5/21/2014 Supercell east of Denver, CO

The last promising day for Pops and I was in Colorado with strong southeasterly winds aiding a post-frontal upslope initiation scheme.  The Denver Convergence Zone never really got cranking given the southeast trajectories, but a storm was able to fire southwest of Denver and moved over the airport with significant hail present (causing some damage to Frontier aircrafts I believe). As the storm pushed east into manageable chasing territory, we navigated northeast of the hook echo in what was becoming a large HP supercell. We caught a glimpse of the reported rapid rotation and funnel clouds, but the storm was not able to constrict the low-level circulation into a sustained tornado.  You will see from the timelapse just how close this was to being a large, wedge shaped tornado.  I think if the surface temperatures were slightly higher, we would have been dealing with a significant event (I was chilly most of the day with a small jacket on!).  We released from tornado chase mode as the circulation became rain-wrapped and positioned far east to enjoy the structure that only lasted for an hour or so, but created some nice photo ops and put a cherry on top to a very successful few days in the High Plains.

PS, Pops is becoming really good at storm feature identification!

Watching planes fly overhead east of the Denver International Airport

About as close to producing a large tornado as you can get...

Timelapse (click to play)

5/20/2014 High Plains Hat Trick

Tuesday completed a 'hat trick' of days with severe thunderstorms.  Yet again, a modest upslope regime contributed to beautiful convection across southeast WY and western NE.  We latched onto the convection southwest of Chugwater and documented it all the way to Scottsbluff, NE. Another timelapse can be found at the very end.

5/19/2014 Sydney, NE to Julesburg, CO Supercell

Monday exhibited another modest moisture upslope regime across the NE panhandle and western WY.  Trajectories turned easterly a little late, but organized convection was able to form near Kimbal, NE and slowly drifted toward Julesburg, CO toward sunset.

It was an interesting storm from a forecasting perspective.  SPC dropped the slight risk during the 1630 UTC update, only to solidly verify the initial morning outlook from Greg Carbin et al. Kudos, Greg et al.!

This (the most southern of) storm provided magnificent photo ops and great scenery as the day drew to a close.  I will take days like these over Oklahoma high-risk tornado setups 99 out of 100 times.  Pops and I also had a chance to resurrect the popular 2013 supercell photo from Nebraska. Overnighting in Julesburg, CO and looking forward to the next couple days.

5/18/2014 James, NE LP Supercell

Sunday featured meager moisture across the high plains in a modest upslope regime.  We awoke in Rapid City, SD and trekked through the Black Hills National Forest before setting our sights on Lusk, WY as an initial target.  The ferry to Lusk was scenic and provided relaxing landscapes before hanging out most of the afternoon in a Family Dollar parking lot.

We were eyeing a developing storm to our southeast near Torrington, WY, and went after it (with some admitted hesitation).  Visually the storm looked great, but the RADAR signature said otherwise, especially after initial development.  Anyway, we stuck with this storm as it morphed into a beautiful high plains LP supercell.  It produced a brief tornado near James, NE (just northeast of Scottsbluff), but mainly just provided an amazing view for the afternoon / evening.

Be sure to watch the timelapse at the end!

Overnighted in Alliance, NE.

 

 

Various pictures of the brief funnel / tornado

5/11/2014 Southeast Nebraska HP Supercell

Skip Talbot, Jennifer Brindley Ubl, and I ventured out to the plains early Sunday morning to setup for an enhanced risk of tornadic supercells along an east to west oriented warm front in southeast Nebraska.  A moderate risk was already in place due to the outstanding forecast hodographs.

Setup perspective via visible satellite and mesoanalysis 

One potential pitfall of this setup was the lack of steep low-level lapse rates, as exhibited by the morning RAOBS.  Nevertheless, we latched on to a rapidly developing supercell north of Hebron as it quickly produced a large (but brief!) multi-vortex tornado.  We could only see the tornado because of our position in the notch.  Despite the difficult storm motion and HP nature of the storm, I never felt at risk of being overtaken because of our very cautious nature.  We quickly got in and out of that area only stopping for a few moments to peek into the bear's cage.  It was a tough chase, indeed, with poor visibility, crappy road conditions, and less-than-ideal cell data service.

The storm was north of the warm front for most of its lifecycle, constantly breathing on air that was chilled from the morning convective outflow.  It did make several attempts to surge toward the boundary, but could never quite latch on and make a right turn.  I have a feeling we would have had a violent, long-track tornado on our hands if that storm could have made a good connection to the WF.

Brief cone tornado (right center) and what appears to be a large wedge tornado (left center)

Skip and I discussing storm structure

Initial large multi-vortex circulation with brief tornadoes

Check out more pictures over on Jen's BLOG.

