast and Key West.

However, many people do not see those forecasts.  Instead, they see national news, local news, and social media.  In that echo chamber, there is a tendency to gravitate toward especially extreme model forecasts and clusters of model ensembles that do not fully account for uncertainty.

Also an issue are misinterpretations of the NHC "cone of uncertainty."  That graphic is not intuitive for the general public, and needs improvement, but even some broadcast meteorologists don't understand it.

Let me show and example of how this effects the information that people receive.  Below and at left is a summary of the Key Messages for Hurricane Irma issued about 3.5 days prior to the landfall of Irma on Marcos Island.  The cone of uncertainty, which encapsulates the entire Florida peninsula and offshore waters.  The National Hurricane Center simply says that there's a treat of hurricane impacts over the weekend and early next week, with a likelihood of hurricane watches being issued on Thursday.

The right hand side provides an example of what people are seeing on social media, which says very strongly that Irma will hit Miami at Cat 4 or 5 on Sunday.  At that time, one could find model forecasts calling for that track and intensity, and advising people to leave was warranted, but the tweet suggests much greater confidence than evident in National Hurricane Center forecasts.

Traditional and social media today provides a firehose of content that is unfiltered and often without context.  At one time, it was difficult to see the forest through the trees.  Today, it is difficult to see the information through the misinformation.  Note that not all misinformation is malicious.  Sometimes it simply doesn't provide the necessary broader perspective.

This is why, in the case of tropical storms and hurricanes, I strongly urge people to monitor forecasts from the National Hurricane Center and local National Weather Service Offices.  While no forecast is perfect, these are the most reliable available.  The National Hurricane Center, in particular, has a remarkable team of scientists, with strong ties to the research and emergency management communities.  Finally, heed the recommendation of local officials.

OK, now that I've warned you about misinformation, let me provide a snippet from the latest forecast.  A bonafide midlatitude trough is expected to move over the Great Basin later this week.  Oh, it is a thing of beauty.

And here's the summary from the National Weather Service [note to my friends their, you forgot your logo :-)]

Source: NWS
I'm not counting the minutes.  I'm counting the seconds.