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 (-4ºC 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.

PUT A SOCK IN IT

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."
Plus.
"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.

HERE IT COMES UTAH!
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.

Monday, September 11, 2017

Not So Deep Thoughts on Irma

Hurricane Irma made two landfalls in Florida yesterday, one in the Keys, the other near Marcos Island on the southwest coast.  The low center subsequently tracked through west Florida and as of 8 AM EDT (6 AM MDT) was near the Florida coast west of Gainesville. 

Source: National Hurricane Center
Impacts cover the entire Florida Peninsula and Keys.  Although "worst case" scenarios did not play out for some, others are suffering severely.  Do not fixate on the news coverage, which shows a small microcosm of storm damage.  Everglades City, for example, wasn't even mentioned in the coverage I viewed yesterday, but reports heavy damage this morning.  Jacksonville is currently experiencing river and storm surge flooding.  News reports suggest almost 6 million people are without power.  Florida took a serious blow along nearly its entirely coastline and interior and it will take some time until we know the scope of it.  Recovery will take much longer.  

News Coverage

If you want to see a race to the bottom, just follow the news coverage of Irma, which has been like a David Letterman stupid human tricks skit.  How many people do we need to see attempting to report in eyewall rain and winds who just a couple of days previously chastised locals who elected not to evacuate and ride out the storm?  I know the first rule in news is "if it bleeds, it ledes," but imagine instead coverage that provides detailed information concerning storm details, winds, surge, and the like.  Something people could actually use.  Even The Weather Channel spent far to much time showing their people in the field and far too little providing information that might be of value to people.  Such a shame.

Official Forecasts

In my view, computer model and official forecasts of Irma's track and intensity from the National Hurricane Center were impressive.  @WxBDM tweeted this marvelous map yesterday showing the National Hurricane Center forecast uncertainty cones from Irma's inception to Florida landfall.  That cone represents the area in which there is a 2/3 chance that Irma will track.  Irma has always been inside that cone, and I believe that includes it's track through its current position in northern Florida.  

Source: https://twitter.com/WxBDM/status/906939915363131397
Intensity forecasts were also quite good, although perhaps made easier by the fact that Irma had the peddle to the metal for much of it's lifetime.  I read a majority of the discussions and forecast advisories issued by the National Hurricane Center with great interest and detail given my Mom's residence in central Florida and I didn't see anything in Irma's subsequent behavior that was not anticipated by the forecasters.  

This is not to say that the forecasts were perfect.  Track uncertainty was even larger north of Florida.  Specificity on wind, surge, and other impacts had shortcomings, although those in part reflect the state of the science.  We now we need to continue to advance the science and improve future forecasts to improve better decision making, but in the context of historical forecasts, Irma's represent a significant achievement. 

Traditional and Social Media

What one "sees" and the impressions one gets today are strongly shaped by both traditional and social media and represents a blessing and a curse.  I can't emphasize enough the importance of tuning out all that chatter and focusing on National Weather Service forecasts and the recommendations of local officials during hazardous weather.  While not perfect, those forecasts and recommendations are the most reliable, don't cherry pick one possible outcome or track unless justified, and offer you the opportunity of taking the best action possible.  

Thoughts on Today, 9/11

Sixteen years ago today, terrorists inflicted a horrific attack on our nation.  In the wake of that attack, first responders and many other heroes answered the call to duty, in some cases giving their lives or sacrificing their long-term health to help others.  Let us remember their sacrifices, and that the call to duty is being answered by many in Florida and the broader southeast US during Irma.  

Saturday, September 9, 2017

"THIS IS AS REAL AS IT GETS"

Sobering words from the National Weather Service Key West Forecast Office in a tweet issued yesterday (Friday) afternoon.

NOTE: Tweet issued Friday with info as of 5 PM EDT.  Access the latest forecasts at http://www.nhc.noaa.gov/

That office is in a heavily fortified building designed to survive a hurricane.  I found it quite emotional watching a video late yesterday of them closing the storm shutters in preparation for Irma.
As I write this Saturday morning, Irma is sliding along the north coast and islands of Cuba.  Maximum sustained winds have dropped to 130 mph as it has been weakened some during interaction with Cuba.


