bluewave

It’s no surprise that September and October have the fastest rising fall temperatures around the region. The figures below are the increase in monthly average temperatures for the new 30 year climate normals from 1981-2010 to 1991-2020. The slower rising November temperatures explain how we were able to get record November snows in recent years. EWR Sep….+1.0 Oct...+0.9 Nov…+0.2 NYC +1.2 +1.0 +0.3 LGA +1.7 +1.5 +0.8 JFK +0.3 +0.2 -0.7 ISP +1.3 +1.4 +0.5 HPN +1.6 +1.6 +0.5

2017 and 1959 were the only two heatwaves I could find at Newark after 9-20. 9-23-17….90° 9-24-17….92° 9-25-17….92° 9-22-59….90° 9-23-59….93° 9-24-59….92°

Endless summer in September doesn’t mean every day for the rest of the month hits 90° at a place like Newark. Plenty of 80°+ days with the potential for several 90s mixed in. So an extended period when most of the days are above average. Newark daily average high and low 9-13…..79/62 9-20…..76/59 9-27…..73/56

The EPS weeklies are in endless summer mode as the WAR continues into early October. 9-13 to 9-20 9-20 to 9-27 9-27 to 10-4

They are finally getting a trough out West. It has been a dueling WAR and Western Ridge pattern all summer. So it looks like the WAR will be going solo for a change.

Sunday into Monday looks like our first chance to make a run on 90° this month. The SE ridge will be near record levels. Tough to sustain cooler departures like the first 5 days of September. KEWR GFSX MOS GUIDANCE 9/09/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 THU 09| FRI 10| SAT 11| SUN 12| MON 13| TUE 14| WED 15| THU 16 CLIMO X/N 73| 61 79| 58 79| 63 87| 70 89| 68 82| 67 84| 69 83 59 76

Dew points back above 70° here on the South Shore. So it’s no surprise that more heavy rain is in the forecast around the region. A continuation of the high humidity theme. Ben Noll posted an expanded version of this for the entire Northeast. I posted the local NYC Metro records of recent years earlier in the thread. Wantagh N/A 77 72 83 S8

A recent paper used the STP to increase confidence in the reports of tornadoes shifting east from the Plains. https://www.nature.com/articles/s41612-018-0048-2 Meanwhile, a robust upward trend is found in portions of the Southeast, Midwest, and Northeast (Fig. 4). No significant increase (decrease) in tornado environments is observed west (east) of the 95th meridian. We believe these trends in tornado environments are significant and have not been documented with this level of detail by previous research. https://www.sciencedaily.com/releases/2018/10/181017172846.htm The researchers tracked the number of tornado reports from 1979 to 2017, while also investigating regional trends in the daily frequency of tornado-environment formation over the same time period, using an index known as the Significant Tornado Parameter (STP). Frequently used for predicting severe weather, the index captures the coexistence of atmospheric ingredients favorable for producing tornadoes. Both the number of actual tornado reports and the historical STP analysis showed the eastward uptick in tornado frequency. "One could argue that because a region's population has increased, more tornadoes are sighted and reported," Gensini said. "But we also identified this eastward trend when using the STP index, which looks at the frequency of tornado environments and has nothing to do with people. This increases our confidence in the reporting trend that we're seeing." The trend is important for understanding the potential for future tornado exposure, damage and casualties. Severe thunderstorms accompanied by tornadoes, hail and damaging winds cause an average of $5.4 billion of damage each year across the United States, and events with $10 billion or more in damages are no longer uncommon.

Current NSIDC daily extent is a little above the 2010s average. It’s at 4,838 million sq km. Extent was just below to the average before the August slowdown.

