Author Archives: wx

Timing update

2 P.M. update

Thursday, March 14, 2019

1).  Recent data shows the upper and lower atmosphere are beginning to “uncouple.”  That means the “sweet spot” of atmospheric conditions that has spawned the severe weather to our west for the past few hours is beginning to fade.

2).  The weakening has enabled the line of storms to slow its eastward progression.

3).  New “best estimate” for pushing through Louisville Metro is now 4:30 to 6 P.M.

4).  Until then, surface winds will continue to be very gusty – up to around 40-45 mph.

5).  When thunderstorms arrive, the primary threat will be strong wind gusts – up to 50 mph or so.  Tornado threat has lowered.

New time estimate

1:45 P.M. Thursday, March 14, 2019

1).  Signs  are showing the upper atmosphere and the lower atmosphere are beginning to “uncouple.”  Basically, that means that the “sweet spot” for severe weather production is fading away.

2).  The general weakening will allow the system to slow its eastward progression.

3).  Best time for Louisville now looks to be 4:30 until 6 P.M.

4).  Strong gusty winds (non thunderstorm) will continue.  Thunderstorm winds could be strong (50 mph or so), but tornado threat is lowering.

Tornado Watch

 

1 P.M. update

Supercells still forming over west KY into SW IN.  Several tornadoes have been reported.

Adjust time of arrival in Louisville area to 3 P.M. – 5 P.M. Otherwise, discussion below still looks okay.

March 14, 2019  Noon

Potentially Damaging Storms late this afternoon

One change since yesterday’s post is the addition of additional moisture into the equation.  The very strong wind fields are still in place.  Now with the added moisture, it looks like nature’s two primary severe weather producers – dynamics and thermodynamics – will interact for a few hours this afternoon.  Luckily for us, the worst should be over before reaching the Louisville area.

Super cells are moving along the Ohio River in western KY and southern IL.  Several warnings have already been issued.  This area of severe weather will move rapidly northeast into southwest IN and then central IN over the next few hours.  It will not affect the Louisville area.

With afternoon heating, additional super cells are likely to form.  Models continue to put the primary threat north of the Ohio River.  However, I wouldn’t be surprised to see additional development over western KY early this afternoon.  Any super cell will be capable of producing large hail and tornadoes.

The threat to Louisville area will be between 4 P.M. and 7 P.M.  as a scattered to broken line of thunderstorms moves through.  Primary threat by that time should be strong winds, but depending upon how things evolve over the next few hours, it could get worse (or better).

Updates to follow…

Severe Storm “potential”, take 3

Wed., March 13, 2019  6 P.M.

Thunderstorms likely tomorrow

This is the third time in recent weeks that the Storm Prediction Center(SPC) has put us in an area of potential severe storms.  We are in a “slight risk” region tomorrow.

The first two times, the situation was the same.  Very strong dynamics (wind fields) but little support from the thermodynamics (heat and humidity).  As the old song goes, it takes two to tango.  Both times, the partnership never happened, so the weather didn’t get to dance.

As is common in the early spring, the (almost) same situation exists again.  But, there are some differences.  Strong dynamics (upper winds, strong surface storm) are once again the prominent feature.  But, the dynamics over the midwest/Ohio Valley will be weakening through tomorrow.  Northward flow of heat and humidity is currently strong, but it also is expected to weaken.

So, overall the threat for severe storms over KY and southern IN tomorrow looks pretty small.  The GFS is weak with storm development while the NAM is a little stronger and more in line with the SPC ideas.  However, it keeps storms pretty weak over KY, but does point out a stronger threat over the northern two-thirds of IN tomorrow afternoon.

Here’s my forecast:

Mostly cloudy and breezy tonight…low…58.  70%  chance for showers and/or thunderstorms after 4 A.M. continuing into mid-morning.  (Rain/storms will be most likely along and west of I-65.)

Another area of showers and thunderstorms will likely cross the area between 4 P.M. and 7 P.M.  tomorrow.  Gusty winds around thunderstorms, but severe weather threat is quite low.  Cooler weather arrives Friday.

Stuff

Tomorrow is Pi Day.  3.14 on the calendar.  Use some math, it won’t hurt (much).

