With some very chilly temperatures and a decent chance of high elevation snow on Thursday, it seems like summer’s last day is giving up without a fight. A second cold front will drop Reno’s high temperature into the upper 50s and will drop the snow level to just above Lake Tahoe. It’s not a particularly wet storm, and once it gets by things should dry up leaving Friday through the weekend dry with temperatures slowly warming back to about 70 by Sunday.

Let’s entertain one more hurricane question, this one from Mary: “This may be a foolish question, but would it be possible to halt a hurricane from forming in its early stages with a squadron of cloud seeding planes or other means, e.g. explosives, just to break it up & disrupt the storm/rotation?”

Wouldn’t that be nice? For time immemorial, mankind has been frustrated by having to live under the old adage, “Everybody talks about the weather, but nobody does anything about it.” And as a result, many interesting proposals have been thrown out for ways to stop hurricanes (and modify the weather in other ways), but none are considered practical and/or effective. We don’t have the means to affect something as large and energetic as a hurricane. The power in a hurricane is so immense that blowing stuff up in them would really amount to spitting in the ocean, as it were.

While the odds of getting any rainfall are slight, fall weather will definitely be felt from a temperature standpoint. A cold low pressure center is rotating through the Pacific Northwest, bringing a cold front through our region. Winds will remain brisk for the next couple of days, and high temperatures will fall noticeably. Tuesday will stay dry, but will cool to the low 70s, and temperatures will drop further to the low 60s with a slight chance of showers by Thursday. Skies will clear as we go into the weekend and temperatures will rebound to the low 70s by the end of the weekend.

After 12 years without a major hurricane landfall, this season unfortunately seems to be making up for lost time. And Irma was closely followed by Jose and Maria, both of which fortunately seem to be turning away from the US mainland, although Maria is definitely threatening some already impacted Caribbean Islands. One reader asked: “With two tropical storms so close together in the Atlantic last week, is it possible for one to catch up with the other and merge to create an even bigger storm? And has that ever happened?” The answer tomorrow.

It looks like the weather will clear up for the weekend, if you can ignore the smoke and haze from area fires. A stable ridge of high pressure on Saturday will result in mostly sunny and hazy conditions with temperatures in the upper-80s. The ridge will build over the next couple of days resulting in highs moving back into the 90s. By Monday, and especially Tuesday things destabilize enough to bring afternoon thunderstorms back into the mix.

As I mentioned yesterday, positive lightning can be much more dangerous than negative (not that negative is anything to sneeze at.) First of all, a positive lightning bolt is generally much longer than a negative one, since it has to reach the top of the cloud instead of the bottom. This alone can add several miles to its length. Because of the greater distance the positive strikes travel, it takes a higher charge to complete the “circuit”, and positive strikes usually carry more current… up to ten times that of standard negative strikes. But what makes them even more deadly is their unpredictability.

Positive lightning strikes can hit more than ten miles away from the thunderstorm, and be literally a “bolt from the blue.” Because of that, the normal precautions that we might take as we hear thunder in the distance may not be there, because the first strike can come long before we would have heard any previous strikes.

To distinguish one type from another, positive lightning usually forks upward from the ground, while negative lightning forks downward from the cloud.

Thunderstorm activity will calm down a bit over the next couple of days as the post-cold front flow becomes more stable. We could still see a few scattered afternoon thunderstorms Thursday and Friday, but they should be few and far between. Temperatures will cool to the low to mid-80s, before warming back to the upper 80s and low 90s over the weekend. At this point the weekend looks to be pretty dry with only a few clouds here and there.

I’ve talked a lot about lightning and , and have given a quick and over-simplified explanation of how lightning occurs. Negative charges from the base of thunderstorms clouds induce a positive charge on the ground, and after a “stepped leader” forms out of the clouds, it causes a “return stroke” from the ground once the negatively charged leader gets close enough to the positive charges on the ground. This generally referred to as “negative” lightning, and is the most common kind. But it doesn’t always work that way… lightning can be positive as well.

Tomorrow I’ll tell you how nature sometimes turns the tables on lightning’s polarity.

A weak southerly flow will continue to bring up a moist and unstable airmass Wednesday creating prime conditions for thunderstorms again. A cooler airmass will also move into the region, dropping the highs to the low 90s Wednesday and the mid to lower 80s for the rest of the work week. There will be just enough heat and moisture around for a slight chance of mainly afternoon thunderstorms through the rest of the week.

Here’re some reasons we don’t report temperatures to tenths of a degree. To begin with, the temperature around any thermometer probably varies a degree or two within just a few feet. The temperature of the air on the ground on a clear night can be 10 or more degrees cooler than the air at eye level (the approximate height where official temperatures are taken). And even at the same elevation off the ground the temperature can change several degrees in different spots in your yard, not to mention in varying places around town. So what makes the cubic centimeter of air around your thermometer bulb so special? It is only getting a representative sample of all the air at the measuring site. If all that air can vary by more than a degree, it is actually lass accurate to pretend a precision that you can’t reproduce.

And remember: Being more precise doesn’t mean you are being more accurate.

After another string of triple digit temperatures, there will be a slow easing off of the heat as more moisture comes up from the south, giving us a few more clouds with scattered afternoon thunderstorms. The high Tuesday will still reach the upper 90s with a slight chance of thunderstorms, and will fall to the lower 90s Wednesday with our best chance of storms then. Temperatures fall off into the 80s for the rest of the week with only a slight chance of storms.

So if thermometers can measure to tenths of a degree, why don’t we report temperatures to that?  Certainly we could report the temperatures to a more exact scale, instead of rounding off to the nearest degree. But the first question I would ask is “Why?” Can you feel the difference between 75.5 degrees, and 75.6 degrees? I can’t tell the difference between 72 and 75 degrees with any certainty, so will sticking in some decimal places do anything for the practical usage of the temperatures for me? But there are other reasons why rounding is actually just as accurate, and I’ll tell you those tomorrow.