Severe Weather Outbreak #2 for the Fall Season in Kentucky

Update 16:45EST November 16th:

 

My concern is that this is a transitional season.  Just like March-May brings the most intense severe weather, there is another severe season that occurs in the fall of the year and we're right in the heart of it.  When you get this kind of model data coming in it really raises some eyebrows.  SPC has already upgraded from Slight Risk to Moderate Risk for a huge part of the Ohio Valley tomorrow.  It's starting to get a little concerning.

 

I'm still seeing good shear, CAPE, moisture, upper support, and favorable time of day for this system to support severe weather.  I think we will see two rounds of storms.  The WRF model shows this well.  The first wave of storms will come through early Sunday.

 

 

 

This first round of storms may bring small hail, gusty winds, and dangerous lightning with it.  After it passes through for the most part during the early afternoon, we may go quiet for a short time.  Then the wind will start to howl and as the cold front approaches from the west a more severe squall line will form and drop into the area.  This squall line looks to strike central Kentucky sometime during the evening hours.

 

 

 

This second squall line may have more severe wind associated with it.  There is also a threat for tornadoes to spin up inside the line as well.  These are the most dangerous type of tornadoes sometimes because they happen so quickly without warning and it's almost impossible to tell exactly where they will strike.  It's not like a supercell that you can easily track.  This happens and then boom it's over. 

 

I strongly recommend keeping a close eye on the weather tomorrow anywhere in the Ohio Valley. Northern Kentucky and all of Indiana and Ohio look to be the most prone for damage tomorrow.

 

-Shawn

 

Previous discussion:

 

The models are starting to indicate that yet another severe weather outbreak may be coming to the Ohio Valley.  Today’s 12Z run of the Euro model is particularly scary looking with good shear, good moisture, and favorable upper dynamics relative to this time of year.  Time of day is also good…not perfect, but good for thunderstorms.  The Euro model is showing as much as 500 joules of CAPE preceding this system Sunday night for much of Kentucky, which isn’t that shabby for November.

 

I will update the blog this weekend with more details.  For now, just file a note in the back of your mind that Sunday night could be dangerous for Kentucky and parts of surrounding states to our west as well.  Be alert!

 

CAPE values forecast off today’s 12Z European model run:

 

 

-Shawn

Halloween Thunderstorms

Update: 19:49EDT 30-October-2013

The latest run of the ECMWF model shows three distinct areas of convection ongoing as of 14:00EDT Halloween  afternoon.

The convective line in eastern Arkansas would then work northeastward into central Kentucky during the late evening.  The timing on the main push of weather looks to be between 20:00 and midnight for the Lexington area.  This doesn't mean it won't storm before then as pre-frontal cells pop up, but the main batch should come through around that time.

Following the main squall line, there may be a second line come through overnight as the airmass driving this system plows through the state.

Ahead of this system, it's going to be very windy tomorrow during the day.  A Wind Advisory is posted currently by the NWS for most of the state.  The ECMWF model predicts sustained winds of 18-24 MPH!  This should mean that gusts will exceed 40 at times.  You should tie down trash cans, loose outdoor furniture, jack-o-lanterns, and anything else that you don't want to blow away tomorrow.

Additionally, there is still a high-end Slight  Risk of severe weather posted for all of Kentucky roughly west of I-75 tomorrow.  Tornado spin-ups along the squall line are a possibility.  If any tornadoes do spin up, these will be the type that are very hard to detect with radar and will hit quickly.  These types of tornadoes have a much smaller warning time.  Therefore, it is critical that even if a Severe T-storm Warning is issued for your location tomorrow, you should still take shelter (as always) as if it were a Tornado Warning instead.

Obviously, most towns have changed trick-or-treat to Friday to protect the children in case of severe weather moving in sooner.  I think this is a great call.  Safety first!

Previous discussion follows:


-Shawn


Right on cue, the wild ride I talked about in my last update has arrived.  We had some of the hottest weather of the year early in October, and that went straight into winter-like temps this past week with lows below freezing and highs that didn't get out of the 40s.  We even saw a few snow flakes mixed in with plain rain for a brief time that did not accumulate at all but for some it was neat to see.

