Thursday, July 26, 2012

7/26 - 1:55pm - Kentuckiana Severe Weather Update

Kentuckiana is right on the edge of what could be a significant severe weather outbreak this evening. Nothing demonstrates this better than the Storm Prediction Center's latest severe weather outlook, which puts us in a Slight Risk but has a 30% severe wind risk running right through the center of Louisville. The reason for this is that faster winds aloft are most prevalent to our north and east so more of a risk area (a Moderate Risk) is needed up there. These winds have the potential to power a large line or cluster of wind-driven storms that could possibly become a derecho just to our north if it sustains itself long enough.

A Severe Thunderstorm WATCH has gone up for areas northeast of Louisville but not including the city. This was needed because severe storms are already affecting areas near Cleveland right now and more will be forming in the near term across Ohio, West Virginia, and Pennsylvania. I suspect a Severe Thunderstorm Watch will be issued for the Louisville area at some point this evening since storms will come through a little later than areas to our north.

Storm timing in Kentuckiana should be after 5pm this evening. The latest High Resolution Rapid Refresh model has storms rolling through the Louisville Metro area at around 7pm but this may vary a bit because this will be highly dependant on where storms fire along outflow boundaries and other surface features. The HRRR suggests that these will be either a broken or continuous line of storms which makes sense given that winds both aloft and near the surface will be from a westerly direction. This also means this could be a wind-driven line of storms so wind damage potential is relatively high here if storms get severe enough. Large hail will be a threat from any of the strongest storms. There may be more than one round of storms this evening in the area through 2 or 3 am since the cold front will not be passing through until that time. This might be a good time to secure your trash cans or any loose articles you have outside your house so that they don't end up in your neighbor's yard...

Sunday, July 22, 2012

7/22 - 10:30pm CDT - Heat Cranks Up in West Tennessee

A few showers at 3:25pm today
Some showers and downpours did make it a little further north than expected today across West Tennessee. Last night's model guidance and thinking was that any of these scattered "pop-up" showers would stay mostly south of the Mississippi border, but a complex of storms moved a bit further north than expected out of Alabama into Middle Tennessee. This complex of storms brought with it a small boundary in the atmosphere that helped get these widely scattered showers going over portions of West Tennessee this afternoon. These have all since faded away and the region should have a stretch of hot and mostly clear weather through at least the middle of the week. Humidity will be on the increase as temperatures get into the upper 90's, so expect some dangerous heat index values well over 100 degrees. Storm chances look like they will now be increasing toward the end of the week as a front drops from the south but temperatures still appear to be heading toward the triple digits since this front likely won't make it far enough south to pass through.

My weathercast from last night's 10pm news on WBBJ in Jackson is available to watch below.

Wednesday, July 18, 2012

7/18 - 10:40pm - Storm Spotting in Your Own Front Yard

Most storms that erupted today across Kentuckiana and West Tennessee were pretty typical. For the most part they were disorganized and each individual storm didn't last very long but a few did get strong enough for some severe thunderstorm warnings. Unfortunately these storms did pack some nasty cloud-to-ground lightning in the city of Louisville and that sparked some structure fires. Later in the day around 7:30pm just after most storms had exited the city there was a spectacular collision of two outflow boundaries near the I-64/I-264 interchange in St. Matthews. These outflow boundaries, one from Clark County, IN and the other from Shelby County, KY in this case, are just rushes of cold air that come out of other storms and create something akin to a miniature cold front. When these two boundaries collided they created an incredible amount of convergence which birthed a complex of storms right over the city. We're talking about the radar being clear at 7:30pm and there being storms on radar in East Louisville at 7:36pm. This collision also created some weak rotation briefly and dropped quite a base cloud as the complex moved south. The cloud created quite a show in my front yard and I was quite surprised to see such a well-defined (and briefly rotating!) updraft base as I was driving down my driveway this afternoon!

Now that all that excitement is over, we're going to be in for more storms tomorrow and Friday. A cold front will be approaching Kentucky and Tennessee from the Upper Midwest that should create a focus for storm development or at least create storms that will send outflow boundaries toward the south to create more storms. These will largely be powered by the heat and humidity that we'll be seeing over the next couple of days but with the front coming into play there's a possibility that storms may form earlier in the day or even possibly in the morning tomorrow and Friday.

Strong winds will be possible with any storm that forms along with more of the same lightning that we've seen around the region today. Storms could reach severe limits thanks to all the moisture in the environment and the front moving closer so the Storm Prediction Center has issued a Slight Risk for severe weather tomorrow for all of Kentucky and some of Northwest Tennessee. Storms will again be possible on Friday as the front moves through, but we'll dry out behind the front for the weekend.

Sunday, July 15, 2012

7/15 - 7pm CDT - The Heat Returns!

