2016-2017 Winter

Another winter has past. It is now spring again. We really had no winter with the exception of the Pacific Northwest where it got cold. Most of America was wondering where is winter. It felt like another spring. How did this winter stack up?

5 Kilometer Gridded Map Of Temperature Anomaly

Most of the US experienced warmer than normal winter. Some had record warmth winter, especially in Texas, Louisiana, Florida, and New Mexico. Washington, Oregon, and Idaho had cooler than normal winter. The mean temperatures tell you a lot. Of course, the devils are in the details.

5 Kilometer Gridded Map Of Minimum Temperature Anomaly

The low temperatures were quite warm in areas where they had record warmth. The areas that were cooler than normal had cooler low temperatures. No surprise there.

5 Kilometer Gridded Map Of Maximum Temperature Anomaly

The high temperature anomaly is not as large as compared minimum temperature anomaly. Low and high temperature can have an impact on overall mean temperature. One can have a cool winter if the low temperatures are high, while high temperatures are low or vice versa.

5 Kilometer Gridded Map Of Rainfall Anomaly

It was very wet, especially in California, Idaho, Wyoming, Utah, Texas, Iowa, and Alabama. Plenty of rain despite La Nina. It was a weak la Nina.

Here is a Northern Hemisphere temperature anomaly map.

Most of the Northern Hemisphere was warm, especially over the Arctic, North America, Asia, and Europe.

Here is a Northern Hemisphere precipitation anomaly map.

The wettest area is over Northern California where they go the lion share of the precipitation.

Here is a Northern Hemisphere 500 millibar level anomaly map.

There was ridging over the Southern US, Alaska, and Europe. The ridging kept things warm under. There is troughing over Northwest Canada, Pacific Northwest, Siberia, and Arctic. That kept things cold for winter.

Here is a worldwide sea surface temperature anomaly map.

The La Nina was weak, while Northeast Pacific off the coast of Alaska was mostly cooler than normal. There is unusually warm water in the Bering Strait and Gulf of Mexico.

America
Temperature: 35.90°F
Low Temperature: 25.94°F
High Temperature: 45.86°F
Rainfall: 8.22

1895-2017 Winter Statistics
Winter Temperature Mean: 32.37°F
Winter Temperature Median: 32.49°F
Standard Deviation: 2.06

Winter Low Temperature Mean: 21.91°F
Winter Low Temperature Median: 21.95°F
Standard Deviation: 2.13

Winter High Temperature Mean: 42.84°F
Winter High Temperature Median: 43.08°F
Standard Deviation: 2.10

Winter Rainfall Mean: 6.76
Winter Rainfall Median: 6.69
Standard Deviation: 0.89

It was an abnormally warm and wet winter. The temperature and rainfall are 1 standard deviation. This is abnormal in terms of temperature and rainfall. Here are the top 10 warmest and wettest winters in America.

Top 10 Warmest Overall Winter
1.) 2015-2016 36.78°F
2.) 1999-2000 36.48°F
3.) 1991-1992 36.35°F
4.) 2011-2012 36.34°F
5.) 1998-1999 36.27°F
6.) 1997-1998/2016-2017 35.90°F
7.) 2001-2002 35.66°F
8.) 1994-1995 35.56°F
9.) 2005-2006 35.49°F
10.) 2004-2005 35.46°F

Top 10 Warmest Low Temperature Winter
1.) 1997-1998 26.74°F
2.) 2015-2016 26.65°F
3.) 1991-1992 26.39°F
4.) 2016-2017 25.94°F
5.) 1982-1983 25.88°F
6.) 2011-2012 25.63°F
7.) 1994-1995 25.56°F
8.) 1998-1999 25.49°F
9.) 1999-2000 25.46°F
10.) 2004-2005 25.42°F

Top 10 Warmest High Temperature Winter
1.) 1999-2000 47.50°F
2.) 1998-1999 47.07°F
3.) 2011-2012 47.06°F
4.) 2015-2016 46.92°F
5.) 2001-2002 46.59°F
6.) 1953-1954 46.51°F
7.) 1933-1934 46.43°F
8.) 2005-2006 46.37°F
9.) 1991-1992 46.32°F
10.) 1980-1981 46.05°F
11.) 1975-1976 45.88°F
12.) 2016-2017 45.86°F

