WKU Meteorology

It’s that time of year again when WKU storm chasers set out on their annual adventure to forecast and document severe weather in the US Great Plains. Dr. Josh Durkee, associate professor of meteorology/geography, along with Dr. Grady Dixon, associate professor of meteorology and climatology from Mississippi State University will lead the group comprised of 8 WKU undergraduate/graduate students (see WKU News Story). This capstone meteorology course more formally known as “Field Methods in Weather Analysis and Forecasting” is comprised of both an in class portion of the course and two weeks of forecasting and storm chasing in the Great Plains. This year’s course kicked off this Monday with the classroom portion of the course. Throughout this past week students have practiced their forecasting skills by examining past severe weather events and they have been closely studying weather forecast models for the upcoming week.

The weather pattern for the majority of the year thus far has not been favorable for tornadoes, which has led to one of the least tornadic time periods in recorded history. The pattern appears to be changing however which will make severe convective storms more probable. The group has been analyzing the best possible day to begin the two week chase. The pattern setting up is bringing the risk of severe storms in the Great Plans by Saturday and continuing into early next week. This has allowed the group to either plan to start the chase Saturday or Sunday depending on the severe weather setup. The distance to reach the Great Plains requires a full day of travel to the Great Plains so the group must leave a full day before the first chase day. With that in mind we needed to decide to leave Friday to chase Saturday or leave Saturday to chase Sunday. While storms appear likely in both Kansas and southwest Nebraska on Saturday, ultimately the group has decided to wait to start the chase day on Sunday which looks to bring a better probability of severe weather along with a better tornado potential in an area from Iowa to Oklahoma. The chase looks to continue into early next week in the south-central Plains. These areas of interest are generally outlined by the Storm Prediction Center’s severe weather outlooks for Sunday (red) and Monday (purple).

The SPC severe weather outlook for Sunday (red) and Monday (purple). These areas are generally where the group is targeting to start the trip.

Want to keep up with the action as we travel the plains in pursuit of severe weather? Here’s how to do so:

1. We will be updating this blog with our daily chase summary of the previous day.
2. On Twitter: ttps://twitter.com/wkustormchase
3. And also on Facebook: https://www.facebook.com/wkumetclimsci

An upper level low centered over parts of southern Missouri will slowly drop southeastward into Alabama by Sunday.  In return, persistent bands of light-moderate showers will continue on its northwestward to southeastward track across the region. There will likely be some breaks in shower activity from time to time this weekend, especially across the Bluegrass region where chances will remain lower than parts of  southern/western KY. Areal rainfall totals of 2-3 inches are expected from late tonight through Sunday, as small creeks, streams will rise as larger rivers are anticipated to reach minor flood stages. The slow moving low pressure system will continue to push through the state by Sunday afternoon, as rain associated with the front should exit the region by Sunday night with low overnight temperatures in the low 50’s statewide.

NOAA/HPC QPF map valid for Saturday 12Z – Sunday 12Z. Areas of heaviest precipitation is expected over south-central KY and points southward across the Tennessee Valley Region.

The image above is from the HPC showing the heaviest rainfall amounts across south-central and western parts of Kentucky. The further south you reside, the better chance for higher rainfall totals exist.

Highs for today will be much cooler as rain is expected for many across the state. High temperatures will struggle to reach the low to mid 50’s for folks that are already receiving rainfall.  The further north and east you live, along with the absence of rain, temperatures will be a bit warmer with high reaching the low 60’s.

SimuAWIPS 2m Temperature and Winds map. Valid for Saturday 22Z.

Tonight we’ll continue to see areal showers across portions of the state with chilly temperatures expected. Overnight lows will drop into the upper 40’s to around 50 degrees across the area with cooler lows for folks along western KY.  Showers will continue through the evening and overnight hours and the upper level trough slowly push towards the east. Multiple flood watches have been issued by the NWS in Louisville, especially across south-central Kentucky where creeks, streams will begin to flood while rivers reach minor flooding stages.  The latest watches and warnings are below as a Flood Watch has been issued from 8/7 am EDT/CDT – Sunday evening for the areas highlighted in dark green.

Latest Watches/Warning via Louisville NWS.

