Central PA - Fall 2021

[TimB]

1 minute ago, Bubbler86 said:

The 850 positive anomalies are outrageous in conjunction with those temps.   I checked out zone forecasts for Ok and Kanas, this Saturday, and they are 10-20 degrees lower. 

So here’s a topic for discussion: if the average high for a particular date is 82 and the GFS models a high of 113 at 4.5 days out, then the actual high is 88, how egregious of a modeling error is that? I mean the GFS is modeling above normal temps, and above normal temps may verify.

[TimB]

Just now, Bubbler86 said:

This site takes the Sept DP's and is comparable to May/Early June

 

 

https://weatherspark.com/y/21982/Average-Weather-in-Harrisburg-Pennsylvania-United-States-Year-Round

 

 

So that would indicate that even in mid-September, one can expect that over 1/3 of the days would have at least slightly uncomfortable dewpoints of 60+, and that 9 out of 15 wouldn’t be that extreme.

[Bubbler86]

1 minute ago, TimB84 said:

So here’s a topic for discussion: if the average high for a particular date is 82 and the GFS models a high of 113 at 4.5 days out, then the actual high is 88, how egregious of a modeling error is that? I mean the GFS is modeling above normal temps, and above normal temps may verify.

Personally I would judge on departure from forecast so its a very egregiously bad forecast in your example. 

[TimB]

2 minutes ago, Bubbler86 said:

Personally I would judge on departure from forecast so its a very egregiously bad forecast in your example. 

So your view on the matter is, a +5 departure on a day when a model showed a +30 departure is just as bad as a +5 departure on a day when a model showed a -20 departure. As a math/stat person, I very much agree. Just didn’t know if I was missing something.

And of course, I would say such an error on D5 should be weighted a lot more heavily than such an error on D15.

[Bubbler86]

2 minutes ago, TimB84 said:

So that would indicate that even in mid-September, one can expect that over 1/3 of the days would have at least slightly uncomfortable dewpoints of 60+, and that 9 out of 15 wouldn’t be that extreme.

I agree with your assertion using that data as a basis.  Its really hard to pinpoint the 9 out of 15 piece but fairly easy to be confident in taking that data and saying its normal for a lot of Sept days to have DP's into the 60's or higher.  Believe the chart suggests that close to half of Sept 7's are above 60 DP. 

[Bubbler86]

8 minutes ago, TimB84 said:

So your view on the matter is, a +5 departure on a day when a model showed a +30 departure is just as bad as a +5 departure on a day when a model showed a -20 departure. As a math/stat person, I very much agree. Just didn’t know if I was missing something.

And of course, I would say such an error on D5 should be weighted a lot more heavily than such an error on D15.

Yes, its all about getting the temp right not playing a 50/50 game of above or below normal.  I believe the agencies that rank model scores (though I think they do it more on fronts vs. temps) have different scales to accommodate length of time out into the 15 days and weighing errors appropriately.   The only time I would not agree with your first sentence is if winter precip is involved.    A winter day where a model suggests 25 and snow but it is 50 and rain is worse (at least to the public view) than a prediction of 40 and rain that turned into 65 and rain. 

[TimB]

7 minutes ago, Bubbler86 said:

Yes, its all about getting the temp right not playing a 50/50 game of above or below normal.  I believe the agencies that rank model scores (though I think they do it more on fronts vs. temps) have different scales to accommodate length of time out into the 15 days and weighing errors appropriately.   The only time I would not agree with your first sentence is if winter precip is involved.    A winter day where a model suggests 25 and snow but it is 50 and rain is worse (at least to the public view) than a prediction of 40 and rain that turned into 65 and rain. 

...and that’s the bottom line. The general public isn’t looking at the GFS, the general public is looking at a forecast on an iPhone app that is a blend of models, and the vast majority of them have no idea where any of the data comes from. Beyond that, if you took 10 random people, even people who have lived in Harrisburg their whole lives, off the street and asked them “what’s the average high in Harrisburg on September 15th,” I’d say a majority of them wouldn’t be able to produce a number within 5 degrees of the actual value.

[Bubbler86]

Just now, TimB84 said:

...and that’s the bottom line. The general public isn’t looking at the GFS, the general public is looking at a forecast on an iPhone app that is a blend of models, and the vast majority of them have no idea where any of the data comes from. Beyond that, if you took 10 random people, even people who have lived in Harrisburg their whole lives, off the street and asked them “what’s the average high in Harrisburg on September 15th,” I’d say a majority of them wouldn’t be able to produce a number within 5 degrees of the actual value.

If more than 2 of them gave an accurate number I would be surprised though there are a LOT of hidden weather weenies in the world.  But even weather weenies do not keep track of average temps by heart.  I suspect at least one of them would say that there is no Dew Point when below freezing...its called the frost point then.  :-). 

 

 

[Jns2183]

So here’s a topic for discussion: if the average high for a particular date is 82 and the GFS models a high of 113 at 4.5 days out, then the actual high is 88, how egregious of a modeling error is that? I mean the GFS is modeling above normal temps, and above normal temps may verify.