Top 10 Wettest Winter
1.) 1997-1998 8.99
2.) 1931-1932 8.86
3.) 1936-1937 8.66
4.) 1982-1983 8.52
5. 1996-1997 8.49
6.) 1978-1979 8.44
7.) 1902-1903 8.23
8.) 2016-2017 8.22
9.) 1915-1916 8.19
10.) 1992-1993 8.17

The overall temperature ties with 1998. The past winter of 2015-2016 is the warmest on record. The low temperature is the fourth warmest on record. The high temperature does not make the top 10 warmest. It shows that low temperatures can be a huge factor. The lack of cold air kept the low temperature warm. However, the wet winter kept the high temperature in check.

Texas
Temperature: 52.97°F
Low Temperature: 40.87°F
High Temperature: 65.07°F
Rainfall: 6.12

1895-2017 Winter Statistics
Winter Temperature Mean: 47.36°F
Winter Temperature Median: 47.30°F
Standard Deviation: 2.37

Winter Low Temperature Mean: 34.95°F
Winter Low Temperature Median: 35.10°F
Standard Deviation: 2.30

Winter High Temperature Mean: 59.75°F
Winter High Temperature Median: 59.50°F
Standard Deviation: 2.85

Winter Rainfall Mean: 4.83
Winter Rainfall Median: 4.72
Standard Deviation: 1.82

Top 10 Warmest Overall Winter
1.) 2016-2017 52.97°F
2.) 1906-1907 52.57°F
3.) 1999-2000 52.10°F
4.) 1998-1999 51.70°F
5.) 1951-1952 51.53°F
6.) 1949-1950 51.13°F
7.) 1956-1957 50.90°F
8.) 1910-1911 50.80°F
9.) 2015-2016 50.77°F
10.) 1908-1909 50.67°F

Top 10 Warmest Low Temperature Winter
1.) 2016-2017 40.87°F
2.) 1906-1907 39.50°F
3.) 1956-1957 39.23°F
4.) 1949-1950 39.10°F
5.) 1991-1992 39.07°F
6.) 2004-2005 39.00°F
7.) 1931-1932 38.87°F
8.) 1937-1938 38.80°F
9.) 1910-1911 38.77°F
10.) 1994-1995 38.57°F

Top 10 Warmest High Temperature Winter
1.) 1999-2000 65.77°F
2.) 1906-1907 65.57°F
3.) 2008-2009 65.23°F
4.) 2016-2017 65.07°F
5.) 1998-1999 64.97°F
6.) 1951-1952 64.77°F
7.) 2005-2006 64.63°F
8.) 1970-1971 64.53°F
9.) 1908-1909 64.23°F
10.) 1975-1976 64.03°F

Top 10 Wettest Winter

Texas had the warmest winter on record. The previous warmest winter was 1906-1907. The reason for the warm winter is largely due to abnormally warm low temperature, which is the warmest on record. The high temperatures is fourth warmest on record. 2000 is the warmest in terms of high temperature. All temperatures are 2 standard deviation, which is definitely abnormally and are out liers. However, rainfall is within 1 standard deviation, which is average.

Upper Texas Coast
Temperature: 61.73°F
Low Temperature: 52.73°F
High Temperature: 70.80°F
Rainfall: 12.25

1895-2017 Winter Statistics
Winter Temperature Mean: 54.06°F
Winter Temperature Median: 54.07°F
Standard Deviation: 2.72

Winter Low Temperature Mean: 44.22°F
Winter Low Temperature Median: 44.13°F
Standard Deviation: 2.80

Winter High Temperature Mean: 63.89°F
Winter High Temperature Median: 63.63°F
Standard Deviation: 2.86

Winter Rainfall Mean: 10.23
Winter Rainfall Median: 9.86
Standard Deviation: 3.51

Top 10 Warmest Overall Winter
1.) 2016-2017 61.73°F
2.) 1949-1950 59.57°F
3.) 1906-1907/1998-1999 58.87°F
4.) 1910-1911/1951-1952 58.77°F
5.) 1956-1957 58.73°F
6.) 1999-2000 58.63°F
7.) 1931-1932 58.30°F
8.) 1922-1923 58.07°F
9.) 2012-2013 58.00°F
10.) 1926-1927 57.93°F

