I’ve talked a lot in recent years about the correlation of very warm Indonesian/west Pacific waters to a stronger SE ridge. I just had another talk with my Maxar contact about the upcoming winter based on it being La Niña combined with very warm west Pacific waters. He said these things:
“West Pacific sea surface temperatures, which are nearby Indonesia, were +2.31 standard deviations warmer than normal in August. This was the second warmest the waters have been in August back to 1950. The only other warmer August was in 1998; although, 2017 and 2016 are close behind at +2 standard deviations above normal for the month.”
“It is also worth noting that the region is where convective activity is normally enhanced during La Nina winters. With the waters being as warm as they are, we are more likely to see further enhancement of the convective forcing beyond that of a typical La Nina. The response results in the further enhancement of the warmer Southeast ridge in winter.”
He then gave me the DJF temperature map for the average of the 3 La Ninas of 1998-9, 2016-7, and 2017-8 and this was the result, an average of +3 to +5 in the SE US (closely matches Bastardi):
At KATL specifically, Dec averaged 48.5 (+3), Jan averaged 46.8 (+3), and Feb averaged 54.4 (+7). The 1981-2010 30 year average for DJF was 45.5. So, DJF of these 3 winters averaged 49.9, or +4.4 vs 1981-2010 averages. But remember that even the 49.9 would still be 30.1 colder than the 2020 summer instead of the 1981-2010 DJF average of 34.5 colder than the 2020 summer. So, it will still be a much more enjoyable season, regardless, for those who don’t prefer summer wx.
“West Pacific sea surface temperatures, which are nearby Indonesia, were +2.31 standard deviations warmer than normal in August. This was the second warmest the waters have been in August back to 1950. The only other warmer August was in 1998; although, 2017 and 2016 are close behind at +2 standard deviations above normal for the month.”
“It is also worth noting that the region is where convective activity is normally enhanced during La Nina winters. With the waters being as warm as they are, we are more likely to see further enhancement of the convective forcing beyond that of a typical La Nina. The response results in the further enhancement of the warmer Southeast ridge in winter.”
He then gave me the DJF temperature map for the average of the 3 La Ninas of 1998-9, 2016-7, and 2017-8 and this was the result, an average of +3 to +5 in the SE US (closely matches Bastardi):
At KATL specifically, Dec averaged 48.5 (+3), Jan averaged 46.8 (+3), and Feb averaged 54.4 (+7). The 1981-2010 30 year average for DJF was 45.5. So, DJF of these 3 winters averaged 49.9, or +4.4 vs 1981-2010 averages. But remember that even the 49.9 would still be 30.1 colder than the 2020 summer instead of the 1981-2010 DJF average of 34.5 colder than the 2020 summer. So, it will still be a much more enjoyable season, regardless, for those who don’t prefer summer wx.
