WKU Meteorology

The last couple of days have been incredible weather-wise. The early part of last week was warm and humid making it feel very uncomfortable. Behind the front which passed through Thursday afternoon MUCH cooler and drier air moved in. In fact if you look at the average of last weeks highs before the front and after the front you clearly see a noticeable difference.

At the Bowling Green – Warren County Regional Airport

Avg High Sunday – Thursday: 89.4 | Avg High Friday – Sunday: 76.0
Avg Low Sunday – Thursday: 68.2  | Avg Low Friday – Sunday: 50.3

The difference in the average highs is over 13 degrees while the difference in the average lows is nearly 18 degrees! Lows dropped into the mid to upper 40s Saturday morning in nearly all of south-central Kentucky and highs only made it to the low to mid 70s. So is summer weather over for good? Well, of course this depends on your definition of summer like weather. If we consider this 90 degree temperatures then yes it certainly is possible. On average the last 90 degree day in Bowling Green occurs on September 9th; last year it occurred Sept. 7th. There is some hesitation whether we have hit our last 90 degree day already this year. This is because there will likely be a few close calls in the next couple weeks, including one later this week. Our pattern expected through late next week (based on long-range models which should be taken with a grain of salt) bring in a couple of trough/ridge sequences. With that said, often times an upper-level ridge is associated with warm weather. Such a ridge will be working its way over the mid-south later this week and long ranges forecasts suggest this possibly occurring again next week as well.

Forecast upper-levels for late this week and mid-week next week. The zig-zag line indicates the axis of the forecast ridges. A ridge is often associated with warm temperatures at the surface. Could we hit the 90 degree mark during these ridges?

What does this mean for the weather this week? By the end of the week it means we will be warming back to above average temperatures (Avg High is 82). This trend will get off to a slow start however thanks to a couple small disturbances during the first half of the week. First, a weak front will push through the Bluegrass State early Monday morning. The front will not bring in more cool air but the clouds will prevent temperatures from getting any warmer than they were today (Sunday). The front will not bring a substantial chance for rain either. Nevertheless do not be surprised if there are a few showers around to start your work week; showers will generally be light. Overall the day will be cloudy to mostly cloudy. By Tuesday the front will push south of Kentucky allowing for partly cloudy skies but by Tuesday Night into Wednesday another weak disturbance moves into the Ohio Valley thus creating the chance for some showers and possibly a storm. The chance for a shower/storm will continue into Wednesday evening and Thursday morning before conditions begin to clear by Thursday afternoon. The warmest day appears as though it will be Friday ahead of the next frontal boundary. On Friday some locations could flirt with the 90 degree mark (thus the hesitation on saying summer is over!).

Forecast valid for midday Wednesday indicates showers and thunderstorms (shades of green circled by the red oval) over the midsouth.

Daily Forecasts:

Monday: 30% chance of showers with mostly cloudy to cloudy skies. Morning low near 61 and a high around 80. Light ENE winds less than 8 mph.

Monday Night: Mostly cloudy skies will become partly cloudy to even mostly clear at times. Very light winds will be out of the ENE. Some patchy fog is possible early Tuesday morning. Low near 59.

Tuesday: Partly cloudy skies with a high near 82. Easterly winds generally less than 8 mph.

Tuesday Night: Increasing clouds becoming mostly cloudy by midnight. 30% chance of a shower after midnight with light southerly winds generally less than 8 mph. Low around 66.

Wednesday: Mostly cloudy to cloudy skies with a 40% chance of showers/thunderstorms.  High near 81.

Wednesday Night: Mostly cloudy to cloudy skies with a 30% chance of showers/thunderstorms. Low around 67.

Thursday: Mostly cloudy with a 30% chance of showers/storms to start the day with some clearing into the afternoon hours. High near 85.

