bluewave

This was one of the strongest La Niña 500 mb summer patterns that we have ever experienced. In our older climate, a La Niña summer 500 mb pattern featured a ridge near Japan and south of the Aleutians. The Atlantic usually had a ridge east of New England. These 3 ridges this summer were some of the strongest we have observed. If this had been the winter with such a strong ridge near the Aleutians and near the East Coast, then it would have been among the warmest on record. So this is telling is that unless we can get some version of mismatch like in January 2022, the winter is going to be very mild again. Probably have to wait until October for some clues to see how the October early MJO indicator evolves. If the winter ridges turn out as exaggerated as the summer, then it will be a very mild winter again. So we need a mismatch along the lines of Jan 2022 with the MJO 8 and more +PNA to counter it. Without pushback we end up with 22-23 warmth again.

Down to 53° here. This was the lowest August temperature for the CT Shoreline since perhaps 2012.

So far the models are not showing any major hurricanes in the Atlantic basin from August 20th through September 1st. This isn’t a typical occurrence for heading into a La Niña winter. The only other years this happened since 1995 were in 2022 and 2000. While the sample size is very small to draw from, 2022 had a very active September with hurricanes Danielle and Earl reaching cat 1 and cat 2 status. The big stories that month were Fiona going Cat 4 and Ian Cat 5. La Niña years since 1995 major hurricanes August 20th September 1st 2022….none 2021….Ida….Cat 4…..Larry Cat 3 2020…Laura Cat 4 2017….Harvey Cat 4…Irma Cat 5 2016….Gaston Cat 3 2011….Irene Cat 3 2010…Danielle Cat 4….Earl Cat 4 2008….Gaston Cat 4 2007…..Dean….Cat 5 2005…..Katrina Cat 5 2000…..none 1999…..Brett Cat 4….Cindy Cat 4 1998…..Bonnie Cat 3 1995…..Louis Cat 4

Extent is lagging pretty far behind area like we saw in 2016.

Pretty unusual to get a cooldown like this in August with such a strong +AO.

NYC is on track for the first August since 2007 with 2 lows in the 50s.

Very sad what happened there.

Yeah, August 2011 was the most extreme rainfall flooding event for me back in Long Beach. Over 10” of rain during that Sunday morning. Most basements experienced flooding. My 2nd heaviest in a short period of time was 5.00” in 90 minutes during June 1995.

We haven’t been used to getting air flow from near the Arctic in August during recent years.

Several stations over 10.00” for August 2024 including the Bronx mesonet and Centereach in Suffolk along with Bethel in CT. https://www.nysmesonet.org/networks/nyc Thu, Aug 1, 2024 93 75 83 69 82 43 64 0.00 W* 4 17 6:35pm Fri, Aug 2, 2024 92 75 83 72 94 51 70 0.61 S* 5 26 6:00pm Sat, Aug 3, 2024 92 73 80 71 92 48 76 1.44 W 5 28 5:30pm Sun, Aug 4, 2024 84 70 76 70 91 64 81 0.47 SW 6 29 4:30pm Mon, Aug 5, 2024 91 73 82 67 88 36 64 0.00 NW 5 21 5:00pm Tue, Aug 6, 2024 92 71 79 71 95 48 77 5.44 W 6 20 6:35pm Wed, Aug 7, 2024 71 63 66 65 98 86 95 0.15 E 8 28 7:30am Thu, Aug 8, 2024 68 64 67 65 99 84 95 0.36 E 9 24 7:40pm Fri, Aug 9, 2024 82 68 77 73* 100* 77* 89* 0.15 S 12 46 1:55pm Sat, Aug 10, 2024 86 73 79 63 100 38 61 0.00 NW 7 20 1:55am Sun, Aug 11, 2024 82 70 76 56 72 37 51 0.00 W 5 21 10:55pm Mon, Aug 12, 2024 81 67 72 56 80 40 58 0.19 NW 5 20 6:55pm Tue, Aug 13, 2024 81 63 72 56 76 41 58 0.00 NW* 5 16 1:00am Wed, Aug 14, 2024 85 69 76 60 81 34 60 0.00 N* 5 21 4:45pm Thu, Aug 15, 2024 87 68 78 60 77 34 57 0.00 NW* 4 12 4:50pm Fri, Aug 16, 2024 88 71 77 64 84 41 65 0.00 E 5 16 5:00pm Sat, Aug 17, 2024 81 70 74 65 87 56 76 0.02 E 7 25 5:35pm Sun, Aug 18, 2024 81 68 73 69 95 70 86 2.39 SE 7 31 8:05pm Month 93 63 76 65 100 34 71 11.21 6 https://dex.cocorahs.org/stations/NY-SF-84 Today: 9.20" Month-To-Date: 12.05" https://dex.cocorahs.org/stations/CT-FR-43 Today: 6.42" Month-To-Date: 10.60"

Could be the first upper 50s in August this week since 2013 in NYC. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Aug Click column heading to sort ascending, click again to sort descending. 2024 64 13 2023 63 0 2022 62 0 2021 63 0 2020 62 0 2019 61 0 2018 65 0 2017 60 0 2016 61 0 2015 63 0 2014 61 0 2013 59 0

We usually don’t see scenes like this on Long Island.

Heaviest rainfall event in Suffolk since August 2014. Radar estimates over 10.00” with actual measurements over 8.00” and 9.00”. Looking like more significant damage to roads and residences than 2014 due to the hilly terrain on the North Shore.

Radar estimates over 6”in SW CT with significant flash flooding reported.

Over 4.5” so far.