Nevertheless, Irma remains a very large, powerful, and dangerous hurricane, and the National Hurricane Center anticipates restrengthening.

Irma will make landfall in Florida, but where will depend on the track.  The so-called "cone of uncertainty" contains the likely path of the low center, and covers most of the peninsula and immediate offshore waters over the Gulf of Mexico.


Wind and storm surge impacts will depend critically on the track, and making this forecast especially difficult is the fact that the storm will track along the Gulf coast.

Let's hope for the best.

Thursday, September 7, 2017

Confessions of an Ivory Tower Meteorologist

Not so random thoughts on this Thursday.

Confessions of an Ivory Tower Meteorologist
I have something that I need to get off my chest.  Something that bothers me deeply. 

I get excited about extreme weather. 

I can barely sleep during weather events like Harvey and Irma, and I'm not even all that interested in tropical meteorology

I feel guilty about this.  After all, these storms are horrific, taking lives and destroying communities.

However, I also feel terror and nausea looking at both forecasts and the aftermath of these events.  It's a weird mélange of feelings. 

Meteorologists Are People Too
The National Hurricane Center is located in Miami.  Our nation is fortunate to have such a dedicated men and women working 24/7 to monitor and forecast tropical storms such as Irma.  Keep in mind that these meteorologists, their families, and their homes are also in the crossfire of Irma. 

Utah Alums Contribute to the Effort
I've been following the activities of an esteemed University of Utah alum and one of our current graduate students who are collecting critical data on Irma on one of the Hurricane Hunter aircraft.  Talk about living the dream! 

So Much Extreme Weather, So Little Time
One of the perks of my job is that I get to spend a lot of time looking at the weather.  A lot.  Your worst weather nightmare is my dream job. 

My preference is winter storms, but I am a weather omnivore.  I will consume whatever is available. 

Over the past two weeks, I've had a diet of all-time record heat, western wildfires and smoke, Harvey's record rainfall and flooding, and now one of the most intense Atlantic hurricanes on record.  Digging into these events challenges my knowledge and provides great teaching moments, but I can barely keep up. 


Mother Nature had better calm down soon.  I've been overeating and am starting to get fat. 

Back to work....

Wednesday, September 6, 2017

Irma Track Troubles

Hurricane Irma remains an extremely powerful and dangerous category 5 hurricane, after passing over St. Martin this morning.

Source: NOAA/NWS/National Hurricane Center
Here's a shot as the system passed over Barbuda overnight.

Source: NOAA/NWS/National Hurricane Center
Wind observations from Barbuda show the remarkable increase in wind speed with the approach of the eye, reaching a maximum sustained velocity of nearly 120 mph and a peak gust of 155 mph before the sensor gave out.

Source: MesoWest
These are simply incredible numbers, especially that the winds at the time were out of the north and the site is on the south side of Barbuda.

From now through Saturday, the center of Irma is expected to track just to the north or along Puerto Rico, the Dominican Republic, Haiti, and eastern Cuba.

Source: NOAA/NWS/National Hurricane Center
Forecasts for Florida and the southeast US are remarkably tricky and depend strongly on when Irma takes the anticipated northward shift in track.  To highlight the abrupt nature of the anticipated track shift, I've put together a loop of the GFS forecast below (based on lower resolution grids).  Note the very steady WNW progression of Irma until it approaches the Florida Peninsula, when it decides to alter course and move northward.


The loop above is just one model solution.  Below shows the tracks produced by the GEFS ensemble, which fan out from the eastern Gulf of Mexico to tracks that don't even reach the US mainland.
Source: Tropical Tidbits
Forecasters will have these and additional tracks from the ECMWF and Hurricane models to ponder.  Today's forecasts are especially critical given the long time scales needed for hurricane preparation and evacuation from the Keys and South Florida. Keep in mind that we are still talking about a 4-5 day forecast from now until Irma is flirting with Florida.  The issues at play at these lead times are well summarized by the 5 AM AST forecast discussion from the National Hurricane Center.