Top 10 Warmest Low Temperature Winter
1.) 2016-2017 52.73°F
2.) 1949-1950 50.63°F
3.) 1931-1932 49.77°F
4.) 1956-1957 49.53°F
5.) 1910-1911 49.33°F
6.) 1998-1999 48.90°F
7.) 1951-1952 48.83°F
8.) 2011-2012 48.70°F
9.) 1922-1923 48.47°F
10.) 1971-1972 48.17°F

Top 10 Warmest High Temperature Winter
1.) 2016-2017 70.80°F
2.) 1906-1907 70.17°F
3.) 1999-2000 69.47°F
4.) 1998-1999 68.77°F
5.) 1951-1952 68.67°F
6.) 2008-2009 68.63°F
7.) 1949-1950 68.57°F
8.) 2007-2008 68.30°F
9.) 1910-1911 68.27°F
10.) 2012-2013 68.10°F

This was a very warm winter and literally abnormally warm. The overall temperature of 2016-2017 exceeds the previous warmest winter of 1949-1950 by 2.16°F! It exceeds by near 3 standard deviations! That is definitely an outlier! The low temperature is also the warmest and exceeds the previous warmest low temperature of 1949-1950. It also exceeds 3 standard deviations! However, the warmest high temperature is a close one. It is only by 0.63°F, which is not a lot. Still, it is 2 standard deviations, which in outlier territory. Winter 2016-2017 is an anomaly in terms of warm temperatures! It goes down in the record books! It was a wetter than usual winter, but within 1 standard deviation. It was due to the heavy rains of January.

Now, let’s look at the Last Frontier, Alaska.

Alaska Divisional Temperature Anomaly

Alaska Divisional Minimum Temperature Anomaly

Alaska Divisional Maximum Temperature Anomaly

Alaska Divisional Precipitation Anomaly

Temperature: 5.73°F
Low Temperature: -1.30°F
High Temperature: 12.80°F
Rainfall: 7.30

1925-2017 Winter Statistics
Winter Temperature Mean: 4.21°F
Winter Temperature Median: 4.57°F
Standard Deviation: 4.61

Winter Low Temperature Mean: -2.85°F
Winter Low Temperature Median: -2.90°F
Standard Deviation: 4.94

Winter High Temperature Mean: 11.26°F
Winter High Temperature Median: 11.67°F
Standard Deviation: 4.31

Winter Rainfall Mean: 8.13
Winter Rainfall Median: 7.91
Standard Deviation: 1.63

Alaska as a whole had a largely normal winter. The average temperature is within standard deviation. The precipitation is also within average as well. While the rest of the Lower 48 was warm, Alaska had a typically Alaskan winter. Even than Alaska can get cold and warm in the winter.

Top 10 Coolest Overall Winter
1.) 1924-1925 -7.20°F*
1.) 1964-1965 -5.03°F
2.) 1970-1971 -3.97°F
3.) 1955-1956 -3.10°F
4.) 1946-1947 -3.07°F
5.) 1942-1943 -2.77°F
6.) 1931-1932 -2.33°F
7.) 1933-1934 -2.23°F
8.) 1974-1975 -2.03°F
9.) 1975-1976 -1.83°F
10.) 1968-1969 -1.53°F

* December 1924 is missing.

Top 10 Warmest Overall Winter
1.) 2000-2001 14.97°F
2.) 2015-2016 14.30°F
3.) 2002-2003 13.43°F
4.) 1976-1977 12.80°F
5.) 2014-2015 11.60°F
6.) 1944-1945 11.30°F
7.) 1985-1986 11.27°F
8.) 1928-1929 11.23°F
9.) 1941-1942 11.03°F
10.) 1986-1987 10.80°F

Top 10 Coolest Low Temperature Winter
1.) 1924-1925 -15.25°F*
1.) 1964-1965 -12.50°F
2.) 1970-1971 -11.47°F
3.) 1955-1956 -10.80°F
4.) 1946-1947 -10.70°F
5.) 1931-1932 -10.60°F
6.) 1942-1943 -9.80°F
7.) 1933-1934 -9.63°F
8.) 1974-1975 -9.43°F
9.) 1975-1976 -9.30°F
10.) 1948-1949 -9.00°F

* December 1924 is missing.

