September Weather Discussion 2019

[CoastalWx]

Just now, HoarfrostHubb said:

Thanks.  I am really surprised at that.  I guess I am just growing accustomed to the warmer autumns

A lot of the rural areas like CON and BDL are getting more and more developments. You can argue the CC side of it, but development is part of it.

[tamarack]

45 minutes ago, yoda said:

Freeze Warnings in N ME tonight... is that early?  Lows in the upper 20s expected in the colder areas looks like as well

Discounting 1976 when we lived right on the St. John River and had fogs all September, my average 1st frost in Fort Kent was Sept. 6.  Don't have the freeze data (28 or colder) for FK, but at my place average 1st frost is 9/17 and 1st freeze 9/29.  Assuming FK still has 1st frost averaging 9/6 (it's probably a few days later now), that 12-day difference translated from my place would land right on tomorrow morning.

[dendrite]

5 minutes ago, CoastalWx said:

A lot of the rural areas like CON and BDL are getting more and more developments. You can argue the CC side of it, but development is part of it.

I think it's mostly CC, warmer autumns, and wetter times. The 60s-80s were pretty dry and cold. CON had a lot of October 1st 32Fs back in the yore days so maybe we're just getting back to those levels after the cool baby boomer period. Even for last freezes...there were lots of Junes in that cool period, but only one before 1964.

 

DateLastFirst

1869May-07 (1869)Oct-19 (1869)

1870May-23 (1870)Sep-13 (1870)

1871May-16 (1871)Sep-19 (1871)

1872Apr-24 (1872)Oct-12 (1872)

1873May-16 (1873)Oct-01 (1873)

1874May-12 (1874)Oct-04 (1874)

1875Apr-29 (1875)Sep-23 (1875)

1876May-16 (1876)Oct-03 (1876)

1877May-05 (1877)Oct-06 (1877)

1878May-15 (1878)Sep-29 (1878)

1879May-04 (1879)Sep-26 (1879)

1880May-15 (1880)Oct-08 (1880)

1881May-05 (1881)Oct-05 (1881)

1882May-16 (1882)Oct-22 (1882)

1883May-14 (1883)Oct-02 (1883)

1884May-31 (1884)Oct-10 (1884)

1885May-04 (1885)Oct-08 (1885)

1886May-01 (1886)Oct-02 (1886)

1887Apr-22 (1887)Sep-24 (1887)

1888May-03 (1888)Sep-29 (1888)

1889Apr-23 (1889)Oct-11 (1889)

1890Apr-29 (1890)Sep-25 (1890)

1891May-06 (1891)Oct-12 (1891)

1892May-01 (1892)Oct-03 (1892)

1893May-08 (1893)Oct-17 (1893)

1894Apr-30 (1894)Sep-26 (1894)

1895May-17 (1895)Sep-15 (1895)

1896May-01 (1896)Oct-10 (1896)

1897Apr-29 (1897)Sep-19 (1897)

1898May-10 (1898)Sep-13 (1898)

1899May-16 (1899)Sep-14 (1899)

1900May-29 (1900)Sep-19 (1900)

1901May-06 (1901)Sep-26 (1901)

1902May-21 (1902)Sep-06 (1902)

1903May-24 (1903)Sep-30 (1903)

1904Apr-23 (1904)Sep-22 (1904)

1905May-05 (1905)Oct-07 (1905)

1906May-21 (1906)Sep-25 (1906)

1907May-23 (1907)Oct-02 (1907)

1908Apr-23 (1908)Oct-05 (1908)

1909May-01 (1909)Oct-18 (1909)

1910May-12 (1910)Oct-08 (1910)

1911May-06 (1911)Sep-14 (1911)

1912May-05 (1912)Oct-03 (1912)

1913May-12 (1913)Sep-15 (1913)

1914May-16 (1914)Sep-28 (1914)

1915Jun-03 (1915)Oct-10 (1915)

1916Apr-25 (1916)Oct-02 (1916)

1917May-04 (1917)Sep-11 (1917)

1918Apr-27 (1918)Sep-23 (1918)

1919May-01 (1919)Oct-08 (1919)

1920May-06 (1920)Oct-07 (1920)

1921May-12 (1921)Oct-25 (1921)

1922May-01 (1922)Sep-26 (1922)

1923Apr-20 (1923)Sep-15 (1923)

1924Apr-29 (1924)Sep-25 (1924)

1925Apr-22 (1925)Sep-23 (1925)

1926May-05 (1926)Oct-12 (1926)

1927May-03 (1927)Oct-10 (1927)

1928May-10 (1928)Sep-29 (1928)

1929May-14 (1929)Sep-20 (1929)

1930Apr-29 (1930)Oct-01 (1930)

1931May-18 (1931)Oct-10 (1931)

1932May-24 (1932)Oct-13 (1932)

