Rainfall Record Ahead?

It started in May, continued all summer long, and now we're on track to have more of it this year than any other in history. What is it, you ask? Rainfall. 2007 has been a very wet year throughout Oklahoma. From spring storms to daily deluges in June, and a visit from Tropical Depression Erin in August, most of Oklahoma hasn't had much of a chance to dry out since April, sending summer dewpoints into the 70's and even the 80's, much to the dismay of Oklahoma residents. Now, with fall barely underway, many locations throughout central and eastern Oklahoma are already within sight of all-time annual rainfall records.

As of the end of September, 50.69 inches of rain had been recorded during 2007 at Will Rogers World Airport; this is within an inch and a half of the all-time annual record of 52.03 inches. If it were to stop raining today at Will Rogers and not rain again for the rest of the year, 2007 would go into the books as the second wettest year ever. The Oklahoma Mesonet shows much the same picture - in the chart above we can see accumulated rainfall in Central Oklahoma for January through September of every year in the Oklahoma Climate Survey records for central Oklahoma. 2007 tops every other year, though 1957 remains a close second. The statewide view is similar, with 2007 running fifth, behind 1957, 1990, 1973, and 1945, still well above average.

So, why has 2007 been such a wet year? The answer lies in a combination of unusual weather systems over the summer. During the latter half of June and early July, much of Oklahoma was under the influence of a very tropical pattern (which we discussed in the June 2007 installment of our Hoot Article Series). Convection flared up daily around a persistent sub-synoptic scale vortex that just wouldn't budge. These daily storms dumped upwards of two inches in localized regions, and remained in the region for nearly three weeks. Then, in mid-August, Oklahoma received a visit from Tropical Storm Erin, which unexpectedly re-strengthened while traversing the state. Erin packed sustained winds of 50 knots and inundated portions of central Oklahoma with over ten inches of rain in a single night.

What can we expect for the remainder of the year? Don't despair - according to the National Center for Environmental Prediction (NCEP), we could soon have a chance to dry out. The NCEP 3 month climate outlook for Oct.-Nov.-Dec. calls for below normal precipitation for much of western Oklahoma, with equal chances for below normal, average, or above normal precipitation in the eastern portion of the state.




Story is © Nate Snook, 2007