bluewave

Don’t really know since it has become such a persistent feature since the 2018-2019 winter.

This looks like it could actually thread the needle. Kicker coming into BC probably will prevent the low from riding too far north. The weak ridge to our east will work against a complete suppression to the south. So a 2” scenario like the 12z Euro has in NYC would be a decent outcome for such a fast Pacific flow pattern. Perhaps there is a 1” downside -upside risk for a 1-3” event in NYC.

The 12z Euro 2” for NYC would be a nice little event.

All the area needs to finish December with a multi-station average of -2 to -3 is to go +2 to +3 from December 17th through the 31st which isn’t very extreme. Models have been notorious for missing the magnitude of both warm ups and cool downs in the long range. Most of the time our climate has above average temperatures. So there are more total opportunities for the models to underestimate the warm ups than the cool downs. This is why the models underestimation of the current cold pattern from back in late November was more memorable. This was our only real colder pattern here of this magnitude since last January. The other repeating pattern has been that the warm ups which follow the cool downs eventually rank higher than the cool downs did. Sometimes it takes several months as last spring and summer were much warmer than the cold last January.

It kind of looks like the current -7 to -8 around NYC Metro will finish closer to maybe a -2 to -3 range by December 31st.

It’s possible that some areas to our south with the strong cold departures through the 10th could finish December close to average with the coming warm up. This also fits the pattern since at least the 1990s of the 2nd half of December warming at a faster rate than the 1st half in our area.

I grew up in Long Beach on the South Shore and we only needed the AC a handful of times back in the 1970s. First for the August 1973 heatwave and then the July 1977 heatwave. We gradually increased the AC usage during the 1980s and especially the early 1990s. By the time we reached 2010, we had three ACs running much of the time compared to only one in the 1970s. Plus there was a rapid expansion of central AC even in Long Beach when it was a rarity near the shore in the 1970s. This is one of the reasons that HVAC is such a good career opportunity for people due to the increased demand in a warming world. As for the UHI issue, there was a 10°+ difference between NYC during 1896 heatwave and the surrounding countryside. This mostly occurs with summer heatwaves where the city absorbs more heat during the day. It also occurs during calm and clear nights with radiational cooling. The growth of skyscrapers in Western Brooklyn and Queens certainly changes the character of the neighborhood and of course you can see the change in the skyline since around 2004. But prior to that that area had densely packed lower rise buildings built of bricks. These new high rises are mainly glass and steel which absorb significantly less solar energy than bricks do. Plus a cluster of tall buildings will create a big area of shade which prevents the streets and sidewalks from absorbing as much heat as they did with smaller buildings with less shadows. The warmest parts of NYC are in Queens near spots like Corona were small to medium size brick structures dominate. So changing from lower rise brick and concrete structures to skyscrapers may not change the UHI much in Western Brooklyn and Queens to really be noticeable to residents there. That’s why I said a drop in the bucket to what was already one of the largest UHI zones in North America. The rural and suburban areas have warmed at a similar rate to places like Corona Queens over the years. So this is why both areas require more summer AC usage than they did during the 1970s. My guess is that the higher dewpoints and maybe stronger winds are probably why a rural spot like the Charlotteburg Reservoir has seen a steeper increase in low temperatures than LGA since 1981.

The increase in development in Western Brooklyn and Queens last 20 years in relation to the totality of the existing UHI footprint is still very small compared the increasing CO2 forcing over the same period. Drop in the bucket for sensible temperatures but a big shift to the character of those neighborhoods that have more high rises than they used to. The skyscrapers replaced already dense low rise urban development that was there previously driving the UHI. It’s not like the new development is replacing a rural area that was great for radiational cooling before 2004.

Not enough for you to notice much of a change in Brooklyn and Queens sensible temperatures since 1980 had the CO2 levels remained steady instead of rapidly climbing. The recent development last 20 years in Western Brooklyn and Queens is a drop in the bucket compared to the overall UHI footprint of NYC which really expanded between the 1890s and 1960s. Add 15-20% to snowfall totals from the late 1800s through the 1980s and the long term downward decline becomes even steeper.

This is due to the overall climate warming since the 1970s and not an expansion of UHI. Even cooler surrounding areas are wall to wall AC usage now from May to September when they weren’t in the past. The warming in rural, suburban, and urban areas has been proportional.

