It's been moist - but how moist?

And record heat again in Phoenix

Starting off today by highlighting a post from my colleague climatologist Brett Brettschneider, who is an incredible follow on BlueSky. I have been wondering just how abnormal the levels of moisture in the atmosphere have been this summer, and I should have known that Brian would be working on quantifying it. This map shows how the precipitable water (PW) - which again is the measure of the moisture that can support precipitation development through the entire layer of the atmosphere - for the month of June compared to past years (back to 1940). As you can see, for pretty much the entire country east of the Rockies it was a top 10 year, and for a large swath across the Great Lakes and Northeast it was the most moist (moistest?) or 2nd highest on record.

While moisture in the atmosphere does not always end up as precipitation on the ground, obviously if there is more moisture in the atmosphere, more precipitation can be produced as well as higher rainfall rates more supportive of flash flooding. Also, because most of the moisture that feeds precipitation is in the lower levels of the atmosphere, generally speaking when PW values are high, it’s humid at ground level. As I mentioned yesterday, numerous studies have shown that climate change is resulting in higher moisture content in the atmosphere supporting higher rainfall rates; warmer air can hold more moisture, and warmer oceans as shown by abnormally high sea surface temperatures, as we have seen this year in the Gulf and Caribbean, provide more water vapor to the atmosphere.

Obviously, this trend of extreme moisture in the atmosphere has continued into July with several major flash floods in the last week. On Wednesday, the most intense rainfall was in the Mid-Atlantic region, where several swaths of 2-5” of rainfall occurred. The heaviest rain looks to have been in central North Carolina, where MRMS radar estimates show up to 7” of rain in the area southwest of Greensboro, where significant flash flooding with water rescues was reported.

This region will remain a potential focus for additional flash flooding today, as scattered to numerous strong thunderstorms with heavy rainfall and gusty winds should redevelop this afternoon and evening, not just in the Mid-Atlantic but throughout much of the eastern United States. Another focus area for severe storms and flash flooding will be in the center of the country, where an upper level disturbance dropping southeast across the region will support the development of scattered strong to severe thunderstorms with damaging winds, large hail, heavy rainfall, and possibly a tornado or two. Slight risks of severe thunderstorms and flash flooding are in place across this region as shown above.

Meanwhile, out west, heat and fire danger will continue to be the concern for another day. Phoenix hit 118F yesterday, breaking the daily record high temperatures of 116F set last year. It marked the third consecutive year that Phoenix hit 118F at some point during the year, the first time that has ever happened. With the morning low only getting down to 93F (tied daily warm record low), the average daily temperature of 105.5F tied for the 7th warmest day on record in Phoenix. Per Don Sutherland on BlueSky, there have been 19 days on record in Phoenix where the daily average temperature was 105F or higher. “Twelve (63%) of those days have occurred since 2023 and 17 (89%) since 2000. 2023-2025 is the first 3 consecutive years with such heat.” The morning low today in Phoenix was 95F, which if it holds will set a daily record and tie for the 4th warmest low ever in the city.

For Friday, the central United States will remain active as a stronger upper level disturbance drives a cold front into the region, triggering strong to severe thunderstorms along with potential heavy rain and flash flooding. Scattered thunderstorms will continue in the East while hot and dry conditions will continue in the West, although the heat will abate some in the Southwest.

Obviously, the flooding catastrophe in Texas remains a huge focus of the weather community, as the confirmed death toll has reached 120 with 150 people still missing. I am planning to do another post later today talking about some of the recent news that has come out about the event with regard to NOAA/NWS and emergency management as far as budget, staffing, activities, etc.

With everything going on with the flooding as well as a couple of Congressional hearings in the last 24 hours that relate to science and weather, I am planning to do a live video at 2:30 pm CT Friday to give some more detail about the meteorology and hydrology of the flooding catastrophe and talk about all of these various stories. Paid subscribers can participate in these live videos via Google Meet (link will be provided) and ask questions via chat; if you cannot participate in the live video and have questions you would like me to address, please feel free to post your question as a comment on one of my posts. A recorded video will be available to all subscribers.

I want to thank again all of the Balanced Weather community subscribers for their support. The events of the last week show the critical importance of the weather and emergency management communities to keeping people safe, and I hope to be able to continue to provide experience based perspectives about these events and all of the issues currently impacting our science and disaster support infrastructure.