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Severe Outflow by R. Edwards

Toward More Accurate Forecast Discussions

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Forecast discussions are an important way for operational meteorologists to explain the reasoning behind the forecast, and to offer additional insights to a more scientifically fluent audience than what’s necessary for public watches, warnings and forecasts. Whether it’s an “area forecast discussion” from a local office, a national center’s technical text, or a private meteorologist’s offering on a storm discussion board, these can be fantastic ways to see the reasoning behind a prediction, to learn why a forecast decision was made, and to educate oneself on the “weather whys”.

As someone who has written thousands of detailed, national forecast discussions over the years–and made more than a few mistakes doing so–I’ve come to understand that any level of timeliness, consistency, writing prowess or even forecast accuracy can be undermined by incorrect or misleading information in the text. If the audience can’t trust the truth of what they’re reading, how can they trust the forecast itself?

If we’re all literally accurate with the terminology and its usage, we’ll be not only correct, but consistent, in our communication. Forecast discussions are meant for reasonably well-educated audiences with some meteorological background–not our moms, kids or siblings. “Dumbing down” isn’t necessary. We should get the terminology and wording right, to the greatest extent our understanding allows. Then we not only communicate with truth, we exude earned authority and credibility, and sometimes, even educate the already well-educated audience.

Good science is good service; there’s no need to choose between the two. Let’s say it right! Avoid map-room jargon and literal inaccuracy while being specific about what’s happening.

Here are some common misuses of terminology from actual forecast discussions that I’ve either seen or received, and more importantly, the reasoning with solutions to improve it. I’ll be glad to add more as suggested and documented.

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BAD WORDING: Trough axis…ridge axis

REASONING: Redundant. A trough is an axis, by definition–in this case, an axis of low pressure or low height. A ridge is an axis of high pressure or high height. This is rather akin to saying, “cobra snake” or “copper metal”.

BETTER ALTERNATIVE(S): Trough….ridge

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BAD WORDING: Diffluent…diffluence

REASONING: Misspelled. The root “fluent” is preceded by the common English prefixes “di” or “con” to denote the sign of the process. This is much like “divergence” and “convergence”. Would you spell the former as “divvergence”? Of course not. So why misspell the other word as “diffluence”? [Unfortunately, this has become very common, even to the extent it has been erroneously programmed into automated spell-checkers.]

BETTER ALTERNATIVE(S): Difluent…difluence

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BAD WORDING: Data shows…data indicates…data offers…

REASONING: Subject-verb error. The word “data” is plural–for the singular “datum”.

BETTER ALTERNATIVE(S): Data show…data indicate…data offer…

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BAD WORDING: A criteria…

REASONING: Subject-verb error. The word “criteria” is plural–for the singular “criterion”.

BETTER ALTERNATIVE(S): A criterion…

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BAD WORDING: Narrow axis…broad axis (of moisture, temperature, CAPE, etc.)

REASONING: Physically and mathematically impossible! An axis is, at most, two-dimensional (if it curves) or one-dimensional (if straight). By definition, an axis has no width; it cannot be “narrow” or “broad” or “wide”. What we usually mean instead is…

BETTER ALTERNATIVE(S): Narrow corridor…wide corridor (or swath…area…field, etc.)

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BAD WORDING: Isolated tornado…isolated tornadoes

REASONING: Redundant. For forecast purposes, all tornadoes are isolated. The terms, “isolated”, “widely scattered” and “scattered”, in meteorology, deal with coverage. Isolated is <15%, widely scattered is 15-24%, scattered is 25-54%, and numerous is 55-100%. Tornadoes--even the very largest ones--cover a very tiny percent of the land area on outlook and watch scales, and most often, even on warning scales. For example, consider a major outbreak day, with multiple violent, long-tracked tornadoes--say ten of them for easy arithmetic. Let's assume the average path length and width of each tornado is 50 miles and 1/2 mile, respectively. [This is a very terrible, once-in-career type of outbreak!] That's 50*0.5*10 square miles, or 250 square miles hit by tornadoes. The average watch covers about 25,000 square miles. Let's now assume the outbreak was extremely dense, and cram all 10 of those extremely high-end tornadoes entirely inside just one average watch (unprecedented!). Even in such crazy circumstances, only 1/100 of the watch area was covered by those tornadoes: a mere one percent (1%)! That's still isolated, by definition, and if there were a category of "very isolated", it would be on the low end of that.