Days at a Glance:

Thursday: Begin the day at 66 degrees with clouds building throughout the morning before scattered to widespread rain showers enter the area by early to mid-afternoon. Accumulations of .10 – .20 of an inch are anticipated area-wide with higher values locally possible. Clouds will stick around throughout the day and clear into the overnight hours. Temperatures will reach 87 before dropping into the afternoon. Winds will be light around 5-6 mph switching from SSW to NW by mid-afternoon.

Friday: Sunrise will be 59 degrees with patchy fog clearing off fairly quickly after daybreak. Sunshine will dominate with fall-like air and temperatures reaching 78. North winds will be persistent and strongest in the afternoon at 12-17 mph before slacking overnight.

Saturday: Beginning the day at a chilly 45 degrees. Sunshine and fall-like air will once again dominate with temperatures reaching 70. Winds will be persistent from the NE at 10-12 mph.

Sunday: Another chilly start at 49 degrees. A sunny morning will give way to clouds into the afternoon hours that will persist into the evening. Isolated light showers are expected if any precipitation at all. At best, accumulations will be a trace – .05 for the area. Temperatures will reach 79 with slight mugginess returning. Winds will be from the south at 5-6 mph before becoming variable by the evening.

Discussion:

The storms were as advertised this afternoon being isolated in nature, but Bowling Green took a direct hit by a strong storm in particular. Frequent lightning, minor flooding on roadways due to heavy rain, and brief gusty winds were the major outcomes. The Bowling Green Regional Airport recorded 1.86 inches of rain with 1.59 of that falling within one hour or less. The WKU Farm Mesonet station only recorded .67 inches, which speaks to the localized nature of precipitation associated with “pop-up” or ordinary cell thunderstorms. Both stations recorded 20 mph gusts.

If you are tired of this uncomfortable, sticky heat, then you are in for a treat. The cold front mentioned in Sunday’s forecast is projected to pass the area tomorrow afternoon. Scattered to widespread showers will bring .10-.20 of an inch of area-wide rainfall with locally higher amounts possible due to embedded thunderstorms. Severe weather is not expected, with localized lightning and heavy rain the major threats.

Clouds will stick around and dissipate overnight. While relief will not be immediately felt, cooler and much drier air will begin to rush into the area overnight Thursday and all day Friday. It’s time to dust off your jackets because Friday and Saturday night will be rather chilly in the mid to upper 40’s by daybreak on Saturday and Sunday respectively. Sunshine will dominate Friday and Saturday with temperatures in the high to low 70’s respectively, but clouds will build into the area once again Sunday afternoon with little to no rain anticipated. This is associated with a very weak and dissipating cold front.

Get out and enjoy the comfortable, beautiful weather in store this weekend as fall makes a pleasant surprise!

Forecaster: Austin Boys

Days at a Glance:

Tonight: Showers and lingering clouds will dissipate into the evening and overnight hours with winds from the SE at 5-6 mph. Only trace accumulations are expected.

Monday: Begin the day with a low of 68. Skies will continue to clear into the morning and afternoon with southerly winds at 5-6 mph. It will be rather steamy with a high of 92. Popup showers due to increasing instability are 10% likely into the latter half of the afternoon with likelihood decreasing by nightfall. Associated showers will be relatively brief and localized with accumulations under .10 of an inch.

Tuesday: Start the day with a low of 70. Clear skies will dominate throughout the day with SSW winds at 11-12 mph. More of the same sticky heat with a high of 93. There is a 20% chance of popup showers likely in the later afternoon hours until nightfall. Associate showers will be relatively brief and localized in nature with accumulations under .15 of an inch.

Wednesday: Begin with a low of 71. Clouds will begin to increase throughout the day, especially into the afternoon hours. Winds will be SW at 5-7 mph with temperatures reaching 92. A 25% chance of popup showers remains as with Monday and Tuesday, but the chance for widespread showers will also increase into the evening and overnight hours.

