ChescoWx

Thanks LV...leaning toward big swings with overall near average temps but above average snow - but let's see where we stand in early November

Hello again from Paul at the East Nantmeal PA Weather Station (www.chescowx.com). Be sure to follow me on twitter at chescopawxman where I am tweeting daily climate reports, forecast updates and weather and drone photos of our beautiful Township. When I wrote my last article, in early August we had just experienced a warmer and wetter than normal July. This included 2 days that exceeded 90 degrees; however, those 2 days would be the only days all summer that exceeded 90 degrees. So technically out township never experienced a heat wave (defined as 3 consecutive days over 90) As I mentioned in my last article down in Philadelphia at the airport, they recorded 35 days over 90 degrees with multiple heat waves. The relative high elevation of our township spares us from many 90-degree days (we only average 4 in a typical summer season) . August would continue our warmer than normal stretch marking the 9th straight month of above normal temperatures. The average temperature was 72.4 which was 2.2 degrees above normal. One big change in our weather was the turn to a much drier pattern that would last throughout both August and September. During August we recorded only 2.71” of rain which was 1.59” below normal. This followed 5 straight months from March through July with above normal rainfall. September would start off wet with 1.16” of rain falling on the 2nd but only another 0.68” would fall over the remaining 28 days of the month. We would end the month with only 1.84” of rain which is 2.90” below our normal September rainfall of 4.74”. No doubt both our Township farmers and residents noticed their fields and lawns quickly turning brown. However, despite the back to back dry months we are still running 110% of normal YTD rainfall with 40.85” of rain and melted snow having fallen in East Nantmeal so far in 2019. September continued our string of above normal temperatures with an average temp of 67.3 degrees (+2.3 degrees to normal). However, we did record our 1st couple of mornings with an autumnal chill as both the 19th and 20th saw low temps in the upper 40’s with the lowest being the 47.6 on the 19th. Those mornings marked the 1st sub-50-degree temperatures in the Township since the 47.4 back on June 4th. Overall for the summer period from June through September we averaged a temperature of 71.3 this was the 45th warmest summer in Chester County since local records began in 1894. The warmest being the 74.7 average recorded way back in the summer of 1900. This year was the 6th warmest summer in the 36 years dating back to 1983. As I write this on October 6th, we have noted a pretty large pattern change that looks to persist through much of the rest of October with cooler and wetter weather in our future. We have not yet recorded a sub-freezing temperature meaning our growing season (days between last and 1st freezes) continues here in the township. The average growing season in East Nantmeal is 188 days. This has ranged from as few as 144 days in 1996 to 233 days in 2005. Today is our 188th day of this growing season. The average date of our 1st freeze is October 23rd; however, it has occurred as early as October 1st in 1993 and as late as November 23rd in 2015. Snowfall is unlikely in the township until late November; however, we have experienced significant snowfalls in the last 8 years most notably the 9” of wet snow that fell on October 29, 2011 and the 7.3” of snow that fell last November 15thand 16th. During November we average just over 1” of snow and during December just under 5 inches. Our normal average seasonal snowfall is 36.6” (fun fact this is the same as Chicago IL) I will hold off on my annual detailed monthly winter forecast until our next issue just before the holidays….however, I am expecting a slightly above normal snow season and at least one major snowstorm of greater than 10”. Until next time I hope all of you enjoy the autumn weather. If you have any questions, please visit my website, follow me on twitter or send me an email. Until next time –All the best! Paul Until next time –All the best! Paul “Some are weather-wise, some are otherwise” Ben Franklin

0.25" of rain overnight here in Western Chester County - AM low is the current 53.4

Today's high stayed in the 50's across most of the high spots in Western Chester County with Elverson at 56.2 / Hawk Hill in Downingtown at 58.3 and West Bradford at 58.0. Today's high in East Nantmeal was the coolest high since the 53.3 back on May 14th. While today's 57.7 was well below our average high of 65.9 it is not close to our lowest max temp for the date of 52.0 back in 1999

We recorded a new daily record high temperature today here in Western Chester County with a high of 87.6 breaking the all-time record of 87 set back in 1927 and local elevation record of 84 set back in 2002.

No such luck with 40's on top of the hills of NW Chester County...our low was only 51.6 - although many spots around me below 500 ft ASL have indeed hit the 40's this morning.

