Rain to Snowstorm is it possible this weekend?

The talk around the internet world is whether or not there is going to be a rain to snowstorm this weekend effecting the Mid Atlantic and the Northeast. Depending on where you read you will see some people are talking a blizzard..others you will see saying snow is not possible in the month of October..Still yet others are saying that guidance does not suggest anything resembling a storm.

Real Wx Services is going to take a approach where we need to look at the guidance and weather history to see if we can come up with a sensible approach to the answer to this question.

Above is the ensemble height anomaly map and you can see that it suggests that we have transient blocking with a positive height anomaly over the Davis Straight.

above is the image from the ECM at 12 Z..

Above is the image from the GFS at 18 Z . This is looking at the 500 mb level. Now if you look at these two images alone you will see that the upper air pattern is fairly similar…the difference lies in where the upper energy is focused. The ECM has the upper energy focused over western PA and western VA while the GFS is back further to the west. Hence the ECM the trough goes negative tilt and we are left with this at 96 hrs…

And then this system rides Northeast up the coast delivering a intense Nor Easter.

However..the GFS since it is further west with the energy, misses the phase and we are left with this:

Misses the phase and we have a low pressure that scoots OTS and just grazes extreme Southern New England locations.

It should be also noted that the 12 Z UKMET does not have a system effecting the east coast during this time range and neither does the 12 Z GGEM..However..one does not have to reflect that far back to see that the GGEM about 48 hrs ago was taking this system (quite strong too) thru Eastern PA into NY State..and it was just less then 24 hours ago that the UKMET was holding hands with the ECM.  The ECM has been consistently showing this system for 4 consecutive runs. So if we just judge by consistency alone then we would have to side with the ECM. It has been the most consistent ..it is also backed up by its ensemble means..it is historically the best verifying model at 120 hours and under and yet there is one more factor I like to look at in reference to the modeling of this system.

Flash back if you would to the year 1996. A full week before the Blizzard of 1996 the ECM was showing  blizzard. Weather outlets and media outlets dismissed the ECM because the rest of the guidance was showing an out to sea solution. Matter of fact it was not till the day before that the rest of guidance caught on to what was happening but by then it was to late as weather outlets all over were just calling for flurries/snow showers including outlets like the weather channel. We need not rehash the amounts that fell from that raging blizzard . The moral of the story is the ECM was alone and verified accurately.

So here we are again but fifteen years later and facing the same dilemma (minus the blizzard thinking) ..

At 18 Z we notice that the GFS has taken what would be considered baby steps in the right direction towards what the ECM is showing. Upper air pattern is very similar..and the system has come further west then the 12 Z

You can tell this by noticing the precipitation how it is more to the NW and then as well the system at 12 Z you could barely see on the right side of the map and at 18 Z it is more noticeable.

Now another thing we need to factor in here is the tool that we used last year which was the NOGAPS.

Now the above is the 12 Z NOGAPS at 108 hrs and notice how it is essentially lock & stock in the same position as the 12 Z GFS? This should raise a red flag that the GFS is being as progressive as the most bias progressive model.

Now lets look at the above image which is also the NOGAPS but this is from the 18 Z run. Notice how the model has come back towards the west? Once again it is further west then what the GFS is suggesting…

So with all the above mentioned we are leaning towards the ECM & its consistency at this point and time and have introduced a scenario map with what we think will be the most likely snow amounts. This map is PRELIMINARY & Highly subject to change… however we want to make readers aware of the potential of what could happen IF the ECM scores another victory.

Now …there is one CAVEAT to this scenario and prelim outlook above and that is Hurricane Rina.

Notice how the GFS is showing the Hurricane effecting Florida..

Shows quite a healthy system effecting Florida.. On the other hand the ECM:

Shows no system effecting Florida.

Latest 00z models :

Only two to three models show the same possibility as the GFS. All the rest of the models suggest that RINA will meet its demise in or around CUBA.

So another potential wild card to throw off the prelim map above is IF the GFS is correct with its RINA effecting Florida cause essentially this would ROB the southern stream vort from its energy and would allow the system to slide off the east coast and OTS.

So that is where we stand right now… we will update this in another 24 hours!