donsutherland1 Posted March 30, 2012 Share Posted March 30, 2012 The last time the temperature fell to 32° in New York City in April occurred on April 9, 2007. The diminishing frequency of freezing temperatures in April is reflected in a larger moderation of April minimum temperatures in recent decades. The mean April low temperature has increased from 43.8° in the 1961-1990 base period to 44.8° in the 1981-2010 base period. The frequency of temperatures reaching 32° or below has fallen more than 28%. The frequency of even colder readings has fallen even more dramatically. Statistics for the 1961-1990, 1971-2000, and 1981-2010 base periods are below: Note: The frequency is the statistical probability. Finally, it should be noted that since 2000, there has been only one year during which the temperature fell below 30° in April (2004). In contrast, there were 2 such years in the 1980s and 1990s, 5 such years in the 1970s, and 4 such years in the 1960s. Link to comment Share on other sites More sharing options...
Analog96 Posted March 30, 2012 Share Posted March 30, 2012 The last time the temperature fell to 32° in New York City in April occurred on April 9, 2007. The diminishing frequency of freezing temperatures in April is reflected in a larger moderation of April minimum temperatures in recent decades. The mean April low temperature has increased from 43.8° in the 1961-1990 base period to 44.8° in the 1981-2010 base period. The frequency of temperatures reaching 32° or below has fallen more than 28%. The frequency of even colder readings has fallen even more dramatically. Statistics for the 1961-1990, 1971-2000, and 1981-2010 base periods are below: The upcoming pattern may offer a few opportunities for an April freeze in NYC. Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 30, 2012 Author Share Posted March 30, 2012 The upcoming pattern may offer a few opportunities for an April freeze in NYC. It will be interesting to see if the pattern can deliver. Link to comment Share on other sites More sharing options...
easternsnowman Posted March 30, 2012 Share Posted March 30, 2012 If you look at the data since 2000 I'm sure the minimum temps are higher than 44.8. Link to comment Share on other sites More sharing options...
NEG NAO Posted March 30, 2012 Share Posted March 30, 2012 The upcoming pattern may offer a few opportunities for an April freeze in NYC. especially the period next thursday 4/5 through friday 4/6 with a nice trough setting up - still to be determined if we will have a coastal storm to deal with-models have been hinting at it. -- would be appropriate for this years opening of the baseball season in NY to have weather issues. After they could have played here many days this past winter with all the warmth Link to comment Share on other sites More sharing options...
pazzo83 Posted March 30, 2012 Share Posted March 30, 2012 It will be tough. We had a pretty solid N/NW wind overnight and the temp only got down to 40. We did have overcast skies for some of the overnight, but I've noticed the 6am hour is typically when the city will bottom out. At that time the skies were clear. Of course for a good chunk of the winter it was tough for the city to get below freezing. If dewpoints get down below 0F like they did earlier this week I could see it happening though. Subzero dewpoints in April are probably not very typical, however. Link to comment Share on other sites More sharing options...
ag3 Posted March 30, 2012 Share Posted March 30, 2012 It will be tough. We had a pretty solid N/NW wind overnight and the temp only got down to 40. We did have overcast skies for some of the overnight, but I've noticed the 6am hour is typically when the city will bottom out. At that time the skies were clear. Of course for a good chunk of the winter it was tough for the city to get below freezing. If dewpoints get down below 0F like they did earlier this week I could see it happening though. Subzero dewpoints in April are probably not very typical, however. 850 temps were high. Models have 850 temps going down to -5 to -6 in the medium range. Link to comment Share on other sites More sharing options...
uncle W Posted March 30, 2012 Share Posted March 30, 2012 there have been no freezing temperatures for April the last four years...The record is five years set during 1959-1963... Link to comment Share on other sites More sharing options...