1st early high level winter forecast from the folks at WeatherBell show a slow start to winter but averaging only slightly above normal temps with snowfall in our area at 125% of normal August 2019 Plenty of potential for a severe winter. East will have to overcome early warmth. SST analogs are amazingly close to a blend of 2013-14 and 2014-15. Warm northeastern Pacific and cooler Nino1+2 usually a great cold signal. Snowfall should be generous.

So far today in Western Chesco Hi/Lo 77.1/65.0 (may drop lower before midnight) +7.8 above normal . Of note tomorrow is the 20th anniversary of Hurricane Floyd....I recorded the greatest single day rain event in Chester County since records began in 1894. On that day my station measured 8.28" of rain. It was a very chilly day for the date with the temp falling much of the afternoon as the rain bands intensified coming in off the ocean and up-sloped into Western Chester County....we bottomed out at 57.4 at 9:11pm. I remember watching water rescues taking place at Route 30 and 340 in Thorndale with boats in the intersection next to the McDonalds rescuing folks who tried to drive through the flooding.

Climate Summary for 9/12/19 for Western Chester County PA

From JB at WB "The folly of putting the cart before the horse with individual storms is standing out most pronounced on the European. I have no changes in my ideas on this being a big snow and ice event from the central plains into the northeast and the idea a center tries to get up in the Ohio valley with a secondary that cuts all the warming. The European has gone from as warm is it could be 4 days ago to a suppressed look that given what I see makes little sense with itself as this kind of trough is likely to capture the southern storm. One thing it is not. is a warm system in the midwest and northeast. It was never that to me, even if a center does cut up because there was going to be so much cold air in the way, it would ice and snow in many places. Of course now the worry is too far to the south, but I am confident on my answer in between. But I use storms in the longer term to make points about what I think is going on. The GFS was abysmal on the clipper Tuesday. After all these years, the same problem it was jumping on the front running short so much it lowered pressures too far north. The heaviest snow at 20 to 1 ratios will be near and north of the 528 thk. Plot your thickness and in the midwest and northeast, if your average thk is 525 start to finish of a 6 hour period of snow, ( start snowing at 522 and rise to 528) you should be in the sweet spot for the 20 to 1. And the system Monday morning will be a pain from DC to ACY, most likely coating to 2s. But again that clipper is coming down with a nice warm front that will force some pretty impressive overrunning But all this is a sign that the ideas have merit. I tweeted out this am that I dont believe it will rain again here in central PA till march 14. I tried to pull that back in 2009 at IAD , saying in late Jan I dont think they would get any rain in Feb, it would be all snow or frozen. IAD did have .25 inches of rain but the rest was all snow. Now that is not to say that a nasty blizzard will hit New England. It is saying, given this is an ensemble, that some of the key markers for an extreme are being hinted at by the model. But the real point is the pattern for the next couple of week has turned the way we thought it would, and even out at day 16, I just dont think that looks bad for what we have been saying going forward. Perhaps love is blind, and I still love what I am seeing. But whatever you do if you are a snow lover in the midwest and now the northeast.. dont put the cart before the horse. For if its backyard snow you are interested in, many of you will not have to wait till what is now day 8"

Latest Wxsim with 12z NAM and 6z GFS has trended significantly colder now has rain this PM transitioning to sleet by 630pm. A mix of sleet and some snow heavy at times overnight with 1.4" of sleet/snow accumulating before tapering off by 10am tomorrow morning. Temps will fall slowly through the day but will remain above freezing till near 4am Tuesday morning.

It does forecast wind speed but it knows where I am between hills north and south to not expect much from a wind perspective...only shows gusts to 30mph...

Latest Wxsim with 12z NAM and 6z GFS has just drizzle and light rain through rush hour tomorrow with only .03" steadier rains move in around noon tomorrow and goes till near noon on Tuesday. Total rain 1.52" with temps remaining in the 30's on Tuesday. Chance of a little wintry precip (flurries) by Friday night....with temps not too far above freezing next weekend

