Author Archives: wx

non-Derby Weekend odds and ends

Sunday, May 3, 2020  5 P.M.

Summary

Weekend forecasts for Louisville were reasonably good although temperatures were several degrees higher than predicted yesterday. If this had been a “business as usual” Derby Day, I wonder how many bad sunburns the infield crowd would have suffered.  Today’s temperature forecast was far worse than yesterday’s.  The expected showers finally arrived, but rain so far has hardly been worth the effort.  We’ll still maintain a chance for a few more light showers until about 8-9 P.M.

Looks like a nice day tomorrow with mid 70’s highs, then a good shot at a more significant rainfall tomorrow night into Tuesday.

Below normal temperatures will prevail from midweek through the weekend.

Forecast Models

Homo Sapiens (that’s us) evolved, we believe between 200,000 and 300,000 years ago, but did not  develop language skills until about 50,000 years so.  So, we’ve been trying to predict the future for at least 50 thousand years.  The first scientific numerical attempts, that I’m aware of,  were by Lewis Richardson in the early 1920’s.  He used equations developed by Wilhelm Bjerknes ( the Farther of modern meteorology) to create a numerical “model” of the atmosphere.  He then extrapolated the input data forward in time.  He produced a 6-hour forecast for two cities in Europe.  Sounds pretty simple, but there are an enormous number of calculations required to move forecast data horizontally and vertically through the atmosphere, even for just six hours.  Working off and on, Richardson took six MONTHS to complete his 6-hour forecast!

The numerical prediction did not produce realistic results.  But, the concept was proven correct. But the huge number of calculations needed proved it was not feasible at the time.

Jump ahead two decades.  During World War II the military wanted some way to speed calculations needed during battles.  Started in 1943 the project ended in 1946 by calculating (very rapidly) trajectories for canon balls by a machine called eniac  (electrical numerical integrator and computer).

Story continues tomorrow

 

 

Rainy night…severe threat very low

Sunday, April 12, 2020   4:30 P.M.

For the past two days the Storm Prediction Center has been predicting a major severe weather outbreak over the deep south into central Tennessee.  They have been including KY and southern IN in the “slight risk” area, but their discussion has included several “ifs” for us.  In essence, plenty of uncertainty for KY/IN.

As the situation has been evolving today, there’s been a good news/bad news scenario developing.  Bad news for the deep south means good news for us.  Mississippi has been hit this afternoon and things look very bad for Alabama, central TN and Georgia tonight.  That major outbreak will block some needed severe storm ingredients from traveling this far north. So, even though we’ll see two periods of showers/thunderstorms tonight, the threat for “severe” thunderstorms will be very low – less than 5%.

Showers/thunderstorms in the local area now will move northeast of Louisville by 8-9 P.M.  Then, we’ll have a 5-6 hour period of dry weather along with rising temperatures!  Another period of showers/t-storms will arrive with gusty winds a couple of hours after Midnight.  This rain system should end during the morning rush hour.

Tomorrow will be cloudy, very windy and cooler.  Temperatures should drop into the low to mid 50’s tomorrow morning and stay steady during the afternoon.  The winds will be tomorrow’s weather feature with frequent gusts over 30 mph and a few gusts over 40 mph possible.

Dry Tuesday?

Monday, March 30, 2020  11 P.M.

I’ve been puzzled since yesterday about the NWS forecast for a 50% chance for rain tomorrow.  All the models have been keeping the rain south of Louisville.  Tonight’s models keep the rain even farther south.  50% seems far too high for Tuesday.  So, a mostly cloudy sky with pleasantly cool temperatures in the 55-58 range appears likely.

A little rain tonight

Sunday, March 22, 2020  6 P.M.

A weak upper air system will pass over the area tonight.  However, it’s not likely to bring much rain.  Low level moisture is very low, so it’s going to take a long time for the rain/snow above us to saturate the air to bring us some rain.  A few sprinkles or patches of light rain are possible this evening.  However, our best chance for some light rain will be for rush hour tomorrow morning.  Overall, total rainfall from this system will most likely be a trace to a couple hundredths of an inch.