 

Stormy evening

Noon, Sat. Feb.23, 2019

Rain, thunder late this afternoon into the evening

Some quick notes…

1).  The forecast for the Ohio River flood in Louisville has lowered about four FEET since yesterday.  Rise above flood stage about midday tomorrow…crest just over 25 feet Tuesday.

2).  Strong storm over the upper midwest will push a cold front through the area this evening.  Showers and thunderstorms will be likely between about 4 P.M. and 10 P.M.  Rain: between .5″ and 1″.

3).  Severe weather is not likely, but we will have strong winds during the night.  Wind gusts are likely above 30 mph over much of the area.  Some gusts could reach into the 40+ mph range near thunderstorms.

4). Strong winds continue overnight and tomorrow – we could see gusts into the 35-45 mph range tomorrow morning.

 

Saturday: wet, maybe stormy

6 P.M. Fri., Feb. 22, 2019

Model differences continue

First, we’ll take a look at rain.  The GFS and NAM have lowered their rain forecast for tomorrow, but the GFS is still about a half-inch heavier.  However, both models are way down from earlier this week.  (If memory serves me, I think the NWS was talking about a 5″-8″ total for the week.  About 2″ fell earlier this week.)  Now, the GFS is around an inch and the NAM is closer to a half-inch!  Current Ohio River forecasts, which include higher rainfall for tomorrow, call for the river to reach flood stage (23′) in Louisville tomorrow late afternoon and crest early next week about 15″ lower than last week’s crest.  If current rain forecasts are correct, that crest forecast will be revised downward.  Good news for the “river rats.”

Over the next 24 hours or so, we’ll see two episodes of rain.  Plenty of heavy rain will fall over southern KY tonight.  Some of the leftovers will push through northern KY/southern IN toward daybreak tomorrow.  That’s the easy part.

Later tomorrow

I hope you’ve heard of the 3 feet of snow at Flagstaff AZ (most in a 100 years) and the 1″ at Phoenix (almost unheard of).  That potent storm is now crossing the southern Rockies and will wreck havoc over the nation’s midsection tomorrow and tomorrow night.  The storm center will stay far to our northwest, but the cold front sweeping eastward south of the storm center is expected to create severe storms late tomorrow.

The highest concentration of severe weather is expected to be over western Tennessee.  The Storm Prediction Center has dropped the northern edge of its “slight risk” area down about 200 miles since this morning.  The western half of KY is in the slight risk area, but IN has been dropped.  But, will severe weather reach as far north as us?

That’s where the models diverge again.  There is no argument about the strong wind fields associated with this storm.  But the GFS and NAM don’t agree that warm, humid air is going to get this far north.  Sometimes the strong dynamics can overcome weak thermodynamics to create strong storms, but usually you’d like go see some help from both sides of the equation.

On that point, the GFS expects the thermodynamics requirement to be met and it’s statistical output prints out a high probability for severe storms around Louisville late tomorrow afternoon or evening.  On the other hand, the NAM holds sufficient moisture south of us and has a much lower severe storm threat for the Louisville area.

This is a gross simplification, but here’s what to watch for tomorrow afternoon.  The NAM is predicting a high tomorrow around 60 – not enough to free much thermodymanics.  Meanwhile, the GFS this morning was saying upper 60’s (latest is 66).  Upper 60’s would significantly rise chance for severe storms.  Still iffy in the mid 60’s, but the lower the “high”, the lower the chance for severe.  So, watch the temperature tomorrow afternoon.  The higher it gets, the higher the storm chance goes.

So, we have the GFS’s erratic behavior lately, the NAM’s accuracy recently, and the SPC backing away from the northward moisture expansion.  As the cold passes through late tomorrow, expect to see a line of heavy showers and some thunderstorms mixed in.  Strong winds will be possible, but “severe” storms are only a small possibility.

NOTE:  By definition, a severe thunderstorm must have at least 58 mph wind gusts.  Many Severe Thunderstorm Warnings are issued for storms that never reach that strength.