Top 10 Warmest Low Temperature Winter
1.) 2000-2001 8.50°F
2.) 2015-2016 8.13°F
3.) 2002-2003 7.53°F
4.) 1976-1977 6.73°F
5.) 2014-2015 5.37°F
6.) 1985-1986 4.60°F
7.) 1944-1945 4.47°F
8.) 1941-1942 4.43°F
9.) 1928-1929 4.27°F
10.) 2013-2014 4.13°F

Top 10 Coolest High Temperature Winter
1.) 1924-1925 0.90°F*
1.) 1964-1965 2.50°F
2.) 1970-1971 3.53°F
3.) 1942-1943 4.27°F
4.) 1946-1947 4.57°F
5.) 1955-1956 4.60°F
6.) 1933-1934 5.20°F
7.) 1974-1975 5.30°F
8.) 1968-1969 5.33°F
9.) 1973-1974 5.63°F
10.) 1975-1976 5.67°F

* December 1924 is missing.

Top 10 Warmest High Temperature Winter
1.) 2000-2001 21.43°F
2.) 2015-2016 20.47°F
3.) 2002-2003 19.30°F
4.) 1976-1977 18.87°F
5.) 1928-1929 18.23°F
6.) 1944-1945 18.17°F
7.) 1985-1986 17.97°F
8.) 2014-2015 17.80°F
9.) 1941-1942 17.63°F
10.) 1986-1987 17.57°F

Top 10 Wettest Winter
1.) 1928-1929 11.89
2.) 1934-1935 11.55
3.) 1943-1944 11.26
4.) 1927-1928 10.88
5.) 1931-1932 10.78
6.) 1984-1985 10.65
7.) 2000-2001 10.61
8.) 1991-1992 10.38
9.) 1989-1990 10.26
10.) 1930-1931 10.22

Top 10 Driest Winter
1.) 1924-1925 3.12*
1.) 1968-1969 4.13
2.) 1929-1930 5.47
3.) 1949-1950 5.52
4.) 1977-1978 5.78
5.) 1973-1974 5.84
6.) 1933-1934 5.87
7.) 2009-2010 5.87
8.) 1981-1982 5.93
9.) 1972-1973 6.07
10.) 1935-1936 6.17

* December 1924 is missing.

The coldest winter since 1925 occurred in 1964-1965, while the warmest is 2000-2001. The wettest winter is 1928-1929, while driest is 1968-1969. Some of Alaska’s warmest winters occurred when the Lower 48 was cold. It shows if it is cold in the Lower 48, it is more likely to be warmer in Alaska. The cold air has to go somewhere. It is largely due to upper level ridging over Alaska, called the East Pacific Oscillation (EPO). It is largely affected by “The Blob”, which I created a data called the Northeast Pacific Warm Pool (NEPWP). The warmer the NEPWP is, the more negative EPO is.

Data came from Divisional Data Select, National Temperature and Precipitation Maps, and NOAA/NCEI Climate Division data: Mapping and Analysis Web Tool

Spring 2016 Report

Flower01

It is deja vu! Spring 2016 was wet like Spring 2015 despite El Nino fading. To make matters worse, there was severe flooding in April and May, which dumped up to 24 inches of rain in both events! That is something you see with tropical cyclones or core rain events with warm core low pressure systems. They are often from tropical cyclones.

For Texas, it has been mostly wet. For others, where’s the rain?

2016_SpringPrecipitationDivisionalRanks

2016_SpringTemperatureDivisionalRanks

America 2016 Spring
Mean Temperature: 53.68°F
Total Rainfall: 9.03

America Spring Temperature (1895-2016)
Mean: 51.10°F
Median: 50.87°F
Standard Deviation: 1.39
Lowest: 56.18°F (2012)
Highest: 47.37°F (1917)

America Spring Rainfall (1895-2016)
Mean: 7.95
Median: 7.95
Standard Deviation: 0.98
Lowest: 5.58 (1925)
Highest: 10.40 (1991)

It was a warm spring, but not a record breaking spring for America. It is nowhere like 2012. The average temperature is 1 standard deviation from the mean in terms of temperature. That is unusual, but not extraordinarily warm. If it was 2 standard deviation or greater that would be abnormal. It was abnormally warm for spring time in America.

