Newman

Should mention KRDG recorded a daily record low minimum of 38 yesterday

Yeah no record lows will be set tonight probably, but forecast lows of 39/40 while the records are 36/37 is impressive. Much below normal

Just got Sub-tropical storm Alpha form off Portugal lol. The gulf storm looks like it'll be Beta...

Can't wait to wake up in the low 40s Sunday

Low of 53 tonight with a dew point of 48? Yes please, bring on Fall

SUMMARY...Thunderstorms are expected to develop from northern Virginia into northern Maryland and southeast Pennsylvania by 21-22Z. A few supercells capable of damaging wind gusts and isolated tornadoes will be the main threats. A tornado watch will likely be needed prior to 21Z. DISCUSSION...As of mid afternoon a progressive vorticity maximum was situated over southwestern PA and will continue east into the Middle Atlantic region during the late afternoon and evening. A band of low-topped convection has already developed in association with this feature extending into northern WV where instability is limited. Farther downstream, a lee trough resides just east of the central and southern Appalachian mountains. East of this feature temperatures have warmed to the upper 80s F with dewpoints in the low to mid 70s contributing to 1500-2000 J/kg MLCAPE despite very weak mid-level lapse rates resulting from warm temperatures aloft. As the corridor of deeper ascent attending the shortwave trough continues east and begins to overtake the western edge of the moist warm sector, additional storms will likely develop from northern VA into southeast PA. Winds in the 850-500 mb layer will undergo a modest increase with approach of the impulse, resulting in 35-40 kt effective bulk shear and 100-200 m2/s2 storm relative helicity. This environment should be sufficient for some organized storm structures including a few supercells capable of locally strong to damaging gusts and a couple of tornadoes through early evening.

Updated Day 2 outlook, 15% wind, 15% hail (new to this outlook), 2% tornado.

18/10/4

Bassfield, MS just got hit by a likely EF4+ tornado with another one right on its heals. Unreal.

The 12z 3k NAM sure is showing some curvy hodographs. This one right around the DC area at 18z:

August PDO data: 2019-01-01T00:00:00Z 0.66 2019-02-01T00:00:00Z 0.46 2019-03-01T00:00:00Z 0.37 2019-04-01T00:00:00Z 1.07 2019-05-01T00:00:00Z 1.03 2019-06-01T00:00:00Z 1.09 2019-07-01T00:00:00Z 1.03 2019-08-01T00:00:00Z 0.38 August AMO data: 2017 0.222 0.224 0.164 0.280 0.311 0.305 0.299 0.307 0.347 0.430 0.349 0.361 2018 0.170 0.059 0.129 0.061 -0.004 -0.014 0.015 0.110 0.159 0.141 -0.124 -0.063 2019 -0.018 0.078 0.118 0.121 0.085 0.171 0.349 0.335

ENSO 3.4 continues to dive: ENSO 4 is as well with plenty of easterly wind bursts nearing 180W:

From 2009, talking about changing global circulations including Hadley Cell/Mid-Latitude Cell disruptions, etc.: http://www.inscc.utah.edu/~reichler/publications/papers/Reichler_09_Widening.pdf

Courtesy to Isotherm, he and I had a small conversation on the disruption of the global jet stream patterns due to the emergence of changing Hadley Cell and Mid-Latitude Cell circulations. As SSTs continue to warm poleward due to the background state and changing climate, we see more convection which acts to disrupt the typical Hadley Cell circulations we know. Typically we see rising air at the ITCZ which spreads poleward and subsides around 30N which creates the Horse Latitudes. With convection being able to fire further north, the Hadley Cell circulations expand which create stronger gradients and subsequently strengthen the mid-Latitude cells. For the United States, that means the Pacific Jet stream becomes stronger. What I mean as "this isn't new" is the warmth of the Pacific and overall global oceans. We've seen warmth of our oceans for awhile now. However, are we finally entering the critical time where we truly do start to see global jet stream changes? Are winters going to be the same again? Or will we see more variability resulting in bigger and more extreme winter events? Have we already seen those changes? I don't know the answers to those questions, but I do know that in theory the global jet stream patterns should be or have already changed in the changing climate.

The PAC jet is still raging due to Pacific Warmth spreading poleward and subsequently expanding Hadley Cells and strengthening the mid-Latitude cell (Pacific Jet). This isn't new, though. The Pacific overall has been warm for the past couple years to a decade. The question is how will the strong Pacific jet trend and/or affect the upcoming winter. Last year the Pacific was so hostile. Could we see a repeat?

ENSO region 4 has cooled in the past week and is at its coolest since a month ago: Likely due to a strong burst of easterly wind stress. The GFS forecast of a burst of westerly wind stress could help to bring the temperatures back up again:

Here's a look at how the SST's have changed since June:

1993-94 anyone? The ONI progression looks similar to what we could see this winter. Perhaps this winter is a touch warmer. Lets say we throw in 1993-94 for a similar west based warmish Neutral regime with its warm PDO and a cool 1+2, 2013-14 for its warm blob south of Alaska (I'm not sold on that blob going away just yet. 2013-14 had a cool Neutral/weak Nina), and 2005 just for its warmer and positive Atlantic/AMO.

New IRI/CPC ENSO probabilities have been posted: El Nino has ended: Here is what the July SST's looked like: The July AMO value finished at 0.350, up from 0.171 in June and the most positive AMO value since Dec 2017.

The current look, featuring cooling in the east based regions of the ENSO with western regions remaining warmer. The PDO is positive with a warm pool south of Alaska, but not to the extent of 2013-14 obviously. A cold pool east of Newfoundland in the Atlantic with warm waters immediately south of Greenland.

I've just started to look towards what this winter may deliver, and 2003-04 seems like a strong analog. It was coming off a prior El Nino winter, it was mainly weak Nino/Neutral during the winter, it had a positive PDO, positive AMO, and low solar activity. However, the summer of 2003 transitioned into a neutral phase much quicker than what is currently forecasted for this summer/fall/winter. I would throw in 2004-05 in case we remain more El Nino, rather than completely neutral. I like 2004's QBO transition into winter as well. It's much better than 2003 and it's close to what I think we could see this winter. A later transition of the QBO could yield later stratospheric impacts deep into winter (February and March, but things like that are fickle and require other variables to look at). 2004-05 also had a warm Atlantic and low solar, but not as warm of a Pacific. 1966-67 is a solid analog with regards to the positive ONI values maintaining closer toward fall/winter. And in case we go more Nina/neutral, it's even greater. That's what I see right now at least.

HRRR agrees with the WWA issued as well.

WWA across SE PA for 2-4". 18z NAM agrees.