Friday, Sept. 16, 2016

Although yesterday’s forecasts for tomorrow’s big game with FSU were generally upbeat…rain before and after the game, but not during…current forecasts show no such thing.  It now looks as though rain gear will be the best fashion statement during the game.

Both the NAM and GFS are still looking toward late night rains, but they are now showing an even higher chance for rain (and possible thunder) during most, maybe all, of the game.  I remember a big win over FSU during a heavy rain about 10-15 years ago, so maybe the now-likely rain is a good omen.

Contrary to the NAM/GFS, the very short term models are now downplaying the overnight rain expectations.  I hope that is wrong as we could certainly use a good, soaking rain.  However, the short term models have been outperforming the NAM/GFS all summer (by a big margin) , so wouldn’t be surprised if the predicted rains tonight are a no show.

Friday Sept. 9, 2016   4 P.M.

Back in August I wrote about an unusually bad string of forecasts the Louisville area has been subjected to this summer.  That week was the worst forecast performance (for a prolonged period) that I can remember.  Individual forecasts, yes, but not such a long string of them.  Well, it has started again.

We did have some isolated showers overnight and a good soaking rain south of Louisville this morning, so far three straight “high probability” showers and thunderstorm forecasts have come up largely dry for Louisville area.  That includes the current time forecasts for Thursday, Thursday night and today.  And, the current forecast for tonight, tomorrow and tomorrow looks to be just as bad (or worse.)

Without getting into specific details, let’s just say that if the most recent models are anywhere near correct, the current “official” forecast isn’t going to be.

Tonight, we’ll see a dying line of rain/storms approach us after midnight.  Like last night they don’t look like they’ll bring any widespread rains.

Tomorrow’s forecast for numerous showers and thunderstorms (60% chance) actually boils down to the possibility of a line of thunderstorms forming over us in the early afternoon… an hour of rain at most.  Both the NAM and GFS are tending have the formation either over us or to our east, so it would no be too surprising of they missed us entirely.  The NAM (and me) are leaning that way.

Then, the 50% chance for showers/thunderstorms tomorrow night is just plain “Crazy Talk.”

Friday, July 15, 2016  3 P.M.

This has become an ongoing problem recently – wide model divergence on thunderstorm chances.  It’s back again today.  Both the GFS and NAM literally ignore the chances for thunderstorms later today while the short-term models develop storms in the area over the next few hours.

With a weak, slow-moving cold front lying over southern IN and plenty of low level moisture available, it should look like a no-brainer for storms.  However, there are some problems.  Even though the surface is moist, the upper air doesn’t appear to have much water to add.  And, there’s no readily available upper air energy to initiate convection.

Still, the surface-based instability is high along the Ohio River.  And we’re in the time of maximum daytime temperatures, so the surface conditions should suffice to create at least some small thunderstorms over the next few hours (until 7-8 P.M.)  The cold front should also be favorable to allowing a nearly solid line of storms to form and drift southeast.  So, it looks like most (if not all) of the Louisville Metro should experience a shower and/or thunderstorm later this afternoon

Wednesday, July 13, 2016  4 P.M.

Looks like my earlier forecast is going to be a bust.  Radar showing nothing happening nearby.  So the heat and humidity rule.

My (former?) friends, the RAP/HRRR have backed off from the idea of afternoon thunderstorms, but still show high chances for a line of t-storms tonight – probably between 8 P.M. and Midnight.  So, at least part of my forecast may still happen.  Could be a good light show tonight.

8 P.M. update

Currently strong line of thunderstorms east of Evansville is racing eastward about 30-40 mph.  It should sweep across the metro area between 10 – 11 P.M.  It is weakening ( and will continue on that path) so no problems are expected.

Wednesday, July 13, 2016  11 A.M.

Once again, the short term models are at odds with the primary models.  Everyone agrees that it’ll be hot and humid today, but the chances for thunderstorms vary considerably.

First, the big models…the NAM doesn’t produce any  chance for t-storms anywhere over KY or southern IN.  The GFS hints at a small chance especially north of the Ohio River, but it’s numerical statistical output is less than 10% for this afternoon.

Meanwhile, the short-term regional models are much more enthusiastic with t-storm development.  The RAP predicts a large cluster of storms over our area late this afternoon.  The HRRR is even more aggressive with an afternoon and an evening storm cluster moving over us.

The Weather Service is sticking with the NAM/GFS, but with a slight nod toward the short term models.  They give us a 20% rain chance today and tonight.

But, the RAP/HRRR were developed for situations such as this.  They are designed to do the fine-tuning between the gaps in the larger models.  And, last week in a similar situation, they did a great job.  I expect the RAP/HRRR to continue doing their jobs well.  So, I’d expect a much higher chance we’ll see t-storms later today…60% chance or higher.

We’ll see how this battle works out in a few hours.