BETTER ALTERNATIVE(S): A tornado…a tornado or two…a few tornadoes…

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BAD WORDING: Deep moisture

REASONING: Misleading. Moisture is everywhere in the troposphere! Instead this usually means a deep layer of (some measure of) moisture. The layer containing that moisture can be deep or shallow. Specify that instead.

BETTER ALTERNATIVE(S): Deep, moist boundary layer…deep saturated layer…deep layer of mixing ratios at least 14 g/kg…deep layer of 50% or higher RH, etc.

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BAD WORDING: Moisture pooling

REASONING: Misleading and colloquial, similar to “deep moisture”. This is one case where using fewer words destroys the real meaning. Again, moisture is everywhere in the troposphere! Instead this misused phrase usually stands for a deep and horizontally restricted layer of enhanced, low-level moisture. Such a condition often occurs near boundaries. It would be more insightful and literally correct to specify the physical mechanism behind that.

BETTER ALTERNATIVE(S): Zone (or corridor or area or deep layer) of relatively rich moisture with an outflow boundary, etc.

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BAD WORDING: Vortice

REASONING: No such word.

BETTER ALTERNATIVE(S): Vortex

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BAD WORDING: Thundershower…

REASONING: No such thing.

BETTER ALTERNATIVE(S): Thunderstorm…

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BAD WORDING: Instability of 2,000 J/kg

REASONING: Erroneous. The writer means CAPE (measured in J/kg, unlike actual instabilities). CAPE and convective instability are not physically the same! CAPE is an indicator of convective instability; but there are some other kinds of instability–for example, Helmholtz or inertial that can happen with no CAPE. The links go to AMS glossary definitions.

BETTER ALTERNATIVE(S): CAPE of 2,000 J/kg

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BAD WORDING: Overrunning

REASONING: Misleading, colloquial overreach. Opinions vary on the validity of the term in very specific situations (See one essay by Monteverdi and another by Doswell), but it’s usually misused anyway. It’s more insightful to specify the actual process involved.

BETTER ALTERNATIVE(S): Frontal lift or warm advection

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BAD WORDING: Strong (or weak) upper-level dynamics

REASONING: Too vague, virtually meaningless. The term is so broad and overused that it encompasses almost limitless possibilities. Most (certainly not all) of the time, its context implies some form of, or contributor to, vertical motion. Be specific, not vague, about what’s happening and why–or if you don’t know, just say so. Don’t use “dynamics” as a black-box, catch-all word. Ambiguity is the enemy of understanding!

BETTER ALTERNATIVE(S): This depends on the situation. Refer directly to the actual physical process at work, whether it’s large-scale vertical motion contributions from differential vorticity advection, a thermally indirect circulation near a jet streak, mesoscale lift sources such as outflow boundaries, or storm-scale internal “dynamics” (the vertical pressure-gradient force), for example. In short, be specific.

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BAD WORDING: Model resolution

REASONING: (Usually) wrong usage. Resolution of a model is not the same as its grid spacing, which is usually what the writer means. However, even then, the writer often does not realize that true horizontal resolution of features occurs only at 4X or more coarser than grid spacing! This very short scientific essay does a great job of explaining the difference.

