USCAPEWEATHERAF

My latest snowfall map and Cape Cod could likely gust past 80mph tomorrow

My latest snowfall map and Cape Cod could likely gust past 80mph tomorrow

A major nor'easter/blizzard is imminent. Blizzard of 2017 is on its way. The northern piece of energy has made a US landfall over NW US at 18z yesterday afternoon or evening and this is the energy that we have been waiting for a sampling of and now that we got models adjusted stronger with the southern vort max and northern vort max. Now there are three jet streams involved. The northern jet stream (AKA Arctic jet stream), southern stream (Pacific Jet) and the sub-tropical jet which situates over the gulf of Mexico, providing the system with a GOM low pressure center and moisture. Ok lets get down to the gist of the models. Models are somewhat different still in their handling of QPF, and storm track as well as intensity and they differ on degree of phasing between all three jet streams. The models have trended stronger with the pacific jet stream energy disturbance over the northern Plains now. this swings southeastward, and depending upon how far south it gets will help determine which model is correct as well as which storm track is correct. On water vapor imagery, one can see a distinct area of vorticity spinning in the atmosphere, this is our southern stream (Pacific jet ) disturbance. With its own moisture source from the Pacific and the Rocky Mountains not doing much to stop the moisture from entraining into the Northern PLains is dumping a good to decent amount of snowfall over the northern Plains towards Detroit, MI. this energy is being forced to the southeast by a large arctic jet gyre or upper level low pressure system diving southward into the Great Lakes tomorrow morning. This trough carries our southern stream disturbance up the east Coast combining with the GULF OF MEXICO energy and low pressure center combined to bring a singular coastal low pressure center that will be rapidly deepening as it head north-northeastward up the East Coast. This earlier phase now expected to happen by most guidance models, is actually allowing the system to track more offshore rather than up the NYC harbor. Benchmark track or Cape Cod track is the final question that needs to be answered. I am going with a forecast mix of the GFS/EURO/NAM models. Using the NAM for QPF output based upon the GFS progressiveness bias in these circumstances in which the storm is allowed to slow down due to the phasing of jets in which the large upper level low phases into the southern stream disturbance and slows it down before departing. I think the low will move from the benchmark to about just east of ACK and CHH producing a mix of rain/snow for coastal Cape Cod and Islands therefore I have Nantucket in the 0-4" range and Harwich to Bourne in the 8-12" range, Chatham will likely see less with 4-8" of snow. the GFS produces a ton of moisture but it falls over the ocean, this is bound to move over land, but where will help determine who gets how much, for now I will leave the 18-24" isolated 30" amounts in banding in the position it is in now. Temperatures tonight will be in the low teens once again. Tomorrow afternoon highs will be near 30F and lows will be near 20F, I don't see how a low 40s ocean warms an arctic air mass with a northerly component to the wind field over Cape Cod, but regardless my forecast carries a mix over Cape Cod therefore only about 8-12" will fall before the changeover. Thunder snows and intense snowfall rates will be likely before the changeover occurs if it does at all. the GFS is all snow except for about a changeover briefly of about .2" of QPF as rain. That shouldn't matter much. the other aspect to this storm is the wind damage and blizzard conditions. I think blizzard conditions are likely even for Cape Cod and the NWS will likely issue a blizzard warning for us instead of a winter storm warning. Hurricane force winds are likely for Cape Cod, Cape Ann and Nantucket and all along the NH and Maine immediate coastline. Also Downeast ME sees only a few inches given that the low tracks west of them bringing in warm air off the ocean from the southeast. Thank you

NAM and its parallel model both show extensive potential for ferocious wind gusts on Tuesday late morning through the afternoon hours. there remains a window of 6-12 hours where winds could gust as high as 105mph according to the NAM model. Stay tuned for further updates.

March 11th 2017 605pm entry: Very cold air mass overhead the Northeastern US tonight. temperatures for Sunday morning lows are around 10-12F over the Cape. Forecasted temperatures won't break 25 the next two days Sunday and Monday. This arctic air mass will be the reason we can expect a snowstorm to occur some time Monday night through Wednesday morning depending upon if the storm slows down at all, right now the 12z and 18z runs today show a progressive but easterly track with less phasing, although I don't think this is about a less of a phase. While common knowledge dictates that the stronger the phase the further west the storm tracks is correct most of the time, the 18z GFS and NAM are both east of the 12z runs positions, and therefore show a faster transfer of energy between the clipper (primary) low and the coastal storm that takes over earlier on the latest guidance. Given nature of the H5 trough, this should allow the coastal storm to intensify rapidly and be in the lower 970mb range, rather than the higher 988mb range the GFS has. Therefore winds should gust between 70-90mph, 70mph if the GFS is right or 90mph if the stronger solutions are correct. Remember the faster the transfer of energy between the primary OH Valley low and the coastal low off the coast of SC occurs, then the further eastward it will travel, I don't expect a far east track, but one down the middle of today's guidance, over the benchmark, east of ACK and CHH of around 970-980mb low pressure center producing a few feet of snow from DC to BOS with NYC to BOS receiving the mega amount of snowfall of around 24-30" of snow. Coastal New England including Cape Cod should remain all snow and receive up to 34" of snow. Those are my thoughts right now, subject to change.

2003 storms one on Feb 7th and another on the 18th brought 12"+ in both storms to Cape Cod.

Brewster sat at 10". but I do remember measuring 17" for NEMO

Storm total accumulation was 17"

Ummm, I got 17" in Harwich, MA, that map has me in the trace to 4" range, that is wrong for the February 8-9th 2013 blizzard.

The March '14 storm was a huge blizzard, but it was about 200 miles out to sea. Anyways, it looks like the pattern gets better for Thanksgiving Week, much colder temps and a huge reservoir of cold air in central Canada shifting eastward into the Quebec, Canada sector. Also storms are starting to get closer and closer to the big deal, the 12z GFS shows a monster.

I brought up the Jan 05 storm as an analog, but there was a huge difference between storms. While the 05 Blizzard was much more dynamic energy wise, the 15 Jan blizzard dug much further southeast before closing off.

There are model runs showing similar characteristics from that Jan 26-27 2015 event as to now for the 16-17th of OCT. There is a lot of energy running around the base of the northeast US trough for this period and models are beginning to show signs of a more energetic disturbance associated with this trough and +PNA pattern. Just something to look after.

The January 26-27th 2015 Blizzard was just that for Harwich, MA. A storm that was originally thought to have brought taint and rain to The outer Cape Cod area, never saw a drop of rain. We got 30.4" of snow, maybe a bit more in certain areas of the region, but we stayed all snow and never went to rain. I read some of that thread a week ago. Man everyone was down on the event three days ahead of time.

Yeah Cape Cod, MA had wind gusts reach 120mph in Eastham, like a mini vortex with microburst potential wind damage.

Probably the benchmark storm ever for Harwich, MA was the Blizzard of 2005. The Blizzard of January 26-27th 2015 was a close second, but nothing will compare to that mega band that hit interior SE MA with 7-8" of snow in 75 minutes time. Snowfall rates were close to 10" in that band. We had several bands reach 5"/hour here on the Cape as well during that blizzard. By 12am midnight on the 23rd we had 12" of snow in an 8 hour period, after that time we had another 23" within another 15 hour period. Extremely amazing for sure.