bluewave

Canadian high pressure should dominate this week with good radiational cooling in the outlying areas. But it appears that we are back to the measurable rain on weekends pattern. Looks like the frontal passage this past weekend will occur again next weekend. Comfortable temperatures and humidity running below average for early September.

Even though the Euro will likely turn out to be too high with the forecast for 20-25 named storms and over 200 ACE, the U.S. temperature forecast for the summer was very good. So this tells there are elements of the climate system that these seasonal models can handle an others they can’t. It will be interesting to see if the Euro does as well with its winter temperature forecast and 500mb pattern next few updates on the 5th of each month.

One of the reasons the Atlantic has been so quiet last few weeks is due to the ITCZ shifting north into the Sahara.

It’s the first time in known history that a El Niño summer ahead of a winter ONI of +2.0 or greater had 7 named storms and 2 category 4 hurricanes develop between August 20th and 31st to be followed by a developing La Niña the next summer with no new storms during this period. 2023 New developments between 8-20 and 8-31 TS Gert TS Emily Cat 4 Franklin TS Harold Cat 4 Idalia TS Jose TS Katina 2024 No new developments

This is an unusually strong MJO 5-6 pattern for early September. It’s one of the few times of the year when we get a cooler to closer to normal temperatures from these phases. So a nice change from recent early September patterns which have been much warmer.

This looks like it will be one of the strongest -PDO summers since 1950. The -PDO pattern was so strong that year that it produced a +13.0 January in Atlanta. While this is not meant to be a forecast for next winter, it just shows what is within the range of possibilities should we get a strong enough Aleutian ridge and deep enough trough out West. We already had a +13.2 with the 21-22 La Niña and -PDO at DFW in December 21. Extreme months like this usually pop up in forecasts very close to the time period. So it’s not usually something that we can forecast from so far out. Hopefully, we get some type of mismatch pattern next winter that takes an extreme winter month off of the table. But it’s something to just be aware of with such extreme -PDOs. https://www.ncei.noaa.gov/pub/orders/IPS/IPS-017CC821-F4F4-4CF6-868A-42E597844BF5.pdf

The atmosphere is becoming so moist that we don’t even need a tropical storm or hurricane to produce this type of extreme flash flooding anymore. We began to see this back in August 2011 when another unnamed low pressure system with training thunderstorms produced more impressive flash flooding in spots than Irene did a few weeks later. The same went for the unnamed system at Islip in August 2014.

Historic warmth for Svalbard.

The forecast from a week ago was actually pretty good. This weekend was always about a front coming through. The only difference is the front slowed down a little from the forecast last Saturday. New run Old run

We are on track for one of strongest -PDO summers on record as the daily index declines again. 2024 -1.55 -1.33 -1.52 -2.12 -3.00 -3.16 -2.97

Back to back top 10 wettest summers for me. Time Series Summary for NEW HAVEN TWEED AP, CT - Jun through Aug Click column heading to sort ascending, click again to sort descending. 1 2009 17.52 0 2 2006 17.45 1 3 2011 17.38 0 4 1972 16.54 0 5 1955 15.30 0 6 2003 14.55 0 7 1952 13.87 0 8 2024 13.77 1 9 2023 13.45 2 10 1950 13.08 0

Yeah, looks like this was the first time that HVN had 30 days with a 75° or higher dew point.

You are missing the point. We are discussing what has already happened and the strengths and weakness of the approaches used over the last decade since the 15-16 super El Niño. You should cut the scientific climate and weather forecasting community some slack since these changes to our climate are happening faster than some of our older technology based models can keep up with . People are just doing the best they can with the technology we have available at the time. The weather and climate is an open and transparent system where everyone can see the results. Big pharma is different since it’s always not immediately obvious whether all the results of a study have been disclosed. So you are making an apples and oranges comparison.

The AMO itself may not be as relevant to the overall North Atlantic SSTs if we continue to see these subtropical record warm blobs east of New England and the Canadian Maritimes. It could result a the shift in tropical cyclone tracks with some areas seeing more activity and other less. But it will be interesting to see how things go in coming decades. https://www.nature.com/articles/s41598-017-11046-x Over the recent few years, striking changes in Atlantic SSTs have occurred in the subpolar gyre, where the cold anomaly that developed from 2013–2015 was termed the ‘cold blob’ in the press13. This cold anomaly resulted from extremely harsh winters of 2013–2015, characterised by strong surface heat loss14 which resulted in persistent cooling of the upper ocean15 and drove deep ocean convection16, 17. Here, we assess the impact of this cooling on the AMO index, and evaluate the observed changes over the past 3 years relative to the cold AMO period of the 1990s. The AMO index, however, masks any spatial distributions in SST changes, and while the AMO index is negative, the subpolar cold anomaly is accompanied by a warm anomaly in the subtropics. We investigate whether the cold subpolar anomaly is likely to persist and consider how the present cold state of the AMO may evolve.