BETTER ALTERNATIVE(S): Model grid spacing (or if using the higher number and the literal meaning) model resolution

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BAD WORDING: DPVA causing (forcing, initiating, triggering) thunderstorms

REASONING: Misleading and false. Vertical motion related to differential vorticity advection is on the scale of cm/s or weaker. DCVA (same as DPVA in the northern hemisphere) makes the environment more thermodynamically unstable by steepening lapse rates, but a stronger source of lift is needed to initiate thunderstorms, within which air rises on the scale of tens of m/s (three orders of magnitude or more stronger than DCVA!). If an updraft is blasting through the sky at 50 m/s, half a cm/s of downward motion from DNVA won’t stop that; however there can be an indirect effect. Stable layers or subsident drying that result from DNVA can make the environment less favorable for storms.

BETTER ALTERNATIVE(S): DCVA destabilizing the environment for thunderstorms

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BAD WORDING: “Energy” in the context of perturbations or the instability they may cause, such as upper-level energy approaching

REASONING: Same as with “dynamics”, but worse. Energy, in many forms, is everywhere in the atmosphere! As such, this word is meaningless.

BETTER ALTERNATIVE(S): As with “dynamics”, this depends on the specific situation. Just state the actual feature or process involved. A more-informed reader is…a more-informed reader!

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BAD WORDING: Strong (or weak) lift or rising motion or subsidence (without specifying the source)

REASONING: Much too vague! Lift or sinking occurs on every scale of the atmosphere, from countless causes, and on a huge range of speeds and scales.

BETTER ALTERNATIVE(S): State the actual cause or process. For example, frontal lift…isentropic lift…sinking motion in cold advection, or whatever other actual process is behind the lift or subsidence.

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BAD WORDING: Shortwave approaching…

REASONING: Incomplete. Waves have both ridge and trough components. Almost always, the writer means shortwave trough, so be specific and say so.

BETTER ALTERNATIVE(S): Shortwave trough approaching…, or if you truly mean the entire wave (ridge and trough), stick with “shortwave”.

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BAD WORDING: Deviate motion

REASONING: Misspelling and/or usage error. Deviate is a verb. Deviant is the adjective form.

BETTER ALTERNATIVE(S): Deviant motion

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BAD WORDING: EF3 tornado intensity (or any other EF rating with the word “intensity”)

REASONING: Tornado rating is not the same as tornado intensity. The EF scale (or before it, the F Scale) is a way of rating tornadoes based on damage–or estimating a probable intensity at the damage point based on damage. However, most damage indicators (DIs) do not go up to EF5, and often there is either no DI or a weak DI. As such, the actual intensity of a tornado at most points cannot be specified from damage alone! The best we can do is estimate–often very crudely at that. Furthermore, many factors go into damage rating, wind intensity being only one of them (others including debris impact, construction methods, exposure, and subjective judgment of the surveyor). In short, the true intensity of most tornadoes is unknown, regardless of damage.

BETTER ALTERNATIVE(S): EF3 tornado damage–or, if referring specifically to wind speeds in the context of the EF scale standards or measured winds, simply EF3 wind speeds.

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BAD WORDING: It is important to note that…it should be noted that… and other “It…that…” statements

REASONING: I see this more often with scientific papers (!), but sometimes in forecast discussions also. These phrases are unnecessary and almost always can be removed completely, saving space. Look, would you note something unimportant? Would you note something that should not be noted? Of course not! So what’s the point? Don’t bother with the wasted words. For more on this needless wording, see the book Eloquent Science by David Schultz, specifically Table 10.2 and adjoining discussion, for a list of these phrases, and alternatives if desired. Again, most of the time you simply can remove the phrase.

BETTER ALTERNATIVE(S): Delete. Start the sentence with whatever came after that phrase–capitalizing the first word, of course.

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Thoughts on the Atlanta Snow Debacle

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      Photo courtesy Georgia D.o.T.

A horrendous winter-weather debacle unfolded in Atlanta and a few other Southeastern cities two nights ago, far, far out of proportion to the puny total of precipitation that fell. Less then three inches of snow basically paralyzed a metro area. As I got wind of this, and as a professional meteorologist with an unnamed entity that I’m not representing here, I couldn’t help but think, “Why”?

