Rainfall Rates, Atmospheric Moisture & Humidity - Part IV

In the previous three posts, I examined WHY it was so dry and warm, the temperatures during and prior and the lack of rain mid month. This post looks at the influence the Rex Block had on the amount of moisture in the atmosphere and the rainfall rates as systems approached from the west and the two tropical system from the south as well as the overall moisture in the atmosphere.

Precipitable Water (PW) is a measurement of the amount of moisture in the atmosphere at a specific location. Roughly, anything under 1" is considered a low amount. Above 1" and especially 1.5 to 2" is considered moderate to high. We use PW to determine whether or not the precipitation event will be significant . The high the PW number, the stronger the downpours.

Here is the animation of PW from September 6 to September 21. Cool colors are very low PW values and warmer colors are high PW values. Focus on the Ohio Valley. See how the ridge (Rex Block) suppressed higher atmospheric moisture movement from the south even as the remains of Francine moved inland. 

A close up of the rainfall rates told a similar story. Warm colors indicate low rainfall rates. Cool colors indicate above normal rainfall rates. Watch the two tropical system head north and either get deflected west and/or fall apart. It was around the 21st when the ridge started to weaken allowing a front to pass from the west. (See purple colors)

Rainfall amounts were only in areas where the Rex Block did not have a pronounced effect.

Humidity levels across northern Ohio were relatively low compared to the overall temperatures especially when compared to other long stretches of 80 degree days in September.

Cloud cover across northern Ohio was well below normal during this time.

What's interesting about this is that the frequency of clear skies with temperatures 80+ is barely 20% in September?

Last year's cloud cover (September)

2022 September cloud cover

2021 September cloud cover

2020 September cloud cover