Interesting Upper Air Flow

We had a few thunderstorms this weekend. Most locations remained dry, humid, and warm. The next few days will feature yet another odd little twist to this most unusual summer: a Northeast upper air

Monday, July 23rd 2007, 3:47 am

By: News On 6

We had a few thunderstorms this weekend. Most locations remained dry, humid, and warm. The next few days will feature yet another odd little twist to this most unusual summer: a Northeast upper air flow.

The main center of the mid level ridge is to our north and this will take very hot temperatures to the northern high plains. Meanwhile as we discussed last week, a cut off low has formed across the east at the base of the main upper level trough. This low currently near the Virginias, will slowly retrograde or move basically northwest with time while the center of high pressure will remain north for the next 3 days. This creates a northeasterly upper air flow for the southern plains, which is extremely rare for spring or summer. Usually in early June we get about 2 weeks of a northwesterly flow aloft. Now in late July we have a Northeast flow. This means storm systems and disturbances that form well to our northeast will flow from the northeast to the southwest with time. Late night and early morning thunderstorm complexes will take a run at our area the next few days, but the trajectory should keep most of these systems to our west. The latest model of the WRF hints some storms may approach extreme Northern OK early Tuesday morning. But again, hopefully the trajectory will slide it just a hair west.

Meanwhile we'll have the normal isolated showers or storms just about every day somewhere in the area, but the next few days areas West of Tulsa would have the better shot. The surface pattern will allow slightly drier air to move into the far eastern OK and western Arkansas areas and this might be just enough to keep isolated storms across the western third. Again, these will be very isolated and most folks will miss out.

If you missed Dick's great explanation of how probabilities really work, once again it's almost certain that it will rain somewhere in the forecast area. That would be a 100 chance for some locations. But those storms will be so isolated and cover about 20% or less of our area at best. Therefore weâ€™ll either stick a 20% coverage on the map or just placed isolated storms on the graphic.

I did a quick temperature study last Friday. The normal monthly average high for July is about 94 degrees. From July 1 to last Friday, our average high has been 89.9 or 90f degrees. Only one day has been at or above 95 and that was 96 on July 16th. Dry air heats and cools efficiently, and while we'll see some slightly drier air in the east, excessively hot temperatures will still be off set by congested cumulus, low level moisture, and green vegetation allowing for increased localized evapotranspiration rates. The result is helping to keep our summer time temperatures in check. This morning some folks in extreme eastern OK are enjoying temperatures in the mid 60s!

By the end of the week, the ridge is expected to drop back down to the southwest and the upper air flow will switch back to a northwesterly flow. Still not a late summer pattern.

Tomorrow: Could the pattern soon allow the Tropics to become active?

Alan Crone