1933May-06 (1933)Oct-14 (1933)

1934May-09 (1934)Oct-02 (1934)

1935May-24 (1935)Oct-03 (1935)

1936May-22 (1936)Sep-26 (1936)

1937Apr-30 (1937)Oct-03 (1937)

1938May-13 (1938)Oct-05 (1938)

1939May-17 (1939)Oct-15 (1939)

1940May-10 (1940)Sep-27 (1940)

1941May-15 (1941)Sep-19 (1941)

1942May-12 (1942)Sep-29 (1942)

1943May-15 (1943)Sep-13 (1943)

1944May-21 (1944)Sep-23 (1944)

1945May-12 (1945)Sep-30 (1945)

1946May-11 (1946)Sep-13 (1946)

1947May-16 (1947)Sep-20 (1947)

1948May-16 (1948)Sep-16 (1948)

1949May-30 (1949)Sep-26 (1949)

1950May-09 (1950)Sep-18 (1950)

1951May-19 (1951)Sep-27 (1951)

1952May-17 (1952)Oct-08 (1952)

1953May-04 (1953)Sep-23 (1953)

1954Apr-29 (1954)Oct-07 (1954)

1955May-20 (1955)Sep-23 (1955)

1956May-26 (1956)Sep-18 (1956)

1957May-19 (1957)Sep-25 (1957)

1958May-15 (1958)Sep-30 (1958)

1959May-18 (1959)Sep-17 (1959)

1960May-03 (1960)Oct-02 (1960)

1961May-31 (1961)Oct-16 (1961)

1962May-13 (1962)Sep-21 (1962)

1963May-24 (1963)Sep-14 (1963)

1964Jun-06 (1964)Sep-15 (1964)

1965May-24 (1965)Aug-30 (1965)

1966May-16 (1966)Sep-26 (1966)

1967Jun-01 (1967)Sep-11 (1967)

1968May-29 (1968)Sep-30 (1968)

1969May-27 (1969)Sep-29 (1969)

1970May-30 (1970)Oct-05 (1970)

1971Jun-06 (1971)Sep-25 (1971)

1972Jun-12 (1972)Sep-29 (1972)

1973May-01 (1973)Sep-21 (1973)

1974May-21 (1974)Sep-24 (1974)

1975Jun-10 (1975)Sep-14 (1975)

1976May-21 (1976)Aug-31 (1976)

1977May-16 (1977)Sep-12 (1977)

1978May-22 (1978)Sep-08 (1978)

1979Jun-26 (1979)Sep-20 (1979)

1980May-29 (1980)Sep-09 (1980)

1981May-20 (1981)Oct-10 (1981)

1982May-05 (1982)Oct-10 (1982)

1983May-19 (1983)Sep-15 (1983)

1984May-19 (1984)Oct-05 (1984)

1985May-15 (1985)Sep-12 (1985)

1986May-14 (1986)Aug-29 (1986)

1987May-14 (1987)Sep-25 (1987)

1988May-09 (1988)Sep-16 (1988)

1989May-09 (1989)Sep-25 (1989)

1990May-31 (1990)Sep-19 (1990)

1991Apr-26 (1991)Sep-22 (1991)

1992May-26 (1992)Sep-24 (1992)

1993Apr-30 (1993)Sep-20 (1993)

1994May-28 (1994)Oct-02 (1994)

1995May-09 (1995)Sep-11 (1995)

1996May-26 (1996)Oct-04 (1996)

1997May-11 (1997)Sep-22 (1997)

1998May-14 (1998)Sep-24 (1998)

1999May-14 (1999)Oct-06 (1999)

2000May-20 (2000)Sep-28 (2000)

2001May-14 (2001)Sep-30 (2001)

2002May-23 (2002)Oct-08 (2002)

2003May-18 (2003)Oct-02 (2003)

2004May-05 (2004)Oct-05 (2004)

2005May-13 (2005)Oct-20 (2005)

2006May-08 (2006)Sep-30 (2006)

2007May-14 (2007)Oct-14 (2007)

2008May-02 (2008)Oct-04 (2008)

2009May-26 (2009)Sep-20 (2009)

2010May-13 (2010)Oct-03 (2010)

2011May-06 (2011)Sep-17 (2011)

2012May-12 (2012)Sep-25 (2012)

2013May-27 (2013)Sep-17 (2013)

2014May-08 (2014)Sep-19 (2014)

2015May-14 (2015)Oct-05 (2015)

2016May-10 (2016)Sep-26 (2016)

2017May-09 (2017)Oct-13 (2017)

2018Apr-24 (2018)Oct-13 (2018)

2019May-09 (2019)-

MinimumApr-20 (1923)Aug-29 (1986)

MeanMay-13Sep-27

MaximumJun-26 (1979)Oct-25 (1921)

[snowman21]

17 minutes ago, CoastalWx said:

A lot of the rural areas like CON and BDL are getting more and more developments. You can argue the CC side of it, but development is part of it.

