BLIZZARD TO IMPACT SOUTHERN NEW ENGLAND - massive impact expected!
Decided to do a new and more complete blog entry dedicated to this snowstorm, given the seriousness of the potential situation. Here is my first and probably final issuance given I have some leeway with potential for higher amounts:
12z NAM/EURO track
12z NAM precip output, added about .5-1.0" of QPF to the highest areas, adjusted west track given potential convective feedback issues
12z NAM intensity, given potential convective feedback, went a little higher then the NAM intensity of 964mb.
12z NAM/GFS timing
Major League Blizzard appears to be underway. Surface cyclogeneis has begun along the northern Gulf Coast states, as intense southern stream impulse continues to gather GOM moisture with intense thunderstorm activity. Lightning was observed at some point earlier this morning, however this has subsided, given extreme shearing of the shortwave as an intense Northern stream impulse continues to dig southward. Another arctic jet impulse appears to be phasing within the upper level trough, this would indicate potential triple phased superstorm levels, we have only once seen before. Still staying a bit cautious on this level.
Storm could compare to the 93 Superstorm/96 Blizzard/05 Blizzard/78 Blizzard. 700mb moisture modeled fields for 12z Sunday, indicate that a massive superstorm like low will be off the Hatteras, NC coastline and is expected to head Northward before heading more eastward with potential of occlusion occurring. We still are uncertain about this timing issue of potential maturity and occlusion of the super surface low. Intensity models deepen it into the lower 960mb range, although based upon surface data, indications are that this low is deeper already then modeled. Still suspect on that at this time.
Surface low should track close to, but just southeast of Nantucket, MA. 850mb and 700mb modeled circulation tracks indicate that heaviest snows should be further northwest then the NAM indicates and potential exists for mid level warming over Cape Cod, and the Islands which could allow the snow to mix with sleet and change to rain for a time. Massive low level jet is expected to develop and deepen as the cyclone exits the coastline around Savannah, GA and then begins heading NNEward. Models disagree to the extent of which the low occludes and westward track. However they have continued to converge on a benchmark track. Intense thunderstorm activity over the Gulf Coast already indicates quite a dynamic pattern evolving with a ton of energy spilling and digging the upper level trough into the southeastern US. At this time, have put Eastern MA coastal and slightly interior regions in the 24"+ zone, given favorable trajectory of the wind off the ocean and climatological positioning of a coastal front associated with such a low pressure track. Extreme 850mb temp gradient likely resembles the positioning of the coastal front from Martha's Vineyard to Cape Ann, however expect the front to end up further eastward then modeled. Given extreme setup of the baroclinic zone and extreme influx of moisture off the Atlantic as an intense 75-85 knot low level jet develops, snowfall rates will increase south to north from the late morning hours across the South Shore, to later in the evening hours on Sunday the further north one heads. Extreme snowfall should be best handled by where the potential best banding occurs. This is still an unknown and the convective elements of the cyclone will greatly effect potential accumulation amounts. Cape Cod, MA and the Islands should experience less snowfall do to mixing problems, however not before 6-12" has fallen and potential backlash comma head rips through the region afterwards. Potential exists for dry slotting, depending upon how far northwest the 700mb circulation ends up. Extreme lift is modeled for eastern SNE which will likely offset any temperature concerns early on.
Winds should increase throughout Sunday night and through Monday morning as surface cyclone deepens at an atomic rate of 2mb/hour as it passes just to the southeast of ACK. Pressure at time of closest passage, could be around 960-965mb and this will tighten the pressure gradient as well as intensify the low level jet. Do to the presence of convection and the low level wind field of close to 70-80knots, winds could gust as high as 75mph on Nantucket and 70mph across Cape Cod, MA. Block Island will also remain close enough to the circulation center for a high impact in wind speeds. Regionwide, especially within the pink areas, winds could be sustained between 25-35mph with gusts to 55mph. Areas within the black area and points eastward could experience gusts up to 60-70mph, with stronger gusts across Nantucket. Expect sustained winds between 30-40mph in this region.
Travel difficulty will begin to increase as Sunday wears on. Travel is not recommended after 12pm, please get travel plans completed and prepare for power outages on the eastern MA coastline. This will be an extremely dangerous Blizzard and safety is your number one priority. Travel should be completed by 12pm tomorrow.
DANGEROUS STORM - One we possibly haven't seen before since 2005.
Weather updates will be found below:
Final snowfall map, adjusted heaviest amounts to the west some given latest model data and surface data of a stronger surface low in the GOM then models indicated, potential for this storm to come further westward then modeled at 12z. Mixing potential could make it as far west as BOS/PVD corridor, although think that surface winds stay too northeasterly so no major changeover is expected. NYC to Portland, ME this is your snowstorm. Very impressive.
Final updated map, scaled back large scale 2'+ amounts, more like isolated 2'+ amounts in best banding. Also scaled back the potential snows on Cape Cod, MA to 6-12" still think dynamics will initially overcome naturally warmer boundary layer. SO a good front end thump seems probable at this time. Winds will become a tremendous issue.