Source: Source: NOAA/NWS/National Hurricane Center
The bottom line is that there is a wide range of possible tracks, and as a result, details of the timing and magnitude of Irma's impacts on Florida and other southeast US states remain uncertain.

Tuesday, September 5, 2017

A Smoky Day Ahead

Over the past few days Utah has fortuitously been located just to the south of some thick, smoky air, but that changed overnight as the winds shifted.  The Wasatch Mountains this morning look more like the Great Smokies.


That photo was taken about 7 am.  As things stand now (8:20 AM) I can barely see the base of the Oquirrh Mountains from my office at the University of Utah.

It's a bit too early to get a good look at the smoke in visible satellite imagery, but we can see it very clearly in ceilometer observations.  A ceilometer is an instrument that sends out a laser pulse and measures the amount and delay of the signal returned to ascertain cloud base height.  Smoke and other particles in the atmosphere, known as aerosols, also scatter some energy back, which is known as backscatter.

The plot below shows a profile of backscatter recorded from a ceilometer at the University of Utah Mountain Meteorology laboratory at Red Butte Canyon.  Time increases to the right and is in MDT.  Note the arrival of dense smoke denoted by the change in color from green to yellow at around 3 AM MDT.  You can also see that the smoke moved over this site first aloft and then near the surface.

Source: MesoWest
Today we will have an air quality double whammy of elevated PM2.5 and ozone.  PM2.5 at the Mountain Meteorology Lab has been running near or above 25 ug/m3 since about 4 MDT (consistent with the plot above).

Source: MesoWest
That rates as "moderate".  Keep in mind, however, that ozone levels the past few afternoons have been at or above the unhealthy threshold (red shading below).
Source: Utah Division of Air Quailty
I'm not sure where we'll end up today.  Sometimes the chemicals accompanying smoke enable a boost in daytime ozone production.   Keep an eye on things if you have concerns.  I'm planning on taking a day off from exercising.

Monday, September 4, 2017

Apocalypse Tomorrow

Smoke has been lingering around the Salt Lake Valley the past couple of days and, if forecast hold, is about to get much worse.

This afternoon's GOES-16 is quite remarkable and shows a thick blanket of smoke across much of the Pacific Northwest streaming off over the high plains.  The smoke here in the Salt Lake Valley is barely discernible, whereas its a thick blanket to our north.


Forecasts from the experimental HRRR-smoke model suggest we're going to see some of that thick smoke here tomorrow.  The forecast for 2 PM this afternoon (2100 UTC) shows vertically integrated smoke concentrations of around 15 mg/m2 over northern Utah, but much higher values to the north.


Concentrations roughly double by tomorrow.  The analysis below shows the situation at 6 PM (0000 UTC).


This should make tomorrow seem even more apocalyptic.

Keep in mind that ozone levels have been in the unhealthy for sensitive groups or unhealthy range the past few afternoon (lower graph below for Hawthorne Elementary in the Salt Lake Valley).  PM2.5 has been a bit elevated because of the smoke, but on the low side of moderate (top graph).


I suspect tomorrow we'll see PM2.5 concentrations rising some and another round of unhealthy for sensitive groups or unhealthy ozone.

I think I speak for everyone when I say I wish summer was OVER!

Friday, September 1, 2017

Hottest Summer Ever in Salt Lake Is OVER (or Not?)

As far as the traditional meteorological definition is concerned (June–August), the hottest summer in the history of Salt Lake City is now in the books.

The average temperature was 80.9ºF, beating 2013 by 0.1ºF.  Your pain and suffering has paid off!
Source: NOAA Regional Climate Centers
If you think that this place is becoming a hot house, you're right.  In Salt Lake City, the three hottest summers on record have all occurred in the past 5 years.  There wasn't a summer on record until 1988 with an average temperature above 77.5ºF.  Starting in 1988, we've had 9 summers eclipse that mark and three summers eclipse 80ºF.

And, while meteorological summer as defined based on the calendar has ended, we're looking at a continuing stretch dominated by high-amplitude ridging and well-above average temperatures.  At least the nights are longer now, enabling temperatures to drop a bit more overnight, and highs will only be in the low to mid 90s.  