I don't think it's more and more developments, at least at first glance. For example, Falls Village which is in the far NW corner of CT by the NY/MA line where it's about as middle of nowhere as you can get in CT, used to have an average first frost of 9/16, and now a decade later it's up to 9/23. I don't think there's too much developing going on in a place with a population just over 1,000 people. Some of it is likely methodology in calculating the average, so it's important to note that the way normals are calculated does change over time, but that likely does not explain all of the moves. We've also seen reduction in snow cover days at some of these middle of nowhere in the woods stations as well like Norfolk at 1400 ft elevation. The Falls Village average last frost moved up from 5/30 to 5/24, so the growing season there has increased by two weeks in the last ten years (officially 50% probability of frost free period was 108 days and now it's 120).

[CoastalWx]

5 minutes ago, snowman21 said:

I don't think it's more and more developments, at least at first glance. For example, Falls Village which is in the far NW corner of CT by the NY/MA line where it's about as middle of nowhere as you can get in CT, used to have an average first frost of 9/16, and now a decade later it's up to 9/23. I don't think there's too much developing going on in a place with a population just over 1,000 people. Some of it is likely methodology in calculating the average, so it's important to note that the way normals are calculated does change over time, but that likely does not explain all of the moves. We've also seen reduction in snow cover days at some of these middle of nowhere in the woods stations as well like Norfolk at 1400 ft elevation. The Falls Village average last frost moved up from 5/30 to 5/24, so the growing season there has increased by two weeks in the last ten years (officially 50% probability of frost free period was 108 days and now it's 120).

Well I did say it's part of it. KBTV is a good example. They have sky rocketed recently, and it's been unique to them. There is obviously a CC part of it, probably the biggest reason in many cases, but there is and will be more and more development around rural areas. It may not have a linear effect. For instance maybe a neighborhood or clear cutting woods is all that is needed to allow for a few extra mph in overnight winds. There goes the rad. 

[Fozz]

These past few days have been a bit cooler than I prefer, so I'm kinda looking forward to the coming warmth.

[HoarfrostHubb]

Dumb question.   But is there a statistical reason for the 30 year rolling averages?

 

[snowman21]

7 minutes ago, HoarfrostHubb said:

Dumb question.   But is there a statistical reason for the 30 year rolling averages?

 

Couple of reasons. There's a WMO standard which began with the 1901-30 normals, so it's been convention for over a century. Also the general statistics rule that you need at least 30 data points to accurately estimate the mean. NCDC does calculate supplemental normals based on other time periods, but the official ones are done over 30 year periods worldwide. Edit: to add to this a quick google search pops up this page from NCDC which basically says the same thing: https://www.ncdc.noaa.gov/news/defining-climate-normals-new-ways

[Fozz]

5 minutes ago, HoarfrostHubb said:

Dumb question.   But is there a statistical reason for the 30 year rolling averages?

30 years is a good sample size but it's also relatively recent enough to reflect something close to current norms. It's kinda arbitrary but it usually works.

[CoastalWx]

28 minutes ago, Fozz said:

These past few days have been a bit cooler than I prefer, so I'm kinda looking forward to the coming warmth.

We usually get our best cold shots around here this time of year, from the NE. Flow off the ocean and low dews add a little evaporational cooling. 80s this weekend.

[Fozz]

4 minutes ago, CoastalWx said:

We usually get our best cold shots around here this time of year, from the NE. Flow off the ocean and low dews add a little evaporational cooling. 80s this weekend.

Is it a similar mechanism to the backdoor cold fronts that are common in the spring, or is this unrelated?

[dendrite]

1 minute ago, Fozz said:

Is it a similar mechanism to the backdoor cold fronts that are common in the spring, or is this unrelated?

Spring backdoors are a special kind of suck. Those are more cold ocean enhanced versus a dry air mass getting evapo cooled over a relatively warm ocean. But either way...N-NE is our most efficient CAA.

 

[CoastalWx]

2 minutes ago, Fozz said:

Is it a similar mechanism to the backdoor cold fronts that are common in the spring, or is this unrelated?

Well both have high pressure helping to usher in colder air. In the spring, it’s usually more temp driven with very cold SSTs, and the strong warming in the interior. Throw in the propensity for cut off lows to our northeast and you have the easiest excuse possible to drive the cold air from northeast to southwest. 

[CoastalWx]

You definitely won’t like 4/1 through about 5/15 or so. It’s pretty sucky. 

[STILL N OF PIKE]

10 minutes ago, CoastalWx said:

You definitely won’t like 4/1 through about 5/15 or so. It’s pretty sucky. 

