The SI Weather
18Oct/13Fri

11:50 AM | 2013 – a year with minimal extreme weather events in the US

Discussion

There have been many forecasts in the news in recent years predicting more and more extreme weather-related events in the US, but for 2013 that prediction has been way off the mark. Whether you’re talking about tornadoes, wildfires, extreme heat or hurricanes, the good news is that weather-related disasters in the US are all way down this year compared to recent years and, in some cases, down to historically low levels.

Tornadoes
To begin with, the number of tornadoes in the US this year is on pace to be the lowest total since 2000 and it may turn out to be the lowest total in several decades. The table below lists the number of tornadoes in the US for this year (through 10/17) and also for each year going back to 2000.
(Source: NOAA, http://www.spc.noaa.gov/climo/online/monthly/newm.html)

Year         # of Tornadoes
2013                    771
2012                   1119
2011                   1894
2010                   1543
2009                   1305
2008                   1685
2007                   1102
2006                   1117
2005                   1262
2004                   1820
2003                   1374
2002                    938
2001                   1219
2000                   1072

Wildfires
Second, the number of wildfires across the US so far this year is on pace to be the lowest it has been in the past ten years and the acreage involved is at the second lowest level in that same time period (table below).
(Source: National Interagency Fire Center; http://www.nifc.gov/)

2013            Fires: 40,306           Acres: 4,152,390
2012            Fires: 67,774           Acres: 9,326,238
2011            Fires: 74,126           Acres: 8,711,367
2010            Fires: 62,471           Acres: 3,233,461
2009            Fires: 78,792           Acres: 5,921,786
2008            Fires: 80,094           Acres: 5,254,109
2007            Fires: 85,822           Acres: 9,321,326
2006            Fires: 96,358           Acres: 9,871,939
2005            Fires: 66,552           Acres: 8,686,753
2004            Fires: 63,608           Acres: 8,097,880
*2013 data through 10/16

Extreme Heat
In addition to wildfires, extreme heat is also way down across the US this year. In fact, the number of 100 degree days across the country during 2013 is not only down for this year, but it is perhaps going to turn out to be the lowest in about 100 years of records (chart below).

100_deg_days
(Source: NOAA, USHCN reporting stations; through August)

The five summers with the highest number of 100 degree days across the US are as follows: 1936, 1934, 1954, 1980 and 1930. In addition to the vast reduction in 100 degree days across the US this year, the number of high temperature records (ie hi max and hi min records) is way down compared to a year ago with 22,965 records this year as compared with 56,885 at this same time last year.
(Source: NOAA, http://www.ncdc.noaa.gov/extremes/records/; through 10/17).

Hurricanes
Finally, as far as hurricanes are concerned and keeping in mind that the season isn't over yet, there have been only two hurricanes so far this year in the Atlantic Basin (Humberto and Ingrid) and they were both short-lived and weak category 1 storms. Also, the first forming hurricane this year occurred at the second latest date going back to the mid 1940’s when hurricane hunters began to fly. Overall, the tropical season in the Atlantic Basin has been generally characterized by short-lived and weak systems.

In addition, this suppressed tropical activity has not been confined to just the Atlantic Ocean. The eastern Pacific Ocean has had no major hurricanes this season meaning there has been no major hurricane in either the Atlantic or eastern Pacific which only occurred one other year in recorded history – 1968. This is actually quite extraordinary since the two basins are generally out of phase with each other i.e. when one is inactive the other is active.

One of the best ways to measure “total seasonal activity” in the tropics is through an index called the Accumulated Cyclone Energy (ACE) which is a metric that accounts for both intensity and duration of named tropical storms. Indeed, the ACE for this tropical season so far in the Atlantic Basin is only 29% percent of normal (through 10/17) when compared to the climatological average from 1981-2010 and it is the 7th lowest since 1950. Elsewhere, the ACE across the northern hemisphere is only 58% of normal and global ACE is 62% of normal.
(Source: Dr. Ryan Maue at Weather Bell Analytics; http://models.weatherbell.com/tropical.php)

Finally, another interesting stat with respect to hurricanes has to do with the fact that we are currently in the longest period since the Civil War Era without a major hurricane strike in the US (i.e., category 3, 4 or 5). The last major hurricane to strike the US was Hurricane Wilma during late October of that record-breaking year of 2005 - let’s hope this historic stretch continues. By the way, just as a point of comparison, in 1954 the US was hit by 3 major hurricanes in less than 10 weeks.

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