As we head into the final week of the month the roller coaster continues.  Temps early this week will moderate back to normal with highs in the 60s.  The weather actually looks to be quite pleasant, so enjoy it!  By Wednesday the next weather system will start to draw closer and by Halloween it will be upon Kentucky with rain and thunderstorms likely.  This is not looking like a good forecast for treat-or-treat at all according to the GFS model.

The GFS model brings the heavy part of the storm in during the evening Thursday and pushes it through during the night.  It shows a 110 knot jet streak overhead so there will be some decent upper air support.  RH values look to be decent for this time of year also.  The real question will be how much instability can we achieve during the day Thursday?

If we get some good insolation and increase in instability we could potentially see a round of stronger storms push through.  The tornado threat at this point looks low, but we will have to watch model trends over the next couple of days to see how this evolves.  The Storm Prediction Center currently has areas just to our south highlighted for severe weather but they do mention that Kentucky could potentially end up being included in the outlook area in later forecasts.  Also, it was looking like a flooding threat from heavy rains might occur but now that is looking less likely.

The ECMWF model is slower and brings the main push of weather through overnight Thursday into Friday morning.  As a result, it shows even less instability and meager CAPE values of a few hundred joules per KG at best.

If this model verifies, the threat of severe weather would be much lower.  It would be possible that some areas in central KY might possibly squeeze in some dry weather during the early evening for trick-or-treat before the rain hits.

It'll take a couple more runs before we can put a finger on the exact timing of this storm system for Kentucky.  The bottom line right now is this:  beautiful fall weather tomorrow will slowly degrade this week and turn into rain by Thursday.  Cooler air will once again spill into Kentucky next weekend behind the cold front and we'll start the cycle all over again.


-Shawn

Cooler Weather is Here to Stay

If Wednesday is "hump day", then this week is "hump week" as we are now firmly into the middle of October.  This, being a transition month, is usually one of the most unpredictable months of the year.  You can have snow or tornadoes, sub-freezing air or mid-80s, sunshine and drought or flooding in any given Kentucky October.  So far in 2013, October has been fairly nice though and for that many of us are thankful.  This is about to change now, and the cold air of Fall is upon us as the sun is approaching the Tropic of Capricorn.

This year has been an odd one, with every single month except February being cooler than average.  It's also been rainy this year with no dry months, let alone drought.  The reason for this is because a blocking pattern established itself in the northern latitudes that resulted in a trough controlling the weather in the eastern U.S. for most of the year.  We saw that trough finally break up in September which is why we had the warmest weather of the year in September and the first week of October.  Interestingly, the GFS model is predicting that the trough is going to return now.  It looks as though the eastern U.S. is going back into the northwesterly flow possibly for the rest of October.

What does this mean for Kentucky?  Well, as you can see on the (clickable) image above, the jet stream is going to take a big dip and when that happens, you get colder air moving in.  This image is valid Thursday the 24th.  The trough is actually going to move in tomorrow with cooler air...but the model is predicting that the trough will actually linger and then become sharper next week.  By Thursday the 24th, Kentucky is firmly in the base of the trough and this will likely bring our coldest temps of the season with frost being likely.

We will NOT have a good shot at snowflakes, contrary to what a certain TV meteorologist in Lexington will start harping on daily now until May.  But we will see showery weather and colder air become more common now going toward November.

It's time to get out the jackets and coats.  And as bad as I hate it...my utility bill is likely going to start going up now because the thermostat will soon get flipped to the "heat" setting.


-Shawn

October Weather in Kentucky Looks More Stormy

My meteorology friends and I have been using one word to describe 2013: boring.  But I suppose that’s a good thing when you consider the shear lack of tornado outbreaks and big severe weather outbreaks across the nation this year.  Here in the Ohio Valley region we’ve spent most of the year locked into a blocking pattern that has kept the flow mostly northwesterly.  As a result, we’ve had above normal precipitation and below normal temperatures in every single month this year, minus February.