UHI was already well established in NYC as early as 1896. Notice the more than +10° low temperature difference between Central Park and rural areas in August 1895. LGA and JFK UHI began to increase with the Queens urbanization and population growth expansion in the 1920s. So this isn’t much of a change from the current 10°+ difference between NYC-LGA-JFK and surrounding areas when UHI episodes are more pronounced like during summer heatwaves and radiational cooling during the winter. Data for August 9, 1896 through August 9, 1896 Click column heading to sort ascending, click again to sort descending. NY NY CITY CENTRAL PARK WBAN 82 NJ NEWARK LIBERTY INTL AP WBAN 76 NY WORLD TRADE CENTER WBAN 75 NJ PATERSON COOP 75 NY BRONX COOP 75 NJ PLAINFIELD COOP 73 NJ ELIZABETH COOP 73 NY PORT JERVIS COOP 72 NY SETAUKET STRONG COOP 72 CT MIDDLETOWN 4 W COOP 72 NY WEST POINT COOP 71 CT BRIDGEPORT COOP 71 NY BRENTWOOD COOP 70 CT COLCHESTER 2 W COOP 70 CT NORWALK COOP 69 CT WATERBURY ANACONDA COOP 69 CT NEW LONDON COOP 69 NJ CHARLOTTEBURG RESERVOIR COOP 67 Data for August 10, 1896 through August 10, 1896 Click column heading to sort ascending, click again to sort descending. NY NY CITY CENTRAL PARK WBAN 80 NJ NEWARK LIBERTY INTL AP WBAN 78 NY WORLD TRADE CENTER WBAN 77 NY BRONX COOP 77 CT BRIDGEPORT COOP 76 NJ PATERSON COOP 75 NY WEST POINT COOP 75 NY SETAUKET STRONG COOP 75 NJ PLAINFIELD COOP 74 NJ ELIZABETH COOP 74 CT NORWALK COOP 74 CT WATERBURY ANACONDA COOP 74 CT NEW LONDON COOP 73 CT COLCHESTER 2 W COOP 73 NY BRENTWOOD COOP 72 CT MIDDLETOWN 4 W COOP 72 NY PORT JERVIS COOP 71 NJ CHARLOTTEBURG RESERVOIR COOP 69 Data for August 11, 1896 through August 11, 1896 Click column heading to sort ascending, click again to sort descending. NY NY CITY CENTRAL PARK WBAN 81 NJ NEWARK LIBERTY INTL AP WBAN 78 NY BRONX COOP 78 NY WORLD TRADE CENTER WBAN 76 CT NEW LONDON COOP 75 NJ PATERSON COOP 74 NJ PLAINFIELD COOP 73 NJ ELIZABETH COOP 73 CT BRIDGEPORT COOP 73 NY SETAUKET STRONG COOP 73 CT WATERBURY ANACONDA COOP 72 NY PORT JERVIS COOP 71 NY WEST POINT COOP 71 CT MIDDLETOWN 4 W COOP 71 CT COLCHESTER 2 W COOP 71 NY BRENTWOOD COOP 70 CT NORWALK COOP 69 NJ CHARLOTTEBURG RESERVOIR COOP 67

The NYC UHI intensity hasn’t changed much since the 1980s on clear and calm nights when we get radiational cooling in the surrounding areas.

https://news.ucar.edu/14009/snowfall-measurement-flaky-history But when we turn to snowstorms in the Northeast, or elsewhere in the U.S., there is an additional factor at work when comparing modern numbers with historical ones. Quite simply, our measuring techniques have changed, and we are not necessarily comparing apples to apples. In fact, the apparent trend toward bigger snowfalls is at least partially the result of new—and more accurate—ways of measuring snowfall totals. Climate studies carefully select a subset of stations with consistent snow records, or avoid the snowfall variable altogether. Earlier in our weather history, the standard practice was to record snowfall amounts less frequently, such as every 12 or 24 hours, or even to take just one measurement of depth on the ground at the end of the storm. You might think that one or two measurements per day should add up to pretty much the same as measurements taken every 6 hours during the storm. It’s a logical assumption, but you would be mistaken. Snow on the ground gets compacted as additional snow falls. Therefore, multiple measurements during a storm typically result in a higher total than if snowfall is derived from just one or two measurements per day. That can make quite a significant difference. It turns out that it’s not uncommon for the snow on the ground at the end of a storm to be 15 to 20 percent less than the total that would be derived from multiple snowboard measurements. As the cooperative climate observer for Boulder, Colorado, I examined the 15 biggest snowfalls of the last two decades, all measured at the NOAA campus in Boulder. The sum of the snowboard measurements averaged 17 percent greater than the maximum depth on the ground at the end of the storm. For a 20-inch snowfall, that would be a boost of 3.4 inches—enough to dethrone many close rivals on the top-10 snowstorm list that were not necessarily lesser storms! Another common practice at the cooperative observing stations prior to 1950 did not involve measuring snow at all, but instead took the liquid derived from the snow and applied a 10:1 ratio (every inch of liquid equals ten inches of snow). This is no longer the official practice and has become increasingly less common since 1950. But it too introduces a potential low bias in historic snowfalls because in most parts of the country (and in the recent blizzard in the Northeast) one inch of liquid produces more than 10 inches of snow. This means that many of the storms from the 1980s or earlier would probably appear in the record as bigger storms if the observers had used the currently accepted methodology. Now, for those of you northeasterners with aching backs from shoveling, I am not saying that your recent storm wasn’t big in places like Boston, Portland, or Long Island. But I am saying that some of the past greats—the February Blizzard of 1978, the Knickerbocker storm of January 1922, and the great Blizzard of March 1888—are probably underestimated. So keep in mind when viewing those lists of snowy greats: the older ones are not directly comparable with those in recent decades. It’s not as bad as comparing apples to oranges, but it may be like comparing apples to crabapples.

The greater issue is the rapid subsurface warming across the Western Pacific mid-latitudes. This resembles more of a shift rather than a function of the old PDO cycles that we have become familiar with in the past. The new subsurface and H300 PDO index does a better job reflecting the magnitude of the shift. https://www.cpc.ncep.noaa.gov/products/GODAS/ocean_briefing_gif/global_ocean_monitoring_current.pdf

This has nothing to do with the SAI. The most recent 30 year data reflecting the warmer climate leaves no doubt as to the relationship. Back in the colder climate era the relationship was much weaker than it has become. Part of this is due to weather patterns becoming more repetitive in a warmer climate probably owing to local tropical SSTs resulting in non-linear convective temperature forcing thresholds being crossed. I understand that the most extreme warming has only occurred over the last 15 to 30 years. So we have a new emergent climate state that is different from the previous colder era. We don’t have the luxury anymore of a relatively stable global temperature regime as was the case from 1880 through 1982. So you had a much longer period where there was only a small increase in temperatures. It gave us a 100 years of correlations to work out and use. I understand that you may have some hesitancy in using the newer correlations derived over the shorter period. But I have been using numerous relationships from this new and warmer period that have been serving me well. But it’s not a 100 year data set to draw from like we had back in the older and colder climate era.