This page is about storm systems in North America that can be characterized by two or three
upper level lows (or vortices or troughs) that merge together to create a bigger or more
intense storm, sometimes resulting in a snowstorm.
Midwest Blizzard of '78
January 24-27, 1978 250mb loop 850mb loop Surface Temp and SLP loop
Essentially Two-vort max powerful phasing. Did three branches of the jet stream phase together You decide: 500mb Wind Speed Loop (0.2MB) 250mb Wind Speed Loop (0.2MB)
Washington Blizzard of '66 East Coast
Storm - Two-vort max powerful phasing
January 28-31, 1966 250mb loop 850mb loop Surface Temp and SLP loop
Did three branches of the jet stream phase together? 500mb Wind Speed Loop (0.2MB) 250mb Wind Speed Loop (0.2MB)
Northeast Blizzard of '78: East Coast
Storm. I think this at least partly had phasing. It's
interesting to note the surface low did a small loop near Cape Cod and Long
Island. February 5-8, 1978
February 1958 East Coast Snowstorm.
This loop is 7 days long - you can see one storm develop offshore and
phase with the polar vortex and then move to Newfoundland before the
February 16-17 storm (the real snowstorm.) This looks like it just
might be Three-vort max phasing on February 16-17. 500mb loop of February 12-19,
1958 250mb loop 850mb loop surface temp and SLP loop
February 1995 East Coast Snowstorm.
500mb loop of February 2-4,1995
February 1983 East Coast Snowstorm.
500mb loop of February 10-13,
Other Strong Phasing Storms
Nearly a three-vort max phasing resulted in a 944mb low in Quebec February 1-3, 1976
Two-vort max powerful phasing -snowstorm for Toledo, Indiana, Ohio, Kentucky, others. January 9-11, 1977 250mb loop 850mb loop Surface temp and SLP loop
Three-vort max phasing January 7-10, 1978 250mb loop 850mb loop Surface temp and SLP loop This storm is also mentioned in Dean and Bosart (1996) and resulted in a surface low of 964mb in Quebec.
- Appalachians snowstorm March 30 - April 1, 2003
- New England storm December 5-8, 2003 (GFS 0 hour) 850mb Animation 250mb Animation Surface Animation
- Some less intense phasing in the Charlotte Snowstorm February 25 - 27, 2004
This was complicated, but I think it counts as phasing and a TROWAL in the Northeast US and southeast Canada.
February 28 - March 3, 2005 250mb vorticity animation 850mb vorticity animation
Some type of phasing and surface low possibly in the 940's (mb) range offshore from Maine
March 8-10, 2005 250mb vorticity animation 850mb vorticity animation
April 24, 2005 Great Lakes snowstorm, TROWAL 250mb vorticity animation
October 14-16, 2005 - New England Floods/Non-named subtropical low 850mb vorticity loop 250mb vorticity loop
another 500mb loop 1000mb vorticity/ Sea level pressure loop
Most of the flooding occurred before these two storm systems really phased together. You might even argue for 3 different vort maxes getting involved.
December 13-16, 2005 500mb vorticity loop 850mb vorticity loop 850mb wind speed loop 250mb vorticity loop Surface Analysis loop
Two upper vort maxes sort of combined in the Great Plains, then a upper vort max/surface low generated on the Gulf Coast and moved northeast, sort of merging with the other low .
January 12-15, 2006 500mb vorticity loop 850mb vorticity loop 850mb wind speed loop 250mb vorticity loop Surface Analysis loop Tropopause Pressure
Strong trough amplification and slow phasing, mostly a rain storm, but a pretty good snow storm for a small portion of Massachusetts and New York, with some snowfall in eastern New York, New Jersey and New England.
January 30-February 1, 2006 500mb vorticity loop 850mb vorticity loop 850mb wind speed loop 250mb vorticity loop Surface Analysis loop Tropopause Pressure
Strong trough amplification, development of a strong ocean storm, possibly considered a bomb.
February 3-5, 2006 "Super Bowl Snowstorm" 500mb vorticity loop 850mb vorticity loop 850mb wind speed loop 250mb vorticity loop Surface Analysis loop Tropopause Pressure
Strong trough amplification, development of a strong low that tracked through eastern Kentucky, Ohio, and southern Ontario, possibly considered a phasing system. The storm dumped several inches of snow north of Detroit in the Thumb of Michigan, one day before the Super Bowl, and also hit areas north and east of Lake Huron, like Sudbury, Ontario, pretty hard.
