bluewave

The higher elevations are the place to be if you like snow in April. Special Weather Statement National Weather Service Albany NY 454 AM EDT Sun Apr 3 2022 NYZ047-051-058-063-031800- Schoharie-Western Albany-Western Greene-Western Ulster- 454 AM EDT Sun Apr 3 2022 ...Wet Snow for Higher Terrain Areas Today... A period of wet snow, potentially becoming moderate to heavy at times, is expected today in the higher terrain areas of the eastern Catskills, Helderbergs and Schoharie County from approximately 8am to 2pm. While areas as low as 1000 feet in elevation could see coatings of snow, elevations mainly 1500ft and higher may see snow accumulations ranging 1 to 3 inches with locally higher amounts near 4 inches in the highest peaks. This may result in slippery travel conditions and motorists are encouraged to use caution if traveling.

The last El Niño couldn’t couple in 18-19 due to how warm the WPAC was. The most recent 3 year La Niña was 98-99, 99-00, and 00-01. But that followed immediately after the super El Niño in 97-98. Weather twitter seems very unsure on what happens with the ENSO going into next winter.

Kind of mixed signals coming from the Tropical Pacific. While the La Niña was strengthening back in March, it has begun to weaken again. The past analogs are all over the place for next winter. https://www.climate.gov/news-features/blogs/enso/march-2022-la-niña-update-three-bean-salad Also, La Niña three-peats (triple dips?) are very rare—only two exist in our more reliable historical record going back to 1950 and both occurred after major El Niño events, which our current event did not. The time evolution of the Niño-3.4 index for the two La Niña three-peats is featured in the darker blue lines in the image below. It is also interesting that out of the eight double-dip La Niñas in our historical record, three ended up evolving into an El Niño for the third winter (red lines) and the remaining three ended up on the cooler side, close to La Niña thresholds, but were ultimately classified as ENSO-neutral winters.

We could pick up over 2.00” of rain with multiple events by the 10th.

Yeah, it was the driest JFM on record for several locations in the West.

Out of season is the new in season. https://www.washingtonpost.com/weather/2021/11/14/tornadoes-connecticut-longisland-november/ Public Information Statement National Weather Service Mount Holly NJ 341 PM EDT Fri Apr 1 2022 ...Preliminary Survey Results for Tornado Near Hilltown Township and Bedminster Township in Bucks County Pennsylvania... The National Weather Service office in Mount Holly NJ is finishing a storm survey for the area near Hilltown Township and Bedminster Township in Bucks County Pennsylvania. The survey is in relation to the severe thunderstorms that moved through the area on March 31 2022. A tornado was determined to have occurred Thursday evening in the area near the Souderton Road and Dublin Pike intersection near the line between Hilltown and Bedminster Townships. The tornado was determined to be an EF1 with estimated maximum wind speed of 100 mph. A final assessment including path length and other results of the survey is expected to be completed and transmitted via a Public Information Statement by early this evening. The storm survey information will also be available on our website at http://www.weather.gov/phi

It was with the special marine warning. Enough MUCAPE above the inversion. So the stronger winds were able to mix down with the very heavy downpours.

The megadrought continues in the West.

