Earlier in the month I noted the 2nd half of March may be on the cooler side. There were signs of the NAO going negative and the ridging returning to the western half of the U.S. According to latest guidance we are heading in that direction. These combinations in an El Nino flow are a recipe for big east coast storms to form.
The NAO is definitely heading into a negative state. This is also shown on the 500mb height anomaly graphics which I will get to soon. This is important because not only is it just the 2nd time this season the NAO will go negative, but it's key to getting an east coast snowstorm happening. It will try to slow down the fast Pacific flow and give upper energies in the atmosphere a greater chance to phase.
The EURO on Saturday morning shows a large Upper Level Low over the center of the country. Notice how the other ULL over New England is trying to exit stage right by moving north and east. This is critical. The greater the separation between these two ULL's, the higher the odds are of this possible Godzilla on Sunday coming to fruition. The reason being the eastern trough has room to amplify and the upper level vorticity gets wrapped in instead of stringing / shearing out like the GFS shows. As this ULL digs south, heights along the East Coast rise (Atlantic Ridge) which paves a path for this storm to track up the coast.
By Sunday morning notice how the ULL that was over New England is out of the picture. In response, the Atlantic Ridge is able to amplify which gives the upper energy associated with the ULL in the center of the country a clear path to track northeast instead of due east. Additionally, the NAO is negative at this juncture so this usually keeps surface low pressure systems closer to the coast instead of well off the coast. The +PNA gives us hope the northern energy coming down from Canada will try to phase into the southern energy. If successful, you can expect a Roidzilla-esque storm to impact the area Sunday into Monday. Right now, the EURO shows a Godzilla storm and that is WITHOUT a phase. So, imagine if it begins showing a phase.
This is what I mean. The storm the EURO shows hitting the area on Sunday is all southern stream driven. From the map above there is no clear phase between the northern and southern branches. That goes to show the potential this system has.
EURO verbatim has this at 989mb. If a phase were to happen, not only would the surface low be tucked in closer to the coast but the pressure or strength would be sub 970mb. Right now NYC Metro is absolutely hammered on the EURO. With a phase - which is entirely possible due to the -NAO/+PNA duo - areas further west would also get into the action while much of the region sees a crippling blizzard.
Here is the EURO again Sunday morning looking at 500mb height anomalies. The block in the northern Atlantic into Greenland is key in this setup. It really does help slow the flow down and allow the upper energies to convene along the coast. Also, the separation between the ULL's is also very important and the EURO does a nice job in showing this. This is why it is the most bullish model with the Godzilla on Sunday.
Both of these images are from the GFS model. The biggest difference between the American and European model is the lack of separation with both ULL's, and the inability of the ULL in the center of the country to dig deeper into the eastern CONUS. The GFS looks very progressive with sheared out upper energy. This is a typical bias of the GFS. Also, I feel the GFS struggles with storms involving a -NAO. I do not think it does a good job of recognizing the block which in turn effects how it handles the pattern downstream.
CONCLUSION:
I actually feel very good about this storm coming to fruition for the area. This is the first storm all winter I have felt good about. It took me awhile to get around to Jonas, but for some reason my gut is telling me this one will happen. I really like the set-up with a -NAO/+PNA. I like how even with no phasing on the EURO it still manages to get a surface low close to the coast with enough cold air in place to support snow. I think over the next 2 days we will continue to see waffling. By the time we get to Friday I think models will begin to hone in on a Godzilla-type storm affecting the area mid day Sunday into Monday late morning.
We will see what happens! Have a great night.
Best,
Francesco Paparatto
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