Sunday will feature more of the same as cooler conditions will stick around as rain chances will continue into the afternoon and evening hours.  High for Sunday will struggle to reach the 60 degree mark across many areas, as widespread rain will continue through the day.

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Sunday night: Showers Likely. Low 50º. Northeast winds 5-7 mph. Chance of precipitation: 60%.

Monday: Chance of showers and cloudy. High: 65º. Northeast winds 5-10 mph. Chance of precipitation: 50%

Monday night: Mostly cloudy. Low: 52º. Northeast winds 5 mph.

Areas across south-central and western Kentucky received 2-3 inches of rainfall over the course of the weekend.  Major flooding concerns for these areas resulted in many flood advisories and warnings as many streams and rivers exceeded their flood stages.  Showers and storms continued to track through the region and by Sunday afternoon, conditions began to dry out.  Overnight temperatures across the area were much milder as temperatures dropped into the low 50’s statewide under mostly cloudy skies.  Patchy morning fog developed late Sunday night and into Monday  but has since lifted into broken clouds for much of today.   Temperatures will be a tad warmer, as thicknesses do increase today, but the lack in the low level return flow and with a moderate amount of clouds in the sky, temperatures will only rise a few degrees warmer than yesterday with highs around 70º.

Latest Visible Satellite imagery for the Region. Decreasing clouds from west to east are expected through the remainder of Monday.

Heading into Monday evening, clouds should continue to decrease as mostly clear skies should prevail tonight with calm winds.  As a result, patchy fog could develop early morning on Tuesday.  Fog is not expected to be widespread, but more so intermittent and confined to the usual fog prone areas.  Low temperatures for Monday night are expected to drop in the low 50’s.

Tuesday we’ll see a weak upper level ridging begin to build over the eastern coast as we’ll be positioned between a high pressure to our easy and low pressure across the Central Plains.  In return, strong southerly breezes will begin to pick up as high temperatures will make a run towards the 80º mark under partly sunny skies.

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Forecast Outlook:

Tuesday night: Mostly clear skies. Low: 56º, light southeast winds expected.

Wednesday: Mostly Sunny. High:81º, southeast winds around 3-6 mph.

Wednesday night: Partly Cloudy. Low: 59º

Thursday: Partly cloudy with a 40% chance of showers/thunderstorms. High: 76º.

Thursday night: Mostly cloudy with a 40% chance of showers/thunderstorms. Low: 54º.

Temperatures to start the week will be mild.  They should near 70 with a high pressure system over our region for the beginning of the week.

Through the middle of the week we will see a cold front, which will bring us rain and then cooler temperatures behind the front.  It will be more of a wind event, but right now we are under a 5% severe weather outlook.

The storms will come in the form of a line on Wednesday.

There is a small amount of CAPE associated with this.  We could see some wind damage with this system right now.  There is absolutely not CIN, which is convective inhibition, which would limit the severe potential, over portions of our area.

So overall, we will see warmer temperatures for the beginning of the week, along with sunny skies.  Then, by the middle of the week, we will see a cold front which will bring with it rain, and a line of storms.  These storms will mainly just bring along moderate winds. After the front, we will see cooler temperatures.

Today: Warm and sunny.  Highs near 70.

Tonight: Partly cloudy. Low near 50.

Tomorrow: Mix of sun and clouds. Highs in mid 70s.

Wednesday: Showers likely.  Highs in upper 50s.

Days at a Glance:

Thursday: High – 84  Low – 65  Precipitation – 100% late in the period starting from 10 pm -11 pm where totals could reach .5 of an inch in total   Winds – S at 20-23 mph  Skies – Partly cloudy becoming cloudy after sunset

Friday: High – 52  Low – 33  Precipitation – 90% residual rain showers very early in the period just after 1 am where totals could reach .5 of an inch before ending shortly after  Winds – W at 14-17 mph  Skies – partly cloudy clearing out into the evening

Saturday: High – 59  Low – 30  Precipitation – 0%  Winds – NW at 6 mph  Skies – Sunny

Sunday: High – 66  Low – 39  Precipitation – 0%  Winds – E shifting into the afternoon and evening SE at 6-7 mph  Skies – Sunny