Discussion:

Increasing clouds since this morning has produced overcast conditions and disrupted our streak of sunny days. Only a marginal chance of precipitation accumulation will persist into the evening and overnight hours as clouds begin to dissipate. The sun will reemerge tomorrow as will this sticky heat that will persist into the middle of the work week. Temperatures will reach the low to mid 90’s Monday through Wednesday with dew points in the upper 60’s. This will make for a unpleasant couple of days, but do enjoy the sunshine. If outside, remember to drink plenty of fluids, especially if performing strenuous activities.

But transition is in the air as a cold front will begin to slide through our area overnight Wednesday into Thursday. Models are having difficulty agreeing to the exact timing, strength, and expected rainfall accumulation of this cold front. A better picture can be made closer to Wednesday but the setup is not looking overly impressive.

GFS 12Z (7am CDT) Thursday showing wind vectors and surface mixing ratio (i.e. amount of atmospheric moisture). Notice the bold black arrows pointing SE across the Great Lakes region. This symbolizes the leading edge of cooler, and much drier air that will filter into our area into the final days of the work week and weekend behind the cold front.

Widespread showers with embedded thunderstorms is possible with severe weather not expected. What can be assumed is a nice relief from the humidity into the final days of the work week and weekend.

Next Forecast: Wednesday

Forecaster: Austin Boys

It has been a wet August for most of Kentucky, which is quite the contrast to this time last year. Here’s a look at the monthly rainfall across the state.

Anywhere from 10 to 15 inches of rain fell around the Bowling Green area this month. Currently, no counties are experiencing any drought.

This time last year much of the western half of the state was under a severe drought or worse and everyone except far eastern Kentucky was in some sort of drought.

August 28, 2012

Overall, this summer will finish much wetter and cooler than last summer. But will this pattern stick with us and bring us a cold and snowy winter?

The Climate Prediction Center doesn’t seem to think so. They are forecasting a higher chance of above normal temperatures and near normal precipitation for the Ohio Valley

But, the Farmer’s Almanac is a different story! They are forecasting a biting cold and snowy winter for southern Kentucky extending up through the Great Lakes. After a winter like the 2012-2013 season, I’m sure most people wouldn’t mind seeing a little more snowfall.

Today:

It was a gorgeous day across southern Kentucky as there were few clouds and the temperatures struggled to make it out of the low 80s. Bowling Green is currently hovering around it’s high temperature for the day at 81 degrees.

Tonight:

We will dip into the upper 50s tonight with clear skies. Make sure you grab your jacket in the morning if your leaving for work early or heading out to class.

Tomorrow: Expect a high temperature of 84 degrees with sunny skies

Tomorrow night: Another cold front will work it’s way into the region tomorrow night, but don’t expect much in the way of rain as only a few scattered showers are expected, mainly north of the area. So if you have any outdoor plans, don’t be too worried. Temperatures won’t be affected by this system much at all as temps will only drop into the low 60s Thursday night and Friday looks to continue the warming trend.

Overall, a nice weekend is taking shape. It will be a little on the warm side, but rain chances will remain low.

Weekend Outlook:

Friday: Sunny, with a high near 85. East wind 3 to 5 mph.

Friday Night: Mostly clear, with a low around 63.

Saturday: Sunny, with a high near 87.

Saturday Night: Mostly clear, with a low around 66.

Sunday: Partly sunny, with a high near 89.

Here’s the forecast for all you folks heading down to Knoxville, Tennessee for the WKU vs. Tennessee football game. (Kickoff is at 11:21 am central time)

Kickoff: 74 degrees and sunny

End of Game: 86 degrees and sunny

Much of Kentucky saw torrential rain yesterday which led to flooding across parts of the Bluegrass. An impulse of energy swept through the region yesterday evening into the overnight hours bringing isolated severe weather. Gusty winds led to down trees and a few power outages near Louisville and flash flooding resulted from a shield of rain with embedded, heavy rain producing thunderstorms moving slowly across central Kentucky. Once the westward moving outflow boundary interacted with the line of storms coming from the northwest, the rain began to move south more rapidly. The storms started to dissipate before reaching the Bowling Green area around 2 am.