Guest Pamela Posted March 30, 2012 Share Posted March 30, 2012 It will be tough. We had a pretty solid N/NW wind overnight and the temp only got down to 40. We did have overcast skies for some of the overnight, but I've noticed the 6am hour is typically when the city will bottom out. At that time the skies were clear. Of course for a good chunk of the winter it was tough for the city to get below freezing. If dewpoints get down below 0F like they did earlier this week I could see it happening though. Subzero dewpoints in April are probably not very typical, however. Well obviously if the wind is blowing it is more difficult for the atmosphere to cool...(unless some sort of sharp cold front just passed through and chillier air is being advected).... Link to comment Share on other sites More sharing options...
forkyfork Posted March 30, 2012 Share Posted March 30, 2012 especially the period next thursday 4/5 through friday 4/6 with a nice trough setting up - still to be determined if we will have a coastal storm to deal with-models have been hinting at it. -- would be appropriate for this years opening of the baseball season in NY to have weather issues. After they could have played here many days this past winter with all the warmth i don't see it happening... the latest gfs shows 850 temps getting no lower than -4c and there's a gradient the whole time Link to comment Share on other sites More sharing options...
Sundog Posted March 30, 2012 Share Posted March 30, 2012 Well obviously if the wind is blowing it is more difficult for the atmosphere to cool...(unless some sort of sharp cold front just passed through and chillier air is being advected).... The city NEEDS the wind to stay up and come from a more northerly direction if they want to see cold lows. This is not the case for anyone outside the city obviously. The city does not radiate well at all and so calm winds would pretty much guarantee not hitting freezing. I don't think it will get cold enough aloft anyway. Forky just posted -4C as the 850 temp on the GFS. That's not going to cut it. Link to comment Share on other sites More sharing options...
SnoSki14 Posted March 30, 2012 Share Posted March 30, 2012 Wouldn't the obvious answer for less April freezes be 1: increased UHI 2: Maybe more cloudier nights than normal 3: Overall global warming since the 1970s among other reasons such as increased wind? Link to comment Share on other sites More sharing options...
Analog96 Posted March 30, 2012 Share Posted March 30, 2012 The city NEEDS the wind to stay up and come from a more northerly direction if they want to see cold lows. This is not the case for anyone outside the city obviously. The city does not radiate well at all and so calm winds would pretty much guarantee not hitting freezing. I don't think it will get cold enough aloft anyway. Forky just posted -4C as the 850 temp on the GFS. That's not going to cut it. There is more potential around Apr 11-12. Link to comment Share on other sites More sharing options...
Guest Pamela Posted March 30, 2012 Share Posted March 30, 2012 The city NEEDS the wind to stay up and come from a more northerly direction if they want to see cold lows. This is not the case for anyone outside the city obviously. The city does not radiate well at all and so calm winds would pretty much guarantee not hitting freezing. I don't think it will get cold enough aloft anyway. Forky just posted -4C as the 850 temp on the GFS. That's not going to cut it. This represents a misunderstanding about a very basic physical science concept. Although radiational cooling is not nearly as effective in an urban area like NYC as it is in the countryside, the air will still cool more readily when still than if it is in motion. Link to comment Share on other sites More sharing options...
Sundog Posted March 30, 2012 Share Posted March 30, 2012 Wouldn't the obvious answer for less April freezes be 1: increased UHI 2: Maybe more cloudier nights than normal 3: Overall global warming since the 1970s among other reasons such as increased wind? The UHI has been pretty much the same since at least 1970, maybe even back to 1960. At least the zones that would actually affect NYC's ability to cool at night. Link to comment Share on other sites More sharing options...
Analog96 Posted March 30, 2012 Share Posted March 30, 2012 This represents a misunderstanding about a very basic physical science concept. Although radiational cooling is not nearly as effective in an urban area like NYC as it is in the countryside, the air will still cool more readily when still than if it is in motion. NYC really does do better on windy nights. In January, if you want NYC to have a chance at 0, you need a Northerly wind going straight down the Hudson River. Link to comment Share on other sites More sharing options...
Sundog Posted March 30, 2012 Share Posted March 30, 2012 This represents a misunderstanding about a very basic physical science concept. Although radiational cooling is not nearly as effective in an urban area like NYC as it is in the countryside, the air will still cool more readily when still than if it is in motion. And I am trying to say that NYC needs CAA in order to reach cold lows, which is not possible if air is standing still. Link to comment Share on other sites More sharing options...
Guest Pamela Posted March 30, 2012 Share Posted March 30, 2012 Wouldn't the obvious answer for less April freezes be 1: increased UHI 2: Maybe more cloudier nights than normal 3: Overall global warming since the 1970s among other reasons such as increased wind? The UHI was just as bad in 1982 as it is in 2012. The "cloudier night" theory might have some validity because it has been demonstrably wetter recently....I'm rather conflicted on the whole "global warming" thing...but I would not discount it as a potential factor... Link to comment Share on other sites More sharing options...