Discussion:

Throughout tomorrow, persistent southerly winds will prime our area with moisture and warm temperatures. The high temperature will once again be in the mid 80’s on a day very similar to today. The main story for this forecast period is the cold frontal passage to impact our area late Thursday night into very early Friday morning. Models are in good agreement that it will pass around 1 am Friday morning with precipitation ahead of the front beginning around 10-11 pm. Expect moderate to heavy rain in a relatively brief amount of time with totals likely to reach one half of an inch. Rainfall should quickly cease after 1 am depending on the exact timing of the frontal passage. The likelihood of severe weather will be on the decline since nighttime cooling will increase the overall stability of the atmosphere. Small to moderate hail will be the main threat, with strong winds likely as well depending on the configuration of the line as it enters our area. Regardless, it is very important that you have weather radios to awaken you in the event of severe weather.

NAM 06Z (1 am) Friday morning surface temperatures, winds, and mean sea level pressure. Notice the distinct N-S boundary traversing our area. This is the cold front.

For Friday, clouds will stick around but will clear out into the evening. Temperatures will be much cooler only reaching the lower 50’s. Cover your plants and gardens since temperatures will dip very close if not at freezing Saturday morning depending on how quickly the skies clear out and if the winds slacken enough. Saturday and Sunday are looking to be beautiful and the start of another warming trend with highs in the upper 50’s and mid 60’s respectively. A light jacket on Sunday morning will be advised since lows will dip into the upper 30’s.

Days at a Glance:

Monday: High – 77  Low – 54  Precipitation – 10% light showers around midnight  Winds – S at 11-12 mph   Skies – partly to mostly cloudy with peaks of sunshine

Tuesday: High – 80 Low – 61  Precipitation – 40% light showers mid-morning into the afternoon associated with a stalling front paralleling the Ohio River to our north  Winds – S at 12-17 mph  Skies – mostly cloudy to overcast

Wednesday: High – 84  Low – 63  Precipitation – 10% light showers mid-morning  Winds – SSE at 12-17 mph  Skies – mostly cloudy early clearing to partly cloudy into the afternoon

Discussion:

After a warm and beautiful weekend, temperatures will remain on the warming trend, but clouds will be more of a presence. A frontal boundary will lose steam and stall out to our north along the Ohio River late Monday night into Tuesday morning. Occasional and spotty showers will be a possibility during this time into the afternoon Tuesday with accumulations under a tenth of an inch. It will remain stationary for most of Tuesday and then progress north as a warm front for Wednesday into Thursday.

NAM 00Z Thursday (7 PM Wednesday night) wind, temperature, and mean sea level pressure. Notice the developing disturbance over the central plains with distinct boundaries taking form to our north and across the upper Great Plains. A snapshot of what’s to come into the latter half of our work week.

South winds will be priming our area with warm, moisture-laden gulf air for the next couple of days. Aloft, a deep disturbance is beginning to take shape, and will provide large-scale ascent for us during the latter half of the work week. With this said, transition is clearly in the air for Thursday and Friday. Further monitoring will continue as the system unfolds.

The AMS/NWA Local Chapter (Meteorology Club) is proud to announce that it will be hosting its first Weather Camp this Summer on July 15 – 19, 2013.  Applications are now being accepted and will be accepted until June 15, 2013.  The cost for the camp is $60 which will go toward Food costs, T-Shirts, and other items that will be needed to run the camp successfully.  This camp will be a day camp only and it will start each day at 9:00 A.M. and will end everyday at 4:00 P.M.  The age group that this camp will be geared toward is Middle School Kids ages 11-14 at the time of the camp.  Our Weather Camp is one of several other camps across the U.S. that are a part of the National Weather Camps program which is geared toward teaching kids the importance of Science and fueling their interest in the Atmospheric Sciences.  What makes our Camp different from others is that it is entirely student led.  For more information about our Camp and to download the Application, go to our website by clicking here.  Also, you can contact Tyler Binkley the Camp Director at tyler.binkley567@topper.wku.edu

Discussion:

The first half of the week has been dominated by warm temperatures with a good mix of sun and clouds throughout. The high today (Wednesday) climbed to 86 degrees at the Bowling Green Airport easily making this the warmest day of the year thus far. In fact we our high was 18 degrees above the average for this time of year. The warmth will come to a screeching halt tomorrow as a very strong cold front will make its way through the area. This front could pack a punch in more ways than one… not only will much colder temperatures move in behind the front but severe storms could also move in along the leading edge of the frontal system.

