Category Labels vs. Distinct Things

Suppose that it would be interesting, useful, or even important to categorize hot days for cities in the Northeast. A day when the temperature at the airport reached 95F or higher could be labeled Category 5 heat. Better yet, label that day a Scorcher. The Glossary of Meteorology would define Scorcher. Climate studies might draw conclusions about the number of Scorchers. To the question there would be a ready answer, What is responsible for this heat? Meteorologists say it is caused by something called a Scorcher. A simple report, Hot yesterday, a bit hotter today could be expanded into an earnest elucidation, Yesterday was not a Scorcher, but today we have a Scorcher because ...

Too often in meteorology an attribute of a thing is cast into a newly labeled category of that thing, and then in no time at all the name of that category is communicated as a distinct, peculiar thing, even though the new thing is basically the original thing, and the familiar label for the original thing adequately, succinctly and more clearly communicates the weather situation.

The jargon bomb is a subcategory of intense area of low pressure. Bomb does not categorize intensity, but rather the time rate of change of the central pressure of the low. If the question is, What is responsible for this wind?, then part of the answer is the large, ineradicable cold area of high pressure to the north of the low. Perhaps a sexy label could be devised for the high's stubborn persistence; anti-bomb? But no need for that. Already there is a long-established, familiar term that most everyone in the Northeast recognizes as labeling the overall pattern of extreme winter weather.

There are many other local labels that succinctly communicate a familiar pattern of wind, temperature, humidity and/or sky condition; examples include Santa Ana, Bora, Blue Norther and, in Arizona, Monsoon. These locally familiar labels are effective precisely because they resist being defined precisely. Instead they are learned as a pattern—know it when you see it. Conversely, when a subcategory of a thing is defined by numerical threshold(s) of attribute(s) of the original thing, it has to be wondered what is intended when using that jargon term for communication since use of the unfamiliar term requires a redundant reiteration of the threshold(s).

The term derecho is like the term bomb in that both terms could be termed second-generation categorizations. Derecho does not categorize the magnitude of the severe winds accompanying a fast-moving line of thunderstorms, but rather the time during which the line remains severe, or equivalently the area swept out by the line during that time. Certainly it is important for forecasters to recognize and for both forecasters and the public not to dismiss an unusually long-lived line of severe thunderstorms. But why not communicate the attributes unusually long-lived for the thing and unusually high confidence for the long-lead-time warning? (What's worse, earnest elucidations about the term derecho these days invariably short-circuit the history, butchering the fact that when the Spanish word for right translates to English straight it is not as a direction but as not evasive, honest.)

Polar air is a thing. It is defined by the climate system, not by an arbitrary numeric threshold. For the same reason, polar front, polar jet stream and polar vortex are all things. Arctic air is a distinct thing, generated by absent sun during the arctic winter. The labels Polar and Arctic are arbitrary jargon, but they are long-standing and deserve to be respected and elucidated. Arctic air—whether stationary, displaced or on the move—is both Weather and Climate, and, because it is generated by minimal sun where absolute humidity is very low, it will always be with us, no matter how much manmade greenhouse gases continue to increase and no matter what schemes may be instituted to reflect a portion of incoming solar energy.

[I acknowledge that at least part of this rant was inspired by the Air Weather Service Back to Basics program of 40 years ago.]