Friday, February 09, 2024

How Cloudy Was January?

January cloud cover was extremely extensive and long lasting across northern Ohio. Here are the top 10 cloudiest January in Cleveland (based on overcast observations):

When we break down the month into 4 cloud cover categories, this is what we found comparing January 2024 to the last 10 years:  26 of the 31 days had overcast skies. No clear days. 

How did northern Ohio cloud cover compare to the rest of the US in January?
Here is the average amount of cloud cover:  Typically the Pacific Northwest, Great Lakes, mid-west and portions of New England are the cloudiest locations.

Map Courtesy: Brian Brettschneider

Here is the ACTUAL cloud cover rankings for January:

The cloudiest regions were southern Michigan, western New York, southern Florida and yes, northern Ohio.  In fact, southern Florida's cloud cover was top 5 all time. Northern Ohio was 3rd cloudiest.

Map Courtesy: Brian Brettschneider

For comparison, this was the cloud cover ranks nationally for last year (2023)

2002 was one of the least cloudy January months in northern Ohio since the early 1950s.  Here was the cloud cover ranking nationally for comparison.

So why so much cloud cover this January vs other years?

Here is a loop showing where the HIGHS and LOWS are located for each day in January. Blue colors are low pressure, warmer colors are high pressure.  The lower the pressure, the more rising air and typically more cloud cover.
Active Pacific jet stream throughout the month. Early January, jet was across northern Pacific with the southern branch across Mexico and the southern US. By mid month, they partially merged then the southern branch become more dominant. This jet stream configuration kept these frequent low pressure system moving across the central US and Great Lakes. 

Great Lakes ice cover is well below average. This has kept the relatively mild water exposed to the frequent weather systems during the month. While the Great Lakes are not solely responsible for the cloud cover, they have contributed to it.