If you’ve been watching radar this afternoon, you’ve been seeing in action what I described above.  If you have watched Louisville radar, you’ve seen rain all around us, but none close to us.  However, if you’ve seen so-called “composite” radar, it looks like we’ve had rain for the past few hours.  In fact, it has been raining aloft, but not reaching the ground.  It’s evaporating before it hits the ground.  You may see gray vertical streaks coming from the clouds.  That’s called virga – falling precipitation evaporating before it reaches the surface

Note:  Composite radar, which most media outlets show, integrates data from all NWS radars in the area.  Locally, what we are seeing is a merging of radar data from our radar (at Ft. Knox) with data from Nashville, Cincinnati, Indy and Evansville.  While our radar sees no rain, the others all show rain aloft over Louisville.  Compositing also creates problems for accurately locating thunderstorms.

Stuff

Being of a certain age, I’ve been closely following the spread of the coronavirus.  I’m also a scientist and have been closely watching the numbers.  As a result, I’m convinced we’ve reached the point of no return. Within the next day or two,  I expect the U.S. healthcare system to become completely overrun.  Our Prevaricator In Chief (PIC) constantly tells us we have all the medical supplies we need.  But where are they?  (Perhaps he sent them to our friends in North Korea?)  It’s obvious PIC has no sense of science.  Many of his serious science statements have been just harmlessly funny.  But, this time, his failure to even consider his science/medical advisers has allowed a great plague to take hold of our citizens.  He was advised of the possible consequences of coronavirus as early as January.  Instead, we got “It’s just the flu” , “Don’t worry about it” and it’s a “Democrat Hoax!”

It looks to me as though the next two weeks (at least) are going to be very bad.  PIC and Congress will throw trillions of dollars at the problem, but it’s not going to do much good.  That’s a lot of money to spend on a “Democrat Hoax”.

 

Storm update- 11 P.M.

Thursday, March 19, 2020  11 P.M.

After Midnight, periods of thunderstorms/heavy rain/possible flash flooding over the southern third of IN, but stay north of Ohio River until about 5 A.M.

Louisville area has showers/thunderstorms 5 – 8 AM.

NO severe thunderstorms are expected, and flash flooding threat fading over the area, especially south of the Ohio River.

Flash Flood, Tornado Watches tonight

Thursday,March 19, 2020

Flash flooding likely: severe storms iffy

A fairly strong upper air disturbance will come across the lower Ohio Valley tonight.  Lucky for us, it’s focused mostly on Indiana.  With this upper system, we’ll see two clusters of thunderstorms overnight.  With the rains of the past two days, periods of heavy rain, especially over southern IN, will pretty much guarantee widespread pockets of flash flooding over northern KY and southern IN.  If you live in a flash flood-prone area, you know the drill.

The first cluster of thunderstorms will be over the area this evening.  The southern side is weak and will provide plenty of rain to west and central KY and initiate some of the expected flash flooding.  But no severe thunderstorms.

The first cluster of storms will be more noteworthy over the southern half of Indiana.  Severe storms are moving over southern Illinois and will race eastnortheastward.  Heavy downpours are likely and a few severe storms will be possible between, roughly, 8 P.M. and Midnight.  Primary threat will be strong winds and possibly some hail.

The second cluster of storms will move through the area between about 2 A.M. and 8 A.M.  This one is much stronger and is likely to produce an outbreak of severe storms from Arkansas, southeast Missouri and southern IL this evening.  By the time this cluster arrives in the Louisville region, it is likely to be weakening.  Plus, atmospheric instability will be diminishing. Also, the strongest dynamics will remain north of our area.

The result will be a very noisy night north of the Ohio River.  Flash flooding will probably become  a serious problem.  Storms will be strong, but probably not severe.  Along and south of the Ohio River, the primary line of thunderstorms most likely won’t arrive in Louisville until 5 A.M. or later.  They will not be very strong, but deposit enough rain to make a very messy rush hour before the exit the area by 8 A.M.

 

Recent trends looking good for us

Strongest storms will stay south and west of Louisville

Thursday, March 12, 2020  4:45 P.M.