April 2-9, 2006 500mb loop Surface loop Two consecutive large scale phasing systems. On April 3-4, the cold upper low over Hudson Bay joined into a storm system moving through the Midwest and Mid-Atlantic, forming two noreaster type lows. On April 7-8 (and 9th) another cold upper low in northern Ontario acted as a crusher for the storm system that moved from the Plains to the Tennesee Valley to the Southeast.
May 2006 500mb loop Incredible 15-day loop.
October 27-29 2006 500mb loop Ohio Valley/Northeast storm amplification.
November 14-16 2006 500mb loop Oklahoma/Tennessee Valley/Ohio Valley storm amplification.
March 7-9, 2008 - snowstorm from Texas to the Ohio Valley to Canada. Phasing of upper troughs occurred in the Ohio Valley area (loop to be added later)
Other storms with phasing
March '58 East Coast storm. You decide if this is phasing or not. March 18-23, 1958
- OH Floods of 1959, ended up as a 976mb () low pressure in Quebec January 15-17, 1959
- Ash Wednesday Storm. You decide if this is phasing or not. March 4-6, 1962
- It looks like this one really changed a lot in 24 hours March 5-7, 1965
- Snowstorm for Toledo, Indiana, Kentucky November 1-4, 1966
- Snowstorm for Toledo and Detroit March 21-23, 1968 500mb Vort 250mb Vort 850mb Vort Surface
- Interior East Coast/New England Storm March 3-5, 1971
- Strong trough amplification after a New Year's Eve snowstorm in the Chicago area January 1-3, 1979
- Storm system studied by Lai and Bosart (1988) November 17-18, 1980
- Snowstorm for Toledo and Detroit on February 10, 1981 February 10-12, 1981
- Snowstorm for Akron and Columbus April 2-4, 1987
- January 24-26, 1988 - this is exactly 10 years after the midwest blizzard. Loop
- Snowstorm for Toledo and Detroit January 14, 1992 NARR Animation January 14, 1992 NCEP Reanalysis Animation
- Midwest snowstorm January 1-3, 1999
- Storm system studied by Strahl and Smith (2001) November 2-4, 1999
- Infamous snowstorm of 2001 March 4-6, 2001
Some storms listed in Bosart and Gaza (1990)
note: Bosart and Gaza did not consider phasing over the Atlantic Ocean except for one instance
February 1-3, 1976 as mentioned above
January 9-11, 1977 as mentioned above
January 8-10, 1978 as mentioned above
- January 25-26, 1978 as mentioned above
-central Canada August 21-22, 1980
- Northern New England January 6-8, 1981
- phasing in the Ohio Valley, the surface low bombed east of VA/MD and ended up at 955mb somewhere in the North Atlantic March 15-17, 1981
- eastern Quebec August 13-14, 1981
November 14-16, 1982
- Maine/New Brunswick March 29-30, 1983
- Hudson Bay July 4-5, 1983
- Northern Canada August 4-5, 1983
- central Canada October 16-17, 1983
- offshore from Nova Scotia June 3-4, 1984
December 5-6, 1985
November 19-21, 1986
February 22-24, 1987 - East Coast snowstorm
Tropical - Extratropical Connections
October 14-18, 1954: Hurricane Hazel
June 20-24, 1972: Hurricane Agnes
October 28 - November 2, 1991 : the "Perfect Storm"
(Hurricane Grace, Extratropical Storm, Hurricane #8) not only this, but look at the upper level trough that moves through the Plains/Midwest on November 1 !
Dean and Bosart (1996) did a climatology of trough mergers and fractures in the Northern Hemisphere. One interesting thing to note is that they decide to categorize trough mergers (phasing) as either a "classic" type or a "vortex merger" type. The "vortex merger" type is where two or more vort maxes rotate around each other and interact inside a larger closed upper low. The "classic" merger is best shown by all of the examples from Bosart and Gaza (1990)
Examples of Vortex Mergers (not specifically mentioned in the paper)
"Snow Bowl" of 1950: November 23 to 27, 1950 250mb loop 850mb loop Surface temp and SLP loop
The surface low moved through Manitoba, MN, and Lake Superior. Then it re-generated a new surface low on the cold front in NC/VA and rotated it north to PA and west to OH, in a loop, and northward to Ontario.