And, if you must ask, yes, this is the hottest "year" on record for the year to date (January–August), although the race was quite tight with three recent years and 1934.  

Source: NOAA Regional Climate Centers
Will the entire calendar year go down as the hottest on record?  Only time will tell.

Thursday, August 31, 2017

Innovations to Help Our Air Quality Are Right in Front of Us

The lack of progress on improve the air quality along the Wasatch Front is deeply disturbing.  Excuses and foot dragging seem to be the modis operandi of the day.

Yesterday, the Salt Lake Tribune reported that many Utah business leaders sent a signed letter to Governor Herbert asking him to propose "bold strategies for addressing air pollution in Utah" and urging the Division of Air Quality "to propose a wide array of strong and ambitious proposals as part the Serious SIP it submits for public comment this fall."  The "Serious SIP" refers to the Strategic Implementation Plan for reducing air pollution in the Salt Lake Valley, as required by the EPA.  The full letter is included with the Tribune article, available here.

The article notes that Bryce Bird, director of the Utah Division of Air Quality, said that "truly innovative air quality solutions that hold promise for Utah are difficult to come by."

While I agree that there is no quick fix, the view that truly innovative air quality solutions are hard to come by is complete BS.  We have never had more opportunities to make choices that dramatically reduce local emissions, and the opportunities are growing.

We now have extremely efficient and effective battery powered lawn equipment including trimmers, leaf blowers, and battery powered lawnmowers.

I replaced my 22-year old gas-powered Craftsman lawnmower with a battery powered one this summer and what an improvement.  The battery powered lawnmower cuts better, is quieter, and doesn't belch out noxious fumes.

How about a batter powered snowblower?  I have one of these too.  It kicks ass.  No fumes and you don't have to tune it up each fall.



Over half of our emissions are mobile.  Yup, there's a solution for that too.  I don't have one of these yet (hanging on to my 14 year old minivan), but one's likely in the future.  


Plus, there are some old fashioned tools available.  These have been around for decades.




Migration from the internal combustion engine is entirely possible today, and it offers the most potential to improve air quality along the Wasatch Front.  Granted, 1.5 million people are not going to run out and buy an electric car tomorrow, and economic factors are a challenge for many in our community, but the argument that there are no truly innovative solutions is complete hogwash.  They are right in front of us.  We should be pursuing every possible avenue to stimulate and encourage migration toward electric vehicles (hybrids and plug-in hybrids also encouraged as a transitional technology).

Of course, electric devices and vehicles do produce emissions if the electricity source is a fossil-fuel power plant.  They also can produce emissions during the extraction of materials and manufacturing process.  However, those emissions are not local and concentrated in an urban area.  Transformation to low-carbon energy production is also essential, but a story for another day.

Wednesday, August 30, 2017

Beware of Sound Bite Harvey Attribution

Imagine the western U.S. equivalent of Hurricane/Tropical Storm Harvey.

Rain nearly nonstop in California for 6 weeks.  Runoff turning the Central Valley into an inland sea.  Sacramento buried under 10 feet of water.  Damages of more than a half-trillion dollars.

Now that would be a climate catastrophe right?

Except, it already happened.

During December.

In 1861.

Granted, the damages were not more than a half-trillion dollars.  That's merely the lower estimate of storm damage if it happened today.  But in December 1861, a megaflood in California killed thousands of people and 800,000 cattle.  A catastrophe by any standards, and it happened before significant global warming.


Source: USGS, Ingram (2013)
I write this to emphasize caution in interpreting the causes and contributors to the severity of floods produced by Harvey during and following the immediate aftermath of the storm.  The meteorology and hydrology of extreme events is mutlifaceted and highly complex and deserving of a more careful and cautious analysis.