Radar loop of Saturday and early Sunday’s storms

The rain cleared out early this morning allowing the heat and humidity to filter back into the area. Expect highs to top out around 85 degrees today with an isolated shower chance due to daytime heating. Another disturbance over Southern Illinois will begin to work it’s way into the region late this evening into the overnight hours, bringing with it a 40% chance of showers and thunderstorms. A slight risk for severe weather exists over the southern portion of Illinois near the outflow boundary. Although severe weather is not likely this far south, any storm development over that region will drift southward overnight.

A 30% rain chance will linger into Labor Day, but as we head into the afternoon hours, the rain chances will begin to diminish. Expect partly cloudy skies with a high near 86 degrees. A cold front will sweep through the region tomorrow evening, helping temperature to dip into the low to mid 60s by tomorrow night and providing much more comfortable conditions for the following days. We will struggle to make it out of the 70s Tuesday as a we look to end up around 79 degrees late afternoon. You will need a jacket if you plan on being out and about Tuesday night as the low temperature will be in the mid to upper 50s.

Weekly outlook:

Wednesday: Sunny, with a high near 81.

Wednesday Night: Mostly clear, with a low around 60.

Thursday: Mostly sunny, with a high near 84.

Thursday Night: Mostly clear, with a low around 62.

Friday: Mostly sunny, with a high near 86.

Friday Night: Mostly clear, with a low around 63.

Saturday: Sunny, with a high near 87.

Today was the last day of our trip in the central plains.  We started the day in Ada, OK.  We did not have a regular forecast discussion, because we as a group did not know if we were going to chase today or not.  We wound up discussing whether or not we were going to chase in the van.  We decided that if we were going to chase, we would head towards Piedmont, OK.  After about an hour or so of weighing the pros and cons of chasing, we decided that it would be in our best interest to not chase and to go ahead and head back to Bowling Green, KY.      We chose not to chase for several key reasons.

The first reason is that due to time constrictions on the van. It would be nearly impossible for us to have chased and then get back to Bowling Green before our deadline for the van.

Another reason is that the topography of our target area is full of hills and trees, so that we would only be able to see the storm for a few seconds at a time.

Another reasons is that there would have been a lot of storm chasers trying to target the same storms that we would target.  This would have added another potential threat to an already dangerous situation.

The final and main reason we chose not to chase was due to the fact that these storms were forecasted to initiate over or move into highly populated areas.  One of the things that we try to do on this trip is to avoid, if at all possible, areas where serious damage could occur and areas that have already been hit by a tornado.  This reason fits with our target because there was a risk for severe weather, and potentially tornadoes, in the same areas that the EF-5 tornado damaged last week.

So with all of those reasons in mind we left Ada, OK between noon and 1pm and reached Southaven, MS by about 8 pm or so.  After we dropped of Dr. Dixon, we then headed off to Bowling Green, KY and got there between midnight and 1 am.  We then rinsed off the van and went our separate ways.  We will be resuming the class portion on Monday so we can compile all of our photos and collect the radar data from the storms we chased.

Day 12 started off with a forecast discussion in Weatherford, OK. There was a moderate risk issued for parts of south central Oklahoma into central Kansas. The original target was for Stillwater, OK. All of the needed ingredients stacked up over that area. We had plenty of synoptic scale lifting from the upper level winds. There was a sufficient moisture axis with dewpoints in the upper 60s. CAPE values for the area were in the range of 2500-3000. Along with that, there was relatively no cap. The environment was great for storms. However, as we were leaving the hotel, we noticed storms firing up just to our southwest. We made the decision to go and at least check those storms out. The supercell we stayed with did not produce a tornado, but it did provide some beautiful structure as it was a low precipitation supercell.

This is what we saw for the majority of the day. We stayed with the southern supercells and ended the day watching a lightning show as the storms dissipated.

