Cut-Off Rain Storm 3/29 - 3/31

An impressive storm system is going to effect the Tri-State area this weekend into early Monday morning. The set-up in the upper atmosphere (500 mb) supports a long duration rain storm with frequent moderate to heavy rains which increases the flood threat, especially in areas where there is still snow / ice and if you live in a flood prone zone.

Timing:

Start: 12pm-1pm Saturday

End: 5am-7am Monday

This equates to 40+ hours of rain falling which when all is said and done could add up to 4+ inches of rain in some spots of the Northeast. Obviously the rain is not going to be heavy for 40+ hours. In fact, there may even be a brief break in the action before it starts up again. Nonetheless, we are still looking at a washout weekend with a potent coastal storm developing.

The 00z GFS 500 mb map by 2pm tomorrow is beginning to show a phase with the northern and southern stream energies in the atmosphere which will result in a strong surface low developing. By this time, rain is streaming up the coast into the northeast ahead of the surface low with the heaviest falling over Long Island. 

Fast forward into early Sunday morning, and now those energies have completely phased with the H5 trough now closed off. At this time, very heavy rain is falling throughout NY state, the northern tier of PA, NNJ, and NYC into LI. 

By Sunday night, the closed off low deepens with the H5 trough now going negative, prompting the coastal low to slow down and bring training moderate to heavy rainfall over parts of the coast from PA into NJ into NYC. 

What is happening here is we are seeing the effects of Atlantic blocking and what it could do to east coast storms. Throughout this winter, we have been in a relatively zonal flow due to a constant +NAO with only a north-Atlantic ridge trying to help slow the flow down. 

This time, the combination of positive heights into Greenland and eastern Canada have forced this storm to CUT-OFF from the jet stream and almost come to a stall off the coast of NJ. The good news is this will not be some 950 mb bomb of a storm that is bringing hurricane force winds to the area. It is expected to remain on the weak side with the worst of the winds along the immediate coast, where 30-40+ mph gusts can be expected. 

RAIN MAP

Region wide, we are looking at 1.50-2.50 inches of rain for the most part. In further assessment, I can see how red-shaded areas receive possibly more than 3 inches of rain due to the positioning of the stalling low pressure storm off the coast of NJ. Some pieces of guidance support this notion of sending bands of rain over this area which would enhance rainfall totals. Obviously flooding in NNJ near the rivers could be a concern, but I do not believe rivers are in danger of flooding since it has been pretty dry of late. However, that does not mean roads that flood easily will not flood. So please keep that in mind. 

Enjoy this miserable weekend, 

Frank

*Please follow www.njstrongweatherforum.com for the latest information.*

Possible March 25th-26th Coastal Storm

Mother Nature may be trying to end this winter with a big bang in the Northeast region of the U.S. with a possible coastal storm looming for early next week. Of course, a lot of uncertainty exists with the exact track of this storm, but I am confident that a storm will develop. Now it's just trying to figure out if it will be a storm for the fishes or one we will have to worry about, which would bring heavy snowfall and high winds to the area if it took a track close to the coast.

The above graphic is the 500 mb level 12z EURO model around Monday morning. 

One important thing to note with the setup for early next week is the sub-tropical jet stream (STJ) will be an ingredient to the evolution of the storm. A stream of energy will travel through the STJ and feed into the coastal storm. A poleward ridge in the west (+PNA) connecting with the ridge over Alaska (-EPO) will help bring down extremely potent northern stream energy which digs into the eastern U.S. and phases with the STJ energy to form the coastal storm. 

Moving forward with the 12z EURO, it closes off the H5 trough which allows the coastal storm to get pretty close to the coast, bringing moderate snow accumulations to the area. Any closer to the coast, this would be a substantial snowstorm with blizzard-like conditions given its extreme strength and size. 

The one thing working against a possible Nor'easter is the fact that there is no high latitude blocking, or         -NAO. Low heights continue to reign over Greenland which means the flow along the east coast is progressive. If the phase is timed correctly and a High Pressure system positions itself where the EURO currently projects it to be, there will be a storm along the east coast bringing snowfall to the region. That is a big if though and there still remains a lot of uncertainty with how strong the energy coming out of Canada will be, and how much interaction it has with the southern stream energy. 

The GFS and Canadian models also develop the coastal storm. The GFS has it well east of the area coast since it phases the storm much later than the other models. However, if you look above, some of the GEFS individual members show some pretty big hits and the GEFS mean itself brings .50-.75 qpf into the area. This is indicative to me that the GFS OP is playing to its progressive bias and it may eventually catch onto the other models and come further west with the storm over the weekend. 