The Atlantic is still near the warmest on record. The last time there were forecasts for an AMO shift back in 2013 to 2017 the weak cooling only lasted for a few years. Then the SSTs reached record levels over recent years. So this could be an indication that aerosol reductions are playing a role and that the reduction is inhibiting a return to a cooler phase. But we may need a few decades more of observations to confirm. https://link.springer.com/article/10.1007/s00704-022-04207-0 Is Atlantic Multidecadal Oscillation a genuine representation of natural variability in the climate system? Or perhaps is it strongly forced by external drivers? In this paper, a data-driven attribution investigation has been performed for the Atlantic Multidecadal Oscillation (AMO) behaviour in the past via a machine learning technique, NN modelling. We clearly see a forced nature of AMO in the last 150 years, with a strong contribution of the forcing coming from anthropogenic sulphates, which induces its typical oscillating behaviour. The following original application of our model to future predictions of the AMO behaviour shows that it shall probably lose its oscillating characteristic features. The only way to recover them is to consider an unrealistic increase in anthropogenic sulphates in the future under a strong mitigation scenario, and possibly a low-power solar regime. Due to the established influence of AMO on climate and meteorological phenomena in several regions of the world, our results can be important to better understand the past and envisage several future scenarios. Discussion of potential AMO shift back in 2013. https://tropical.colostate.edu/Publications/sidebars/fogarty_and_klotzbach_2014.pdf

This is a great explainer on why we only had 5 named storms so far and models like the Euro were forecasting over 20 for the season. But as we saw with Beryl, individual systems that are able to form with the record SSTs can become very intense. Many have been commenting in this unusual AEW behavior so far this season especially for a La Niña with record Atlantic SSTs. https://news.ucar.edu/132966/dampening-seeds-hurricanes

Another top 5 warmest summer for many stations across the Northeast.

The exception to that was 09-10 to 17-18 with the very high concentration of BM snowstorms. Starting in 18-19 we shifted to more of a coastal hugger, cutter, and suppressed southern stream pattern. While all the winters going back to 15-16 were warmer to record warm in the Northeast, we still had a very favorable Pacific through the November 2018 snowstorm. Then we entered the very hostile Pacific phase that winter. People were willing to overlook all the warmth from 15-16 to 17-18 since the benchmark put on a real show for snow lovers. But warmth and a hostile Pacific won’t cut it around here for good winters. 20-21 really went against the grain for one the strongest +PNA patterns for such a robust La Niña. Seems like a piece of that repeated briefly in January 22. Since then it really has been pretty much a shout out for winter. Hoping we can at least see some snowfall improvement over the last two winters even though the early signals are there for a potential 10th warmer than normal winter in a row for the Northeast.

It remains to be seen since there is such a small sample size of inactive years between 8-20 and 8-31 during La Ninas.

We had a much stronger sea breeze influence this El Niño to La Niña transition summer. So the only spot around NYC metro to reach 40 days like Newark did in 2016 and 2010 was Harrison away from local sea breeze at the airport. To our SW Hightstown away from the sea breeze only needs 2 more to reach 40. Data for January 1, 2024 through August 29, 2024 Click column heading to sort ascending, click again to sort descending. NJ HARRISON COOP 40 NJ NEWARK LIBERTY INTL AP WBAN 33 NJ CALDWELL ESSEX COUNTY AP WBAN 33 NJ TETERBORO AIRPORT WBAN 31 NJ TETERBORO AIRPORT COOP 29 NJ CANOE BROOK COOP 27 Data for January 1, 2024 through August 28, 2024 Click column heading to sort ascending, click again to sort descending. NJ HIGHTSTOWN 2 W COOP 38 PA READING REGIONAL AIRPORT WBAN 37 PA PHILADELPHIA FRANKLIN INSTITUTE COOP 37 PA NORRISTOWN COOP 35 NJ SOMERSET AIRPORT WBAN 35 Data for January 1, 2016 through December 31, 2016 Click column heading to sort ascending, click again to sort descending. NJ CANOE BROOK COOP 49 NJ NEWARK LIBERTY INTL AP WBAN 40 NJ HARRISON COOP 40 NJ TETERBORO AIRPORT WBAN 36 NJ TETERBORO AIRPORT COOP 36 Data for January 1, 2010 through December 31, 2010 Click column heading to sort ascending, click again to sort descending. NJ CANOE BROOK COOP 59 NJ NEWARK LIBERTY INTL AP WBAN 54 NY MINEOLA COOP 52 NJ RINGWOOD COOP 51 NJ HARRISON COOP 50 NY LAGUARDIA AIRPORT WBAN 48 NJ CRANFORD COOP 46 NY BRONX COOP 45 NJ TETERBORO AIRPORT COOP 41 NJ TETERBORO AIRPORT WBAN 40

