Pittsburgh/Western PA Fall 2023 Discussion

[TheClimateChanger]

Chilly morning, especially outside of Allegheny County with some upper 30s noted in the north. Some of the coldest lows in the region include 39 at Zelienople (PJC), Youngstown (YNG), and Franklin (FKL), 40 at New Castle (UCP), 41 at Washington (AFJ), 42 at Butler (BTP), and 43 at New Philadelphia, Ohio (PHD). The Virginia Tech mesonet site in the Canaan Valley National Wildlife Refuge (an elevated frost hollow) dropped to 30.6F.

[TimB]

And yet, inexplicably, PIT was the only observing site in the region that failed to get below 50.

[TimB]

Looked at PWS near the airport and every single one of them easily got into the 40s, some as low as 42 or 43. I know there’s a cold bias on those, but I’m just not buying the 50.

[TimB]

That said, it is nearly impossible to get into the 40s in September nowadays. From 1935-2004 (70 years) every single September had at least 4 days get below 50. Since 2005 (18 years), 6 Septembers have had 3 or fewer days get below 50, and this year is looking pretty likely to be the 7th. In fact, this year has a chance to be the 5th September out of the past 9 that had two or fewer days get below 50. Really puts into perspective how much we’ve screwed up September and fall.

[TheClimateChanger]

23 minutes ago, TimB said:

Looked at PWS near the airport and every single one of them easily got into the 40s, some as low as 42 or 43. I know there’s a cold bias on those, but I’m just not buying the 50.

Interesting. Although by 10 am, it's running right in line with all of the other local airports.

I did look at some local PWS in the western Allegheny area, and they were mostly in the upper 30s to mid 40s this morning. But by 10:15 am, upper 50s and low 60s areawide. I do think it might be running a bit warm, but PIT has never done well in radiational cooling compared to much of the area. A lot of asphalt and its site on a flattened hilltop are not exactly conducive for radiational cooling. Many of the traditionally cooler sites are in valleys or at least on valley slopes with higher terrain in the vicinity.

[Ahoff]

Finally, officially dropped to the 40s

[Ahoff]

Looks to stay below 70 today.  Probably first time since June.

[TimB]

2 hours ago, Ahoff said:

Looks to stay below 70 today.  Probably first time since June.

As always, it’s going to be a close call whether Pittsburgh somehow got there.

[TimB]

And if we did get to 70 today with the warm stretch coming up, we could be looking at the 2nd September in the last 5 years that didn’t have a single day fall short of 70 after only one in the 148 years prior.

[Ahoff]

69 today.

[TheClimateChanger]

24 minutes ago, Ahoff said:

69 today.

Nice.

[TheClimateChanger]

Incredible Starlink pass this evening. They were very bright in the night sky.

[TheClimateChanger]

While not the official observational site anymore, Allegheny County Airport (AGC) has received only 0.22 of an inch of rainfall so far this month. Looking through the observational records, which encompass 502 months of data [July 1, 1935 to September 15, 1952, as the official observational site; and February 1, 1999 to present with the installation of the ASOS], the driest month recorded at AGC is 0.53" in November 1939.

Here are the 10 driest and wettest months observed at AGC (obviously September 2023 is not yet done). September is a month that can be very wet or very dry. It is generally a drier period of the calendar year, but occasional visits from remnant tropical cyclones can produce copious amounts of rainfall.

Officially, at Pittsburgh International Airport (PIT), there has been 1.30" of rain this month, with 1.14" of that occurring on the 7th (the bulk of which fell in a single hour).

[TheClimateChanger]

GFS suggests the dry pattern persists through at least the end of the month. Will need to keep an eye out for any rogue tropical development, however.

Here is the total QPF on the 12z run through 6z on 10-1:

[TimB]

16 minutes ago, TheClimateChanger said:

GFS suggests the dry pattern persists through at least the end of the month. Will need to keep an eye out for any rogue tropical development, however.

Here is the total QPF on the 12z run through 6z on 10-1:

Worth noting that the other globals aren’t as dry during that period, nor are the ensembles, and that the day 6-10 outlook from the CPC predicts above normal precip. That isn’t to say the GFS won’t score a big win, but it’s an outlier at the moment.

[TimB]

Euro made a move towards the GFS, not a drop of rain for the duration of its run. Endless above normal temperatures too.

