Another Quick Update

The 18z NAM is not terribly far off from what the 12z Euro shows in terms of wrap-around precipitation Friday evening. You can see the 500 mb low closing off just south of Montauk Point, A closed 700 mb low overhead, with a strong cold conveyorbelt/comma head signal southwest of the 700 mb low over SE NY/NW NJ. On the bottom right panel you can see QPF >0.25″ in a small area near Sussex County, NJ. We’ll have to see how this plays out but the Euro isn’t the only model that says Friday night could be interesting in SNE.

Temperatures in the boundary layer will be key. The 18z NAM shows 2m temperatures near 40F in the valleys but upper 30s in the hills of SNE which makes me think snow accumulation is a possibility above 500′ and especially above 1000′ if this solution comes to pass. I haven’t had time to load up the BUFKIT soundings yet so I’m ballparking here. Notice the enhanced blob of 3 hour QPF (0.2″-0.25″) near New Haven as the comma head swings through. Strong winds as well… sustained 15-25 knots it looks like across most of CT.

This is going to be an interesting event. It’s unusual that one of these setups delivers so we’ll have to see. Too early to get too excited but this could be a quick-hitting, dynamic event. We’re still >72 hours out so things undoubtedly will change some.

Ryan

Not So Fast… Update on Friday Night/Saturday AM Storm

Moments after I posted my last entry I got a look at the 12z Euro which spins up yet another massive storm, stalls it east of the NH seacoast, and delivers a massive CCB thump of rain/snow to all of SNE. QPF values >0.5″ for most of us.

850s look cold enough for snow but there will most certainly be boundary layer issues at the coast. The Euro looks to me like 2-4″ or 3-6″ of snow in the interior hills of SNE with little accumulation for BOS/BDL/PVD/BDR.

This is by far the most amped up (and amplified!) solution so I’m not biting yet.

Torch is still on (on the Euro) for the following week with a Lakes Cutter.

Tuesday Update

Thought it was time to update a few of the posts in the last several days with some of my latest thinking.

Friday Night/Saturday Morning Storm
The models have backed away from the 12z Euro showing a major “bomb” over New England with impressive CCB snows down to the coast. I’m not surprised as sometimes you can get one run that really shows things exploding then everything backs off. With a deep closed low and plenty of dynamics I still think there will be some wraparound flurries but accumulating snow doesn’t seem terribly likely. Wind will be an issue overnight Friday and I think 50 mph wind gusts are possible in some towns with rapid pressure rises and a strong pressure gradient as the low departs to the northeast.

Pattern Change – Delayed But Not Denied?
The key to this pattern change is what’s going on in the north Pacific and particularly in the Gulf of Alaska. For the last 2 weeks a very strong series of upper level lows has brought brutal cold and storminess to Alaska and has driven a monster jet into British Columbia. Whistler ski area northeast of Vancouver has had their snowiest November ever. This jet stream setup as flooded the continent with warm, Pacific air. No good.

The 12z GFS Ensembles do show this pattern breaking down by day 7 (next Monday or Tuesday) with the trough over Alaska being replaced by ridging which essentially kills the north Pacific jet. The +EPO which has flooded North America with warmth will switch signs and become negative. This teleconnects to big cold in the northern Plains and northern Rockies as it allows the Polar Vortex to swing south east of the continental divide. On the right you can see the surfadce temperature and 500 mb height anomalies with a +EPO pattern. Our pattern the last several weeks resembles this. The models agree on no sustained blocking in the North Atlantic, but a wholesale shift in the Pacific. On the left is a composite for a -EPO/+NAO regime and you can see near normal height anomalies in the northeast and strong negative anomalies in the northern Rockies/northern Plains. What El Nino???????? At least for December 1-7 this is what the GFS ensembles and Euro ensembles seem to indicate so though the pattern has changed I don’t think we’re going to do much better than average in the northeast with the potential for above normal (+1/+2) given an awful storm track through the Great Lakes.

