bluewave

Only a few days between a snow squall warning and severe thunderstorm warning and possible tornado in PA.

Those 1982 to 1994 Arctic outbreaks were focused south and west of NYC. The airports in DC and Philly also made it to -5 or colder. So there was a very sharp temperature gradient near the Hudson River. Time Series Summary for WASHINGTON REAGAN NATIONAL AIRPORT, VA - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1982 -5 0 2 1994 -4 0 - 1985 -4 0 Time Series Summary for PHILADELPHIA INTL AP, PA - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1984 -7 0 - 1982 -7 0 3 1985 -6 0 4 1994 -5 0 Time Series Summary for ALLENTOWN LEHIGH VALLEY INTERNATIONAL AIRPORT, PA - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1994 -15 0 2 1961 -12 0 3 1984 -11 0 - 1942 -11 0 4 1954 -10 1 5 1985 -9 0 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 Lowest Min Temperature Missing Count 1 1934 -14 0 2 1985 -8 0 - 1933 -8 0 4 1982 -7 0 - 1943 -7 0

I started an April thread for anyone that wants to discuss it.

Looks like a cooler start to the month with lingering blocking followed by an eventual warm up as the SE Ridge returns.

This March may be the first time that an Arctic outbreak near the end of the month took NYC out of contention for a top 10 warmest month. 9th warmest through the 25th Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Mar 1 to Mar 25 Missing Count 1 2012-03-25 51.9 0 2 2010-03-25 49.0 0 3 2016-03-25 48.5 0 4 1921-03-25 48.3 0 5 1903-03-25 48.2 0 6 1945-03-25 47.8 0 7 2020-03-25 47.7 0 8 1946-03-25 47.6 0 9 2022-03-25 46.7 0 10 2000-03-25 46.2 0 - 1979-03-25 46.2 0 Currently 17th warmest through the 30th Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Mar Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 1945 51.1 0 2 2012 50.9 0 3 1946 49.8 0 4 2016 48.9 0 5 1921 48.4 0 6 2010 48.2 0 - 1903 48.2 0 7 2020 48.0 0 8 2000 47.2 0 9 1979 46.9 0 10 1977 46.7 0 11 1973 46.4 0 12 1898 46.1 0 13 2021 45.8 0 - 1985 45.8 0 14 1998 45.4 0 15 1936 45.2 0 16 1990 45.1 0 - 1987 45.1 0 - 1986 45.1 0 - 1929 45.1 0 17 2022 45.0 1 - 1995 45.0 0

It would be great if the future ECMWF and HRRR model upgrades can increase resolution enough for exact wind gusts around NYC buildings.