Latest radar trends and short term forecast models are strongly indicating that we’ll get plenty of rain this evening, but severe weather will not reach the Louisville area.  Severe storms are forming along the approaching cold front over western KY and dropping rapidly southeast.  That area of severe storms is heading toward central Tennessee.

Meanwhile, area of showers and non-severe thunderstorms has been expanding over  SW IN and is moving our way.  Cold front may produce some gusty winds as it passes through the Louisville area between 6:30 and 8:30 this evening.  Our biggest problem will be with heavy rain and possible areas of flash flooding.

 

 

Two rounds of thunderstorms this evening

Thursday, March 12, 2020  4 P.M.

Cluster of rain/thunderstorms in the area now is not showing any signs of severe weather,  Instability is very low, but the dynamics are quite strong.  Nevertheless, severe weather is not expected with this area.  However, stronger storms appear likely later this evening.

Current showers/t-storms are forming along a warm front slowly pushing north.  Once we get into the warmer/moister air south of the front, we’ll have the potential for slightly higher instability for a few hours.

During that time, a cold front will be moving over southern IN/western KY.  That system should pass through our area between 6 and 8 P.M.  The front is already creating severe weather to our west.  Instability should still be weak, but the wind fields will be strong enough to create a strong wind threat – possibly severe (58 mph or more) in a few areas.  Atmospheric structure favorable for tornadoes should remain south and west of Louisville.

After 8 P.M., threat for severe weather will move south and east of Louisville area.

Even less snow tomorrow

Fri., Feb. 7,2020

Weak Clipper brings a little more snow

A weak Alberta Clipper dropping into the Ohio Valley tonight and tomorrow morning will leave a minor calling card in its wake.  Available moisture is lacking and the clipper does not appear strong enough to force much lifting this far south.  The clipper’s path is expected to pass over southern IL/IN.  That sets up central IN for a possible 1-3″ accumulation tonight and early tomorrow.

Meanwhile, south of a clipper’s path, not much happens.  In reaction to the clipper moving north of us, we’ll see southerly winds tonight.  That’ll hold temperatures in the low to mid 30’s.  Precipitation south of a clipper’s path historically is little or none.  So, even though some light snow is possible late tonight and tomorrow morning, accumulation will be in the “little or none” category.  Probability for measurable snowfall is about 50%.

Tomorrow morning marks the last snow chance for about a week, at least.

Grasping at more straws

Thursday,Feb. 6, 2020

Light snow possible late tonight

Snow chances have been few and far between this winter.  We started with tad about an inch of grass-only snow in November and haven’t been able to match it since.  However, we’ll see two chances over the next two days.  Best chance for breaking past one inch will come Saturday morning.

A strong upper level trough is passing over today, but so far is having trouble with surface development.  That problem should end tonight as a major surface storm will be developing/accelerating northeastward along and just east of the Appalachians tonight.  Latest forecasts have the storm path a bit farther east than earlier models.  That’s bad news for the Louisville area.

We were expected to be in the western edge of snowfall from this system.  Now, it looks like we’ll be “really” on the edge.  Far southeastern KY could get up to 6″ overnight.  As you head northwest from there, snowfall will lessen.  Bowling Green, Lexington and NE KY should be in the 2″-4″ range.  E-town, Bardstown, Shelbyville, and Henry County will likely be in the 1″-2″ zone.  West of that, snow will fall off quickly. SE Jefferson County could get up to .5″ while downtown will probably get a dusting.  North of the Ohio River…little to nothing.

In the Louisville area, snow is likely to begin about 3-4 A.M. and probably be over around 7-8 A.M.  Any accumulations will be on grassy areas.  Roads should be wet, but icy conditions are likely on some bridges and overpasses.

As the upper trough moves eastward tomorrow, a (probably) weak Alberta Clipper will run southeastward along the backside of the trough.  Models are projecting another area of light snow with the clipper and put us in its projected path.  I’ll check back on that tomorrow.

Stuff

Together, Kobe Bryant and LeBron James played in every NBA Championship Finals from 2008 until 2018.  But, they never played each other.