We been talking about this system a lot on facebook over the past few days and posting the various model runs. We have seen from the GFS multiple tracks of the low pressure area and multiple scenarios played out from an all out snowstorm across the east to an out to sea scenario to a heavy rainstorm. The GFS has now fallen in line with the rest of the guidance ..such as the European Computer Model , the GGEM or Canadian Model and the British model aka the UKMET. All these models, outside the GFS have been showing an inland runner travelling northwards across East Central PA .. Folks lets be clear about something ... when you have this type of track in the heart of the winter you would NOT be looking at a snow storm for those that are in the track of the low or east of the low pressure . We are not in the heart of winter so this holds true even more so.
In order for this storm to come up the coast it means that the heights have to rise and when the heights rise it means the southeast ridge flexes its muscle and warm southerly winds are ahead of the storm system. Hence those east of the low or in the path of the low are in the warm sector of the storm system and would be looking at very heavy rain.
Lets look at the guidance tonight and we will look at the GFS first ...
Now, even on tonights GFS model the model is still running to the east of the rest of the guidance..but never the less you can see the warm sector and you can see the rainfall that occurs and how the snow is well inland..
The above is the GGEM and once again you can see the inland track that would take this low across east central PA and then into central NY..
UKMET is also showing an inland runner..
And finally the ECM ...
You can see on the ECM @ 48 hrs that the 540 line is well to the west and the 850 line or the black line in the lower right hand image is across the PA/NY border and then by 72 hrs the 540 line shifts east along with the 850 line. You can also see how inland the low is . So while the in between frames are missing ..the low pressure area would travel inland much like the GGEM/UKMET models and this would as we explained above cause the heights to rise and the SE ridge to flex its muscle and put those east of the low into the warm sector.
There is simply no guidance to support a SNOWSTORM in E PA or NJ... Now as the arctic front crosses the area if there is any moisture left behind the front that is when the region to the east could see some snow occur..but for the most part it will be rainfall ...
So for Now we are taking a blending of the models and we came up with the following scenario..
Now the one thing that all these models have in common is the tight isobars around the area of the low pressure. This means that there is going to be strong and gusty winds involved with this system.
The other aspect will be the heavy rains for those areas that see majority rain.
Its been awhile since we have updated this blog. We have been doing the majority of the updating on the facebook page for Real Wx Services.
If one were to look at Climate Prediction Center it would appear as if a pattern change is on the way.
Definitely shows a much below normal pattern in the 6-10 day outlook. Do the teleconnections support this happening? Well...lets look at them...
First the MJO which is in the circle of death...
This basically implies it has little bearing on the weather outcome and it could go either way with warmer then normal or colder then normal dependent on the other teleconnections.
Now what we did with these teleconnections is we drew two circles on each one. One is black which represents where the teleconnection is NOW...or Presently. The other is yellow which represents where we could be headed..
The PNA is negative presently but is shown to spike positive but then shown to dip right back down negative once again. This would indicate a period of ridging into the west which would teleconnect to a trough into the east...
And lo and behold we see this is the case starting at 144 hrs out or next weekend. Trough in the east and ridging into the west.
Now lets look at the AO ...
Presently the AO is very high but it is shown to be on the decline and then some members take it negative while other members keep it positive. This is important for sustained cold you want to see the AO negative and stay negative in tandem with that positive PNA...
Finally the NAO is currently very positive as well but like the AO is expected to decline and then the members are once again split with some going and staying negative but some staying positive. So this gives us mixed signals ...
What is clear is that there will be a shot of cold air next weekend....thanks to the PNA spike.. Lets what the progression here of this...
Troughing still in place at 168 hrs out on the ECM tonight...
At 192 hrs we have a reinforcing trough moving in as the other one moves on out.. Still pretty progressive flow that we are experiencing....
But then what happens...
Progressive flow begins to move that trough out and we see at day 10 ....
Things are pretty much starting to moderate and the flow has become zonal and pacific driven once again.
So we do get a cold shot that will be coming in by Next weekend but there after with the teleconnections giving mixed signals but the drop back down in the PNA indicates that we are not going into a sustained cold pattern but rather a couple days of colder weather during that PNA spike.
The severity of that cold shot will be dependent on just how the AO reacts... does it go strongly negative or does it stay positive BUT declined? We think the latter .
Remember in order to get locked in sustained cold weather you want to see a sustained positive PNA and a negative AO and a negative NAO.... We are not seeing that we are only seeing a temporary spike in the PNA before once again declining and bringing some semblence of the Southeast ridge and zonal flow back into play...
So right now we are cautiously optimistic on a pattern change. We really would like to see the teleconnections switch to the more favorable combination before we can jump on "a pattern change is happening"...
Note the GFS has a cold bias when it comes to beyond 180 hrs so ...we have not included that in this discussion.