The taller buildings actually cool the surrounding areas since they cast very large shadows. https://mdpi-res.com/d_attachment/remotesensing/remotesensing-13-03797/article_deploy/remotesensing-13-03797-v2.pdf 5. Discussion Three factors, trees, building heights, and impervious surfaces, including bright surfaces, are primarily responsible for surface temperature heterogeneity in our study site. The replacement of vegetation by heat-trapping and non-porous urban materials alters surface conditions such as albedo, thermal capacity, and heat conductivity. Such transformation alters radiative fluxes between the surfaces and the lower atmosphere [4]. Trees reduce heat in two ways. Firstly, the shadows resulting from the tree control the total amount of radiation absorbed per unit surface area of heat-trapping materials. Secondly, trees return more surface heat to the atmosphere through evapotranspiration and reduce surface temperatures. Similarly, shadows cast by high-rise buildings reduce the amount of solar energy absorbed by the urban heat-trapping surfaces, and so there will be less heating effect. Guo et al. [14] observed a positive impact of building height and density on land surface temperature. They further observed higher land surface temperature associated with medium building height and a lower building density. Krüger et al. [39] showed a direct link between urban climate and building heights. Similarly, we found a slightly higher surface temperature in medium-height buildings (ranging between 10 and 15 m), but the temperature decreases when the heights increase beyond 15 m together with its variability. This indicates that the relationships between surface temperature and urban structure are more likely associated with urban types. Generally, the shadows cast by tall buildings cover large urban impervious surfaces in the areas having more height variability. In addition, because the Sun is at a lower elevation in September cause longer shadows in comparison with the summer seasons. Likewise, Zheng et al. [40] observed adverse effects of building heights on land surface temperature in residential areas of Beijing. However, the shadow effect on surface temperature varies with the time of the day and the day of the year. The shadows from high-rise buildings influence temperature, similar to how vegeta- tion affects surface temperature [41]. Mutual shadows created by tall vegetation, such as in forests, eliminate any existing gaps in forests. Even if some gaps exist between high-rise buildings in cities like New York, the mutual shadows cast on the wall of the buildings and the ground reduces heating effects. Additionally, when the height variability increases, the shadows can effectively cover the adjacent building walls up to hundreds of meters away depending on the Sun’s azimuth [42]. Under such conditions, less incident radiation will likely be absorbed on the urban surfaces (horizontal and/or vertical), leading to cooler urban surfaces. Wang and Xu [12] also indicate that land surface temperature decreases significantly with building height differences and brings a cooling effect. Our results show that surface temperature increases with increasing fractions of imper- vious cover (both impervious-medium and dark surfaces). This indicates that dark urban surfaces, mainly low-rise multi-family walk-up buildings with an average number of floors of 3.15, produce fewer shadows contribute to the urban heat. Surfaces with brighter covers show an increasing surface temperature trend. Usually, bright surfaces increase surface albedo, i.e., reflect more and absorb less solar radiation than other impervious surface materials [43]. It is expected that surface temperature would decrease with bright surface cover due to its high albedo. However, due to its low heat capacity, even the bright impervious surface can heat the surface easily and quickly. Most bright surfaces are rooftops and industrial plants, which are constantly exposed to the Sun. Moreover, the bright surface is surrounded by dark and medium-dark heat-trapping surfaces. The presence of these heat-trapping darker materials may amplify the surface temperature. For the impervious-dark and impervious-medium surfaces and roofs, not much light penetrates the surfaces, incident radiation is not reflected back to the atmosphere is used to heat the surfaces, causing increased surface temperature. Using high spatial resolution satellite data, we characterized the shadows, green vegetation, impervious surfaces, and their brightness and identified each component’s impact on surface temperature in our study site

The heat Island around the 5 boroughs and Newark pretty much maxed out by the 1930s and 1940s.The nearby suburbs filled out in the 1951-1980 climate normals period. So the 1981-2010 and 1991-2020 climate normals periods warming were fully a result of the warming climate.

UHI peaked at Central Park in 1910 before declining and then slowly rising again. https://pubs.giss.nasa.gov/docs/2008/2008_Gaffin_ga00100w.pdf

But 1917 to 1936 had much colder intervals than the period from the 1870s to the early 1910s. Time Series Summary for NY CITY CENTRAL PARK, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1934 -15 0 2 1917 -13 0 3 1943 -8 0 4 1933 -6 0 - 1918 -6 0 - 1899 -6 0 - 1882 -6 0 - 1880 -6 1 5 1914 -5 0 - 1896 -5 0 Minimum 30-Day Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Value Ending Date Missing Days Period of record: 1869-01-01 to 2022-03-29 1 19.0 1918-01-24 0 2 19.3 1918-01-25 0 3 19.3 1918-01-27 0 4 19.5 1918-01-23 0 5 19.6 1918-01-26 0 6 19.6 1934-02-28 0 7 19.8 1934-02-27 0 8 19.8 1918-01-28 0 9 20.1 1918-01-22 0 10 20.1 1934-03-01 0 11 20.3 1918-01-21 0 14 20.3 1893-01-22 0 15 20.3 1918-01-07 0 17 20.4 1918-01-08 0 18 20.4 1936-02-21 0 19 20.5 1893-01-20 0 20 20.7 1918-01-04 0 - 20.3 1918-01-06 0 - 20.3 1918-01-05 0 - 20.3 1893-01-21 0

Yeah, there was a rapid cooling of the North Atlantic during the 1970s. They are still not sure what caused it. So we had all those record cold winters in the late 1970s and early 1980s. 1982 and 1985 were the last 2 times that Newark almost made it down to -10°. An Anatomy of the Cooling of the North Atlantic Ocean in the 1960s and 1970s https://journals.ametsoc.org/view/journals/clim/27/21/jcli-d-14-00301.1.xml 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 Lowest Min Temperature Missing Count 1 1934 -14 0 2 1985 -8 0 - 1933 -8 0 3 1982 -7 0 - 1943 -7 0 4 1936 -4 0 - 1935 -4 0 5 1994 -2 0 - 1977 -2 0 - 1963 -2 0 - 1961 -2 0 6 1984 -1 0 - 1981 -1 0 - 1980 -1 0 - 1979 -1 0 - 1976 -1 0 - 1942 -1 0 7 2016 0 0

