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New record high PNA of 4.00 on 8/6/21 obliterates old record!

GaWx

GaWx

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The GEFS runs of the last few days have been predicting an unusually strong +PNA coming up in early August. Yesterday’s run was stronger than Friday’s run and today’s run is even more impressive with a likely new record high +PNA peak (records back to 1950) (see below)!

Today’s PNA started the very sharp rise as has been forecasted by the GEFS for days although it didn’t quite reach 2 with it at 1.67 vs yesterday’s 0.51.

As mentioned, today’s GEFS PNA forecast peak is even higher than the last 3 days. It implies a higher chance to exceed the daily record high of 3.397 (records back to 1950), which was set on 9/24/2008! Moreover, it suggests an even better chance to exceed the current record of two days at 3+ during one peak, which was set 9/23-24/2008.

Today’s GEFS suggests a good chance for it to exceed 3 tomorrow. It still has a slight fall for 8/3 and then near steady on 8/4 although both may barely remain at 3+ (will be close). Then, it still has a second rise, which is even more prominent than the prior forecasts. It has it easily above 3 on 8/5-6 with a new record high peak above 3.397 quite possibly being set on one or both days! It is suggesting over 3.5 on both days! Then it falls some on 8/7 although it may still be at 3+ for the last time. Afterward there is a sharp fall 8/8+.

So, today’s forecast suggests not just a good shot at a new record high peak but also a very good shot at a new record high # of days at 3+ with as many as six days during 8/2-7, which would absolutely obliterate the current record (back to 1950) of Sep of 2008’s two days at 3+!

B9957B2F-6673-4055-97DE-928ACAA62B87.gif
 
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Very interesting. Forgive my ignorance…what is the expected weather impact for the SE with this happening in August. Thank you for posting!
 
k0skinne said:
Very interesting. Forgive my ignorance…what is the expected weather impact for the SE with this happening in August. Thank you for posting!
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My guess would be below normal temps for us, while our cold source regions of western Canada remain mild. So, like last year, a little below normal but no major outbreaks of cold since western Canada and NW US will be mild. Now, for the experts to weigh in.
 
k0skinne said:
Very interesting. Forgive my ignorance…what is the expected weather impact for the SE with this happening in August. Thank you for posting!
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YW.
1. My stats show an average of a modest BN temp at KATL in summer with a strong +PNA but with high variability. So, having an AN at KATL during a strong +PNA peak isn't at all unusual in summer even though it isn't favored. In winter, the correlation to BN at KATL (SE US) is stronger.

In the current case, KATL and the well inland SE is headed for a BN period though most of FL is looking more like near normal.

2. This event is going to last only through the first third of August. So, there's no indication of long-lasting effects from it. I'm following it mainly for the records, themselves, which are fascinating to me.
 
GaWx said:
YW.
1. My stats show an average of a modest BN temp at KATL in summer with a strong +PNA but with high variability. So, having an AN at KATL during a strong +PNA peak isn't at all unusual in summer even though it isn't favored. In winter, the correlation to BN at KATL (SE US) is stronger.

In the current case, KATL and the well inland SE is headed for a BN period though most of FL is looking more like near normal.

2. This event is going to last only through the first third of August. So, there's no indication of long-lasting effects from it. I'm following it mainly for the records, themselves, which are fascinating to me.
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Im looking at Nashvilles forecast and it looks solidly above normal for quite some time starting late this week. When does the cool down begin?
 
GaWx said:
YW.
1. My stats show an average of a modest BN temp at KATL in summer with a strong +PNA but with high variability. So, having an AN at KATL during a strong +PNA peak isn't at all unusual in summer even though it isn't favored. In winter, the correlation to BN at KATL (SE US) is stronger.

In the current case, KATL and the well inland SE is headed for a BN period though most of FL is looking more like near normal.

2. This event is going to last only through the first third of August. So, there's no indication of long-lasting effects from it. I'm following it mainly for the records, themselves, which are fascinating to me.
Click to expand...
?
 