Good to be back in chase mode.

Large rain-wrapped circulation along I-80 just southwest of Lincoln, NE

What was left of the circulation as it passed over Lincoln

Time lapse of the day

Verification, Please!

This post is influenced by a fairly recent Area Forecast Discussion (AFD) by a lead forecaster at the National Weather Service Forecast Office (WFO) in Davenport, IA (DVN).

I emphasize the word lead as lead forecasters are tasked with overseeing forecasts issued during their respective shift.  The lead forecaster is a senior-level position, culminating in many years of experience in the National Weather Service or similar forecasting enterprise. For those unfamiliar, there are three forecasting level positions at the WFO level starting at Intern Meteorologist status, then promotion to General Forecaster (often referred to as Journey level), and finally Lead Forecaster.

A few disclaimers before we get started.  First, I am in no way criticizing the local WFO in which this forecast originated from.  In fact, I spent a fair amount of time volunteering in the DVN office during my undergraduate days at Northern Illinois University.  In my (probably biased) opinion, they exemplify a great office with several forecasters, administrators, and staff that I still consider colleagues today.  I learned forecasting and research tips at DVN that I still frequently use today.

Secondly, I do not wish to get into an argument about the content of the AFD in question or debate about the limits of modern day forecasting.  I am simply using this space to dissect and provide (hopefully) constructive criticism to what I felt was a particularly poor discussion of the long-range prediction of weather across the (what I thought was supposed to be limited to!) DVN area.

In case you missed it, the AFD I am referring to is posted below.

This discussion was posted on 5 February 2014 at 2:33 PM CST:

ISSUED AT 233 PM CST WED FEB 5 2014

Long term discussion:

MAJOR REGIME CHANGE STARTING DAYS 5 INTO DAY 10 NORMALLY SUGGEST
MAJOR CHANGES IN SOLUTIONS AND PREDICTABILITY NEXT SEVERAL DAYS.
THIS CHANGE WILL RESULT IN MUCH WETTER CONDITIONS ALONG WEST COAST
WITH MILDER TEMPERATURES AT/BEYOND DAY 10 FOR CENTRAL US. THE
MAGNITUDE OF ENERGY CHANGES IN THE PACIFIC ARE AMONG THE HIGHEST
I HAVE SEEN OVER A 5 DAY PERIOD USING MULTIPLE SOURCES IN 35 YEARS
OF ANALYSIS. THE MEANING...THIS WILL NOT BE A MINOR CHANGE AND
SHOULD RESULT IN MAJOR TEMP/MOISTURE CHANGES LASTING MANY WEEKS
AND QUITE POSSIBLY MONTHS. TELECONNECTION WEIGHTING SUPPORTS MAY
RESULT IN AN ACTIVE SPRING...MUCH MORE TYPICAL THAN WHAT HAPPENED
LAST YEAR WHICH THIS AUTHOR CORRECTLY ASSESSED WOULD HAPPEN LAST
WINTER. THERE MAY BE SIGNIFICANT CHANGES IN KEY INDICES USED IN
TELECONNECTION TECHNIQUES NEXT SEVERAL WEEKS DUE TO THIS REGIME
CHANGE. THIS WILL BE QUITE EDUCATIONAL TO MONITOR. THE REGIME WE
ARE ON A TRAJECTORY FOR...FAVORABLY SUPPORTS HIGHS IN THE 50S AND
POSSIBLY 60S AT TIMES BY LATE IN THE MONTH...QUITE A CHANGE FROM
PAST 2 MONTHS. THE WEST COAST AND INTER-MOUNTAIN REGION WILL SEE
IMPRESSIVE RAIN TOTALS FOR AT LEAST THE NEXT FEW WEEKS. THIS MAY
CONTINUE BASED ON ANALOGS AND STATISTICAL WEIGHTING IN
TELECONNECTIONS LOCALLY USED BY THIS AUTHOR...FOR MUCH OF THE
EARLY TO MID SPRING...POSITIVE IMPACTS TO WESTERN DROUGHT...HIGH
PW/S WOULD SUPPORT FLOODING RISKS THOUGH.

COMMENT...KEEP IN MIND REFERENCES MADE LAST FALL BY THIS AUTHOR IN
AFD/S THAT CORRECTLY DIAGNOSED OUR RISK AND THE REALITY OF PROLONGED
COLD OVER MUCH OF NORTH AMERICA.

This sparked discussion among students in the CoD meteorology lab, most notably several trying to find signs to point to the claims being made re: temp/moisture changes lasting "many weeks and quite possibly months."  They asked me, "Is this for real?"