[TimB]

This final third of September looks to continue to be pretty seasonable. If we could just toss out the 5 really hot days early in the month, the rest of the month was just about normal. But we can’t, so we’ll probably end up close to +2. Not terrible by recent standards.

[TheClimateChanger]

[TheClimateChanger]

A little bit of D0 noted in parts of western Pennsylvania in the most recent drought monitor update. Somewhat surprised southwest Pennsylvania has escaped the D0 so far.

In the threaded record, this year has been the 34th driest to date (out of 153 years).

Limiting the comparison to Pittsburgh International Airport records, as the downtown site tended to be a bit drier, it's the 16th driest (out of 72 years). As you can see, only three years this century have been drier to date (2002, 2016, and 2009), and one of those three (2009) is essentially in a tie with this year with just 0.03" less.

At Allegheny County Airport, it's been the 4th driest, out of 41 complete years of records (1936-1952, 2000-present).

 

[TheClimateChanger]

Similar situation in northern West Virginia. I used a cutoff of 25 missing days to avoid bad data - of course, even a handfull of missing days could potentially affect these numbers.

Using the above cutoff, MGW is in 18th place (out of 122 years).

Wheeling is in 13th place, out of 67 years - although several years could have received more rainfall than shown due to missing data. Interestingly, Wheeling has received quite a few more recent dry years since the installation of the ASOS at the county airport than other sites. I wouldn't have expected it to be drier there, given its elevation several hundred feet above the river.

Allowing for up to 50 missing days, HLG is in 15th place of 80 years. It might be surprising that a lot of the additional years had more rainfall, but often the missing data is simply the observer not indicating 0 precipitation fell. Of course, anytime 28 or more days are missing, there could be an entire month's worth of data missing.

[Gordo74]

Really nice, seasonal September so far.

[RitualOfTheTrout]

1 hour ago, Gordo74 said:

Really nice, seasonal September so far.

Yeah, Im enjoying this. No heat or air needed as an added bonus.

Not mad about nissing that tropical over the weekend either, but Id be crying in December at that cutoff. 

[TimB]

Given that the 48 observed at PIT earlier this month will likely end up being our low for the month, here’s a look at the top 10 warmest monthly lows for September since observations moved to the airport in 1952:

 

Notice that every September from 1952-1995 got below 45 but 11 of the 28 years since haven’t.
 

Also notice that all 63 Septembers from 1952-2014 got below 47 but 5 of the 9 years since haven’t.

Warm temperature records that used to be rare are now happening every other year.

[Ahoff]

Next week looks fairly cool.  Wouldn’t the surprised to see some 40s as the week progresses.

[TimB]

38 minutes ago, Ahoff said:

Next week looks fairly cool.  Wouldn’t the surprised to see some 40s as the week progresses.

Normally I’d agree, but the near continuous cloud cover should keep us from radiating much at night.

[Ahoff]

2 hours ago, TimB said:

Normally I’d agree, but the near continuous cloud cover should keep us from radiating much at night.

Looked clearer towards the end of the week and highs still only upper 60s and low 70s, wouldn’t be too hard.  We’ll see though.

I was noticing the amount of trees starting to change colors already.  Not a lot, but definitely noticeable.  No doubt the dry weather and cool days and warm nights lately have helped.

[Ahoff]

5 minute obs have AGC temp at 57 for 1:00pm.  That’s seems really low.  I was just out near the airport and while cool, it didn’t feel that cool.  Interesting.

[TimB]

7 minutes ago, Ahoff said:

5 minute obs have AGC temp at 57 for 1:00pm.  That’s seems really low.  I was just out near the airport and while cool, it didn’t feel that cool.  Interesting.

It’s also allegedly raining there?

Other places further east where it’s raining are also cold. Latrobe is at 54 and Indiana at 52. As the rain bands advance west, it’ll cool things off.

[Ahoff]

17 minutes ago, TimB said:

It’s also allegedly raining there?

Other places further east where it’s raining are also cold. Latrobe is at 54 and Indiana at 52. As the rain bands advance west, it’ll cool things off.

Must be.  It is raining at my house, which is a little further west.

[TimB]

I’m thinking the 64 reached at PIT an hour ago ends up being the official high for the day. Coldest day of the young fall season.