Currently a 1004 mb low pressure system is located near the St. Louis, MO region with a warm front extending to the east into southern Ohio and the strong aforementioned cold front extending south through Arkansas and into Louisiana. Both of these fronts have been the focal points for severe storms today. Tornadoes have been reported in both Arkansas and Missouri along with numerous other severe weather reports that continue to come in at this hour. Severe weather watches extend along these areas of thunderstorms including a tornado watch for parts of western Kentucky. This is all headed toward the south-central Kentucky area but the question is how will it effect us?

Current thinking is that a line of thunderstorms will continue to move in our direction along and ahead of the front some of which could be severe. In fact the Storm Prediction Center has outlined all of south-central Kentucky in a slight risk for severe storms. Areas along and east of I-65 have been included n the 30% probability area.

A slight risk of severe storms has been outlined by the SPC for all of south-central KY for Thursday. This includes an area of 30% probability east of I-65.

Several things are coming together to create this possibility:

• A diffluent flow is present in the upper-levels which should help create synoptic scale lifting
• A strong closed area of low pressure with an associated area of vorticity is located over at 500 mb will be moving over the Midwest
• Around a 50 kt low-level jet will be advecting warm moist air from the Gulf of Mexico as well as helping to increase low-level shear
• Warm and moist air at the surface will allow for at least weak to moderate instability of around 250 – 500 j/kg
• A strong cold front will create lift
• Finally an area of 35-45 knot surface to 500 mb bulk shear

NAM forecast reflectivity (left), CAPE (center), and MSLP/winds/temp (right) for around 1 pm Thursday.

These conditions are all setting the stage for possible severe storms with threats of hail and damaging winds. It appears that directional shear and even speed wind shear will be minimal and thus the threat for tornadoes is also small. This however does not rule out the possibility of a spin up tornado along the squall line much like what we had in late January near Smith’s Grove in Warren Co. If any storms are able to initialize ahead of the squall line, these storms would also pose an increased risk of severe weather as well but these storms are not expected to be widespread, if at all, in our area. Overall though, expect a line of storms to move in between 9 am and 1 pm that could very well contain bowing segments which could lead to strong to severe winds. Some hail is also possible with these storms. Lastly and not to be outdone is the flash flooding potential as 1 to 2 inches of rain is likely and it could fall very quickly within thunderstorms.

SPC day 1 Total Precipitation indicates 1 -2 inches of rainfall possible in south-central Kentucky.

After the storms pass through rain will continue into the evening before ending. Colder air will make its way into the area as well as temperatures will drop into the low 40s by Friday morning. Our high Friday will be much cooler as well only reaching the upper 50s to near 60. Saturday morning temperatures will likely drop into the upper 30s and some frost is possible. We’ll make a nice rebound this weekend however as conditions clear and temperatures warm back into the 60s for Saturday and the 70s by Sunday. Data is currently suggesting a return to the 80s by early next week.

In summary expect:

•  A line of strong to possibly severe storms to pass through the area tomorrow.
• The timing of these storms should be between 9 am and 1 pm for south-central KY
• The main threat will be damaging winds with bowing segments in the line of thunderstorms, hail and isolated tornadoes are also possible.
• Heavy rain will accompany thunderstorms and 1 -2 inches rain is possible by tomorrow afternoon. Flash flooding is possible is association with the thunderstorms.

Daily Forecasts:

Thursday: Thunderstorms and rain are likely; some storms could be severe and rainfall between 1 and 2 inches is possible. Cooler with a high near 74 early before dropping into the 60s throughout the afternoon. Winds will be breezy from 10 – 20 mph.

Thursday Night: Rain will have ended but skies will remain overcast. Cool with a low near 41. West winds from 5 – 10 mph.