The purple zone are the areas I feel are in line to see coastal storm impacts come Tuesday of next week. I do think there will be snow, but I am uncertain about how much will fall. Could be a coating to a few inches or it could be much more. Snow will not be the only thing to worry about, though. Coastal flooding and high winds will also be possible impacts. 

The blue zone may also feel coastal storm impacts but the phase will have to occur much sooner than where current guidance has it to be. This is definitely possible still, but with the progressive pattern along the east coast, I could see how only the immediate coast benefits from this storm. If the NAO were negative I would feel differently. 

Nothing is set in stone yet and the models have been pretty horrific of late. Just realize that the potential for a big storm is there early next week with very cold temperatures (much below normal for this time of year). 

Enjoy your weekend and follow along at www.njstrongweatherforum.com for the latest information

Frank

Possible Snowstorm March 12th-13th

There is growing confidence that a possible snowstorm will effect the Northeast U.S. mid next week as the ingredients needed for one to occur are beginning to show consistency on the models. It seems this winter has been relentless with the constant cold and frequent snowfalls. This type of pattern just does not want to let go. Not yet at least.

Most people have already seen this graphic since I posted it on my forum yesterday. The players involved are as follows: 

1. East-based blocking to help lock in the cold air over the northeast with the PV in northeast Canada. 

2. A ridge in the west to help the arctic jet s/w energy dive into the heart of the country and possible phase with polar jet s/w energy. 

3. A strong piece of s/w energy coming down the backside of the PV (polar s/w energy). 

The biggest question is...IF there is a phase...WHERE does it happen? If there is no phase there will not be a big disruptive storm. It would be a weaker storm with lesser impacts. A phase of the various short wave energies in the upper atmosphere would develop a potent storm bringing many impacts of heavy snow, rain, wind, and possible coastal flooding. 

As of now, the two most reliable models are saying YES, there will be a phase which will result in a big storm for mid-week next week!

When we take a look at the 12z EURO model run from today at H5, we can see the important pieces of energy coming together. The energy circled in south-central Canada is the polar jet energy, the one near the 4 corners is the arctic jet energy, and the one over Louisiana is the southern stream energy. There is triple phase potential with this storm (when all 3 pieces merge together and develop a monster storm), but that does NOT look likely right now. 

Guidance suggests that the southern stream energy will escape ahead of the other two northern stream pieces and shear itself out once it approaches the southeast coast. All pieces of guidance are showing this right now, but there does exist the small chance that they're handling the energy wrong. Right now, I am going to agree with guidance and say that we should only be focusing on the Arctic and Polar energies. 

If we take a look at the GFS H5 maps now, we'll see it has the same general idea as the EURO. The one blemish it does is hold back some of that northern stream energy near the Rockies which is why the storm system on the GFS is not as strong as the EURO has it. This is unusual because the EURO has a bias of holding back western energy, and the fact that it is not, tells me the GFS is WRONG in this aspect. You can also see how the GFS keeps the southern stream apart from the northern stream, so the phase only occurs between the Arctic and Polar energies (no triple phase). 

The result is a great looking trough on the east coast going negative and producing a potent Nor'easter bringing heavy snowfall to much of the northeast US, besides the Philly and DC Metro areas. Although the EURO / GFS are in somewhat of an agreement right now with a storm effecting the area next week, I am not sold yet on the track of the storm.

The 3 main global models used in the weather industry each show different tracks for the possible storm next week. A EURO / GFS track would bring plowable snow accumulations to much of the interior northeast including NYC Metro area. The Canadian model, CMC, is still not impressed with the setup and believes there will NOT be a phase (which I talked about earlier in the blog). It keeps the heavier snow accumulations in northern New England instead.

My current thoughts are there will be a widespread snowstorm for much of the northeast next week, but how far south and to the coast does the accumulating snow get? Since the storm is tracking from the Midwest and moving in a general west-east direction due to the Polar Vortex located to the north preventing the storm from cutting, even after it phases, it should bring a swatch of heavy snow to much of PA and NY state into New England. Those are the areas I think right now are in a prime spot to expect a snowstorm next week. The areas of uncertainty is along I-95 from DC to NYC (Boston will be cold enough to support all snow). If the PV trends further south, the track of the storm will also be further south and more cold air gets into coastal areas to keep precipitation in the form of snow. A likely scenario I see playing out is for the coastal areas to start as rain and gradually change to snow as the storm deepens and track off the coast, changing the direction of the winds. It is VERY possible that the changeover occurs quickly and much of the storm falls as snow and not rain for coastal areas too depending on the timing of the phase and location of the PV. 

We'll see how this plays out! Please follow the www.njstrongweatherforum.com to get the latest infromation on the storm. 

And for those wondering, winter will continue into the third week of March. But we are all warriors by now, aren't we? 

Have a great weekend

Francesco Paparatto