It was much wetter as a whole. In fact, the Spring 2016 rainfall total is exceeds by 1 standard deviation. It was a wet spring for most of America.

Texas 2016 Spring
Mean Temperature: 66.27°F
Total Rainfall: 11.90

Texas Spring Temperature (1895-2016)
Mean: 64.76°F
Median: 64.73°F
Standard Deviation: 1.76
Lowest: 69.67°F (2012)
Highest: 59.93°F (1931)

Texas Spring Rainfall (1895-2016)
Mean: 7.37
Median: 7.05
Standard Deviation: 2.34
Lowest: 2.53 (2011)
Highest: 16.48 (2015)

It was warmer than normal for spring in Texas. It is 1 standard deviation from the mean.

It is wet, but not like 2015, which was wetter. Actually, it is the eighth wettest spring on record as it ties with 1914. It was indeed a wet spring for Texas, like last spring. Having two wet springs back to back is a rarity. Here is the top 10 wettest spring in Texas since 1895.

Top 10 Wettest Spring In Texas
1.) 2015 16.48
2.) 1957 14.75
3.) 1905 12.59
4.) 1941 12.43
5.) 1900 12.36
6.) 2007 12.16
7,) 1922 11.97
8.) 1914/2016 11.90
9.) 1997 10.85
10.) 1929 10.79

Many of the wettest springs occurred when El Nino is developing (1914, 1957, 1997, and 2015), persistent (1905 and 1941) or dying (1900 and 2007). 1922 was La Nina, while 1929 was Neutral. It shows that El Nino does have an impact on spring rainfall,whether is strengthening or dying. Interesting to note hurricanes made hurricanes made landfall in 1900, 1929, 1941, 1957, and 2007. Two were major hurricanes, Galveston Hurricane and Audrey in 1957.

Upper Texas Coast 2016 Spring
Mean Temperature: 71.07°F
Total Rainfall: 20.77

Upper Texas Coast Spring Temperature (1895-2016)
Mean: 68.54°F
Median: 68.42°F
Standard Deviation: 1.69
Lowest: 72.83°F (2012)
Highest: 63.37°F (1931)

Upper Texas Coast Spring Rainfall (1895-2016)
Mean: 10.58
Median: 10.02
Standard Deviation: 4.53
Lowest: 2.43 (2011)
Highest: 24.75 (2015)

It has been a warm spring. It is nearly 2 standard deviations from the mean. It was abnormally warm spring. It is the eighth warmest spring for Upper Texas Coast. Here is the top 10 warmest spring in Texas since 1895.

Top 10 Warmest Spring In Upper Texas Coast
1.) 2012 72.83°F
2.) 2011 72.03°F
3.) 2006 72.00°F
4.) 2000 71.57°F
5.) 1967 71.43°F
6.) 1963 71.40°F
7.) 1908 71.37°F
8.) 2016 71.07°F
9.) 1991 71.00°F
10.) 1925 70.97°F

Spring 2012 was warm everywhere, especially up north. 2011 was very warm as well. Who could forget Summer 2011? It was Hell for sure, which was made worse by the drought. The warmth is due to abnormally warm low temperatures. All that heavy rain makes the air more humid. Humidity keepers temperatures from going too cold or hot. It is the seventh warmest low temperature for spring. Here is a divisional ranking map of low and high temperatures.

2016_SpringMinTemperatureDivisionalRanks

2016_SpringMaxTemperatureDivisionalRanks

It was very west for Upper Texas Coast. It exceeds 2 standard deviations, which makes a near outlier. In fact, it is the third wettest spring on record! Yes, third wettest. There have been two back to back wet springs in the Upper Texas Coast. Here is the top 10 wettest spring in Upper Texas Coast since 1895.