A few showers are ongoing across West Tennnessee right now, but this is quite a bit less than what was expected today. Dry air rotating around a area of high pressure has moved into the region because this high has nudged a bit further westward than originally forecast. This means that a majority of the shower activity has stayed west of the Mississippi River, but a couple thundershowers could still pop up before sunset. These should mostly dissipate before the overnight hours.

Heat and humidity are on their way back as a large ridge of high pressure moves eastward over the next few days. This should surpress storm chances a little bit, but not entirely because temperatures aloft will still be a little cool. This heat at the surface and the slightly cool air aloft should create the typical "summertime pop-up storm" environment that we're used to seeing in the afternoons this time of year. Temperatures underneath this ridge of high pressure should be in the lower to middle 90's in West Tenneessee and middle 90's until Wednesday in Kentuckiana. A front dropping south on Thursday will trigger higher rain chances in both Kentuckiana and West Tenneessee and there could be some slightly cooler temperatures behind the front for Kentuckiana. Things look to remain hot all week long in West Tennessee!

I'm in Jackson, TN right now getting ready for the 10 O'Clock news on WBBJ this evening before going back to Louisville tomorrow. Check out my Hokey Weather Fact from last night's show on the left and be sure to tune in to WBBJ tonight at 10 for a new one!


Thursday, July 12, 2012

7/12 - 11:45pm - A Festive Forecast

Tomorrow is the beginning of the Forecastle Festival at Waterfront Park in Louisville. Unfortunately rainfall could be an issue as a stationary boundary begins to move northward from North Mississippi overnight. This boundary will bring even more moisture into the area and a source of lift, the boundary itself, which should bring in some ongoing showers and storms tomorrow morning. The short-range models right now are suggesting that there may be a break in the action after 2pm, which you'll see in the NAM simulated radar image on the right. Disagreement among the models exists over whether the storms will re-fire and make an impact in the area later on in the afternoon. My thoughts on this are that storms may have trouble getting going again in the late afternoon since the morning's activity will be hanging around well into the early afternoon, but that the presence of the frontal boundary will compensate quite a bit for this. Expect then for storms to possibly re-fire and move into the area sometime after 5pm. The good news here for festival goers is that I don't think storm coverage will be quite as high during this second round, so there's a good chance the Waterfront may be able to dodge storms if they remain scattered.

Daily storm chances will continue on Saturday and Sunday as the moisture from the current system sticks around and a bit of upper-level support kicks in thanks to a trough passing through the Great Lakes region. These storm chances will be a bit lower than tomorrow's though because there won't be much of anything to trigger them, like a front, aside from daytime heating in the afternoon. Long story short, bring a rain jacket or poncho if you're going downtown for Forecastle this weekend. Temperatures will top out near 80 tomorrow as the clouds and rain move through, but it will warm into the mid 80's for the weekend in Louisville.

Speaking of this weekend, I'm going to be a busy guy! On Saturday I'm heading down to Jackson, Tennessee to do the Saturday and Sunday evening shifts of weather at WBBJ-TV. This means you'll see me on the 6pm and 10pm newscasts this weekend if you're in the viewing area. It's been almost three months since I've done weather on TV, but I'm very excited to be getting back into it this coming weekend and again on Saturday night next weekend. Be sure to tune in!

Tuesday, July 10, 2012

7/10 - 11:55pm - A Tale of Two TV Stations

Let's start with weather first, shall we? Today was hot in Louisville, much hotter than anticipated because dry air that made its way into the area allowed temperatures to rise quite a bit. We're talking about a high temperature that was 95 degrees today, which even though is very warm, it was still cooler than what we experienced during last week's massive heat wave. Tomorrow should be a little cooler as moister air moves in again from the south.

Daily rain chances will be ramping up Thursday in Louisville as a trough develops to the west of the Mississippi River. It's already been raining in West Tennessee a bit this week, but more is on the way through the weekend as this trough gets its act together and a warm front moves northward. The rain is still needed in West Tennessee as drought conditions persist throughout the region. This rain will keep temperatures down in both regions, which is good news after all the heat! Between this past morning and Sunday morning there could be over 6 inches of rainfall  in West Tennessee and North Mississippi according to the Hydrometeorological Prediction Center (HPC). Flash flooding issues may crop up in some of the heavier thunderstorms.

Now, to the two TV stations. The first TV station in question here is WBBJ-TV in Jackson, TN where I'll be at on Saturday and Sunday night doing weather. It's been nearly three months since I've been on air in West Tennessee so I'm happy to be coming back this weekend and next weekend too for the Saturday night shows! The second TV station in question is WAVE-TV in Louisville. Today I went in to meet with Kevin Harned and the gang at the station and came out a WAVE 3 Weather intern. This has been "in the works" for awhile but today it was made official and I'm extremely excited to be sharing this news! I'll be at WAVE a couple days a week until mid-August. My duties will be mostly web-based with social media, blogs, etc, but I'll also assist with any needed TV-related tasks. I'm so thankful to be able to intern at the station I grew up with and to work with such a great team of meteorologists!