For your reading enjoyment From JB at WB this AM "The tornadoes and severe weather in Mississippi are a sign that a front running impulse is coming out. That impulse is going to carve the path for this low to move along. The Euro wants it over Chesapeake bay for instance, and then the primary goes toward it. I think its likely to be off the Delmarva by tomorrow night, and that is where the big low winds up on Monday. Now consider this. Its so warm it cant get any warmer. What do I mean by that? Well all the warm air for the system is already on the playing field. Because winds are mainly west in the southern sector of the storm, there is no transport of warmer air into the center as it moves east. Instead the cooler air cmes flying in underneath and as the center moves further northeast, it starts drawing cooling are into it from the northeast . The front running system causing those tornadoes is HUGE in this for this should get off the mid atlantic coast tomorrow and when it does, establish the path for the primary center, after it moves up into WVA, to move along. The warm air that is around now has gone into developing the storm as heights fall over it, but there is no warm inflow. The air mass to the northeast is low level cold air, Its way the new HIRES NAM is cooling this so dramatically, its seeing all this and too little back in central Pa simply because of the ideas I have analogged this too ( 3 storms that were warm that turned into big interior snows as centers drew cold air in, and precip processes cooled the air, late March 1984, Dec 1992, late March 1984). The warm advection leads to strong upward motion. Saturated air that may be 38 degrees at NYC is lifted and that can cool quite a bit, Meanwhile he sounding turns Isothermal and a bunch of people start turning over to snow west of the track to the upper low. as soon as the warm advection cuts off, which should be Monday as all the cooling gets around it, a bunch of people start turning over to snow That is the key. So what I do is figure out all the scenarios I see and weight them. Lets look here at State College. If I blend my 3 analogs it comes out to a foot. But suppose I look at modeling, take the average of the Canadian UKMET US models, ensembles and operational. I may have 10 samples I am looking at Now we got 15 with March 84 and Dec 1992 and 9 with the early 93 March storm. That is 39 for a total . the contribution from 7 models is only 7 So lets say there are 7 objective inputs adding up to 7 inches ( 1 each) and then my 3 analogs which tack on another 39 ( 15,15,9) . This gives me 10 tools totaling 46, which is an average of 4.6, hence the forecast of 3-6 put out a couple of days ago. NYC I said 1-3. This is not to get into a fight over either place Its to demonstrate a forecast method where you don't simply go into depression/elation cycles over model. The time to flip out is Tuesday morning if there is nothing on the ground , not over models. But if you can come up with storm typing, then as the storm gets closer, you can eliminate the options. Forecasting is not putting out 10 different options before an event. If you change your forecast 9 times, then out of 10 samples you were wrong on 90% of them. And what's more you cant go back and claim a forecast was right. You can say, that idea was better, but I pulled it off the table. I really think the answer to the forecast questions is not the models, but identifying EVERYTHING you can and then weighting it. The models are simply doing that. Their variance shows that obviously they disagree. So what is needed for the right answer. YOU! I don't care if you have a degree or not, if you love the weather and you love getting out there then you should put out your ideas. This is another libertarian rant against those that think its "irresponsible" for untrained guys to be posting forecasts. That is arrogant. I am suggesting a method that I use that you might want to try, sharing what I do. I am also suggesting that there is a philosophy that can make it easier not to swing all over the place when models do or do not go your way"

Sheesh! Let's get this back where it belongs.....on weather JB from WB with his thoughts on the pattern change coming.... "But that is how these storms can be , the first one mainly north of US 6 and east of te Hudson river Wednesday but that one in the 7/8 period, the one I think is going out under the block , that is the next one . Now the big thing is that may be so strong is it pulls the other one in. In any case back over a week ago when we were sounding alarms about how warm this thaw may or may not be, and of course I may just be being stubborn, I mentioned how it could end with some wild storm changing to snow in the northeast. Not as likely in the midwest, ( outside of flurries) as the colder air has to come in from the northeast first But as soon as that positive gets to and west of Hudson bay, look out. Game on"

Agreed....this is not a good comment on a weather site.....the majority of the counties (incredibly 84% of all counties in our country voted for Trump - that is a mandate!) in the United States voted for the "moron" you mentioned who will be our President later this week. You can personally dislike the man...but please respect the office!

All I can say is we have by far the best NWFO in the country! I do not say that lightly...the reputation of Mt. Holly is top notch!! I love to hear other opinions like JB / DT / WB / LC etc. - however when push comes to shove my only go to spot for the best forecast is unquestionably my NWS point and click!! Keep up the great work NWSFO Mount Holly!!

JB goin "boom" with his late Jan and Feb thoughts this evening.... "So what is the big deal with it getting warm for mid month? The fact is this reminds me alot of the 67-68 thaws, where we were in 1993 and 2013 and the thaws of of 14-15. At the end of those winters, no one was talking about the thaw, but about how long and strong winter was. Remember Endless summer. Perhaps when we get to April we may think the same thing about this winter.Yes the thaw is coming but I think it gets blown up A boom boom boom boom"