Notice the question isn’t, “Who is to blame?”, but is the more fair and balanced, “Why?” That’s a deliberate distinction. Asking questions, trying to get to the bottom of things, and finding holes in the Integrated Warning System that lead to disasters, is not the same as blaming. If you can’t understand the difference, stop reading right now. The rest will make no sense.

Being an atmospheric scientist and forecaster by trade, my first inclination was to look at the available public- and private-sector predictions for the event. My impression was they, while not perfect, they generally were very good–including and especially the forecasts from NWS Peachtree City. Contrary to the impulsive, borderline slanderous scapegoating by the Georgia governor and city officials, with no understanding or justification of how forecasting uncertainty works, I came away with the impression that an extremely difficult forecast was performed fairly well. This story on the backlash from some private-sector meteorologists illustrates that well.

Were all the forecasts from all sources good? Probably not. James Spann, Birmingham TV meteorologist for whom I have a great deal of respect, perhaps was too hard on himself when he said, “Days like yesterday, unfortunately, are part of my job. There have been bad forecasts in the past, and there will be bad ones in the future. Football coaches don’t win every game, and we don’t get every forecast right. But, when you lose, you do deep study into what went wrong, and work to be sure it doesn’t happen again.” The undercurrent there, however, is that forecasting cannot be totally right; and to expect perfection is just plain stupid. Please understand a key part of what James stated: There will be bad ones in the future. His ethic of learning and improvement is exactly the right attitude to take–not only in weather forecasting, but in preparedness for bad weather (more on that below).

Meanwhile this quote from Nathan Deal illustrates the problem that politics causes: “If we closed the city of Atlanta and our interstate system based on maybes, then we would not be a very productive government or a city. We can’t do it based on the maybes.” News flash, Nathan: forecasting necessarily involves maybes. It’s called uncertainty, and is unavoidable in forecasting. Get used to it, and plan accordingly, instead of complaining about forecasters failing to meet impossible standards of perfection.

While those ignorant blowhard politicians thunder their hollow indignation across the TV screen and throw the local NWS under the bus, I’d like to put Peachtree City up for a medal. Although not a forecaster by trade, Marshall Shepherd offered a hugely appreciated and very well-reasoned summary of the problem, including a strong message of thanks to the forecasters. So…thank you, Marshall. You beat me to a lot of the same points, and saved this BLOG entry from being even longer than it already is.

To that, there’s little I can add regarding the forecasting. A better predictive performance with such a hard and uncommon (for them) type of event as a sub-mesoscale northern edge of a snow band–especially more than a few hours out (when a winter storm warning was in effect)–would be demanding the unreasonable. Alas, because the response to the event and the resulting impact thereof each were so ghastly (which is out of control of the meteorologists), such an award isn’t likely to happen. That’s a shame.

Response and preparedness–which are two different but interlocking facets of the Integrated Warning System–absolutely do matter! The readiness in Atlanta, both governmentally and on individual levels multiplied by hundreds of thousands, was nothing short of wretched. Even in Dallas, San Antonio and Houston–cities of roughly similar metro populations as ATL that are farther south in latitude–hasn’t experienced an ordeal like that in their winter-weather events. Could it be that even in those places, just enough folks know to cancel plans in advance when winter weather is forecast?

Vehicular traffic is horrid in Atlanta on many a fair-weather day, and just one or two well-misplaced wrecks can render the situation FUBAR. Have you looked at a road map of that place? There are hardly any gridded, straightforward alternative routes to the freeway system, which itself looks like twisted noodles. Throw hundreds of thousands of vehicles onto that nonsensically chaotic spaghetti diagram at once, and into conditions for which few of their drivers are individually experienced or prepared, with essentially no pre-treatment or treatment of roads thanks to lack of suitable equipment, material and foresight at the civic level, and voila! You get what they got. In such gridlock, with the cars that can spin their wheels going nowhere in the process, the situation goes from FUBAR for a couple of hours to unprecedented and dangerous stasis. This was preventable.