April 1982 was the latest 21° low and 30° low max on record for NYC. It was a 100 year event for the colder climate of that time. So in our warmer climate, we haven’t seen anything close to that type of April blizzard or cold. The latest highs in the 30s was 4-29-1874. Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Season Length 1982 04-07 (1982) 21 12-09 (1982) 19 245 1881 04-05 (1881) 21 12-11 (1881) 20 249 1874 04-05 (1874) 20 12-14 (1874) 16 252 1923 04-01 (1923) 12 01-02 (1924) 20 275 1915 03-30 (1915) 21 12-11 (1915) 21 255 First/Last Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Difference 1982 04-07 (1982) 30 12-13 (1982) 24 249 1881 04-05 (1881) 30 11-25 (1881) 30 233 1887 03-29 (1887) 29 12-01 (1887) 23 246 1894 03-27 (1894) 30 12-28 (1894) 17 275 1878 03-25 (1878) 30 12-24 (1878) 22 273 First/Last Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Difference 1874 04-29 (1874) 38 11-13 (1874) 36 197 1904 04-20 (1904) 37 11-17 (1904) 38 210 1887 04-18 (1887) 38 11-11 (1887) 39 206 1875 04-18 (1875) 32 11-04 (1875) 39 199 1872 04-16 (1872) 39 11-21 (1872) 37 218 1940 04-13 (1940) 35 11-26 (1940) 35 226 1918 04-12 (1918) 35 11-26 (1918) 39 227 1894 04-11 (1894) 39 11-09 (1894) 37 211 1882 04-11 (1882) 38 11-18 (1882) 34 220 1942 04-10 (1942) 37 11-14 (1942) 32 217 1909 04-10 (1909) 39 11-25 (1909) 39 228 1900 04-10 (1900) 39 11-16 (1900) 39 219 2003 04-09 (2003) 39 12-02 (2003) 36 236 1982 04-09 (1982) 39 12-10 (1982) 35 244

First time that LGA had two record highs during the first week of a March followed by record low tie during the last week. 3/1 71 in 2017 68 in 1972 62 in 2004+ 3/2 67 in 2004 66 in 2017 66 in 1972 3/3 65 in 1967 62 in 1961 60 in 2002 3/4 69 in 1946 65 in 1974 62 in 2008 3/5 72 in 1976 69 in 1964 68 in 1961 3/6 68 in 2022 64 in 1976 62 in 2004 3/7 74 in 2022 69 in 2009 69 in 1987 3/25 18 in 1940 19 in 1956 21 in 1960 3/26 20 in 1960 21 in 1947 25 in 2014+ 3/27 23 in 2014 24 in 1975 25 in 2001+ 3/28 23 in 1982 24 in 2022 24 in 1975 3/29 25 in 2022 25 in 1959 26 in 1943 3/30 23 in 1970 28 in 2008 28 in 1941 3/31 24 in 1964 28 in 1969 28 in 1950

This is the full thread with all the supporting material.

Thursday could be another one of these out of season severe events with a few tornadoes possible for the warm spots around the region that can destabilize enough.

Sure. It must be related to our rapidly warming winters. There were only 3 years between 1950 and 1990 with the coldest NYC annual daily temperature departure occurring in the MAM spring period. But there have been 7 years since 1993. Most of the time the coldest departure happens during the winter. These spring blocking patterns in recent years are also contributing. So while spring has been warming along with winter, the winter warming rate is higher. Plus the February 21 to March 20 high temperature has been rising rapidly since 1991 while the low between March 21 and April 20 has been slowly declining. So a pattern that supports early blooms and the potential to still get hard freezes. This hard freeze happened following a top 10 warmest March 1 to 27. All years in NYC with coldest annual temperature departure occurring during the spring since 1950 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2022-03-28 -18.6 2022-01-15 -17.9 2022-01-21 -15.1 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2021-05-30 -18.0 2021-05-29 -17.7 2021-04-02 -14.9 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2020-05-09 -20.4 2020-05-08 -14.6 2020-11-18 -14.2 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2007-03-06 -24.0 2007-03-07 -22.7 2007-02-05 -21.2 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2002-03-22 -17.0 2002-12-09 -16.4 2002-12-04 -16.3 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 1998-03-12 -16.5 1998-03-11 -14.7 1998-12-31 -14.4 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 1993-03-18 -22.2 1993-12-27 -21.2 1993-03-19 -19.0 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 1978-03-05 -18.7 1978-02-04 -18.5 1978-02-05 -18.2 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 1967-03-18 -28.2 1967-03-19 -25.5 1967-03-17 -23.4 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 1956-03-25 -19.5 1956-03-19 -19.0 1956-07-06 -18.1 1956-03-18 -17.7