The competing marine heatwaves angle may be part of the equation. I don’t think it’s a coincidence that the only other recent time this happened was in 2022. Now that the models are forecasting the tropics to become more active in early September something similar happened after a quiet August in 2022. We don’t know yet whether September will manifest in a similar way to 2022, but the record warmth closer to the Gulf is concerning for any storms that can get in there. 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

One of the few parts of the East that have been really dry just to their west.

First 95° of the season for JFK. THE KENNEDY NY CLIMATE SUMMARY FOR AUGUST 28 2024... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1948 TO 2024 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 95 227 PM 98 1948 81 14 74 1973 MINIMUM 72 1249 AM 53 1986 66 6 67 AVERAGE 84 74 10 71

August 2024 was the 9th month in the 2020s with over 10.00” of rainfall for at least some portion of the OKX forecast zones. We haven’t had a 5 year period before with this many months over 10.00”. So this is even more impressive than 2003 to 2018. Aug 2024 Mar 2024 Dec 2023 Sep 2023 Jul 2023 Sep 2021 Aug 2021 Jul 2021 Jul 2020 Sep 2018 Aug 2018 Aug 2014 Jun 2013 Sep 2011 Aug 2011 Oct 2010 Mar 2010 Jun 2009 Sep 2008 Apr 2007 Oct 2005 Sep 2004 Jul 2004 Sep 2003 Jun 2003 Monthly Data for August 2024 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. NY PORT JEFFERSON STATION 0.3 SSW CoCoRaHS 15.58 CT NEWTOWN 4.6 SE CoCoRaHS 15.51 NY ST. JAMES COOP 15.49 CT NAUGATUCK 1.7 NNE CoCoRaHS 13.40 CT SOUTHBURY 2.3 W CoCoRaHS 12.83 CT STAMFORD 1.0 S CoCoRaHS 12.70 NY CENTEREACH 1.3 NE CoCoRaHS 12.64 NJ NORTH ARLINGTON 0.7 WNW CoCoRaHS 12.35 CT RIDGEFIELD 2.4 NNE CoCoRaHS 12.29 CT DANBURY COOP 12.27 NY SEAFORD 0.4 SE CoCoRaHS 12.18 CT BETHEL 4.5 SSE CoCoRaHS 12.01 CT RIDGEFIELD 3.7 NNE CoCoRaHS 12.00 CT MONROE 0.8 W CoCoRaHS 11.97 CT RIDGEFIELD 3.6 N CoCoRaHS 11.74 CT NEW CANAAN 3.8 N CoCoRaHS 11.66 NJ MAPLEWOOD TWP 0.9 SE CoCoRaHS 11.59 NY SETAUKET-EAST SETAUKET 0.7 SSW CoCoRaHS 11.54 CT HERITAGE VILLAGE 0.2 E CoCoRaHS 11.17 CT BETHEL 3.5 NNE CoCoRaHS 10.97 NY MOUNT SINAI COOP 10.90 NJ MONTVALE 1.8 ESE CoCoRaHS 10.81 CT BROOKFIELD 3.3 SSE CoCoRaHS 10.81 NJ WANAQUE RAYMOND DAM COOP 10.66 CT BETHEL 0.5 E CoCoRaHS 10.66 NJ OAKLAND 1.0 ESE CoCoRaHS 10.58 NJ CHARLOTTEBURG RESERVOIR COOP 10.50 NJ HARRISON COOP 10.38 CT PROSPECT 1.9 ENE CoCoRaHS 10.28 NJ MONTCLAIR 0.7 N CoCoRaHS 10.22 NJ WAYNE TWP 0.8 SSW CoCoRaHS 10.16 NY SELDEN 1.6 ESE CoCoRaHS 10.13 NJ LITTLE FALLS TWP 0.5 WNW CoCoRaHS 10.12 NJ RINGWOOD 3.0 SSE CoCoRaHS 10.04