GaWx said:
YW.
1. My stats show an average of a modest BN temp at KATL in summer with a strong +PNA but with high variability. So, having an AN at KATL during a strong +PNA peak isn't at all unusual in summer even though it isn't favored. In winter, the correlation to BN at KATL (SE US) is stronger.

In the current case, KATL and the well inland SE is headed for a BN period though most of FL is looking more like near normal.

2. This event is going to last only through the first third of August. So, there's no indication of long-lasting effects from it. I'm following it mainly for the records, themselves, which are fascinating to me.
Click to expand...

Thank you for the info. Yes, very interesting to mark the records and I appreciate your sharing.
 
Aug 2nd update:

Today's PNA didn't quite make it to 3 as it was 2.88. Even so, it's the highest in 12 years and the fun is just starting. Today's GEFS forecast, if anything, is for a slightly higher peak than the prior run had meaning it is still calling for a new all-time record high. It is forecasting 3+ for 8/3-6 with a close call for 8/7. So it is calling for 4-5 days of 3+. The current record for any one peak is only 2 days of 3+ (records back to 1950) , which was in Sep of 2008. So, this would shatter that record!

PNAgefs080221.gif
 
GaWx said:
YW.
1. My stats show an average of a modest BN temp at KATL in summer with a strong +PNA but with high variability. So, having an AN at KATL during a strong +PNA peak isn't at all unusual in summer even though it isn't favored. In winter, the correlation to BN at KATL (SE US) is stronger.

In the current case, KATL and the well inland SE is headed for a BN period though most of FL is looking more like near normal.

2. This event is going to last only through the first third of August. So, there's no indication of long-lasting effects from it. I'm following it mainly for the records, themselves, which are fascinating to me.
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If we see a repeat of this in winter it certainly would help our chances with scoring a major storm.
 
Today's update has the first 3+ PNA day since 8/1/2009 with a 3.21 This is only the 7th on record. Still looking for an all-time record high during the next two days. The current record (back to 1950) is 3.397.

PNAgefs080421.gif
 
Today, the PNA is at an amazing 3.73, which obliterates the old record high going back to 1950 of 3.397, set on 9/24/2008! The GEFS suggests there will be one more very high day tomorrow:


PNAgefs080521.gif
 
We got an even higher PNA of 4.00 today (smack dab at the top of the chart), which absolutely obliterates the previous all-time old record peak for any date back to 1950 of 3.40!! This also makes it three days of 3+ for this event, which breaks the previous record of two days in 2008. and we may even get one more tomorrow:

PNAgefs080621.gif


I have noticed that despite this record high PNA today, the 500 mb pattern today doesn't look nearly as impressive to the eye as prior days. To be sure, the W NA ridge/E NA trof was quite impressive for summer/most impressive to me on August 2, when the PNA was "only" at 2.88:

RecordPNAh5080221at0ZDeepestTrofB4pnaHi.png

However, today's H5 on the day of the PNA peak is already much flatter:

RecordPNA080621at0Zh5NotImpressiveDayOfRecord.png

It is almost as if there's a lag in the daily PNA calculation. So, nothing is showing up of note now at h5 but it was showing up impressively a few days ago.
 
@GaWx

Any idea what the +PNA was during the arctic blast of 1985?
 
J.C. said:
@GaWx

Any idea what the +PNA was during the arctic blast of 1985?
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Although it wasn't anywhere near an extremely high amplitude PNA, it was a solid ~+1 for many days helping to pave the way for the Arctic blast. It actually ties with the great Jan-Feb 1977 period for having had the longest period of +0.80+ dailies during DJF at 24 days (in 3rd place is the 21 days during Jan of 1981)(see below).