I have looked into how they determine model errors vs actual forecasts vs observed and god help you if you don’t have a strong background in statistics. I sorta understand it, and maybe could explain it when I have time to review my notes, but it is not intuitive. I suspect it’s more correct doing it how they do it, but I was hoping to find more localized analysis and that seems not possible unless you posses a login for noaa to access certain information


.

[Bubbler86]

36 minutes ago, TimB84 said:

...and that’s the bottom line. The general public isn’t looking at the GFS, the general public is looking at a forecast on an iPhone app that is a blend of models, and the vast majority of them have no idea where any of the data comes from. Beyond that, if you took 10 random people, even people who have lived in Harrisburg their whole lives, off the street and asked them “what’s the average high in Harrisburg on September 15th,” I’d say a majority of them wouldn’t be able to produce a number within 5 degrees of the actual value.

Euro still insisting on extremes next week. 

[paweather]

10 minutes ago, Bubbler86 said:

Euro still insisting on extremes next week. 

Euro stinks. No extremes, it will be sunny and nice. 

[Bubbler86]

9 minutes ago, paweather said:

Euro stinks. No extremes, it will be sunny and nice. 

3:20 PM on Sept. 7th, 2021...paweather has stated that the "Euro stinks".  Wanted to make sure I had a searchable time and date stamp on your post :-). 

[Bubbler86]

SPC maps for tomorrow

 

 

[paweather]

7 minutes ago, Bubbler86 said:

3:20 PM on Sept. 7th, 2021...paweather has stated that the "Euro stinks".  Wanted to make sure I had a searchable time and date stamp on your post :-). 

HAHA! Yep. Going with the GFS all winter long. 

[canderson]

3 hours ago, sauss06 said:

The pool is closed. So yes, yes we can! 

River is always open, if you like catching weird biblical disease. 

[canderson]

1 hour ago, paweather said:

HAHA! Yep. Going with the GFS all winter long. 

Bold strategy, Cotton.

I’m sticking with the ICON. Tried and true! 

[Itstrainingtime]

High for the day was 85 - we'll see if we add a few to that tomorrow. 

[Bubbler86]

Looks like someone "talked" WPC into issuing a FFW for Eastern PA. Throw the science out the window.  It's gut feeling time.   
Just like on these boards, peoples true thoughts come out in seemingly agnostic postings. The AFD writing Met for Phl thinks tomorrow is a big risk day
while CTP's met is reaching for the sun screen and thinking its a nothing burger. 

SPC/WPC continue to place MRGL outlooks for Excessive Rain and
SVR over the eastern 1/3 to 1/2 of the CWA for Wed afternoon and
evening, INVOF a nearly north-south lee trough. Marginally
stronger llvl winds and vorticity will occur across our mid and
upper Susq Mainstem counties where the close proximity of the
aforementioned warm front will create a very low prob of a few
transient supercells and perhaps an isolated, weak tornado
(indicated by PCs inclusion of the 2% risk area over CTP`s
eastern zones in their Dye outlook). Heavy rainfall risk is
highest well east of my CWA, and WPC was talked into a
Day 2 SLGT risk over far eastern PA for Wednesday afternoon/eve.

[Superstorm]

Starting to move my focus to winter….what are we looking like? A weak La Niña pattern?


.

[Bubbler86]

18Z GFS... from 6Z Fri the 17th  until 18Z Mon the 20th,  the temp at MDT stays between 60 and 65 the entire time.  

[Blizzard of 93]

4 hours ago, canderson said:

Bold strategy, Cotton.

I’m sticking with the ICON. Tried and true! 

Lol…I will go with the Canadian whenever there is a doubt…!

[Bubbler86]

10 minutes ago, Blizzard of 93 said:

Lol…I will go with the Canadian whenever there is a doubt…!

King CMC

[Blizzard of 93]

21 minutes ago, Bubbler86 said:

King CMC

I still miss the DGEX !

[Bubbler86]

58 this AM.

 

SPC upped/expended the risk for today.  So did the NWS Zones which now say 1-2" of rain for some in the LSV (tonight).  5% tornado is also back to MDT now. 

[TimB]

GFS is back to wanting to shut off the heat before it gets too ugly. I see nothing of the sort on the EC or CMC.

[canderson]

Yesterday I didn't think there would be much severe, but today looks better than I expected. Will be isolated in nature but rain should be heavy for many. 

[Bubbler86]

12 minutes ago, TimB84 said:

GFS is back to wanting to shut off the heat before it gets too ugly. I see nothing of the sort on the EC or CMC.

The GFS is close to be more hot than we want though.  So it appears its going to be a close call.  GFS would suggest we make a run for -8 Sept Departure. 

[Bubbler86]

@Blizzard of 93, the 3K Nam suggests I would get to mow again next weekend. 

 

[TimB]

25 minutes ago, Bubbler86 said:

The GFS is close to be more hot than we want though.  So it appears its going to be a close call.  GFS would suggest we make a run for -8 Sept Departure. 

I don’t see a -8 in anyone’s future, even if the GFS pans out.

[Bubbler86]

Just now, TimB84 said:

I don’t see a -8 in anyone’s future, even if the GFS pans out.

Highs in the 60's for several days would put MDT into the mid negatives even with night time lows not being so low.  That would be 10-15 departures for highs.  There are 3 on the 6Z GFS for MDT but there were a few more on the 18Z last night.