You been pimping 80’s like A giddy school girl for this weekend 

you going Anywhere ?

[CoastalWx]

1 hour ago, STILL N OF PIKE said:

You been pimping 80’s like A giddy school girl for this weekend 

you going Anywhere ?

No lol. It’s no hype though. More like Sunday.

[HIPPYVALLEY]

I thought the Euro looked pretty warm overall for next week.  Talk about boring weather but I'll enjoy the warm and dry pattern while it lasts.

[Damage In Tolland]

Gonna be 90 hit at BDL and BOS one or both weekend days. Possibly Monday too. Sunday most likely . Friday starts long string of 80+

[snowman21]

BDL has reached 90 from Sep 22 and later 16 times in its history, while BOS has done it 16 times also (6 of those occurrences were before BDL's existence).

Since 1980, 6 times at BDL and once at BOS.

The back to back 90s (bolded for dates where both stations did it simultaneously):

BDL 9/22-23/1914

BDL 9/22-23/1970

BDL 9/25-26/2007

BDL 9/24-25/2017

BOS 9/22-23/1895

BOS 9/22-23/1914

BOS 9/22-23/1970

Single dates where both reached 90 (excluding the above):

9/22/1931

10/7/1963

9/22/1980

9/26/2007

[Lava Rock]

Gonna be 90 hit at BDL and BOS one or both weekend days. Possibly Monday too. Sunday most likely . Friday starts long string of 80+

Terrible

[powderfreak]

3 hours ago, CoastalWx said:

Well I did say it's part of it. KBTV is a good example. They have sky rocketed recently, and it's been unique to them.

This month's departures so far... like clockwork that BTV starts the month with a +2 departure over the other stations.  Burlington and Montpelier have seen remarkably consistent 2 degree difference all summer in departures.  MVL has been a little less but once we get into winter, the differences can increase to 3-degrees of departure difference with the snowpack differences from Champlain Valley to east of the Spine.

You'd think it would be baked into climo already but the departure differences definitely show something else going on.  It's been years now of 1.5-3 degree departure differences.

BTV... -0.5

MPV... -2.5

MVL... -2.0

Chilly first half of September though, as anything below normal in the means at BTV is a big deal these days.

[kdxken]

1 hour ago, Damage In Tolland said:

Gonna be 90 hit at BDL and BOS one or both weekend days. Possibly Monday too. Sunday most likely . Friday starts long string of 80+

Stay safe!

 

[powderfreak]

Saturday/Sunday/Monday look pretty damn warm.  MOS is flirting with 80F on Sunday up here, and I bet Sun/Mon have the larger departures because of the high mins. 

[kdxken]

"Early autumn heat is not unusual, but we haven’t seen any extreme heat — meaning temperatures in the upper 80s or even 90s — in late September and October for quite a while.

We know that over the past several decades temperatures have warmed up, but what is interesting is that the absolute extreme highest temperatures in fall have not really changed. You might be surprised that our warmest temperatures after Sept. 20 mostly occurred prior to the year 2000. Of the top 20 warmest days in late September and early October, only one has occurred this century."

https://www.bostonglobe.com/metro/2019/09/17/first-new-england-will-see-frosty-weather-then-around-this-weekend-what-going/UOHsiadw2w0N9D2LRcGObI/story.html?p1=Article_Feed_ContentQuery

[HoarfrostHubb]

45F here attm.  This stretch has been fantastic.   The warmup will feel nice though

Dry dry dry

[moneypitmike]

23 minutes ago, HoarfrostHubb said:

45F here attm.  This stretch has been fantastic.   The warmup will feel nice though

Dry dry dry

It really has been with a few more to go before a comfortable mild-up follows.  No big deal.  It seems that nearly every 10-days out depiction has been a bust for about the last year.  Winter and summer alike.

[dendrite]

43.4F min...BKN skies.

MAV is down to 33F at CON. It seems to drop a degree every 6hrs. SFM with a sneaky 30F.

[dendrite]

Looks like a couple of torchy days here and then back to seasonably warm. So it's AN for a while, but nbd really. Great timing for a warmup.

[Damage In Tolland]

After the mild front Monday night end of week heats right back up again. Sucks

[Damage In Tolland]

Awful news from Donny Sutherland in NYC thread.

Among those five cases, 2015 made a transition from predominantly negative AO values to predominantly positive ones during the fall. The combination of the AO's recent increase to the strongest positive values since April and some of the extended range guidance leave open a scenario where the AO is currently in the early stages of evolving to a predominantly positive regime. Such an outcome would also favor a warmer than normal fall and possible warm start to winter in the Middle Atlantic and southern New England regions. For now, this is merely a hypothetical discussion of one potential path toward winter. Many other variables are involved. The only idea that carries weight at this time is that the possible evolution reaffirms the longstanding signal for a warm fall.