If the NYC -18.6 departure can hold through next fall and early winter, then it will be the 3rd year in a row with the coldest daily temperature departure occurring in the spring. The coldest annual departure normally happens during the winter. So this could be a first for 3 consecutive years in the spring if it holds. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2022-03-28 -18.6 2022-01-15 -17.9 2022-01-21 -15.1 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2021-05-30 -18.0 2021-05-29 -17.7 2021-04-02 -14.9 Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Date Avg Temperature Departure 2020-05-09 -20.4 2020-05-08 -14.6 2020-11-18 -14.2

Yesterday was the 2nd latest date at LGA that the high didn’t get over freezing. RECORD EVENT REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 730 PM EDT TUE MAR 28 2022 ...RECORD LOW MAXIMUM TEMPERATURE SET AT LAGUARDIA NY... A RECORD LOW MAXIMUM TEMPERATURE OF 32 WAS SET AT LAGUARDIA NY TODAY. THIS BREAKS THE OLD RECORD OF 36 SET IN 1966. 3/25 32 in 1940 34 in 1974 34 in 1956 3/26 34 in 1947 35 in 2014 36 in 1971 3/27 36 in 1955 39 in 1982 39 in 1975+ 3/28 32 in 2022 36 in 1966 38 in 1959 3/29 34 in 1974 35 in 1984 40 in 1965+ 3/30 34 in 1970 39 in 1941 40 in 1990+ 3/31 36 in 1970 36 in 1969 37 in 1964 4/1 42 in 2001 43 in 1964 44 in 2011+ 4/2 39 in 2021 40 in 1993 43 in 2018 4/3 39 in 1978 43 in 1962 43 in 1943 4/4 36 in 1975 41 in 1972 42 in 1944 4/5 38 in 1995 39 in 1944 41 in 1975 4/6 40 in 1982 41 in 1975 42 in 1971+ 4/7 30 in 1982 37 in 2003 39 in 1967 4/8 38 in 2003 39 in 1972 39 in 1956

The storm with the severe potential on Thursday may have near record low pressure for March in parts of Wisconsin and Michigan.

The latest EPS says it will take time for the blocking pattern to relax. Has a brief warm up with severe thunderstorm potential this Thursday. Then below normal temperatures and blocking continues into April. Getting some hints that that a warmer SE Ridge pattern returns around April 12th March 28th to April 4th April 4th to 11th Warmer SE Ridge pattern returns for the 12th

We need some type of extreme blocking these days to make a run on record lows.

This is the coldest Arctic outbreak following 4 days reaching 70° at Newark by March 27th. The previous record was a low of 26° set in 2016. Newark dropped to 23° this morning for the first time following such a warm start to spring through the 27th. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Number of Days Max Temperature >= 70 Jan 1 to Mar 27 Lowest Temperature after Mar 27 1 2012-03-27 8 38 2 1946-03-27 6 32 - 1945-03-27 6 33 3 2020-03-27 5 32 4 2022-03-27 4 23 - 2016-03-27 4 26 - 1990-03-27 4 28 - 1987-03-27 4 31

Locally 3” of snow with that streamer stalled in place over CT. Be interesting to see how much Eastern LI has picked up. That band has been very persistent.

Looks like the big weather swings will continue. Euro has low 20s around NYC Monday and Tuesday mornings. Quick rebound back to near 70° on Thursday. The next storm and cold front may be accompanied by an early season severe thunderstorm outbreak later Thursday. A high shear and low CAPE event with the potential for embedded spin ups. Then a return to colder to start April but not as cold as the next few days.

One part of our warming climate is that the highest temperature is rising rapidly from Feb 21 to March 20. But the coldest temperature from Mar 21 to Apr 20 has been slowly declining since 1991. So this allows earlier spring blooms to be followed by hard freezes. Probably is related to all this spring blocking following early starts to spring.