Joe’s Weather Blog: A surge of heat with a rain chaser (FRI-7/23)

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KANSAS CITY, Mo. — Do you know there is no “official” definition of a heat wave? I’ve written about it before: what is a heat wave? It would seem reasonable to say that heat waves are different in different parts of the country For example, this is the hottest time of the year in Kansas City. We typically are near 90° for highs. Is it consecutive days above 95°? 100°? That’s only 5-10° above average.

If we were to switch seasons and take you into the worst of winter when the average high is in the upper 30s, and I say the high for a few days in a row is near 32°, is that a cold wave? I doubt it.

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Forecast:

Today: hazy sunshine. We are really seeing more smoke from the fires out west filter out the sunshine. Highs in the lower 90s.

Tonight: Fair and mild. Lows in the lower-to-mid-70s.

Tomorrow: Hotter with highs in the mid-90s and heat index values near 105° or higher in spots.

Sunday: Scattered storms are possible. This may knock a few degrees off the highs. Low-to-mid-90s with heat index values again near 105°+.

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Discussion:

Then there is the humidity factor in the whole thing and the heat index. We’ve had numerous days in the past, because of higher dewpoints, that the heat index is above 100° even with temperatures near average, for multiple afternoons in a row. Is that a heat wave?

A Google search shows this via the NWS:

What is a heat wave? A heat wave is a period of abnormally hot weather generally lasting more than two days. Heat waves can occur with or without high humidity. They have potential to cover a large area, exposing a high number of people to hazardous heat. Heat can be very taxing on the body; check out the heat related illnesses that can occur.”

There isn’t really a number qualifier to this.

Common sense though is something a bit different, and the NWS is concerned about the inner-city overnight lows especially. When the inner city, because of building construction and the heat island effect, doesn’t cool off at night as efficiently, they will issue an excessive heat warning. That is the case for the next five days into next Wednesday. In reality, it will get extended for at least another day later next week. Maybe more.

So some meteorologists will say a heat wave is when highs are 95°+ for three straight days. This is arbitrary but that’s fine. My point is that there isn’t a defined definition to what a heat wave really is. If we had a heat index(!) at or above 95° for three straight days, is that a heat wave? No. That is normal for Kansas City. If the temperatures are near 100° with lower dew points (like the heat/drought of 2012) allowing lows at night to still drop off despite highs almost every day near or above 100°, is that a heat wave? It was actually reasonably desert like here that summer, unlike most summers when we have the thick humidity.

Anyway, just some rambling for you and something to think about.

So let’s talk about the heat.

Yesterday we only got into the upper 80s. There was a lot of haze/smoke in the atmosphere. The visibility at KCI was reduced in the afternoon to 6-8 miles which is unusual for an afternoon haze/smoke situation in the Kansas City area. This is because of the fire smoke that is in the atmosphere. It worked itself closer to the surface.

It’s still out there this morning and there are haze restrictions again to start the day. There isn’t a lot of wind either, so it’s possible that we could see a minor temperature reduction because of it today. Dew points will be typical for the season today.

Tomorrow on the other hand will be a hotter day. We should more easily get into the mid-90s with dew points near or above 70°. That means the heat index will be near or above 100, to perhaps near 110° in spots. Northwest Missouri especially may see an extra degree or two in the afternoon, as a weak front/wind shift will be wandering down to the south maximizing the heat, on the assumption of enough sunshine.

Then that wind shift will be near the area on Sunday. That means there is a small rain chance early Sunday morning and a few more chances on Sunday. All this may contribute to extra clouds in the region. That could knock a few degrees off the potential highs.

Monday clouds and rain chances will again knock us a few degrees. So odds favor tomorrow being the hottest and most uncomfortable day with continued muggy conditions (typical for July) on Sunday and Monday.

Then we start to see the hotter air reassert itself. Tuesday will be like today, then it gets hotter. In my opinion, the weather next Wednesday and Thursday, perhaps Friday will be the true “heat wave” (assuming we’re going with the three-plus days of 95° definition).

There may be a front that cuts the heat off though on next Friday. At some point if that happens it has to rain again, perhaps heavily.

It’s possible that we never truly have a “heat wave” if you go with three straight days of 95° plus.

All this is really semantics.

This is normal weather for us in late July with this being the hottest time of the year.

Finally a few other items: the fires out west are really tragic. Within that though and in a terrible drought, there are monsoonal rains affecting parts of the west. Arizona has seen some heavy rains (in parts of the state) and flash flood watches/warnings are in effect in areas of severe drought. So goes life in the desert out there.

The fires though are still going and getting bigger in some cases. Look at this.

Then there is this, which actually goes into effect on Aug. 2:

That type of Wireless Emergency Alert on your phone may indeed be triggered on some rare occasions in this area.

Our feature photo comes from Kevin Kirkwood out towards Tonganoxie, Kansas.

Have a great weekend…stay hydrated…and I’ll check in on Monday

Joe

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