After just having had a +4 peak PNA, one may think a +1 is minimal. But it absolutely is not, especially if lengthy and in winter as far as the tendency toward a cold SE. Consider that during the ~6,500 DJF days since 1950, there have been only a mere 3 days....that's right, 3 days with a PNA of 2+ or once every 2,000 days or so/once every 24 winters. Moreover, those 3 days were only in the low 2s and all 3 days were in the very end of Feb (1968 and 1983). The cooling effects on the SE of a +1 to +1.5 PNA peak in winter are actually typically stronger than that from a +2 to +4 PNA peak at most other times of year. It is deceptive.

On that note, I still can't figure out why there have been so many more very strong PNA peaks in JJAS and early O, especially AS and early O, than the rest of the year. Since 1950, there have been a whopping 53 2+ peaks during JJAS and early Oct vs only seven 2+ peaks the rest of the year!

1985 1 1 0.783
1985 1 2 0.996
1985 1 3 1.149
1985 1 4 1.173
1985 1 5 1.064
1985 1 6 0.974
1985 1 7 1.057
1985 1 8 0.918
1985 1 9 0.901
1985 1 10 0.880
1985 1 11 0.869
1985 1 12 0.965
1985 1 13 0.997
1985 1 14 0.852
1985 1 15 0.885
1985 1 16 1.011
1985 1 17 1.038
1985 1 18 0.970
1985 1 19 0.922
1985 1 20 0.985
1985 1 21 0.948
1985 1 22 0.859
1985 1 23 0.880
1985 1 24 0.933
1985 1 25 0.833

*Edited
 
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Today, we got one last 3+ with a 3.40. That makes four 3+ days in a row. This is amazing because during the prior 71 years, there was only one time that there were as many as two days in a row! So, this event is by far the greatest +PNA in the 71 years of recorded history. Could this have been a once in several hundred+ year event? Quite possibly.
 
GaWx said:
Although it wasn't anywhere near an extremely high amplitude PNA, it was a solid ~+1 for many days helping to pave the way for the Arctic blast. It actually ties with the great Jan-Feb 1977 period for having had the longest period of +0.80+ dailies during DJF at 24 days (in 3rd place is the 21 days during Jan of 1981)(see below).

After just having had a +4 peak PNA, one may think a +1 is minimal. But it absolutely is not, especially if lengthy and in winter as far as the tendency toward a cold SE. Consider that during the ~6,500 DJF days since 1950, there have been only a mere 3 days....that's right, 3 days with a PNA of 2+ or once every 2,000 days or so/once every 24 winters. Moreover, those 3 days were only in the low 2s and all 3 days were in the very end of Feb (1968 and 1982). The cooling effects on the SE of a +1 to +1.5 PNA peak in winter are actually typically stronger than that from a +2 to +4 PNA peak at most other times of year. It is deceptive.

On that note, I still can't figure out why there have been so many more very strong PNA peaks in JJAS and early O, especially AS and early O, than the rest of the year. Since 1950, there have been a whopping 53 2+ peaks during JJAS and early Oct vs only seven 2+ peaks the rest of the year!

1985 1 1 0.783
1985 1 2 0.996
1985 1 3 1.149
1985 1 4 1.173
1985 1 5 1.064
1985 1 6 0.974
1985 1 7 1.057
1985 1 8 0.918
1985 1 9 0.901
1985 1 10 0.880
1985 1 11 0.869
1985 1 12 0.965
1985 1 13 0.997
1985 1 14 0.852
1985 1 15 0.885
1985 1 16 1.011
1985 1 17 1.038
1985 1 18 0.970
1985 1 19 0.922
1985 1 20 0.985
1985 1 21 0.948 -8F ATL
1985 1 22 0.859
1985 1 23 0.880
1985 1 24 0.933
1985 1 25 0.833

*Edited
Click to expand...

Thank you for pulling that data. So in other words, we have never seen of +2-+4 in the heart of winter...makes me wonder what it would look like if we did. I knew it had to be at least a +1 for January 1985 to happen.
 
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