BLOG: Why Do We Use Dew Point and Not Relative Humidity?

Meteorologists talk about the “dew point”. A LOT. This is especially true in recent years. Many people undoubtedly remember watching weathercasts on TV in which the presenter only talked about “relative humidity”. The problem with relative humidity?

It’s kinda useless.

Let me explain why. Imagine if you will 2 cups with water in them. The smaller cup is 100% full of water. The larger cup is only 1/2 full, BUT there is more water in that cup than in the smaller cup.

dewpoint

If we think of the atmosphere as our “cup”, the relative humidity is much higher in the situation on the right but there is actually MORE moisture in the air in the situation on the left. In February it can be 21 degrees with a relative humidity of 100% but that does not mean it is humid. In July, it can be 90 degrees with 32% relative humidity and still feel stifling because of the AMOUNT, or VOLUME of moisture in the atmosphere.

So that’s why, especially in the Summer, we rarely talk about relative humidity. It can be very deceiving. The dew point is not.

In our part of the country, dew point become a big deal when they get well into the 60s and 70s. In mid-Summer, dewpoints in the 50s are a nice treat.

dewguide

BLOG: When is The Rain Going To Stop???

Originally posted on Chief Meteorologist Eric Wilhelm's Blog:

We are pretty much ALL tired of the rainy weather at this point. We have had measurable rain (more than a “trace”) 13 out of 21 days this month. A handful of rainfall totals:

Warren 7.78″
Howland 7.31″
N Wilmington 5.63″
Boardman 6.13″
Airport 5.57″

Yards are water-logged and many outdoor plans have been ruined. I am getting asked frequently…when is this pattern going to change??

There are finally signs that it is about to change.

The reason for the wet June? It can mostly be blamed on a persistent ridge of high pressure over the Southeast. This atmospheric traffic cop has deflected a large chunk of the moisture coming out of the Gulf of Mexico into the southern Plains, the Mississippi Valley and the lower Great Lakes/Ohio Valley.

OLDPATTERN

This week will not be as wet as recent weeks but there can still be rain in spots late tonight/tomorrow morning…

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BLOG: When is The Rain Going To Stop???

We are pretty much ALL tired of the rainy weather at this point. We have had measurable rain (more than a “trace”) 13 out of 21 days this month. A handful of rainfall totals:

Warren 7.78″
Howland 7.31″
N Wilmington 5.63″
Boardman 6.13″
Airport 5.57″

Yards are water-logged and many outdoor plans have been ruined. I am getting asked frequently…when is this pattern going to change??

There are finally signs that it is about to change.

The reason for the wet June? It can mostly be blamed on a persistent ridge of high pressure over the Southeast. This atmospheric traffic cop has deflected a large chunk of the moisture coming out of the Gulf of Mexico into the southern Plains, the Mississippi Valley and the lower Great Lakes/Ohio Valley.

OLDPATTERN

This week will not be as wet as recent weeks but there can still be rain in spots late tonight/tomorrow morning and again Thursday into Thursday night.

After that…a pattern change is set to take place. Will it rain occasionally? YES. But will it rain has frequently and as HARD as it has rained over the past few weeks? NO! The reason? The weather pattern is going to revert back to the pattern we have had over the last couple of winters. A BIG ridge of high pressure in the West and a trough setting up over the Great Lakes and Northeast:

FUTURE

That will keep the juiciest air locked up over the Gulf of Mexico…..reducing our opportunities for tropical downpours and frequent thunderstorms.

This pattern will also produce some very comfortable weather for the Valley at the end of June and through at least the 4th of July. That means no 90+ degree heat, no long stretches of uncomfortable humidity and some good “sleeping weather” at night. Enjoy!

Eric

Weather Forecasts, Analysis, Opinion For Northeast Ohio, Western Pennsylvania From 21 News Chief Meteorologist Eric Wilhelm

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