 

That’s all about to change, however.  In my last write-up I talked about how this consistency in the pattern is what leads me to believe it will break up soon.  Looking at the latest model data, that may be exactly what’s about to happen.  The jet stream is starting to move around more now and going into October the GFS model is predicting the jet to go wild.  A very wavy looking pattern, which we call a “meridional flow” pattern, is predicted to take shape in the coming weeks.  When this happens, it shakes up the weather nation-wide.

 

 

I expect that the first truly cold air of the season is coming to the Rocky Mountains soon.  We may hear the first echoes of the “S-word” mentioned by national TV weather personalities as some huge troughs begin to dig into the western U.S.  Here in the Ohio Valley, Kentuckians can expect more variability in the weather with potential episodes of heavy rain and more frequent shots of colder air moving in.

 

Because of the cool, wet summer we just experienced I’ve been using 2004 as a good analog year to compare to when looking at what may be coming for the end of this year.  This might not turn out to be a good year to use after all.  In 2004 the 70s and 80s that we saw all summer continued through October.  What was labeled as “cool” in July became “warm” by the time we were deep into fall.  Winter ended up being mild overall, with one historic snowstorm around Christmas that mainly affected the Louisville area with a couple feet of snow, and another cold snap in late January, but otherwise temperate and rather dry.  This year is starting to follow a different course already with the cool air of summer looking like it will turn into cold air sooner.  You certainly cannot predict winter accurately from months away and I will not try.  But the overall pattern this year will likely be colder and snowier than what we ended up seeing the last time we had a cool summer.

 

It should be fun to watch this play out.  In the meantime, as the growing season comes to and end now we’ll all be on the lookout for that first frost of the season.  If the GFS computer model is on to something, we might not have to wait too much longer.

 

 

-Shawn

Some Early Thoughts on Winter 2013 - 2014

 

The weather pattern all year has been one that features a lot of blocking across Canada which has largely kept the eastern U.S. in a trough.  As a result, the eastern part of the nation has been cool and wet, while the western part of the nation has baked.  The consistency of this pattern for the first 8 solid months of the year has been pretty amazing.  The last cool summer similar to this was nine years ago, when the Lexington official reporting station never hit 90°F the entire year.

 

Summer 2013 is starting to wind down now.  Meteorological autumn begins in just 20 days.  This has led many including myself to start wondering what the end of the year may bring.  If this pattern that has been locked in all year were to remain in place going into late autumn and early winter, we could be looking at ferocious winter weather with snow and very cold weather being likely.  In fact, the summer I mentioned earlier resulted in a massive snowstorm just three days before Christmas 2004 in which Louisville saw two feet of snow and the Lexington area got in on some of the action as well.  So with 2013 going the way of the unusually cool and wet summers it does make you wonder what could by lying ahead for us.

 

On the other hand the amazing consistency of the pattern we’ve seen is also what makes me think it will break up soon.  It’s just a matter of time until the blocking breaks up and allows the jet stream to start moving around again.  Interestingly, this is what the GFS model is currently showing for the second half of August.  It lifts the jet northward, and takes the flow across the United States into a zonal setup.  Basically, this just means that you don’t have huge ridges and troughs…the flow is simply west to east across the nation.  This would result in a more stagnant airmass, as well as an increase in temperatures for us and a lack of rainfall compared to what we have been seeing.

 

 

The question of course becomes:  Is this a temporary switch to more average summer weather at the very end of summer or is this the beginning of the next major pattern flip?  That is the huge question because again, if the current pattern were to take us into winter we’d have big problems.  But if this switch at the end of August is the beginning of an overall pattern flop, then winter 2013-2014 will be anybody’s guess.  Time will tell and of course I’ll be watching for signs.  In the meantime, it appears that summer is going to give us one final attempt at mustering up some hot and humid air to close out the season for 2013.

 

 

-Shawn