Saturday, July 7, 2012

7/7 - 10:30pm - Massive Heat Wave Ends with Storms

Today capped off the longest, hottest stretch of weather in Louisville that most people can remember. Today's 106° high at Louisville International Airport was the hottest it's been since July 14th, 1936 when it got to 107°. That temperature is Louisville's all-time record high and if we didn't have as many clouds as we did this afternoon in the city we would have met or broken it. This ends nine days of 100°+ weather, which is the third-longest stretch of triple digits ever recorded according to NWS Louisville.

Storms that will develop tomorrow will be ushering in cooler temperatures, which is welcome news! The bad part is that some of these storms may be severe due to the incredible amount of energy they'll have at their disposal from all the heat. Temperatures in the mid 90's tomorrow with sunshine and high humidity will power an awful lot of instability, or the tendency for air parcels to rise and create thunderstorms. A cold front sinking down from the north that will be stalling out once it passes just to our south will be the focus for storm chances starting tomorrow in the early afternoon in Louisville and lasting through Monday morning.

The main threats from these storms will be wind and hail, but there could also be a threat for some rotating storms too. While winds don't look favorable for any sort of big tornado problems tomorrow, a couple of these rotating storms may get just enough juice to put down a brief spin-up. EHI values in the adjacent image take into account both instability and helicity, which is a product of wind shear. The elevated values you see are powered mostly by instability and just a little bit of helicity, so again, winds aren't that favorable here. The Louisville area is no stranger to summertime tornadoes as you may remember a series of four of them that touched down in late June of last year.

Given the chances for some severe wind and hail tomorrow, the Storm Prediction Center has issued a 15% Slight Risk area for Kentucky. A better chance for severe weather (30%) exists closer to the East Coast where upper-level winds will be stronger as a trough digs down a bit into that area.

Thursday, July 5, 2012

7/5 - 11:30pm - Louisville Urban Heat Island This Week

It goes without saying that it's been incredibly hot this week in Louisville. This is all thanks to an expansive ridge of high pressure over the center of the country. High temperatures have been record-breaking every day this week except Tuesday when the high at the airport was below 100. This stretch of triple digit temperatures dates back to June 28th and there appear to be at least two more days of 100-plus weather ahead. The urban heat island effect, which causes temperatures in concrete and asphalt-filled urban areas to be higher than more vegetated suburban and rural areas, has been pretty apparent with the extreme heat. Temperature readings at Louisville International Airport have been consistently higher than other observation sites within the city and this is easy to see when comparing the high and low temperatures for each day this week with surrounding stations. Below you'll find the high and low temperatures for each day of the week so far at Louisville International Airport (KSDF), a personal weather station in Shively (West Louisville), Bowman Field, and a personal weather station in Fisherville (East Louisville):

Thursday July 5th

Louisville Airport 104/78 | Shively 100/72 | Bowman 102/78 | Fisherville 98/72

Wednesday July 4th

Louisville Airport 102/76 | Shively 101/76 | Bowman 99/76 | Fisherville 97/69

Tuesday July 3rd

Louisville Airport 97/73 | Shively 97/73 | Bowman 96/72 | Fisherville 93/67

Monday July 2nd

Louisville Airport 100/73 | Shively 99/73 | Bowman 99/71 | Fisherville 96/67

Sunday July 1st

Louisville Airport 103/74 | Shively 102/75 | Bowman 101/72 | Fisherville 99/70

I've sorted the data above from most urban (the airport) to least urban (Fisherville), so it's not hard to put together that temperatures generally decrease as you get further away from the dense center of Louisville. The Fisherville observation station is located in a valley in the eastern portion of the county, so the low temperatures each morning are a bit cooler than they would be otherwise due to cool air settling into the valley at night. High temperatures at this station shouldn't be affected by the valley and this checks out because I've been keeping an eye on the observations in Shelbyville, which is down the street from Fisherville, so to say. This warmth due to the urban heat island near the airport is significant because this is where the official temperatures for the city are taken. If it's 100 degrees at the airport, the rest of the city is probably seeing temperatures a degree or two cooler.

This difference in temperature between the airport and the rest of the city was the focus of some research I published in April for a class at Mississippi State University. I used quite a bit of historical data to figure out how much the urban heat island "distorts" the temperatures at the airport. Go check out my research by clicking this link to a blog post I penned earlier this year.