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Coldest May through September in last 120 years in NW Chester County PA

ChescoWx

By ChescoWx,
in Philadelphia Region

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ChescoWx

ChescoWx

Posted
Posted

Hello all,

It looks like September will finish with an average temp of 61.6 (-4.0 below normal). This marks the 5th consecutive below normal temp month with both August (-4.2) and September finishing at the sub 4.0 departure mark. Of greater interest is the fact that the July/August/September period was the 5th coldest within my 120 year dataset and the Aug/Sept duo was the 2nd coldest. As impressive as that may be...the last 5 months from May thru September were by far the coldest such 5 month period (a combined 11.1 below) the next closest was 1976 with a -7.7 departure.

May (1.2)

June (1.3)

July (0.4)

Aug (4.2)

Sept (4.2)

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chubbs

chubbs

Posted
Posted

Hello all,

It looks like September will finish with an average temp of 61.6 (-4.0 below normal). This marks the 5th consecutive below normal temp month with both August (-4.2) and September finishing at the sub 4.0 departure mark. Of greater interest is the fact that the July/August/September period was the 5th coldest within my 120 year dataset and the Aug/Sept duo was the 2nd coldest. As impressive as that may be...the last 5 months from May thru September were by far the coldest such 5 month period (a combined 11.1 below) the next closest was 1976 with a -7.7 departure.

May (1.2)

June (1.3)

July (0.4)

Aug (4.2)

Sept (4.2)

 

I'll take 1976 as an anolog. Nice 3-year stretch of winter weather from 76/77 through 78/79. 

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famartin

famartin

Posted
Posted

Hello all,

It looks like September will finish with an average temp of 61.6 (-4.0 below normal). This marks the 5th consecutive below normal temp month with both August (-4.2) and September finishing at the sub 4.0 departure mark. Of greater interest is the fact that the July/August/September period was the 5th coldest within my 120 year dataset and the Aug/Sept duo was the 2nd coldest. As impressive as that may be...the last 5 months from May thru September were by far the coldest such 5 month period (a combined 11.1 below) the next closest was 1976 with a -7.7 departure.

May (1.2)

June (1.3)

July (0.4)

Aug (4.2)

Sept (4.2)

Paul, remind me what site you are using for comparison (i.e. to extend your record back 120 years)?

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ChescoWx

ChescoWx

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Paul, remind me what site you are using for comparison (i.e. to extend your record back 120 years)?

Hey Ray,

 

National Weather Service Cooperative observers W.T. Gordon(1894-1930); Howard Pyle(1930-1946) and the National Weather Service 1946-1997 - and yours truly since 1997

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ChescoWx

ChescoWx

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I was hoping more for the site names ;)

Ray,

An interesting story (well at least for a weather weenie like me!) as back in the late 90's I started to do some research on the data for Chester County. The most comprehensive and relatively representative data set was the Coatesville observations recorded with daily hand written data starting with the original US Department of Agriculture Weather Bureau in January of 1894....this changed to the  Department of Commerce Weather Bureau in December 1941. When I first searched for data from the NWS or co-op observers I could only find the data from November 1948 thru 1998 available via the PA climatological website. When I asked for data further back I was told it had not been converted to a format for uploading to the internet. I was undaunted and ended up purchasing the handwritten observations for the observers I mentioned above (January 1894 till October 1948) and during many long plane trips for my "real job" I converted every day's observations from the handwritten format to an excel template for every day from 1894 thru 1948 and then used an OLAP tool called TM1 to "marry" the 2 datasets together. I was then able to run queries and routines to produce daily, monthly and yearly climate averages/records and events for Chester County for the periods of record above along with my personal observations starting in 1997. I then uploaded all of this information to my website (www.chescowx.com) that I started back in 1998. About 2 years later I noted that some of the data that I now had on the internet began showing up as the "official" data of record for the Coatesville OBS sites which changed with the move to near KMQS in 1983.

 

Of note these OBS were taken at different locations/elevations across an 8.8 nautical miles radius between 1894 and today and elevations ranging within 275 ft of each other. This likely makes this about as reliable a continuous source as any for the Western Philadelphia Suburbs.

 

As I have often told my wife....there are many worse hobbies I could indulge in!

 

Thanks!

Paul

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  • 1 month later...
Vogan

Vogan

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With November approaching the half way point our current departure here in NW Chesco is at 2.1 degrees below normal. If November finished below normal this will mark the 8th month this year our of 11 months that will go into the books as below normal in temps. 

I would be very interested in hearing your thoughts on what set of temperatures makes the most sense for determining historical means. Are you using the entire record, a thirty year block or something else? Thanks.

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chubbs

chubbs

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Paul

 

Playing around with your data I plotted seasonal snow for chesco and phl. Relative to phl, chesco did real well before 1930, only so-so between 1930 and 1980 and better again after 1980 but not as good as the early years.   Wonder if these dates are related to changes in the measurement sites or some other change in the record. . 

post-1201-0-35462800-1384556114_thumb.gi

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ChescoWx

ChescoWx

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I would be very interested in hearing your thoughts on what set of temperatures makes the most sense for determining historical means. Are you using the entire record, a thirty year block or something else? Thanks.

Hi Vogan for temps I use the entire data set from 1894 to Present

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ChescoWx

ChescoWx

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Paul

 

Playing around with your data I plotted seasonal snow for chesco and phl. Relative to phl, chesco did real well before 1930, only so-so between 1930 and 1980 and better again after 1980 but not as good as the early years.   Wonder if these dates are related to changes in the measurement sites or some other change in the record. . 

Hey Chubbs

I think the move in 1983 to near KMQS made some difference with the move up in elevation of about 300ft

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famartin

famartin

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My obs run mighty close to KMQS and other similar weatherunderground sites....At this elevation in the area. As evidenced by my 90+ analysis I did a few weeks back....

Yes, but as you mention there was a 300 foot elevation increase from the earlier records, another, what, 100 feet to your house?  400 foot differences are incompatible.

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Vogan

Vogan

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Hi Vogan for temps I use the entire data set from 1894 to Present

This is my first year compiling a climate record for my location. It is a non-official "hobbyist" record. I have access to a record at Millersville University that goes back to 1914. I have found that their mean temps are within 2/10 of a degree to my mean for the year. I am currently using the last 30 years from the MU records for my means. I may extend that time period.

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ChescoWx

ChescoWx

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Thanks Ray! good stuff on the link

It looks like I am 1 mile outside the acceptable range from Thorndale and 4 miles from KMQS - plus almost 400 feet higher than Thorndale and about the same as KMQS and the observer site......  so although not perfect I will continue to use that data set for a base set - but will continue to "massage" and update the local climate base by doing some sub-analysis on my current location dataset which is at 10 years this month and keep building from there.

Thanks!

Paul

 

http://www.nws.noaa.gov/directives/sym/pd01013007curr.pdf

 

Bottom of page C3, "Station moves":

 

"A move is always assumed to be incompatible if the new equipment location is greater than 5 horizontal miles from the original equipment location and/or the difference in elevation is 100 feet or more."

 

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