Madden-Julian Oscillation

As I expected the MJO keeps on trucking. Should be entering Phase 6 by Turkey Day and out of the Maritime Continent toward more favorable SSTs over the west Pacific. You can actually see today the MJO index gained quite a bit of amplitude putting to rest to thought that this MJO wave was going to die out. Eventually this wave will reach the Dateline and given high SST anomalies back in the Indian Ocean I have no reason to believe we won’t see another MJO wave develop on this one’s heels.

December 1-7th Call
Given the GFS/Euro ensembles decent agreement in a strong -EPO ridge developing with little sign of north Atlantic blocking I’m reasonably certain that the northern Plains/Rockies will average below average in this time frame. Here in southern New England I’m expecting just above normal temperatures thanks to a storm track that will favor the dreaded Lakes Cutters.
BDL +1.5F
I’ll try and have a month of December call out in the next few days!
Ryan

The MJO Keeps on Truckin’

The Madden-Julian Oscillation is a weather/climate phenomenon near the Equator which can have big impacts on the weather up here in the Mid Latitudes. The MJO has been linked to strong oceanic Kelvin waves, the onset of an ENSO (El Nino) event, and even the development of tropical cyclones. The MJO is something that can help bridge weather and climate and give us an idea what is happening in the future. For example, the location of an MJO wave can also have an impact on our weather (for example phase 8/1/2 is favorable for cold weather in the northeast this time of year).

The MJO has been active recently with a substantial MJO wave that started near Africa and the western Indian Ocean and is now near New Guinea and Indonesia. In the Outgoing Longwave Radiation image posted to the left you can see strong negative OLR anomalies (which is a proxy for convection) now centered near Indonesia. The big question is whether this MJO wave (which has weakened will continue east toward the International Dateline which would teleconnect to a pattern change in North America.

The graphic on the right shows the progression of the MJO (counter clockwise or easterly) from the African coast, through the Indian Ocean, and now toward Indonesia. The wave which was quite substantial and had a high amplitude has fizzled some (the further from the origin – the higher the amplitude and stronger the wave) but it is trucking along toward Phase 5. I expect this wave will continue toward the Dateline and it’s amplitude should increase a bit as it heads toward more favorable Sea Surface Temperatures.
You can see negative SST temperature anomalies between the north coast of Australia and New Guinea which is likely stifling MJO activity for the time being but as the wave propogates east it will run into more favorable SSTs and should increase in amplitude. If the MJO enters into phase 7/8/1 this should favor an increased chance for cold during the first half of December. This dynamical MJO forecast from the GFS ensembles indicates the MJO weakens quite a bit but they have been showing this for the last week or two and that has yet to happen. My guess is that this wave will continue and we will see a pattern change as the convection teleconnects to a different east pacific/north american wave train.
Ryan

A White Black Friday?

Quick update here for some of the new data I’m looking at this afternoon. The 12z Euro develops a major storm (sub 980mb in western Maine) by Friday afternoon which is similar to what the models had yesterday but much further east. Some of our other computers had shown a strong storm as I mentioned yesterday but were trending west with it (which would be warmer/wetter). It appears today that the trend last nighta nd today is a sizable one offshore and that makes big snow a possibility in the Adirondacks and Green/White Mountains with some snow a possibility in southern New England.

Here in Connecticut the Euro shows a substantial cold conveyorbelt snow event on Friday (maybe a couple inches) statewide. This seems overdone to me with the storm being overphased and too strong but I feel like Friday night/Saturday morning will be sharply colder, quite windy (50 mph?), with some snow possible. Whether or not we see accumulation remains to be seen. We’ll have to see what the shortwave in question wants to do.

The 12z GFS and GGEM both have some snow in here late Friday or early Saturday. Now that the shortwave is onshore in British Columbia (and not over the data sparse Pacific) the model runs should begin to converge on a solution.

I’ll keep you posted.

Ryan