Photo by Tyler Smith

We began the morning in Andover, KS.  The SPC had issued a moderate risk over much of the eastern panhandle of Texas into parts of western Oklahoma, and extended up slightly into southwestern Nebraska.  After our morning discussion we decided to head towards the Woodward, OK area.

Surface analysis for 7:15 a.m.

Upper level wind speeds were favorable along with sufficient moisture, lift and instability across the area near Woodward.  However there was the chance that storms could become linear as some of the large scale lift and moisture convergence slightly hinted at this, which would decrease the chance for any isolated supercell development.  This seemed to be the case as we headed towards Wheeler, TX around 3:30 pm and spent most of the day staying ahead and observing this squall line.  The cell we were observing had a tornado warning but did not last long as it lost rotation strength fairly quickly.  We stayed with this storm for a while as the structure was still pretty nice looking.

As this storm seemed to lose intensity we moved out of position to look over data a little while longer until we noticed a cell just south of Elk City, OK.  As we arrived on this cell it was tornado warned for a short while before losing strength fairly quickly.

This was a screen shot of the base reflectivity and base velocity of this storm just after the tornado warning lifted.  There was still some rotation as you can see with the couplet in the velocity image, however nothing dropped as the rotation lost strength.

We finally started heading back towards the hotel for the night and around 9:05 pm there was a possible, brief sighting of a rope tornado near New Cordell, OK.  There is still no confirmation on this tornado so as of now it is just speculation.

Today was a fairly busy day driving with high expectations as the SPC had painted a good chance for severe storms.  We did not encounter any extreme supercells, though we did still see some excellent structure and observed a couple storms as they were tornado warned.

We started the day in Salina, KS after staying there overnight and catching much needed rest from the previous day’s chasing. As is usually the case we met at 9 am for a forecast discussion led by one of the students on the possible areas of severe weather. The Storm Prediction Center had outlined a very larger area under a “Slight Risk” of severe storms which extended from Texas to Wyoming and from Kansas to Michigan. When forecasting for a target area for our group to chase, the area can’t be half of the US and thus we must look more closely at the conditions needed for severe weather and narrow it down to choosing the best area. Morning surface analysis of current weather conditions offers a good deal of insight into where our target will be.

Surface analysis valid for 8:15 am overlaid with forecast 500 mb winds (purple arrows) and 850 mb winds (light blue arrows). Surface analysis by Ryan Difani.

At around 8 am an a analysis of the surface revealed a low pressure system located in south-central Kansas just east of Dodge City with a dry nose of air pushing in toward the low from the southwest. This dry nose can often be the focal point for thunderstorm initiation however in this case the dry nose was well mixed until pushing all the way back to NE Texas where the dryline was located. A well-mixed dry nose is less likely to initiate thunderstorms. The analysis also indicated very warm moist air moving north (green arrows) from Oklahoma and Texas into central Kansas near the low pressure. The 500 mb (purple arrows) and 850 mb (light blue arrows) winds forecast by the computer models was overlaid on the surface analysis to better locate a target. Upper level support is essential for thunderstorm development and maintenance and especially for severe thunderstorms as the upper level winds will create wind shear. At 500 mb the strongest winds were located in NE Colorado/Panhandle of Nebraska which was closer to the main upper level trough. Then there was also a general 500 mb flow from west Texas across Kansas and into Iowa. At 850 mb  a low-level jet would be present into the panhandle of Texas and also flowing from central Texas into Oklahoma and turning east through southeast Kansas. When overlapping all of these features needed for severe storms and also forecast helicity (a measure of the ability to maintain a rotating updraft) a few targets we’re becoming apparent. One being in northeast Colorado another being in the panhandle of Texas and finally the one that appeared most promising to us (plus we we’re already there) was in the Salina, KS region. There was an upper-level disturbance (vorticity maximum) that was pushing through Kansas that was going to provide enhanced lift in this region as well which was clear on the morning visible satellite imagery.