Top 10 Wettest Spring In Upper Texas Coast
1.) 2015 24.75
2.) 1997 22.18
3.) 2016 20.77
4.) 1900 19.54
5.) 1957 19.32
6.) 1929 19.06
7.) 1914 18.54
8.) 1944 18.33
9.) 1993 18.32
10.) 1905 17.60

Many of the wettest springs for Upper Texas Coast occurred when El Nino is developing (1914, 1957, 1997, and 2015), persistent (1905) or dying (1900). 1944 had a developing La Nina from Neutral. 1929 was Neutral. April and May 1929 had heavy rain that led to massive flooding in the Houston area. The 1929 flood is considered an epic flood on par with December 1935 and Tropical Storm Allison in 2001. It shows that El Nino does have an impact on spring rainfall,whether is strengthening or dying. Interesting to note hurricanes made hurricanes made landfall on Upper Texas Coast in 1900, 1929, and 1957. Two were major hurricanes, Galveston Hurricane and Audrey in 1957.

Could this be a harbinger of things to come? America has not seen a Category 3 or stronger hurricane since Wilma in 2005. Now, if we lowered Category 3 by 1 mph from 111 mph to 110 mph, than Ike would be a major hurricane. Even than, America has not seen a major hurricane make landfall since 2008, which is a long stretch. Keep in mind, hurricane re-analysis is happening, so this long stretch of no Category 3 or stronger hurricanes we are seeing may not be the longest.

Northeast Pacific Warm Pool

NEPWP

I first noticed an area of warm water in the Northeast Pacific in the cold Winter of 2013-2014. I call it the Northeast Pacific Warm Pool (NEPWP) and created an anomaly data from NOAA ERSST v3. The NEPWP Region is between 35°N and 50°N and 165°W and 135°W. It goes back to 1870 and anomaly is based on 1981-2010 average. Here is the Northeast Pacific Warm Pool data I created from 1870 to 2014. Keep in mind, any data before 1950 should be taken with a grain of salt as they are not directly measured.

Here is what the 500 millibar (18,000 feet) Geopotential Height anomaly looked like this past winter winter.

20132014Winter_500mbGeopotentialHeight_Anomaly_NH

Notice a great deal of ridging over Alaska, Gulf of Alaska, and Siberia. The ridging over Alaska is the negative phase of East Pacific Oscillation (EPO). It is the Pacific equivalent to the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). So, how does NEPWP and EPO correlate. Here is data for meteorological winter (December to February), spring (March to May), summer (June to August), and fall (September to November). The data is from 1948 to 2014 up to Summer. The EPO link is daily, but I converted it to monthly.

DJF NEPWP EPO
r = -0.45
p < 0.05

MAM NEPWP EPO
r = -0.47
p < 0.05

JJA NEPWP EPO
r = -0.37
p < 0.05

SON NEPWP EPO
r = -0.40
p < 0.05

NEPWP and EPO are strongly correlated. Cooler NEPWP is more favorable for positive EPO, while warmer NEPWP is more favorable for negative EPO. Warmer water allows ridging to develop over Alaska and Northwestern Canada. NEPWP could give us an idea about EPO even before 1948. A warm NEPWP have negative EPO, while cool NEPWP have positive EPO. Of course, correlation does not mean caustation, but it is a factor.

The ridging allows cold air to come down to the Lower 48, which lead to an Arctic blast and cold winters. As the Lower 48 froze, Alaska, Northern Canada, and Western US are warm due to the ridging. The previous two winters were quite warm compared to this past winter. Here is a surface temperature anomaly map of Winter 2013-2014.

20132014Winter_SurfaceTemperature_Anomaly_NH

Notice that the Eastern two-thirds of North America is quite cold. The polar regions are unusually warm as it is with the Western US. The ridging made those areas warm and caused the jet stream to pull in cold air that is normally in the polar regions. The ridging also plays a role in precipitation as a map shows which areas are drier and wetter than normal.

20132014Winter_PrepRate_Anomaly_NH

The Western US is very dry. No surprise they are in a drought, especially in California, which is really dire. The ridging shunts the low pressure systems away from California and Western US. Interesting to note that Alaska is not dry despite the ridging, but the Bering Sea and western point of Aleutian Islands are dry. Interesting fact, the Aleutian Islands are the westernmost and easternmost point in America as it crosses the 180 degree longitude. Some of the Aleutian Islands are west of 180 degrees longitude in the Eastern Hemisphere.