Let's think back to the California Megaflood of 1861.  It it happened today, how would the press and public view it?  It would be unprecedented in "modern" (20th century or later) times and viewed as a disaster at least on par with Harvey. Paleoclimatic evidence suggests that such events have a "return interval" of 300 years, so we know such an exceptional event is possible when natural variability brings all the key ingredients together.  On the other hand, we expect global warming to serve as an amplifier of events of this type (see The Coming Megafloods).  In addition, we've changed the landscape of both the mountains and the Central Valley in ways that greatly affect hydrologic response.  So, will the next California megaflood be natural, caused by global warming, or caused by our land-surface modifications?  One can imagine all sorts of great clickbait headlines, but clearly, the causes are mutifaceted.

And, it is especially difficult to quantify the effects of global warming on a single event.  Global warming is having an effect on our weather and there are good reasons why we expect heavy precipitation events to increase in frequency and become more severe.  We should be concerned about this.

However, careful analysis is needed to truly understand the ingredients leading to the flooding produced by Harvey and the degree to which global warming has contributed to an increase in the likelihood of an event of such magnitude.  

Further, I am concerned about giving people a false impression that climate change is the only issue at play when it comes to our vulnerability of natural disasters.  Most scientists recognize this is the case, but the headlines command the attention of the public.

Andrew, Katrina, Harvey, and other tropical cyclones serve as reminders of our incredible vulnerability to natural disasters.  Paraphrasing Will Durant, "Civilization exists by meteorological consent, subject to change without notice."

In addition, we aren't prepared for the climate of the 20th century, let alone the one coming in the 21st century.  As a society, we are not only exposed to extreme weather events associated with heavy precipitation, but we're essentially doubling down on that exposure through ongoing, concentrated development and poor land-use practices and planning in vulnerable areas.

If we are to build a more weather and climate resilient nation, we need to recognize the multifaceted nature of the challenge.  Harvey serves as a wakeup call (unfortunately, we've had them before) and is not the last jaw dropping weather disaster we will face.

Tuesday, August 29, 2017

Misery Continues

Houston and the surrounding area are absolutely snake bit.  Tropical Storm Harvey now sits over the Gulf of Mexico just south of Galveston.  Although the precipitation area has broken up some, Houston and environs remain in one of the main shields.


It's been absolutely unbelievable how that area has been a magnet to precipitation for this event.  Such a shame.

It ain't over yet.  We all want this thing to be over, but Harvey will continue to float around SE Texas and western Louisiana through tomorrow.  The National Weather Service is calling for 2-3 inches today and another 2-3 inches tomorrow for the Houston area.  These numbers are lower than seen earlier this week, but are going to slow the recovery.  Let's hope that the stronger bands and precipitation regions spare the area.

Perhaps I'll write more later, but right now I've reached a point of numbness.

Monday, August 28, 2017

Where Will Harvey Go?

Now Tropical Storm Harvey now holds the record for the longest time remaining a named storm (i.e., with at least tropical-storm-force winds) after landfall in Texas.   At present, it is having a significant impact not only on Texas, but also southwest Louisiana, where the brunt of Harvey's randbands are currently moving onshore.  


Harvey is currently moving slowly southeastward and back over water.  It is expected to remain offshore through Tuesday, before making another landfall, somewhere along the northeast Texas Gulf Coast.  Although some strengthening is possible, Harvey is not expected to regain hurricane status prior to landfall.  


Nevertheless, it really isn't the wind, but the precipitation and flooding, that is the main issue with Harvey, and unfortunately he's going to continue to be a problem for Texas and Louisiana for the next few days (and longer in terms of recovery). 

Beyond that, Harvey is expected to move slowly up the lower Mississippi River basin, although the cone of uncertainty for the probable storm track is quite broad.  

Now, let me annoy mobile users with a very large loop, and perhaps violate all of my principles about extended range forecasts, by showing a GFS 10-day forecast loop (click to enlarge).  In this particular forecast, the upper-level trough spawned by Harvey is caught up in the circulation of the western ridge and, remarkably, slides eastward across the US-Mexico border, eventually reaching Baja and Southern California. 


Of course, if that were to happen, the main impact of Harvey would likely be to contribute to an increase in monsoon convection and precipitation.    