With our target city being the city we stayed overnight in, there was no rush and the group actually took things easy at the hotel until noon. Then after eating lunch the group enjoyed some time outside at Kansas Wesleyan University while waiting for storms to fire. By 4 pm there was a rapidly developing thunderstorm off to our northeast that dropped a tornado by 4:30. This storm was out of our reach and in an area of trees and hills which we don’t desire to chase in. This storm was an indicator of the kind of environment we we’re near though which was obviously conducive to rotating supercells. Then by around 5 pm we we’re keeping a close eye on a developing storm that was poised to move right past us in Salina and once the storm appeared to be gaining strength we moved a few miles north to the town of Bennington. This rapidly developing thunderstorm developed a funnel cloud just west of Bennington by 5:30 pm. It was confirmed by other spotters that the funnel did touch down and thus was a tornado.

Funnel cloud which was a confirmed tornado (via other spotters) just to the west of Bennington, KS. Photo by Ilea Schneider.

We then re-positioned ourselves on a dirt road about a half mile east and slightly south of Bennington. By this time a rapidly rotating wall cloud was ongoing and tornado development appeared again likely.

Rapidly rotating wall cloud just west of Bennington, KS. Photo by Andrew Schuler.

At around 5:46 pm the tornado touched down just west of Bennington and quickly grew to a large wedge tornado that was likely around a half mile wide at times.

The wedge tornado that was just west of Bennington, KS. Photo by Ilea Schneider.

Photo of the WKU students observing the wedge tornado just west of Bennington, KS. Photo by Dr. Josh Durkee.

The wedge tornado still just west of Bennington, KS beyond a wheat field. Photo by Andrew Schuler.

What was most interesting about this tornado is that it was nearly stationary and only slightly moved (less than a couple of miles) for it’s entire life cycle which lasted around ~35-45 minutes. The below radar loop from ~5:45 to ~6:15 of the supercell demonstrates this (click for image for loop). The left panel is storm relative velocity which gives an indication of the winds within the storm. The bright green and bright red colors side by side just west of Bennington are indicative of a strong circulation; this was indeed the tornado. The right panel is base reflectivity with the classic supercell with a hook which is also indicative of the circulation/tornado. Our location is indicated by the small white circle and dot. This loop was compiled by and courtesy of Dr. Grady Dixon from Mississippi State University.

The tornado often went in and out of the sight as rain sometimes obscured our view. We lost a visual of the tornado for the final time between 6:15 and 6:30 when the tornado became wrapped in rain and then we moved to make sure we would not be hit by any hail.

The partially rain obscured wedge tornado. In this photo the southern edge of the tornado can be clearly seen but the northern edge is difficult to differentiate from the rain. Photo by Andrew Shuler.

We pushed east, south and finally back west on I-70 to gain a better view of the storm. We moved north again to toward the base of the storm around 7:15 and some rotation was noted off to our northwest next to a colorful precipitation shaft. The rotation soon weakened and we decided to move south toward our hotel and possibly intercept another storm along the way.

Rotation could be noted on the left side of this image while the precipitation shield displayed a blue/green color. Photo by Andrew Schuler.

The other storm remained weak and thus we continued to push south to our hotel in Andover, KS just outside Wichita. We of course hoped that no one was being affected by this tornado and we are happy to report that no deaths or injuries resulted from the tornado and that there were only few structures that were damaged.

We conducted our forecast discussion in the morning and left North Platte, Nebraska. Our target area was Smiths Center, Kansas which is extremely close to the geographic center of the conterminous United States!

Photo by Veronica Hall

We stopped at a park or two to throw around a Frisbee and catch up on some sunshine. Initiation of storms began around 6pm and we chose a storm to the south versus one to the north due to chaser convergence. The northern storm had a tornado touch down, but was hardly visible due to rain obstruction. The southern storm was smaller, isolated, and relatively quite. We headed back to the hotel and chowed down on local specialty pizza in Salina, Kansas.

Photo by Veronica Hall