Wonder what the geopotential height anomaly is like at 18,000 feet (500 millibar level) during a moderate and strong warm NEPWP. I define moderate warm NEPWP is 0.5 to 0.899 or 5.0 to 8.99 above 1981 to 2010 mean, while strong warm NEPWP as 0.9 or 9.0 and above 1981 to 2010 mean. Here is a map of what it looks like. All anomaly maps from here are for winter from December to February and since 1950.

DJF_ModerateToStrongWarmNEPac_500mbGeopotentialHeight_Anomaly_NH

Notice ridging over Alaska, the warm water allows ridging to form, which is a negative EPO. There is troughing over Northern Canada and Greenland, which is a positive NAO. Interesting to note there is ridging over the Southeast US. How is winter temperature like during a moderate and strong warm phase of NEPWP?

DJF_ModerateToStrongWarmNEPac_SurfaceTemperature_Anomaly_NH

Interesting to note that Canada and Northern US is very cold when there is a moderate and strong NEPWP. The Southern US is warm, which is rather interesting. Overall, Southern US is warmer and Northern US and Canada is cooler during the winter with a moderate and strong NEPWP in place. The troughing over Canada and Greeland keeps Canada and Northern US colder, which bottles up cold air. A positive NAO gives the Southern US a warmer than normal winter. Opposite when NAO is negative, which is colder than normal.

Wonder what a warm NEPWP does to rainfall? Here is a precipitation rate map.

DJF_ModerateToStrongWarmNEPac_PrepRate_Anomaly_NH

The Western US and Canada is very dry. That is no surprise as California is in a severe drought at the time of this article. Parts of the Southeast, Midwest, to East Coast is wetter than normal. Overall, a warm NEPWP does not have much impact on precipitation in the winter.

Regardless, there have been big freezes and major winter events when there is a moderate and strong warm NEPWP. Late January to early February 1949 had a huge Arctic blast. January 1962 had a huge Arctic blast which is considered one of the big freezes in history as it set temperature and surface pressure records. Winter of 1978-1979 is one of the coldest winters on record for America since 1895. It occurred when America saw back to back cold winters in the late 1970s. December 1989 had a huge freeze that is on the level of 1886, 1895, 1899, and 1983. A year after the December 1989 freeze, another huge freeze hit in December 1990, which hit the Western US. An epic White Christmas came in 2004 for Texas.

It is opposite when the NEPWP is in a cool phase. I define moderate cool NEPWP is -0.5 to -0.899 or -5.0 to -8.99 below 1981 to 2010 mean, while strong cool NEPWP as -0.9 or -9.0 and below 1981 to 2010 mean. There is troughing over Alaska, Siberia, and Southeastern US. There is ridging over Northern Canada and Greenland. Troughing over Alaska is a positive EPO, while ridging over Northern Canada and Greenland is a negative NAO.

DJF_ModerateToStrongCoolNEPac_500mbGeopotentialHeight_Anomaly_NH

So, how is temperature affected by cool phase of NEPWP? Here is a temperature anomaly map.

DJF_ModerateToStrongCoolNEPac_SurfaceTemperature_Anomaly_NH

It is not as warm during cool NEPWP. As mentioned, since there is ridging over Northeastern Canada and Greenland, it shunts the cooler air down south. The ridging over Northeastern Canada and Greenland is a negative NAO. As a result of ridging, Northeast Canada and Greenland is warmer than normal. It is cold over Alaska, Northern Asia, and Siberia due the trough locking up cold air. Does cool NEPWP have the opposite affect on precipitation from warm NEPWP?

DJF_ModerateToStrongCoolNEPac_PrepRate_Anomaly_NH

Western US and Canada are wet, which is opposite from warm NEPWP. Southeast Texas, Southeast, and Northeast have wetter than normal winter. The Northeast is not affected by cool or warm NEPWP. It has more of an affect west of the Mississippi River. Cool and warm NEPWP have impact on rainfall on different areas. It could dry in one area and wet in the other area.