It will be interesting to see if NYC can record their first 50s in August this week since 2013. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Aug Click column heading to sort ascending, click again to sort descending. 2024 64 14 2023 63 0 2022 62 0 2021 63 0 2020 62 0 2019 61 0 2018 65 0 2017 60 0 2016 61 0 2015 63 0 2014 61 0 2013 59 0

3 hr radar estimates near Stamford, CT around 3.00”.

Could be some flooding from Long Beach to Freeport with radar estimates over 2.00” so far.

The KB block was so strong in July that the +NAO vortex got pushed further SE than usual into NW Europe. It may also be related to the increased SAL over the tropical Atlantic this summer.

22-23 was another case of Buffalo and Marquette having a top 5 snowiest season with a top 10 warmest winter. You guys pulled off the same feat in 01-02. Tough for stations away from the LES to have one of their snowiest winters when it is so warm relative to the means. Forecasting an overlap like that is outside the reach of seasonal forecasts. Time Series Summary for Buffalo Area, NY (ThreadEx) - Oct through Sep Click column heading to sort ascending, click again to sort descending. 1 1976-1977 199.4 0 2 2000-2001 158.7 0 3 1977-1978 154.3 0 4 1995-1996 141.4 11 5 2022-2023 133.6 0 6 1983-1984 132.5 0 7 2001-2002 132.4 0 8 2013-2014 130.3 0 9 1909-1910 126.4 0 10 1957-1958 124.7 0 Time Series Summary for Buffalo Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1931-1932 34.6 0 2 2023-2024 34.5 0 3 1889-1890 33.7 17 4 2015-2016 32.9 0 - 2001-2002 32.9 0 5 2011-2012 32.5 0 6 2022-2023 32.3 0 - 2016-2017 32.3 0 - 1997-1998 32.3 0 7 1879-1880 32.2 2 8 2019-2020 31.9 0 9 1948-1949 31.8 0 - 1881-1882 31.8 0 10 1952-1953 31.7 0 Time Series Summary for Marquette County Area, MI (ThreadEx) - Oct through Sep Click column heading to sort ascending, click again to sort descending. 1 2001-2002 319.8 0 2 1996-1997 272.2 0 3 2000-2001 268.0 0 4 2022-2023 265.1 0 5 2008-2009 246.0 0 6 1995-1996 235.9 1 7 1989-1990 234.9 0 8 1981-1982 233.8 1 9 2006-2007 230.5 0 10 1984-1985 229.0 0 Time Series Summary for Marquette County Area, MI (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 2023-2024 25.2 0 2 1997-1998 23.6 0 3 2001-2002 23.0 0 4 2011-2012 21.7 0 5 2015-2016 21.5 0 6 1982-1983 21.0 0 7 1986-1987 20.7 0 8 2022-2023 20.5 0 9 1994-1995 20.0 0 10 2016-2017 19.7 0

The Bronx would easily go over 10.00” for August with more training convection like that. Thu, Aug 1, 2024 93 75 83 69 82 43 64 0.00 W* 4 17 6:35pm Fri, Aug 2, 2024 92 75 83 72 94 51 70 0.61 S* 5 26 6:00pm Sat, Aug 3, 2024 92 73 80 71 92 48 76 1.44 W 5 28 5:30pm Sun, Aug 4, 2024 84 70 76 70 91 64 81 0.47 SW 6 29 4:30pm Mon, Aug 5, 2024 91 73 82 67 88 36 64 0.00 NW 5 21 5:00pm Tue, Aug 6, 2024 92 71 79 71 95 48 77 5.44 W 6 20 6:35pm Wed, Aug 7, 2024 71 63 66 65 98 86 95 0.15 E 8 28 7:30am Thu, Aug 8, 2024 68 64 67 65 99 84 95 0.36 E 9 24 7:40pm Fri, Aug 9, 2024 82 68 77 73* 100* 77* 89* 0.15 S 12 46 1:55pm Sat, Aug 10, 2024 86 73 79 63 100 38 61 0.00 NW 7 20 1:55am Sun, Aug 11, 2024 82 70 76 56 72 37 51 0.00 W 5 21 10:55pm Mon, Aug 12, 2024 81 67 72 56 80 40 58 0.19 NW 5 20 6:55pm Tue, Aug 13, 2024 81 63 72 56 76 41 58 0.00 NW* 5 16 1:00am Wed, Aug 14, 2024 85 69 76 60 81 34 60 0.00 N* 5 21 4:45pm Thu, Aug 15, 2024 87 68 78 60 77 34 57 0.00 NW* 4 12 4:50pm Fri, Aug 16, 2024 88 71 77 64 84 41 65 0.00 E 5 16 5:00pm Month 93 63 76 65 100 34 70 8.81 6

My observation with the two storms in late December 2022 was that it was another two cases of the south based -NAO linking up with the Southeast ridge right before the storm. So the primary lows cut west of Boston and NYC. In the older days when the Southeast ridge was much weaker this could have been one to perhaps two snow events from NYC to Boston. So the main effect of the near record -AO that month was to hold the departures closer to average in the Northeast. If we had a more +AO instead then it could have been closer to a +6.5 winter departure nearly as strong as 2001-2002. But the -AO in December held the departure closer to +5 in NYC. Feb 23…+5.2 Jan 23…+9.8 Dec 22…-0.6…..-AO kept the departure lower …………..+4.8

It will be interesting to see the HREF once this gets into its range. The Euro has a weak secondary low that stalls the convection Sunday night. These have produced heavy rainfall events in the past especially in August. So it will be interesting to see the exact track in later runs.

A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. Frequently Asked Questions on Arctic sea ice The block back in June set the all-time record for the highest 500mb heights over that section of the Russian Arctic for the month of June.