I had no answer for them.

Instead of telling them what I really felt, I played nice and began to investigate long-range signals using "local tools and techniques" that I have found to best diagnose dominant modes of atmospheric variability in the Northern Hemisphere.  We first settled on the sentence with "energy changes."  We were not quite sure what the forecaster was referring to.  Energy is measured in Joules (J) and typically not displayed on a 2-D spatial plot.  Perhaps the forecaster was referring to wind (a vector quantity driven by horizontal temperature gradients as defined by thermal wind) maximums at the tropopause level (jetstream) associated with Rossby waves traversing the Pacific?  This section was unclear.  Furthermore, how will these "energy" changes influence US weather for months to come?  Will blocking in the Pacific force a western CONUS trough?  We were mostly lost.  During the latter half of the discussion, I felt like I was being sold snake oil.  This section contained little/no scientific discussion,  mixed with hand-waving black-box teleconnection weighting, and spiced with two tablespoons of chest bumping.

What teleconnections are being weighted?  Why?  What research papers suggest this is a valid methodology?

I happen to be quite interested in teleconnection relationships put forth by this author, but admittedly, am not sure which of the many are being discussed above.  For sake of explanation of variability, let's quickly glance at the dominant mode of Northern Hemisphere variance (The Madden-Julian Oscillation [MJO]) and ENSO (the El-Nino Southern Oscillation; explains much less of the variability), both of which have been extensively studied via research.

MJO has exhibited no strong signal over the past month and continues so show no significant signs of tropical convective forcing (shown below). EDIT:  As of the first draft of this BLOGpost, MJO is becoming slightly more active.

Phase diagram showing the evolution of the last 40 days of observations along with the 15 day ensemble GFS forecast. The yellow lines are the twenty ensemble members and the green line is the ensemble mean (thick-week 1, thin-week 2). The dark gray shading depicts 90% of the members fall in this area and the light gray shading indicates 50% of the members.

Okay, well what about ENSO?:

Thus, the forecast period in question actually corresponds to ENSO neutral conditions (via the ensemble mean) making it difficult to point to any clear signs of equatorial pacific oceanic/atmospheric forcing even when discussing a transition cycle.

This gets to a much larger issue with using individual teleconnections.  Using regional spatial indices often result in poor prediction of weather conditions in other parts of the world.  Uh, surprise! Earth's atmosphere is a chaotic system!  There is no single teleconnection or magic bullet that will solve the issues associated with a Lorenz system.  Instead, these teleconnections are playing in concert together, each bringing their own influence on temperature and precipitation patterns worldwide.  This may have been the intent of the forecaster above, but the reader is left to guess.

Speaking from a persistence and snow cover perspective in conjunction with Atmospheric Angular Momentum (AAM), I would say there is a better chance for central US temperatures to be *below* average by the end of the month and continue into the first half of March, instead of the 50s/60s F suggested above!  From my particular perspective, I care less about the fact that this is an AFD for the DVN CWA talking about western US weather and more about the fact this it is strictly baloney!  This is much better fodder for a BLOG setting where one can more fully elaborate on the processes and teleconections in questions.

Here is the verification of 2-m temperature analysis since the issuance of the above AFD:

2-m T anomaly for 2-5-14 to 2-23-14 via reanalysis

Obviously, not a great forecast, but again, that is not necessarily the point of this post.  Instead, if you are to go out on a limb with such a forecast, let's be transparent with some metric of verification. POD/CSI/FAR please!  While an unverified forecast can still add value, I see no way a forecaster can improve his/her skill without some sort of verification metric.

1/3-9/2014 Eleuthera, Bahamas

Jenna and I ventured to the Bahamas after the New Year to catch up on some much needed R & R.  This was our first visit, specifically to the long-skinny island of Eleuthera. The laid-back culture and friendly atmosphere was a much needed diversion from the Chicago suburb hustle and bustle (especially after dealing with travel issues on Delta Airlines).  Driving on the left side of the road was a little weird at first, but we quickly got used to it.  The weather conditions weren't perfect, but we did enjoy three days with mostly sunny skies.  We spent most of our time at Ten-Bay beach, where low-tide was a spectacular site.

"Road" leading up to our rental.  This was actually a nice road compared to others on the island.

Cruise ship on the horizon of Long Pond Beach

Club-Med Beach (pretty rough water for this area)

Starfish underwater at Ten-Bay Beach

Ten-Bay Beach at low tide

Manta-ray cruising around at Ten-Bay Beach

Walking the shores of Long Pond Beach at sunrise

Low-tide sunrise at Long Pond Beach

Rental for the week (North Palmetto Point)

Afternoon low-tide at Long Pond Beach

Panny from the shore of our rental with decaying convection (and a rainbow)

 

Skylapse outside of the rental

The Truth Is, You Gave a Lousy Forecast

"Of course I couldn't possibly be talking about you."