November 6-8, 1953
-Eastern Ohio snowstorm December 5-7, 1962
-You have just got to watch this 12-day loop. Cut off lows! February 24 - March 7, 1965
- The storm that sunk the lake freighter Daniel J. Morrell Daniel J. Morrell picture on Lake Huron Wikipedia article on Daniel J. Morrell
November 27-30, 1966
Buffalo Blizzard of 1977: January 28-29, 1977 250mb loop 850mb loop Surface loop
Three vort maxes rotated around each other in Eastern Canada. The southern one caused the snow, lake effect snow, and blizzard conditions in the Great Lakes, especially Buffalo and Watertown.
May 5-7 1989 : late(est) season snow in Toledo
October 18-21 1989 : early season snow in IN and IL
Millennium Snowstorm: East Coast Storm December 29 to 31, 2000
- North Platte NE page on blizzards and case studies
Robert S. Gaza and Lance F. Bosart "Trough Merger Characteristics over North America," Wea. Forecasting Vol. 5 No. 2 (1990) pp. 314-331
Chung-Chieng Lai and Lance F. Bosart "A Case Study of Trough Merger In Split Westerly Flow," Mon. Wea. Rev. Vol. 116, No. 10, (1988) pp. 1838-1856.
Jennifer L. S. Strahl and Phillip J. Smith "A Diagnostic Study of an Explosively Deepening Extratropical Cyclone and and Associated 500-hPa Trough Merger," Mon. Wea. Rev. Vol. 129 No. 9 (2001) pp. 2310-2328
Devin B. Dean and Lance F. Bosart, "Northern Hemisphere 500-hPa Trough Merger and Fracture: A Climatology and Case Study," Mon. Wea. Rev. Vol. 124 No. 12 (1996) pp. 2644-2671
Several of these storms involved two-vort max phasing, although the
airflow interaction with the Rocky Mountains complicates things.
Plains Blizzard of 1949, January 3-5, 1949 250mb loop 850mb loop Surface loop
Dakota Blizzard and Severe Weather Outbreak, March 24-28, 1950. 250mb loop 850mb loop Surface loop This storm broke sea-level pressure records in KS, NE, CO, IA, and SD, lowest pressrure 969.5mb in Sioux Falls SD.
Cut off low March 11-15, 1951
Snowstorm and Severe Weather Outbreak, February 26-28, 1958 250mb loop 850mb loop Surface loop
Blizzard and Tornado Outbreak November 17-19, 1958 250mb loop 850mb loop Surface loop
Sea Level Pressure Loop (long)
Plains Blizzard of 1966, March 2-5, 1966
Upper Midwest Snowstorm, April 7-11, 1973
Plains and Upper Midwest Blizzard of 1975, January 10-12, 1975 250mb loop 850mb loop Surface loop
Edmund Fitzgerald Storm/Blizzard, November 9-11, 1975
Chicago Blizzard of '79 January 12-14, 1979 NARR Animation January 12-14, 1979 NCEP Reanalysis Animation 250 loop 850 loop Surface loop
Near the end of this animation, you can see a second vort max moving into the system, traveling through Manitoba and Minnesota.
January 14, 1979 00z 300mb wind speed
October 28 - November 2, 1991
Minnesota Blizzard/snowstorm October 31 - November 1
Plains and Upper Midwest Blizzard of 1996, January 17-20, 1996
Blizzard and Severe Weather, November 9-11, 1998. This storm broke sea-level pressure records in Minnesota and reached a low of about 972mb in Minnesota.
Northern Plains Blizzard, ice storm, and tornadoes/severe weather November 26-28, 2005 - 500mb Loop 250mb Loop 850mb Loop Surface Analysis Loop
April 11, 2008 - strong trough amplification in the central Plains
The Great Christmas Storm of 2009
December 22-23, 2007 - two upper lows combined in the Upper
500mb plot from 12z December 23
The purpose is to provide high quality information on historical storms
and provide links to weather information. The "Toledo Snowstorms" web page includes my own research of many snowstorms.