Yeah, that gets to prior experience and normalcy bias which are discussed in the article below. https://theconversation.com/why-do-people-try-to-drive-through-floodwater-or-leave-it-too-late-to-flee-psychology-offers-some-answers-157577 While playing in or driving through flood waters are avoidable risks, the latter involve adults who generally know the risks – much to the frustration of emergency authorities. So what convinces people make risky decisions in a flood? Drivers in our study reported that they saw a majority of people in other vehicles (about 64%) driving through the floodwater, while only 2% were turning around. Seeing others do something often leaves people with the impression this behaviour is typical and relatively safe, an effect known as “normalcy bias”. In 15% of cases we studied, passengers also put pressure on drivers to cross. When things go wrong, they can go very wrong Another key reason involves prior experience and perceived probability of adverse outcomes. While 9% reported a negative outcome (such damage to their car or having to be rescued), 91% reported proceeding without any incident. The reasons for these crossings were not sudden or impulsive, but often involved what the person saw as “careful consideration” of everyday needs — such as the need to get to work or buy groceries. This presents an obvious challenge for emergency authorities. While most people succeed without issues, the cases where something goes wrong can be catastrophic and in some cases fatal. So, how do we convey the very real risks of floodwater? How do we highlight the need for people to prepare an evacuation plan and avoid entering floodwater?

I don’t think that we are over-warned for flooding. The NWS usually gets reports verifying their flash flood warnings. With last weeks event, not much the NWS can do to solve societal issues. The illegal basement apartments in NYC have been around for a long time. They exist due to the lack of affordable housing in NYC. As for all the cars stuck on flooded roads, people often underestimate the depth of water. Every flash flood around the world has videos of people driving into floods and getting stuck. Maybe we need NWS spotter type education for the general public on the dangers of driving into floods.

It’s been a challenge to string 5 or more cool days together like we just did from 9-1 to 9-5 https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=32&network=NJCLIMATE&station=NJ6026&year=2021&var=avg&gddbase=50&gddceil=86&how=diff&cmap=jet&dpi=100&_fmt=png

This may be the furthest north along the East Coast that a post tropical or tropical cyclone has spawned an EF-3 tornado.

While we will eventually surpass the 2012 extent minimum, the summer pressure reversal since then has made it a challenge. But even a lower Arctic pressure summer like this year was able to dip below 5 million sq km on NSIDC extent. Extents never fell this low before 2007.

The last few years stand out when compared to the rest of the doppler era of much better radar detection.

These great tweets from the NWS Mt Holly highlight how extreme our weather has become.

This is going to be the first winter with the new warmer 1991-2020 climate normals. So the NYC new average for DJF rose from 35.1° to 36.2°. It will be interesting to see if the warmer averages make it easier for NYC to finally sneak in a cooler than average winter. Every winter since 15-16 in NYC has been warmer than normal.

The latest Euro seasonal for DJF has a similar 500 mb pattern to 2017-2018.

Larry will be a surfers special. Building swells peaking by later in the week. The very large wind field will result in a top 10 surfing period for the year. Beach patrols will probably close the ocean to swimmers.

August experienced the slowest rate of NSIDC extent loss of the whole post-2007 sea ice era. The sea ice only declined by 1.498 million sq km between 7-31 and 9-1. Notice how the August rate of decline has slowed after 2012 relative to the previous 6 years. In order to beat the 2012 extent minimum, we would need extreme May preconditioning like 2020 combined with August declines in excess of 2.3 million sq km. Dr. Francis had a great recent paper on this August slowdown in recent years. NSIDC August declines in millions of sq km 2021….-1.498 2020….-1.929 2019….-1.673 2018…..-1.639 2017…..-1.914 2016….-2.347 2015….-2.318 2014…..-1.655 2013…..-1.701 2012….-2.795 2011….-2.089 2010…..-1.641 2009….-1.663 2008….-2.449 2007….-2.154 https://iopscience.iop.org/article/10.1088/1748-9326/abc047 LETTER • THE FOLLOWING ARTICLE IS OPEN ACCESS Why has no new record-minimum Arctic sea-ice extent occurred since September 2012? Jennifer A Francis1 and Bingyi Wu2 Published 23 November 2020 • © 2020 The Author(s). Published by IOP Publishing Ltd Environmental Research Letters, Volume 15, Number 11Citation Jennifer A Francis and Bingyi Wu 2020 Environ. Res. Lett. 15 114034 Abstract One of the clearest indicators of human-caused climate change is the rapid decline in Arctic sea ice. The summer minimum coverage is now approximately half of its extent only 40 yr ago. Four records in the minimum extent were broken since 2000, the most recent occurring in September 2012. No new records have been set since then, however, owing to an abrupt atmospheric shift during each August/early-September that brought low sea-level pressure, cloudiness, and unfavorable wind conditions for ice reduction. While random variability could be the cause, we identify a recently increased prevalence of a characteristic large-scale atmospheric pattern over the northern hemisphere. This pattern is associated not only with anomalously low pressure over the Arctic during summer, but also with frequent heatwaves over East Asia, Scandinavia, and northern North America, as well as the tendency for a split jet stream over the continents. This jet-stream configuration has been identified as favoring extreme summer weather events in northern mid-latitudes. We propose a mechanism linking these features with diminishing spring snow cover on northern-hemisphere continents that acts as a negative feedback on the loss of Arctic sea ice during summer.

