Sunday, October 30, 2016

End of October Monster NE US Storms

25 years ago today coastal communities were dealing a powerful unnamed nor'easter that was nearing peak intensity as it moved towards New England.  High winds, cycles of major coastal flooding and heavy rains pounded the Northeast coast.  5 years ago today millions woke up in the dark after a stunning major snowstorm rocked the region.  4 years ago today millions more woke up with no power, many downed trees/power lines and coastal flooding not scene in decades along coastal areas from Hurricane Sandy.  Let's review these storms and then ask the question why late October seems to be a favorable time for generational weather systems.

The Perfect Storm October 28-November 2, 1991
On October 27, 1991 a cold front exited the east largely without incident.  At the same time Hurricane Grace was a Category 2 storm in the SW Atlantic near Bermuda.  A non tropical low formed on the cold front near Nova Scotia that began to move back towards New England.  Thanks to a set of rare atmospheric conditions that NWS Boston meteorologist Bob Case said take place only once every 50-100 years an explosive storm developed.
NOAA GOES 7 Infrared Satellite October 30, 1991
Strong high pressure across eastern North America contributed to the formation of this storm.  It stretched from the Gulf Coast to Greenland.    The strong pressure gradient between this (1043 mb in Canada) and the deepening extra tropical surface low brought hurricane force winds to the Northeast.  More damaging was the swells and storm surge caused by the giant storm.  Here is how the upper atmosphere evolved from October 28 8 PM to October 30 8 PM.  The big image to focus on is the blue and red 500 mb upper air chart on the right.
10-28-1991 Upper air 8 PM via NOAA/NWS/NCEP reanalysis 
The configuration here shows ample cold Canadian air pouring into the Northeast thanks to the ridge.  The Atlantic trough and Hurricane Grace are feeding off the warmer Atlantic waters.  Moving forward 24 hours
10-29-1991 Upper air 8 PM via NOAA/NWS/NCEP reanalysis
The ridge in SE Canada is strengthening while the nor'easter has absorbed Grace and continues to deepen as well.   By October 30 a major storm is crushing the east coast with wind and waves.
10-30-1991 Upper air 8 PM via NOAA/NWS/NCEP reanalysis
The Perfect Storm would stall over the Gulf Stream and it took on tropical characteristics.  The storm became a category 1 Hurricane but it was left with no name.  Damage in coastal New England rivaled some of the great storms in the regions history including the 1944 Great Atlantic Hurricane, 1962 Ash Wednesday Nor'easter, the Blizzard of 1978 among others (NOAA).  Inland it wasn't as bad as it could have been as the strongest winds were closer to the coast.
Storm Damage Rebecca Rd Scituate, MA
In summary cold Canadian air, warm tropical air and a hurricane created a monster in late October 1991.   See here for Channel 5's image gallery of the event.

Snowtober- The Halloween Nor'easter October 28-28, 2011
2011 is a historic weather year in Southern New England.  It started in winter with 4 NESIS rated snowstorms.  On June 1 we had the EF-3 Springfield tornado, in late August Hurricane Irene slammed into the region and in late October we had Snowtober.  The heaviest snow missed SE MA/RI but around 8" fell in Southern Worcester County.  Upwards of 1-2 feet fell in Western MA, CT, NY, and NJ.
NESIS Halloween Nor'Easter snow totals/ratings 
This was the second major weather event I covered as a professional.  I first posted on October 27 about the incoming threat. I broke it down even further on October 28 before one final update on October 29, the day of the storm.  One thing I missed with that forecast was the developing nor'easter pulling the remnants of Hurricane Rina into the storm.  That added extra moisture and energy into the storm.  Here is the surface map for Friday October 28 at 8 PM.
WPC Surface Analysis Friday October 28, 2011 8 PM
Four features to point out.  First high pressure over the Northeast.  This has locked in cold Canadian air.  Second is low pressure in Georgia.  This is the main surface low that will develop into the storm.  Third see the low along the US/Canadian border in Minnesota?  That will add energy to the storm and phase (combine energy) the northern and southern jet streams.  Finally in the Southern Gulf of Mexico between Mexico and Cuba is the remnants of Hurricane Rina.  Moving forward to Saturday 8 AM here is the upper atmosphere
10-29-2011 Upper air 8 AM via NOAA/NWS/NCEP reanalysis 
The big dip in the Great Lakes is the northern jet moving towards the east coast where a favorable environment for strong storm formation exists.  By 8 PM a closed surface low has formed and a classic mid winter nor'easter was on our hands in late October.
WPC Surface Analysis Saturday October 29, 2011 8 PM

This was by far the most significant winter storm of the 2011-12 season.  In fact this storm helped change the jet stream.  For the next year the atmosphere was mostly zonal meaning mild Pacific air flooded the US.  Still the damage from 2011 was done.
Telegraph UK photo of Belmont, MA October 30, 2011 snow damage
Post Storm visible satellite image showing where snow fell
In summary the northern and southern jet streams phased off the east coast while ingesting the remnants of a tropical cyclone.  At the same time Canadian high pressure locked cold air in place.  The result was a historic late October storm.  As for the next storm it hit a few hundred miles south of the region which spared most of New England from a devastating blow.

Hurricane Sandy October 28-29, 2012
Hurricane Sandy is second to only Hurricane Katrina when it comes to insured loses from a tropical cyclone.  Sandy brought strong winds, heavy rain, heavy snow, and a devastating storm surge to the most populated region in the States.   The center hit Southern NJ but severe coastal impacts occurred as far away as Newport, RI.  Inland high winds brought down trees and power lines.

Tuesday October 23, 2012 first thoughts
Thursday October 25, 2012 Sandy gains strength
Saturday October 27, 2012 Timing/Impacts
Monday October 29, 2012 The Day Of
The aftermath part 1

Sandy was a fascinating meteorological event. Over 100 people lost their lives in the US.
WPC Surface Analysis Monday October 29, 2012 2 PM
A cold front captured Sandy and turned the storm into a hybrid hurricane/nor'easter.  That is a common theme for these late October storms.  Some sort of tropical cyclone is either ingested or is acquired by an early season winter trough.  It is rare but sometimes a winter like trough is able to descend into Eastern North America.  The SW Atlantic/Caribbean Sea/Gulf of Mexico are all capable of supporting a hurricane in late October.  This tropical energy combining with non-tropical lows produces exceptionally strong storms in the Northwest Atlantic Ocean.  
Hurricane Sandy Damage in New Jersey
Hurricane Sandy damage in Rhode Island (via MassLive)
Thankfully it is quiet this Halloween.

-Zack Green

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