Even when the NEPWP is in a moderate to strong cool phase, freezes and major winter events have happened. Late January to early February 1951 had a huge freeze that covered North America and is one of the greatest freezes between 1949 to 1962. Houston had the longest below 32°F for 5 days in the 1951 freeze!

It shows that NEPWP is not the only factor when it comes to winter weather. There is El Nino Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO), NAO, AO, and EPO. NEPWP is certainly a factor and it influences EPO.

2011 Hurricane Season So Far and Stats

We are now in October of the 2011 Atlantic Hurricane Season. So far we have 16 storms, 4 hurricanes, and 3 major hurricanes with an Accumulated Cyclone Energy (ACE) of 99. So, how is this season stacking up to be? Is it truly an active season? All statistical values are from 1870 to 2010.

16 Storms
Mean = 9
Std Dev = 4.02
Kurtosis = 2.88
S.E. Kurt = 0.41
Skewness = 1.14

We are way above average in number of storms. Anything above a standard deviation of 4 is extremely active.

4 Hurricanes
Mean = 5
Std Dev = 2.61
Kurtosis = 0.75
S.E. Kurt = 0.41
Skewness = 0.80

We are close to average in number of hurricanes. It is within average. Anything +/-3 is above or below average is unusually active or inactive.

3 Major Hurricanes
Mean = 2
Std Dev = 1.75
Kurtosis = 0.84
S.E. Kurt = 0.41
Skewness = 1.10

We have an average number of major hurricanes so far this season. Anything above standard deviation of 2 is active, which would be 4 or more major hurricanes.

ACE of 99
Mean = 91
Std Dev = 54.28
Kurtosis = 0.40
S.E. Kurt = 0.41
Skewness = 0.93

We are withing average of ACE for the 2011 season. Anything above standard deviation of 54 is hyperactive, which would be 145.

ACE/Storm of 6.2
Mean = 9.78
Std Dev = 4.22
Kurtosis = -0.18
S.E. Kurt = 0.41
Skewness = 0.58

The ACE/Storm is rather low, but within the average. Below average ACE/Storm would be below standard deviation of 4.22 or 5.56 or less ACE/Storm.

25% Became Hurricanes
Mean = 0.59 (59%)
Std Dev = 0.17
Kurtosis = 0.89
S.E. Kurt = 0.41
Skewness = -0.29

The percentage of storms that became hurricanes in the 2011 season is unusually low, at 25 percent. In a normal season, 59 percent of storms become hurricanes. Even if we subtract the standard deviation of 0.17 from the mean, it is 0.42 or 42 percent.

18.8% Became Major Hurricanes
Mean = 0.21 (21%)
Std Dev = 0.15
Kurtosis = -0.02
S.E. Kurt = 0.41
Skewness = 0.56

The percentage of major hurricanes is within average. An Atlantic season with 6 percent or less would be an outlier. The last season with such a low percentage was 1994. No major hurricanes formed in 1994 as it was a quiet year due to El Nino.

The last time we had a season with many storms in a short time was 2005, which is the most active season record. 2005 had 28 storms, 15 hurricanes, and 7 major hurricanes with an ACE of 248. 2005 is an outlier, except some things and I will show you that.

28 Storms
Outlier

15 Hurricanes
Outlier

7 Major Hurricanes
Outlier

ACE of 248
Outlier

ACE/Storm of 8.9
The ACE/Storm in 2005 is within the mean. The reason is many of those storms in 2005 formed close to land. The ACE/Storm of 2004 was 14.9 because only 15 storms formed that year and many formed in the open Atlantic, intense, and were long lived.

53.6% Became Hurricanes
The percentage of storms that became hurricanes in 2005 is also within in the mean. 15 hurricanes is an outlier in that regard, but when it comes to percentage, not so. Keep in mind that 28 storms formed in 2005 and that right there is an outlier.

18.8% Became Major Hurricanes
The percentage of storms becoming major hurricanes is also within the mean. 1999 had 12 storms and 5 became major hurricanes, which is 41 percent, which makes it more than 0.15 (15 percent) standard deviation above the mean.

Source of data.
NOAA HRD-How many tropical cyclones have there been each year in the Atlantic basin? What years were the greatest and fewest seen?