Friday: Cooler with a high of only 59 under mostly to partly cloudy skies. Winds from the west a 8 – 18 mph.

Friday Night: Frost possible with a low near 35 under partly cloudy skies. Winds will be light to 8 mph.

Saturday: Mostly sunny skies a warming up with a high around 64.

Sunday: Mostly sunny with a morning low in the low 40s and a high in the mid 70s.

Daily Forecasts:

Sunday Night: Partly to mostly cloudy with a low near 54. South to southwest winds 3-8 mph.

Monday: Partly to at times mostly cloudy and warm with a high near 77. Breezy with south to southwest winds at 10-20 mph.

Monday Night: Partly to mostly cloudy skies with a low around 59. South to southwest winds at 3-8 mph.

Tuesday: Mostly to partly sunny skies with a high around 80. South to southwest winds 10-15 mph.

Tuesday Night: Partly to mostly cloudy with a low near 60. South winds from 5-10 mph.

Wednesday: Partly to mostly cloudy a warm with a high near 80.

Thursday: Increasing clouds Wednesday night with a 70% chance of thunderstorms after midnight and into the morning hours. Some storms could be severe. Temperatures will drop from the 60s early into the 50s.

Discussion:

After a chilly and much below average March and even a cool start to April, spring has finally made it’s two and half week late arrival this weekend… better late than never! Temperatures soared into the 70s both Saturday and Sunday, in fact, the high of 76 at the Bowling Green Airport makes today the warmest day so far in 2013 and the warmest since October of 2012! It’s unlikely that will be the last time we can make that statement this week as temperatures will remain in the mid to upper 70s through the first half of the week. It’s even possible that some locations in south-central Kentucky crack the 80 degree mark on Tuesday and Wednesday.

Temperatures have finally warmed thanks to a zonal flow in the upper levels (as opposed to a trough which would bring in cold air) combined with a high pressure system located over the southeast. This surface high in the southeast along with a low pressure to our west have brought warm and moist southerly winds into Bowling Green. This pattern will hold through Thursday and thus until then warm temperatures will continue. A few disturbances will pass just to our north through the first half of the week and thus the occasional stray shower or storm is possible.  This will also create a mix of clouds and sun through the first half of the week.

The southerly flow (red arrows) created by the low pressure to our west and the high pressure to our east will keep the warm weather in place through Wednesday.

Wednesday night into Thursday morning is when the storm system to our west will finally move east and into our area. Anytime you have very warm air ahead of a strong system there is the risk of severe weather and this is in fact the case Thursday morning. At this time confidence is increasing that a squall line will push through Kentucky late Wednesday night/early Thursday morning. Of course the exact timing is too difficult to pinpoint at this time. Severe weather in the form of high winds and spin up tornadoes appear possible but this is very contingent on all the right conditions coming together. This system is still days away and thus the specifics and details are yet to be determined but at least be aware that severe storms are possible in the aforementioned time frame. Further updates will be given here on the WKU meteorology blog addressing the severe weather potential. Until then, stay tuned and enjoy the warm spring temperatures.

Day 4 severe weather outlook as of Sunday places the severe weather threat just to our west on Wednesday.

Conditions across the area have been very nice although a cool start kicked off our Saturday morning.  Overnight lows dipped into the  upper 30’s to around 40 degrees in many locations across south-central KY.  Mostly clear skies and calm winds through the overnight hours helped temperatures drop a couple degrees cooler than advertised.  Clear and cool conditions have prevailed for the morning hours, but things are beginning to warm up nicely.  With the retreat of the jet stream to the north, much milder air will continue to works it way into the Ohio Valley Region.  A surface ridge aligned from Michigan through Tennessee will continue to keep conditions rather calm with warming temperatures throughout the day.  Projected highs will be warmer today, with temperatures reaching the upper 60’s for folks to our north with low 70’s across south-central KY.

Surface Temperature Map Valid for 21Z Saturday. (Twister Data)

Looking ahead for this evening, conditions should remain calm, quiet, and nice.  Mild overnight lows are expected as temperatures drop to around 50 degrees.  Mostly clear skies will remain through the overnight and into our Sunday with light and variable winds.