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Hot and humid weather and a lesson on dewpoints

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SUMMARY

Hot and muggy weather has arrived, folks, and it’s going to stick around a while. Our dewpoint is already 68 degrees, which means it is very humid outside. I explain dewpoint in the Discussion below if you’re interested.

We have only slight chances of afternoon showers/storms today. Most of us will stay bone dry. Tomorrow and Sunday our rain chances tick up a bit with so much heat and humidity around. The storms that do fire off in these air masses can be quite intense, so keep that in mind. It’s the kind of storms with lots of cloud-to-ground lightning, very gusty winds, and torrential downpours of rain.  Just be aware that those storms will be few and far between, but you want a place to get if you find yourself under one.

Be safe in the heat. Drink lots of water and limit your time in the afternoon heat/sun.

I will end by saying that the Meet and Greet in Rinnie went so very well last night! I honestly expected maybe a half dozen people and we ended up with at least two dozen by the time the evening was over! That’s a really good turnout for a Meet & Greet, as many folks just don’t like to fool with such things. We had plenty of food and good fellowship.  Now, it’s time to start knocking on doors, which I’ll be doing tomorrow and every Saturday until election day.

Below are some of the pics from the Meet & Greet. It was hot but we had some nice refreshments to cool off with! ha

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DISCUSSION

Like I said, the dewpoint is already in the upper 60s. So, what is the dewpoint exactly? Does it have anything to do with dew?

Well, sorta but not exactly. There, clear as mud, right? ha

The dewpoint is the temperature at which saturation will occur. In other words, it’s the temperature at which your relative humidity will be 100%. At that point, it’s either raining, snowing, or you have super dense fog; the air is saturated.

So, that means if we have a dewpoint of 68 degrees we would see 100% humidity if the air temperature were to be 68 degrees. Right now, our air temperature is 81 degrees. That’s only 13 degrees away from saturation, which means the air is really humid.

If dewpoints get above 65 the air feels thick and heavy with moisture. Dewpoints in the 70s are downright oppressive. When the air is this moist, it’s hard for your body to cool off because your sweat can’t evaporate. Evaporation is a cooling process and without that evaporation your body can’t cool down efficiently. That’s when things get dangerous for ya.

Dewpoint temperature changes much more slowly than air temperature. While the air temperature quickly rises into the low to mid 80s today, the dewpoint will hang out about where it is right now. As the day warms, the difference between the dewpoint and air temperature becomes greater, which means we get farther from the saturation temperature and the air is drier. This is why humidity is highest in the cooler mornings and lowest in the warmer afternoon.

As the night air cools and the temperature gets closer to the dewpoint, the air once again gets more moist and dew will form on the grass, etc. So, there is a bit of a connection to dew and the dewpoint.

Another interesting tidbit is that the air temperature can NEVER drop below the dewpoint. Never. This is one of those rare instances in atmospheric science when we can say the word never with 100% certainty. If we have a dewpoint in the winter time of 33 degrees, we can say that unless that dewpoint drops one more degree, we cannot have freezing rain. You can also get a feel for your overnight low temps by looking at your dewpoint. You know your air temp will not drop below that dewpoint, so you can get an idea of what that low might be, especially if you keep in mind that dewpoint doesn’t change dramatically with time unless a front is moving through to change it.

Dewpoint is a really good measure of the amount of moisture in the air. Our dewpoints will be in the upper 60s and lower 70s this weekend, so it will feel quite oppressive.

I hope you understand dewpoint a bit better now! As always, you can always ask me questions (mark@weathertap.com).

My article in the Fentress Courier this week was about this hurricane season getting off to such an early start and what it means for the whole season. I’ve included that article below. We had the disturbance in the Caribbean we were watching, but it appears to have died on the Yucatan Peninsula. That happens to a number of systems every season. That Peninsula has spared the U.S. and Mexico a great many number of storms!

You all have a great weekend and stay cool!

Hurricane Season 2018

We have already had our first named storm of the 2018 hurricane season. In fact, Tropical Storm Alberto developed before the hurricane season had even begun! The season officially starts on June 1.

Since we had our first named storm so early in the year, that has led to me getting a lot of questions about just how bad this tropical storm season will be. If the first named storm developed before the season had even begun, that surely means we are in for a rough hurricane season, right?

Not necessarily.

Looking back at records, there appears to be no correlation between pre-season storms and whether a hurricane season will be active or inactive. It would be like us getting a tornado outbreak in February and saying that we were guaranteed to have an active tornado season, based only on that one outbreak. The conditions that created the February outbreak would likely have no influence on tornado outbreaks that may occur the rest of the spring.

We also have to keep in mind that it only takes one storm to make a bad hurricane season. Consider this, in August of 1992 the first named storm of the season formed in the Atlantic and moved toward south Florida. It was August before we had our first named storm.

The storm quickly strengthened and hit south Florida as a category five hurricane, the strongest category we rank a hurricane by. That was the only significant storm of that season, but it left south Florida a complete disaster zone.

It only took one storm hitting a populated area.

It is nice to get relief from hot and dry weather when these tropical systems move our way and bring rainfall. We just hope the storms bring only relief this summer, and not coastal grief.

 

2 thoughts on “Hot and humid weather and a lesson on dewpoints

  1. Thanks Mark for the response about the TAP Talk Blog. I will use this for future comments…i can understannd the TAP Talk thingy now…
    have a nice weekend,
    ronnie stone

    1. Thanks, Ronnie! You do the same. And stay cool!

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