Guest Pamela Posted March 30, 2012 Share Posted March 30, 2012 NYC really does do better on windy nights. In January, if you want NYC to have a chance at 0, you need a Northerly wind going straight down the Hudson River. If it is actually "doing better" on the windy night...then in all likelihood there is an element of cold air advection present...i.e. colder air is displacing warmer air that was previously in place....which, as I stated in the original post, would likely indicate that a cold frontal passage has recently taken place. As stunted as radiational cooling may be in the urban setting...if a 2 or 3 day old anticyclone is parked over the region...based on the laws of physics...calm surface winds should aid in the cooling of air temps at the surface and horizontal motion should inhibit cooling. Link to comment Share on other sites More sharing options...
pazzo83 Posted March 30, 2012 Share Posted March 30, 2012 The city NEEDS the wind to stay up and come from a more northerly direction if they want to see cold lows. This is not the case for anyone outside the city obviously. The city does not radiate well at all and so calm winds would pretty much guarantee not hitting freezing. I don't think it will get cold enough aloft anyway. Forky just posted -4C as the 850 temp on the GFS. That's not going to cut it. Yea a good 10mph due N wind can chill the city pretty well. If the wind is calm the temp stops dropping at like 10pm, and oftentimes will rise around 2-3am with the latent heat release from the buildings/concrete. Link to comment Share on other sites More sharing options...
pazzo83 Posted March 30, 2012 Share Posted March 30, 2012 This represents a misunderstanding about a very basic physical science concept. Although radiational cooling is not nearly as effective in an urban area like NYC as it is in the countryside, the air will still cool more readily when still than if it is in motion. Not in Manhattan. Temps won't drop here at night with a calm wind after a point. Link to comment Share on other sites More sharing options...
pazzo83 Posted March 30, 2012 Share Posted March 30, 2012 If it is actually "doing better" on the windy night...then in all likelihood there is an element of cold air advection present...i.e. colder air is displacing warmer air that was previously in place....which, as I stated in the original post, would likely indicate that a cold frontal passage has recently taken place. As stunted as radiational cooling may be in the urban setting...if a 2 or 3 day old anticyclone is parked over the region...based on the laws of physics...calm surface winds should aid in the cooling of air temps at the surface and horizontal motion should inhibit cooling. All the buildings etc absorb the heat during the day and keep the surface air much warmer at night in calm conditions. Link to comment Share on other sites More sharing options...
Alpha5 Posted March 30, 2012 Share Posted March 30, 2012 Another one of these threads? We KNOW the globe has been getting a tad warmer (you can debate AGW all you want, but thats fact), but NYC has seen incredible warming because of UHI. I think people need to look at stations in the suburbs like HPN or maybe somewhere on the island where UHI doesnt corrupt records. Pulling out NYC data and sounding alarm does nothing in 2012 Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 30, 2012 Author Share Posted March 30, 2012 If you look at the data since 2000 I'm sure the minimum temps are higher than 44.8. The average low temperature in the April 2000 through April 2011 period is 45.3°. Link to comment Share on other sites More sharing options...
Isotherm Posted March 30, 2012 Share Posted March 30, 2012 If it is actually "doing better" on the windy night...then in all likelihood there is an element of cold air advection present...i.e. colder air is displacing warmer air that was previously in place....which, as I stated in the original post, would likely indicate that a cold frontal passage has recently taken place. As stunted as radiational cooling may be in the urban setting...if a 2 or 3 day old anticyclone is parked over the region...based on the laws of physics...calm surface winds should aid in the cooling of air temps at the surface and horizontal motion should inhibit cooling. Nice explanation. If you've got a stale airmass in place with 850's steady or rising, a windy night should not produce a colder low temperature than calm conditions. However, as you noted, most of the time NYC's minima occur on the night after a cold frontal passage, when CAA is still strong. So while the northerly wind direction does tend to bring the colder temps into NYC, the principle reason for these lower temps is falling temps in the mid levels as CAA occurs (thus mixing down to the lower boundary layer). Link to comment Share on other sites More sharing options...