Individuals: There is individual responsibility in this! Be aware of the forecast–the very latest forecast, since they can and do and should change as the event gets closer. Pay heed. If you’re inexperienced at driving on ice and snow, then don’t drive in ice and snow. Stay at home. Leave the roads clear for those who really need to be out there. If already at work, stay there awhile and let things clear up–it’s a warm place and beats sitting in traffic the same amount of time or longer with a hundred thousand other lemmings, burning gobs of fuel, stressing over being stuck, risking hypothermia should the need to evacuate the vehicle arise, and potentially being hit by idiots sliding into you.

State and local governments: All disasters are local. This means it’s up to you to be ready–not 1-3 days before, but months before. It’s not up to forecasters to do the impossible and tell you exact snow depths tomorrow down to the block and lot. You have to make decisions based on uncertainty! Deal with it…that’s your job. Maybe it’s not “cost-effective” for a big southern city that does get pretty cold sometimes to have access to lots of sand and salt trucks, and the sand and salt to go therein, and a strategic contingency plan with short-fused, priority-driven disbursement of the vehicles and material. Fine–don’t complain, then, when the cost/benefit ratio you so carefully weighed turns out to be wrong and comes back to bite you hard. Learn from this and quit trying to play childish blame games. Cooperate across city and county and school-district borders instead of myopically operating as insular little fiefdoms; the North-Central Texas Council of Governments (“230 member governments including 16 counties, numerous cities, school districts, and special districts”) is a great template to follow! Finally, emergency management exists for a reason, and this qualifies as an emergency. Make use of that expertise already located right under your noses.

Politicians: Admit your mistakes, for once, in a very specific manner, with clearly stated plans for how you’re not going to repeat them. Quit trying to blame those least deserving of it (and as public servants, least in a position to defend themselves). The Ray Nagin school of blame-shifting should have been closed long ago.

Media: You are the mainline communicators between meteorology and the public. I have one “don’t” and a lot more “do’s” here. Don’t give mixed signals, multiple model forecasts, and other confusing messages. Do keep it clear and straightforward. Do express uncertainty, and use that to convey the “better safe than sorry” message. Do keep up with changes in the forecast, because uncertainty mostly tends to shrink as the event gets closer. Do everything possible to encourage caution, safety and preventative avoidance of the roadways in a winter-storm scenario.

Forecasters: You (we) did well, overall. Not perfectly, but under the circumstances, not bad either. We all can learn and improve from this event, as James alluded. Remember: there’s more to consistently reliable forecasting than just models. Some folks actually hand-analyze surface and upper-air charts, investigate satellite imagery, examine and modify real soundings, and perform other physically insightful diagnostics of the actual atmosphere before ever invoking the prognostic models. Thorough analysis is the difference between merely seeing and truly understanding. This is also part of Snellman’s “Forecast Funnel” approach and is time-tested. The day we let the models do our jobs for us is the day those jobs can be automated.

This event was a woeful concatenation of misfortunes: natural forecast uncertainty, unprepared and ignorant individuals times hundreds of thousands, communications failures, badly designed transportation options, terribly ill-prepared governmental entities, and the worst timing of a snow event with respect to a weekday commuting scenario. The bottom line: Winter weather is only as bad as your preparedness for it. Take heed, Atlanta, and do it better next time. Let’s all learn from this, lest it be repeated.

Best of Other BLOGs Lately

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I’ve been bereft of BLOGging of late, at least in this medium.

Truth be told, I’ve had an intermittent case of writer’s block. When the block lifts and I get an imaginative spurt, I’m in bed, in the shower, driving, at work, or otherwise indisposed from capturing prosaic lightning in a bottle that can be expressed here; and its luster fades fast along with my memory of specifics. Lacking the time, opportunity or creativity lately to devise much of my own prose while in a position to compose it, I shall divert loyal readers’ attention to some thought-stimulating entries by friends and colleagues of mine in the BLOGosphere, along with recent chase and photo entries I’ve made elsewhere.