Updated forecasts put the Ohio over flood stage by Saturday

6 P.M. Thursday, Feb. 21, 2019

Another heavy dose of rain by Saturday

Models continue to generate 2″-3″ of rain from the expected rain system due to arrive tomorrow night and depart Saturday night.  Adding that information to the river forecasts puts the Ohio River at Louisville over Flood Stage early Saturday morning  AND continuing to rise through early next week.

Meanwhile, most of KY will get some rain tonight.  Only the northern areas should escape the light rain.  Along and north of I-64 should stay dry as a weak disturbance moves east over the Gulf states tonight.  Only the GFS brings rain as far north as Louisville this evening.  And that would be only a very small amount.  The other models keep us dry.  The GFS hasn’t been on its game lately, so I’ll stick with the dry forecast.

Calmer weather for a couple of days

4 P.M. Feb. 20, 2019

Ohio River on the rise again.

Current hydrological forecasts have the Ohio in Louisville rising to just a inch or so from flood stage by Monday morning.  In the short term, I think that forecast will be revised downward since rainfall last night and today has fallen, in general, a half-inch to one inch shy of forecasts.  Plus, the highest amounts (southwestern Indiana) fell in areas that will drain into the Ohio downriver from Louisville.

Mostly light rain will move east of I-65 by 6-7 P.M. this evening.  Then two dry days lie ahead.  We’ll keep plenty of clouds around, but temperatures will reach about 50 tomorrow and a few degrees warmer on Friday.

Looking ahead

The next big storm to reach us will arrive Saturday and persist about 24 hours.  This one also projects as a big rain-maker.  Current estimates are in the 1″ to 2″ range, down a bit from earlier forecasts.  This storm will determine the fate of the Ohio River here in Louisville.  Another rain in the forecast range could easily put the river out of its banks by early next week.

Looking farther ahead

A lot has been said about an abrupt change back to a much colder pattern around March 1.  Call it “Polar Vortex, Chapter 2”!  Well, the GFS has been predicting some snow on arrival (now looks like Feb.28th) and a substantial snow about March 4 or 5.

Unfortunately, that all changed with this morning’s GFS.  It is now pushing much less cold air southward, as happened last time.  We could still have some light snow upon the cold air’s arrival, but it won’t hang around long enough to prevent the March storm from being rain.

DON’T give up hope!  The GFS has been acting very shaky (wild forecasts) since yesterday’s 18Z (1.P.M.) run, so it could all shift again.

Stuff

Of the world’s “big cats” (lions, tigers, leopards and cheetahs), only the cheetah cannot roar. They , however, can purr.  They also can accelerate to 70 mph in three seconds!

 

 

 

Wet night ahead

4 P.M. Tue., Feb. 19, 2019

Models continue warming trend

Latest NAM, HRRR and RAP models all show a warming and later arriving rain system tonight.  Onset now looks to be 10 P.M. or later tonight.  Wouldn’t be surprised if precipitation begins as a brief period of snow and/or sleet but quickly changes to rain.  No snow accumulation and no icy road road problems.

Rain will be heavy at times tonight and again late tomorrow.  Models still pointing to around 1.5″ to 2″ by tomorrow evening.

Indiana snow forecast has changed.  Southern one-third of IN will see anywhere between a trace (near the Ohio River) up to an inch or two near Columbus before the change to rain.  The northern two-thirds of the state could see 4″+ totals, especially east of I-65.

Models continue the warming trend

Noon Tue., Feb. 19, 2019

Heavy snows for much of Indiana, not for us

The GFS and NAM have pretty much given up on snow for Kentucky.  Louisville area may get a brief dusting, but no problems.  Southern Indiana counties that touch the Ohio River get less than an inch between 9 P.M. and Midnight.  Farther north accumulations will build – Scottsburg should see 1″-3″ while from Seymour north 4″+ of snow is likely.

If Jefferson County gets any snow (9 -11 P.M. will be our chance), it’ll not be enough to cause any road problems. But, heavy rains could create some problems for the morning commute. Rain will lighten during the day, but another surge of heavy rain could make a mess of the evening rush as well.

The GFS and NAM both project 1″-2″ of rain over the next 36 hours.  The NWS projects 2″-3″.  If the total goes that high, renewed flooding is possible on smaller rivers and streams.  Either amount of rain would not be enough to create any problems on the Ohio