It's an interesting forecast, but it needs to be noted that Harvey is moving into an area of strong deformation where potential tracks are likely to "bifurcate" into two routes, one similar to the one above, another moving eastward.  Plus, there's always great uncertainty at such time ranges.  So, at present, I share this simply as a curiosity.  

Plus, I can note that the next 10 days, other than a brief system brush by later this week, Utah will be dominated by ridging.  Maybe some monsoon moisture can sneak in here or we get a thunderstorm for cooling, but for the most part, it looks like our hot summer weather will continue into early September.  

Sunday, August 27, 2017

Flooding "Beyond Anything Experienced"

There is no historical analog for the impacts of Hurricane Harvey.  The precipitation numbers being pumped out by our forecast models a couple of days ago were jaw dropping and beyond comprehension.  Unfortunately, those forecasts are coming to fruition.  

The numbers on the map below are 24-hour precipitation totals from the Texas Mesonet that I believe are since 7 AM CDT yesterday.  A significant swath of the area from northeast of San Antonio through the Houston area received more than 6 inches of precipitation.  Multiple stations in the Houston area reported more than 10 inches of rain, with a maximum of 18.02".  

Source: Texas Mesonet
Major flooding is occurring along streams and rivers across the region.  

Source: NWS
The National Weather Service Houston/Galveston forecast office has a graphic showing points that are forecast to reach major or record flooding stages, emphasizing that the impacts are "unknown and beyond anything experienced." 

Source: NWS
Humans like analogs as they help us put things into context, but that's not possible with this storm.  This morning I thought of the California Megaflood of 1861 (see http://wasatchweatherweenies.blogspot.com/2017/02/california-megafloods.html) as I surveyed data from Texas, as it affected such a large swath of the Central Valley, however, the meteorology and hydrology of California are drastically different from Texas, as well as the type and intensity of development there in 1861 compared to Texas in 2017.  

Ultimately, we're left with the reality that we are hurtling into unknown territory, with millions affected.  

Saturday, August 26, 2017

Harvey Landfall and Continued Deluge

Last night I kept an eye on the radar and surface observations in Texas as Harvey made landfall.  The image below shows the situation at 0135 UTC when the eye was just beginning to move over the barrier islands.


At that time, it was clear that Corpus Christi would be spared the worst of the winds.  Although they still had a miserable night, the eyewall, indicated above by the ring of high (yellow) radar reflectivity, where the strongest winds are concentrated, would pass just to their northeast.

Additionally, the right side of the eyewall was moving over Matagorda Island State Park and the Aransas National Wildlife Refuge, areas that are relatively undeveloped.


However, it was also clear that Rockport was spending a remarkably long time in the slow-moving eyewall.  I have never been through a hurricane, but colleagues who have spent time on the ground in or near the eyewall describe it as a terrifying experience.  The minutes must have ticked by like hours for those who remained in Rockport.

Harvey has been downgraded to a tropical storm, but while the winds have weakened, the flood threat is growing.  Water is the agent that delivers many hurricane/tropical cyclone impacts and the worst is far from over.   The National Weather Service rainfall analysis shows widespread accumulations in excess of 2 inches from near Corpus Christi to Houston, with more than 10 inches locally between Corpus Christi and Victoria, with the latter measuring 6.47."

Source: National Weather Service
Unfortunately, this thing is just getting started and Harvey is a slow-moving, moisture-processing system.  The NWS Weather Prediction Center rainfall forecast for 7 AM CDT this morning (Saturday) to 7 AM CDT next Saturday calls for 15-30 inches along the central Texas Gulf Coast with local accumulations of 40".

Source: National Weather Service
Information on streamflow and flood stages along rivers and streams in south Texas is available at https://water.weather.gov/ahps2/index.php?wfo=crp. One river forecast to reach a record stage is the San Bernard River.  Remember, this is a forecast, and much will depend on the amount and rate of rainfall in the drainage area for that river.

Source: National Weather Service
It's going to be a very long week in Texas.

Meanwhile, here in Utah, I was surprised to get sprinkled on this morning on my hike up Baldy and Hidden Peak.  A brief rainbow appeared, clearly indicating that there's a pot of gold in Snowbird village.  Must be Octoberfest...