I'm resurrecting a blog title from an old TCHE article in light of recent snowfall forecasts (for the 12-21/12-22 period), most of which originated on Facebook and Twitter.  I hesitate to call these "forecasts," as they were simply regurgitated images of model output posted at face value, without any meteorological interrogation.  As an example, here is a popular image that was viral on social media sites by late Monday afternoon:

156 hr. "Total Snowfall" forecast from the ECMWF model initialized 1200 UTC December 16, 2013    

This eye-candy was often accompanied with hyperbole like, "LOOK OUT central IL!", or "Watching a major winter storm coming this weekend!"  For the meteorological novices reading,  this image is a forecast of "total snowfall" 6 1/2 days in advance from the European (ECMWF) model.  The image paints a heavy stripe of snow (~15-25 in.) from north-central MO through central IL and into northern IN.  You might be saying to yourself, "Uh, that didn't happen!"...and...you're right!  In fact, most of this region did not receive any snowfall from the most recent cyclone, as seen below:

Actual snowfall verification from the 12-21/22-13 cyclone

 As you can see, the heaviest axis of observed snow fell roughly 200 miles further northwest than the model forecast and also totaled nearly 10 in. less in terms of magnitude.  

So, what went wrong?

Meteorologically, nothing!

While this was obviously a poor numerical weather model forecast, error only arises when a human interprets this solution as reality.  This is not necessarily a ploy to get people to stop posting such images (although that would certainly be nice!), rather I would like to see interrogation of the meteorological fields and discussions of features that would support or refute the forecast in question.  This is obviously not feasible on Twitter, yet I keep seeing such images posted.  Every snowfall. Every severe weather outbreak.  Pictures of various model fields with hype abound.  Where are the discussions of vorticity, thermal advection, and frontogenesis; or analysis of variables such as pressure, temperature, and specific humidity that are actually simulated by the governing equations driving the "sexy" model fields?  

They're around, just not on social media sites.  In fact, I closely followed the Area Forecast Discussions leading up to this event from WFO KLOT (Chicago) and KDVN (Davenport), and I must say they were quite impressive (you can find such discussions here).  Both offices discussed uncertainty in the model fields and provided physical meteorological reasoning behind their forecasts.  While these forecasts were far more accurate (in the true sense of the word), they were not the first forecasts for the event.  Similar to what many are seeing in main-stream journalism, there seems to be a rush to get the word out first, regardless of fact-checking or care for accuracy/precision.  It seems that simply being the first to announce a snowstorm a week in advance is more important than getting the forecast correct!

As the event drew closer, images kept popping up of  "snowfall" plots slowly shifting the axis of heaviest snow further northwest with each run.  I put "snowfall" in quotation marks, as this is not actually a post-processed model output field for the ECMWF, rather a simple 10:1 ice:liquid ratio multiplication, which can itself be a source of significant error depending on the vertical thermal profile.  These slow shifts to the northwest were not surprising to me, especially after analyzing low-level potential vorticity fields.

The point here is to suggest better communication practices for meteorologists when dealing with folks who may have little/no meteorological training.  Posting an image of 240 hr. snowfall as your forecast may draw you more followers, but where's the verification?  You're lucky most people have a short memory!  These posts are doing disservice to meteorologists everywhere and helping to perpetuate "the weatherman is always wrong" stereotype.  Forecasting is an imperfect science that should be expressed with probabilistic forecasts and associated uncertainty.

Let's strive to be better weather journalists.

6/28/2013 High-based Supercell north of Seibert, CO

After awaking in Wichita, KS, we targeted northeast Colorado for a low probability of high-based supercells. The environment was characterized by a moderately unstable air mass (mostly due to steep low-level lapse rates. With such low surface dewpoints (upper 30s!), it was uncertain if any storms could become severe. While coming up on Burlington, CO, we noticed some towers to our immediate northwest. We turned north out of Seibert, CO, and latched onto a rapidly developing severe storm on state route 59 north of Seibert. We proceeded to chase this cell for a little over four hours! The storm displayed nice high-based structure and a very cool hail curtain. In fact, we sampled the hail curtain (when I felt the VIL was down to appropriate levels) and were able to find hail up to penny size. Overall, Friday was a successful and quite photogenic high-plains chase. Overnighted in Colby, KS.

Cool hail curtain north of Seibert, CO

Pretty high-plains sunset

Timelapse of the storm