Rain Footprint And Its Effect On Temperatures


Sunday, July 17th 2011, 11:41 am
By: News On 6


Just exactly do we mean by the expression "rain footprint"? Well if you look at the top map on the right you will see an OK Mesonet map showing the 2" soil moisture around the state, This past Wednesday morning, the northern portions of Osage county and surrounding areas received significant rainfall while the rest of us missed out on those generous rains. That is very evident when looking at the soil moisture map.

A more subtle effect is noted when you look at the high temperature map from yesterday which is the bottom map from the OK Mesonet. Notice triple digits except for northern Osage county into Washington County. Notice in particular Hominy at 103 and Foraker at 98. That may not be a big deal, but it certainly is noticeable and measurable. The difference is due to more of the sun's energy being used to evaporate that moisture and also used by plants for transpiration which means less of the sun's energy is available to heat things up.

By the way, in case you are wondering how Miami and Jay - which do not have the rain footprint yet - managed to stay below triple digits, the more easterly wind component has maintained even higher dew point temperatures there and there is somewhat of a lake effect as well.

Now, if we could just get some more generous rains to spread over the rest of the state. Unfortunately, those chances are pretty much in the slim to none category. Except for a slight chance of an isolated storm or two in the more terrain favored locations of E OK during the afternoon hours, our rain chances are minimal.

That also means lots of sunshine during the day and generally fair overnight skies. Dew point temperatures have been rising to around 70 during the overnight hours and mixing out into the low-mid 60s during the day. That is enough moisture to put the heat index another 2-6 degrees above the actual air temperature which just adds to the discomfort. Keep in mind, if you are in the direct sunlight, that will add another 10-15 degrees to what it feels like. In other words, be very cautious with the outdoor activities.

A light E to SE wind today and Monday will become more southerly as the week progresses which will likely result in temperatures rising another degree or two. In other words, the heat wave is expected to continue throughout the coming work week.

Is there any relief in sight? Well, the longer range guidance continues to suggest that the dominant ridge aloft will drift further westward putting us into a cooler, wetter NW flow pattern. But that pattern change is at least 10 days off and any significant changes at those time ranges are suspect. In other words, I am taking a wait and see approach before getting too excited about our prospects for a change in this oppressive heat wave.

In the meantime, stay tuned, stay cool, and check back for updates.

Dick Faurot