Areas like PA that get frequent snow squalls could probably use a VSL system like they have in other parts of the country. https://safety.fhwa.dot.gov/speedmgt/ref_mats/fhwasa12022/chap_6.cfm In order to provide an in-depth analysis of the VSL systems and to obtain additional information on their use in wet weather and issues related to sight distance and stopping distance, various States with active VSL systems were interviewed. These States were chosen from the list of known U.S. installations of VSLs, which can be found in Appendix B, based on their relevance to the purpose of this guide, the level of experience each governing agency had with VSL systems, and the agency's willingness to share detailed information about their systems. The States below have VSL systems that currently incorporate weather conditions in their speed-setting criteria. 6.1 Alabama Alabama DOT (ALDOT) currently operates a VSL system on a 7-mile section of Interstate 10 in Mobile, Alabama. The section of roadway where the VSL system is implemented previously had a very high number of vehicle accidents due to visibility issues caused by fog. Following a very severe crash in 1995 involving 193 vehicles, ALDOT chose to deploy this low visibility warning system. The VSL system collects data from remote vehicle detectors, fog detection devices, and visibility sensors. The visibility sensors use forward-scatter technology and are installed roughly every mile. The data is reviewed by the TMC operators, who then manually change the speed limit based on the existing weather and traffic conditions. The operators use charts that detail what the posted speed limit should be based on driver visibility. The speed limits are changed in increments of 10 mph within the range of 35 to 65 mph. The system controls a total of 24 VSL signs, but is divided into six zones, in which the speeds in each zone can be set independently. Table 1 below shows the speeds and other strategies based on visibility distance (19 https://www.roadsbridges.com/lake-effect In Lake County, Ohio, winter weather spells trouble for a stretch of I-90 between S.R. 528 and S.R. 44. Over a 10-year span, more than 800 winter crashes were recorded along this corridor. On Dec. 8, 2016, an intense snow band that produced massive squalls contributed to a bus crash that led to a multi-car pileup of more than 50 vehicles, a scene all-too familiar to local responding agencies that witnessed a remarkably similar incident in December of the previous year. Northeastern Ohio is no stranger to winter weather, where areas of Ashtabula, Geauga and Lake counties can see more than 100 in. of snowfall annually. Unique to regions surrounding the Great Lakes, lake-effect snow can deposit more than 1 in. per hour, drastically reducing visibility and resulting in rapid accumulation. Lake-effect snow occurs when fronts of cold air pass over warm bodies of water. The location of I-90 along Lake Erie’s shore makes it a prime candidate for lake-effect squalls, known to surprise even the most experienced drivers. “Drivers experience a rapid change in weather and road conditions,” explained Lake County Sheriff Daniel Dunlap, regarding winter on I-90. “After driving 60 to 70 mph on relatively clear roadways, they basically come to a curtain of snow. Over a distance of 3-4 miles, [accumulation] can go from very little snow to well over a foot of snow.” After much discussion, partnering agencies agreed that a 10-mph speed-limit reduction was the first step in encouraging drivers to understand the unique threat that snow squalls posed in this corridor. Finding a fix Looking for a quick way to reduce the risk and severity of multi-car and secondary crashes, on January 2017 the Ohio Department of Transportation (ODOT) temporarily reduced the 70-mph stretch of I-90 between S.R. 91 and Vrooman Road to 60 mph through April 1. Ongoing discussions with the Lake County Sheriff and Ohio State Highway Patrol made it apparent that speed was a high contributing factor to severe winter crashes. Speed data from the day of the December 2016 crash showed that even after entering the lake-effect snow band, vehicles had continued to travel in excess of 70 mph. While the seasonal 10-mph speed-limit reduction on I-90 through Lake County caught the attention of the highway’s frequent travelers and local media, critics questioned its effectiveness. On days where no winter weather was predicted during the three-month period of the temporary reduction, commuters found themselves frustrated by the lowered speed limit. At the time, the Ohio Revised Code only allowed for the use of variable speed limits (VSL) within construction work zones. Interest in establishing a VSL corridor grew as local agencies and motorists discussed the safety of the corridor. “If we can get people to slow down, that will give them more reaction time when there’s a crash ahead,” said Ohio State Highway Patrol Lt. Charles Gullet. “I definitely feel [variable speed limits] will be a step in the right direction to reduce crashes in that area.” Legislation was passed in Summer 2017 that gave ODOT the go-ahead to move forward with designing a VSL corridor on I-90 between I-71 and the Ohio and Pennsylvania border. The limits of the project were narrowed to the stretch of I-90 between S.R. 44 and S.R. 528, a span that once saw 11 to 50 crashes per snow event—some that were multi-vehicle pileups. With only a few months to install the new system before winter began in Ohio, ODOT was tasked with the challenge of showing the public that change was on the way. Plans for the new VSL corridor were finalized and sign fabrication began. In preparation for the upcoming snow and ice season, temporary VSL signs similar to those used in work zones were placed in four eastbound and four westbound locations on I-90.

The potential for some needed rainfall in early April as the southern and western parts of the area have been dry recently.

Several of our stations just missed a top 10 warmest March due to the Arctic outbreak at the end of the month. ISP tied with last year. Notice how many recent years have seen top 10 warmest Marches. Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Month of Mar Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2012 47.3 0 2 2016 45.5 0 3 2010 45.1 0 4 1973 44.9 0 5 2020 44.8 0 6 1977 43.4 0 7 2000 43.2 0 8 1995 42.9 0 9 1991 42.7 0 10 1979 42.6 0 11 2022 42.4 0 - 2021 42.4 0

The issue of radar coverage gaps across the US has been known for years. Most of the time the issue comes up in the event of tornadoes. Tornadoes require a long enough lead time for people to get to safety. So issuing warnings for rotating storms is a good practice to give a long enough lead time in the event action needs to be taken. I am sure the local NWS meteorologists would like more radar sites in their forecast zones. The point of the article that I posted is that traffic was moving too quickly for the low visibility and slick road conditions.The local NWS forecast mentioned that there would be snow squalls in the area. Hazardous road conditions whether warned or not often lead drivers to make poor decisions. We probably need a better education campaign on how drivers can avoid these pitfalls. While the story below pertains to flooding, the same can be said about ice and snow. 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?

A warning probably wouldn’t have made much of a difference. Many people just ignore them anyway. We have seen how many people drive their cars into flash floods with or without specific warnings. Cars and trucks were maintaining their speed without slowing down when they encountered the squall. https://www.inquirer.com/weather/snow-squall-pennsylvania-81-philadelphia-weather-20220329.html The squall, part of what Martin called an eight-hour siege, blew up a bit sooner than forecasters expected and in advance of the “main event” squalls in the afternoon. The weather service didn’t issue a warning for it. It likely wouldn’t have made much difference: A squall might be so short-lived that it’s over by the time a warning is issued. And the ones on Monday were “small … in and out in a couple of minutes,” he said. “You can’t get a lot of lead time with something like that.” Radar hole? It is uncertain whether it was a factor in terms of advance notice, but AccuWeather’s Walker said the accident site is not well-observed by radar. It is on the outer edge of radar ranges, since it is about equidistant from the weather service devices operated by the offices in Mount Holly, State College, and Binghamton, N.Y. Monday’s squalls had low cloud tops, and they might have eluded the radar peripheries. The human factor John Blickley, an official with the Schuylkill County emergency management agency, said he was amazed at how many of the vehicles appeared to be maintaining their speeds despite the blizzardlike conditions. “I think there are some people who are naturally oblivious,” said Pennsylvania State Police Trooper David Beohm.

Cool and rainy pattern on the EPS through March 11th with lingering blocking and a fast La Niña Pacific flow. Storm systems will be racing across the country every few days. Then a warm up with more of SE Ridge in mid-March. April 4-11 April 11-18

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