ChescoWx

.03" of rain so far today

For anyone in Chester County if interested I have started a new Facebook Group page. This will be strictly about the weather. Including weather observations, analysis, forecasts, your photos and discussions specifically related to the unique climate and weather of Chester County PA. During active weather it will broaden the focus to across the entire PA/NJ and DE area. Thanks and I hope to see you there!! Paul https://www.facebook.com/groups/chescowx/

46.3 up on the ridges - valley spots hit the low 40's - coolest here since the 45.4 on May 30th. Below is how many Septembers have finished with above average temps over the last 10 years PHL - 8 of 10 / Phoenixville - 8 of 10 / Chesco - 6 of 10 / KMQS - 6 of 10 / Octoraro Lake - 6 of 10 / Glenmoore - 4 of 10

Only made it down to 52.2 here in the relatively higher spots in Chesco...looks like will finish September a little over 1 degree above normal for the 49th warmest September on record. Rainfall wise the 10.03" is good for the 3rd wettest September behind only the 14.48" in 1999 and the 10.58" in 2003

This AM's low of 51.2 was our lowest since the 50.3 on June 23rd

I have updated the analysis with 2 more COOP sites (Devault and HoneyBrook). So we now have all 8 NWS COOP sites across Chester County. I have also added a linear trend line for all 8 sites. This indicates that (4) four COOP sites show a linear cooling trend - (1) one is near steady and (3) three show a warming trend.

A strong line of thunderstorms is developing across Western Chester County PA - temperatures will drop about 10 degrees behind the line as the cold front passes off to the east

Highest wind gust here 26mph since March 26 - rain just 2 miles west of East Nantmeal - WXSIM shows 2.15" of rain today

Thanks Phil! Paul

Some interesting data which for the 1st time that I could find - shows how the actual data has been tweaked with post observation adjustments to in this case dampen the warmth earlier in the 20th century to better support warming vs. today. Let's look at the long term weather records for Allentown PA (ABE). The data used for the ABE data set is sourced from the NWS COOP data from the ABE Gas Company from 1912-1938 and since then from The ABE Airport through today. So, when I looked at the data in the ABE raw data file I could see where in the daily observations they began to make adjustments (usually chilling down the nigh time lows) to chill down the period - adjustments downward were main for all 27 years between 1912 through 1938....with the largest adjustments applied between the period 1912-1930. This adjustment as you can see below where I highlight how the adjustments impacted the average temperature trend lines. This allows the pre-ABE airport data to now report significantly cooler and helps amplify the warming trend as we move into the more recent decades. Again no surprises as we have discussed but this is the first time I have been able to quantify the adjustments and see how the data was tweaked to better support the warming story. Thoughts?

.04" of drizzle overnight

So in looking at the data - both the Top 10 cool falls and warm falls led to well below normal snow seasons (normal in Chester County PA is 36" of snow) ....so we can't say the ENTIRE fall season is a strong predictor of the upcoming winter snow season

0.10" since last evening. Yesterday's high of 82.8 was our warmest reading in September and warmest since August 30th.

Thanks Mike! I always hope I don't bore folks with some of this data but my old finance background - always has me doing some data analytics. The facts are so often different than what we feel.... Paul

Fall season (September-November) average temperatures and trend lines by decade for all available long running Chester County PA NWS COOP Sites. Also a list of the Top 10 individual chilliest and warmest fall seasons by location. Does a chilly fall mean more snow?? stay tuned....

9 of the 1st 11 days of September have averaged below normal temps - the next week will average above normal for most of the week before cooler again about 10 days from now

0.71" storm total from last night through this AM

Just like August we start off September with the 1st 5 days with well below normal temps.

While the Philadelphia Airport clocks in with their 11th warmest summer ) June 1 - August 31 - Some Chester County PA Station Summer average temps and the all-time summer rank (years of station history) - none recorded anything close to a top 10 summer ChescoWx - 73.0 - 40th warmest since 1894 Glenmoore - 73.3 - 38th warmest since 1956 Phoenixville - 74.5 - 31st warmest since 1893

MyRadar is my go to app for phone

Rain Total in East Nantmeal via VP2 was 4.60" - of interest the Tempest was only 3.84 an hour ago and it would now appear they have adjusted it up to 5.81" - I will await the "official" CocoRahs reading when I get home