My beautiful and enormously gifted wife Elke, a writer and thinker of an extraordinarily insightful and gifted nature, recently began a BLOG, Sojourner between the Eternities. She doesn’t write much these days, but when she does, it’s powerful. Here was her entry as her father lay in what would be his death bed. The few entries she has so far are but a tiny tip of the vast and seemingly limitless reservoir of spiritual and natural insight she possesses, and which I get to behold on a daily basis. Maybe I’ll be able to dig up some absolutely dazzling old e-mail writings of hers on natural wonders that she may post there too. In the meantime, check out the fine tribute to their dad that her brother Gernot wrote (edited lovingly by Elke before publishing online). She also took the photo of her dad and his wonderful wife Sue, who is a dear friend of ours and beloved as a grandmotherly figure by my kids.

Weatherwise, please check out Patrick Marsh’s discussion on preliminary tornado reports versus actual tornadoes. In the aftermath of the recent three-day severe episode from Oklahoma to the Atlantic Tidewater, the issue of tornado-report confusion has reached a crescendo. Simply put, tornado reports are not the same as actual tornadoes! In fact, at least 30 different reports of the same Sanford/Broadway/Holly Spring/Raleigh NC tornado came in, all now distilled to one tornado. I cannot emphasize this enough; daily report logs are PRELIMINARY and WILL change as events are surveyed and Storm Data compiled over a span of weeks. Do not take same-day or next-day tornado counts literally!!!!

Mike Smith, in one of his latest entries, gave much-appreciated kudos to convective outlooks, watches and warnings for the recent Carolinas/Virginia tornado outbreak, with a nice discussion leading into how much more deadly an event like this might have been in the days before the integrated warning system got this reliable. In addition, the 1630Z outlook (before any tornadoes) was upgraded to tornado probabilities supporting a “HIGH RISK” in the area that later got hardest hit. Mike’s plea for tying down of mobile homes is one that should be heeded. While this step won’t do much good against EF3+ tornadoes, it can save lives in the great majority of events that are weaker, and the residents are not afforded time to reach adequate shelter nearby. I would take it a step further and urge mobile home residents, whether in tied-down units or not, to leave and position themselves in or within a few minutes’ access of a sturdy permanent structure whenever a tornado watch is issued. Yes, the probability your particular place gets hit is low, even on a major outbreak day like that; but I suspect the families of those who were severely hurt or killed would testify that it is a chance not worth taking.

Chuck Doswell just posted a slam-dunk piece on Monday-morning quarterbacking, specifically the second-guessing of official, national severe storms forecasts by pompous little second-guessing ignoramuses who seem to appear out of the woodwork from time to time in the storm-chasing world. Hey: Talk is cheap. Back it up! I used to live in Missouri, so…show me. Prove your self-proclaimed superiority on a consistent basis, with daily and publicly available advanced forecasts of all three specific forms of severe weather all year long, and the post-event verification statistics to back up your claim. Any blind chicken can get a worm sometimes; and even a busted clock is right at once or twice a day (depending on if it specifies a.m. and p.m.). Who can outperform the experts time and again? Step up and take Chuck’s challenge…if you dare. Otherwise, I call BS to any second-guessing fools.

Storm observer and saxophonist Bob Hartig posted a fine rant on the failure of highway department contractors to account for severe weather in their work. I agree with some of his critics who say the chasers (and public at large) need to be aware of these construction zones and severe weather threats themselves. While that’s true, it doesn’t absolve the managers of these projects and crews for their responsibility to minimize hazards also—and that includes advanced awareness of severe-storm situations.

I actually have been doing a little BLOGging–summaries of my first two storm intercept trips of the season to reactivate our Storms Observed This Year BLOG for…this year! If you’re interested, check out my reports, with a few photos, on the US-412 storm in northern Oklahoma, and three supercells (including the tornadic Tushka storm) in southeastern Oklahoma.

Finally, I have been keeping up with Image of the Week, adding a new personal favorite from my outdoor photography portfolio on a weekly basis, in hopes that others can enjoy the images and gain inspiration in some way regarding the outcomes of God’s handiwork in the land, water and sky around us.