Finally, it is over; the month of May that is. And, what a month it was.
Statewide, it was the wettest month on record, not only for May but for any month of the year; and it was not even close as we shattered the previous record month which was Oct 1941 and its statewide average of 10.75”. The final number for this past May now stands at an astounding 14.40” for a statewide average, 9.58” above normal according to the good folks at the OK Climate Survey.
As for Tulsa, the official number stands at 14.77” for the month which is still a far cry from the 18.00” in May of 1943. As for the records for any month, this past May comes in 5th behind the following: Sep 1971 18.81”, May 1943 18.00”, Oct 1941 16.51”, and Jun 1904 14.87”. Again, those are the ‘official' readings as maintained at the local NWS office. Obviously, your particular location may have some very different numbers, but this at least gives us a feel for the historical context of what we have endured this past month.
Notice the first three maps, courtesy of the OK Mesonet. The first image shows the total rainfall across the state at over 100 locations for the last 30 days. Since the first few days of May were dry and so was the last day, this accurately represents the May rainfall for OK. The second map shows the statewide totals for the last 60 days; in other words Apr-May. The point is that the long-standing drought which began in the fall of 2010 received a significant dent this past April and then was essentially broken in May. As to how far behind we were over the 4 ½ years of drought, from the third map you can see that some locations were more than 48” behind on their normal rainfall over that time frame.
On a year to date basis here in Tulsa, we are now in 4th place behind 1973, 1915, and 2008.
As for the causes of these recent historic rains, the most common explanation appears to be the developing El Nino in the equatorial Pacific Ocean. Yep, weather events half way around the world can have a noticeable impact on our local weather.
As for tornadoes, you may recall that statewide we set a record last year with only 16 tornadoes for the entire year, and 4 of those were in May of last year. The numbers are still being crunched, but the preliminary estimate for May of this year is over 60, which is far from record territory but still significant.
As might be expected, given the cloud cover and at least some rainfall on 22 of the days, this past May was also 1.4 degrees cooler than normal. That followed on the heels of a much warmer than normal April and a warmer than normal March. So, our Spring will go down as warm and wet; in fact, we tied a record for earliest last freeze as the last freeze of the cool season was on Mar 6.
With all the recent moisture and the lush, green vegetation, will that have any impact on what to expect this summer? By the way, we are now into the summer season which is recognized as the calendar months of Jun-Sep. I know, the calendar has different dates based on astronomy, but from a climatological perspective, summer is considered to be the calendar months of Jun-Sep.
Notice the last two maps which are the outlooks from the Climate Prediction Center for the summer season. Clearly, they are expecting our summer to average below normal with respect to temperature and above normal with respect to rainfall. This is largely based on the anticipation that the developing El Nino alluded to earlier with continue to amplify through this summer.
At least as you can see on our forecast page, we will finally be getting a break in our daily dousings with only a minimal chance of a few spotty showers on any given day. But, it will also be very warm and humid as we finally get to see some sunshine.
So, stay tuned and check back for updates.