This page presents the results of an analysis performed to objectively rank events based upon how far synoptic-scale fields depart from "normal":

where:

field = The observed field
X = the daily mean value for the variable at that location
sigma = the daily mean field variability (standard deviation) for that location

Therefore, N is measured in the number of standard deviations from normal.

This departure is calculated for each of four variables: temperature, height, wind, and moisture.

Then, the maximum N-value for each variable is found (M_TEMP, M_HEIGHT,M_WIND, and M_MOIST respectively).

The total departure is then the full-troposphere mean (1000hPa -> 200hPa) of these four departures:

The expected return period for a given M_TOTAL value illustrates the rarity of high values of M_TOTAL.

The database used covers the years from 1948 through the end of last month and is limited to the eastern United States, extreme southeast Canada and the Gulf of Mexico.

The top 20 M_TOTAL values, their dates, case description and references (if available) are shown below. The database is further broken down into the top cases by variable and by month at the end of the page.

Four-panel plots of the conventional synoptic analyses and associated anomaly fields are available by clicking on the date.

Dataset used:

• NCEP Reanalyses:
  from NOAA-CIRES Climate Diagnostics Center (CDC), Boulder, Colorado

Sincere and deep gratitude go to NCEP, NOAA-CIRES, and CDC for providing historical and current reanalysis data online.

For further details of this project, see:

Hart, R. and R. Grumm, 2001: Using normalized climatological anomalies to rank synoptic-scale events objectively. Mon. Wea. Rev, 129, 2426-2442.

Rank	Date	MTOTAL	Description	References
1	00Z09JAN1956	4.950	"The Great Atlantic Low"	Ludlum 1956
2	12Z15JAN1995	4.722	Deep Gulf of Mexico Storm
3	00Z14MAR1993	4.576	Superstorm of 1993	Kocin et al 1995; Dickinson et al 1997
4	12Z11JAN1975	4.566	Severe Minnesota Blizzard
5	12Z08JAN1998	4.536	NE US/SE Canada Ice Storm	Gyakum and Sisson 1999; DeGaetano 2000
6	12Z28DEC1980	4.469	Deep Carolina Coastal Low
7	12Z17MAR1983	4.464	Low-latitude intense cyclone	Dickinson et al 1997
8	00Z26NOV1953	4.396
9	00Z16OCT1954	4.391	Extratropical Hazel	Knox 1955; Palmen 1958
10	12Z08JAN1958	4.356
11	12Z19JAN1977	4.340	Historic Florida Freeze	Schwartz 1977
12	12Z19JAN1996	4.307	NE US Flooding/Snowmelt	Leathers et al 1998
13	00Z10JAN1978	4.260	Deep NE U.S. Storm
14	12Z31OCT1993	4.232	E. U.S. Elevation Blizzard	Grumm and Nicosia 1997
15	00Z04FEB1970	4.201
16	12Z22DEC1972	4.199	Deep Gulf of Mexico Storm
17	12Z11DEC1950	4.192
18	12Z17NOV2002	4.185	Southern/Central New England Ice Storm
19	12Z26JAN1978	4.179	The Cleveland Superbomb	Gaza and Bosart 1990; Hakim et al 1995,1996
20	00Z20OCT1989	4.179	SE U.S. Record Cold & Snow
21	12Z22JAN1959	4.176	Severe E. U.S. Snow/Ice Storm	Treidl 1959

Robert Hart, PSU (hart@ems.psu.edu)
Richard Grumm, SOO, NWS CTP (rgrumm@supercel.met.psu.edu)