You would never guess that Newark had 40 days reaching 90° by just looking at how cool the big summer holiday weekends have been. Newark high temperatures May….29….52° May….30….53° May....31….76°….Memorial Day Jul…….3…..70° Jul……..4….84°….Independence Day Jul……..5….89° Sep……4….82° Sep…….5 Sep…….6…..Labor Day Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 90 Missing Count 1 2010 54 0 2 1993 49 0 3 1988 43 0 4 2002 41 0 - 1991 41 0 5 2021 40 118 - 2016 40 0 - 1983 40 0 - 1959 40 0

NYC has had the wettest June 1st to September 3rd by a wide margin. 6 out of the top 10 wettest years have all occurred since 2003. It’s also interesting that so many new snowfall records have happened over this same period. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Precipitation Jun 1 to Sep 3 Missing Count 1 2021-09-03 31.26 0 2 2011-09-03 25.23 0 3 1927-09-03 23.89 0 4 1975-09-03 22.40 0 5 1989-09-03 22.39 0 6 2006-09-03 22.14 0 7 2003-09-03 21.54 0 8 1928-09-03 21.41 0 9 2009-09-03 21.38 0 10 2007-09-03 20.62 0

Great write up from the Northeast Regional Climate Center. http://www.nrcc.cornell.edu/services/blog/2021/09/03/index.html Tropical Depression Ida dropped catastrophic amounts of rain on parts of the Northeast on September 1. A swath of the region stretching from eastern Pennsylvania and northern/central New Jersey through the New York City metro area and into southern New England saw rainfall totals of more than 6 inches. In fact, a corridor of 8- to 11-inch rainfall totals were found in southeastern Pennsylvania, northern/central New Jersey, and the New York City area. Newark, NJ, saw 8.41 inches of rain, making it the site’s all-time wettest day on record and already making September 2021 the site’s fourth wettest September on record. LaGuardia Airport, NY, also recorded its all-time wettest day with 6.80 inches of rain. Meanwhile, Bridgeport, CT, which saw 5.77 inches of rain, experienced its wettest September day. Rain fell at a rate of 3 to 5 inches per hour in some locations, with the bulk of the daily rainfall accumulating within a six-hour period in most areas. Newark, NJ, recorded its all-time wettest hour on record, seeing 3.24 inches of rain between 8 and 9 pm. The site’s one-hour rainfall, two-hour rainfall total of 5.06 inches, and six-hour total of 7.88 inches all qualified as 500-year storm events, meaning they have a 0.2% chance of happening in a given year. Similarly, Central Park, NY, had its all-time wettest hour on record with 3.15 inches of rain from 9 to 10 pm. That record had just been set less than two weeks prior from Tropical Storm Henri. Central Park’s two-hour rainfall of 4.65 inches and six-hour total of 6.63 inches also both qualified as 500-year storm events. Many of these locations had just seen excessive rainfall from tropical systems Fred and Henri a few weeks prior. With saturated soils, waterways already running high, and the deluge from Ida, dozens of streamgages reached major flood stage, a water level high enough that “extensive inundation of structures and roads” and “significant evacuations” are possible. In fact, water levels reached historic levels at several long-term sites. For example, Brandywine Creek at Chadds Ford, PA, which has records to the early 1900s, reached 21.04 feet, approaching the operational limit of the gage and beating the previous record of 17.15 feet from September 17, 1999. Similarly, the Raritan River at Manville, NJ, which also has records back to the early 1900s, reached a new record high water level of 27.66 feet. In addition, several more long-term sites reached near-record water levels. The Schuylkill River at Philadelphia, PA, reached 16.35 feet, its second highest crest on record and just below the all-time highest water level of 17.0 feet set back on October 4, 1869.

Luckily, these people were rescued from the basement by a family member.