Sundog Posted March 30, 2012 Share Posted March 30, 2012 Another one of these threads? We KNOW the globe has been getting a tad warmer (you can debate AGW all you want, but thats fact), but NYC has seen incredible warming because of UHI. I think people need to look at stations in the suburbs like HPN or maybe somewhere on the island where UHI doesnt corrupt records. Pulling out NYC data and sounding alarm does nothing in 2012 The UHI for NYC hasn't changed in at least 40 years. Link to comment Share on other sites More sharing options...
Sundog Posted March 30, 2012 Share Posted March 30, 2012 Nice explanation. If you've got a stale airmass in place with 850's steady or rising, a windy night should not produce a colder low temperature than calm conditions. However, as you noted, most of the time NYC's minima occur on the night after a cold frontal passage, when CAA is still strong. So while the northerly wind direction does tend to bring the colder temps into NYC, the principle reason for these lower temps is falling temps in the mid levels as CAA occurs (thus mixing down to the lower boundary layer). I don't think anyone has said otherwise. On average, a steady northerly wind will be colder for NYC than calm conditions. How many times do we get a steady northerly wind when there's no CAA involved? I'd venture to say not very often at all. Link to comment Share on other sites More sharing options...
bluewave Posted March 30, 2012 Share Posted March 30, 2012 April temperatures are rising at the second highest rate of all the calendar months at NYC. According to the NCDC, it's a +.54 degree F/decade rate of increase. Link to comment Share on other sites More sharing options...
uncle W Posted March 30, 2012 Share Posted March 30, 2012 April ten year averages... NYC Central Park obs since 1870... decade......temp...high...low...max...min...ave max ave min...precip...snow...B.S. 1870's........47.9...53.3...41.1....na...20..........na........na........3.86"....1.8"....10.0" 1880's........48.5...52.9...46.0....84...21.........77.6.......27.4.....2.92"....0.7".....3.0" 1890's........49.3...52.3...46.4....90...24.........79.1.......28.2.....2.59"....0.8".....3.0" 1900's........49.6...52.2...46.6....84...24.........77.7.......30.4.....3.94"....0.6".....5.0" 1910's........50.6...55.1...47.8....92...22.........79.6.......29.3.....3.78"....2.3"....10.2" 1920's........50.2...56.1...47.3....90...12.........82.6.......28.3.....3.62"....0.9".....8.5" 1930's........49.9...53.7...47.9....89...28.........79.0.......31.9.....3.46"....0.6".....6.4" 1940's........51.4...56.9...46.1....91...24.........79.7.......31.5.....3.33"....1.1".....6.5" 1950's........52.4...55.0...48.2....85...23.........81.1.......31.7.....3.82"....1.0".....4.2" 1960's........52.1...55.9...49.0....91...28.........82.9.......31.8.....3.33"....0.1".....1.2" 1970's........52.2...55.2...47.9....96...25.........84.2.......29.1.....3.82"....0.1".....0.4" 1980's........53.3...56.2...51.2....88...21.........79.9.......31.8.....5.59"....1.0".....9.6" 1990's........53.2...55.7...50.5....91...23.........81.3.......32.4.....3.77"....0.1".....0.7" 2000's........53.5...56.1...49.8....96...29.........86.3.......32.0.....4.67"....0.5".....4.0" 2010's........56.1...57.9...54.3....92...35.........87.5.......37.5.....4.17"....trace trace 1870- 2009..........51.0...54.8...47.6....na...na.........80.8.......30.4.....3.72"....0.8".....5.2" 1980- 2009..........53.3...56.0...50.5....na...na.........82.5.......32.1.....4.68"....0.5".....4.8" Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 30, 2012 Author Share Posted March 30, 2012 Another one of these threads? We KNOW the globe has been getting a tad warmer (you can debate AGW all you want, but thats fact), but NYC has seen incredible warming because of UHI. I think people need to look at stations in the suburbs like HPN or maybe somewhere on the island where UHI doesnt corrupt records. Pulling out NYC data and sounding alarm does nothing in 2012 With the possibility of one or two decent cold shots in April (modeled from time to time), it makes sense to take a look at the trends concerning the City's freezes. In looking at the data, I noticed that the City had not had a freeze since 2007 and then calculated probabilities and frequencies relative to the three most recent climatic base periods. The conclusion was that April freezes are becoming less common. Also, FWIW, I ran some of the numbers for Danbury (DXR). The results are below: Finally, this was not intended to be an AGW discussion or climate change discussion. Otherwise, it would have been posted in the climate change forum. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.