2014-2015 Winter

Spring has arrived as days get longer each day. It has been a winter of really cold or warm. The Northeast basked in deep freezes and snow. The Western US was warm like if summer stayed. How did Winter 2014-2015 stack up? Let’s start with America.

America
Temperature: 34.44°F
Rainfall: 6.04

1895-2015 Winter Statistics
Winter Temperature Mean: 32.31°F
Winter Temperature Median: 32.48°F
Standard Deviation: 2.02

Winter Rainfall Mean: 6.74
Winter Rainfall Median: 6.69
Standard Deviation: 0.88

The average winter temperature is outside the standard deviation of the mean. It was an abnormally warm winter. The US had its 99th warmest winter on record, tying with 1932. In fact, it is in the top 20 warmest winters since 1895.

Top 20 Warmest Winter
1.) 1999-2000 36.48°F
2.) 1991-1992 36.35°F
3.) 2011-2012 36.34°F
4.) 1998-1999 36.27°F
5.) 1997-1998 35.90°F
6.) 2001-2002 35.66°F
7.) 1994-1995 35.56°F
8.) 2005-2006 35.49°F
9.) 2004-2005 35.46°F
10.) 1953-1954 35.33°F
11.) 1933-1934 35.28°F
12.) 1982-1983 35.27°F
13.) 1952-1953 35.25°F
14.) 1920-1921 34.80°F
15.) 1980-1981 34.73°F
16.) 1975-1976 34.59°F
17.) 1931-1932/2014-2015 34.44°F
18.) 1986-1987 34.42°F
19.) 2012-2013 34.32°F
20.) 1930-1931 34.03°F

How come despite the bitter cold winter in the Northeast. The Western US had a very warm winter. The Western US is much larger than the Eastern US. Here is a division temperature ranking.

2014-2015_WinterTemperatureDivisionalRanks

Notice the Eastern US had cold winters, while Western US had warm winters. I know that the Northeast had cold January and February as shown in this map.

201412_WinterTemperatureDivisionalRanks

201501_WinterTemperatureDivisionalRanks

201502_WinterTemperatureDivisionalRanks

Some areas had their coldest February on record. Winter came rather late. December 2014 was quite warm as seen this divisional map. It was like if winter did not want to come in December 2014.

So, why this happened you ask? Here is a upper level map at 18,000 feet of Northern Hemisphere.

2014-2015Winter500mbGeopotentialAnomaly

2014-2015_500mbGeopotentialHeightMean_NH

There is ridging over Alaska and Western US. The ridging over Alaska is the negative East Pacific Oscillation (EPO), West Pacific Oscillation (WPO), and positive Pacific North America Teleconnection (PNA). The ridging diverts cold air into the Northeast, where there is troughing. The persistant troughing allows cold air to come down south from the Arctic and Siberia. The troughing over Northeast Canada and Greenland is a positive North Atlantic Oscillation (NAO). Normally, a positive NAO favors warm winters for the US. However, since EPO and WPO are negative, while PNA is positive, it overpowered a positive NAO. It shows that NAO is not the only factor for cold winters. It is vice versa when NAO is very negative, while EPO and WPO are positive, while PNA is negative.

How did 2014-2015 Winter treat Texas?

Texas
Temperature: 47.77°F
Rainfall: 4.89

1895-2015 Winter Statistics
Winter Temperature Mean: 47.28°F
Winter Temperature Median: 47.27°F
Standard Deviation: 2.31

Winter Rainfall Mean: 4.82
Winter Rainfall Median: 4.72
Standard Deviation: 1.83

Winter was normal as it is close to the mean. It was nowhere like last winter, which was much colder. To make that up, it was wetter than last winter. More rain fell than last winter, which was a dry winter. That is a good thing as Texas is still reeling from the drought. How was the Upper Texas Coast like?

Upper Texas Coast
Temperature: 53.60°F
Rainfall: 9.64

1895-2015 Winter Statistics
Winter Temperature Mean: 53.96°F
Winter Temperature Median: 53.90°F
Standard Deviation: 2.63

Winter Rainfall Mean: 10.24
Winter Rainfall Median: 9.86
Standard Deviation: 3.53

Temperature and rainfall were within average even with a weak El Nino. There was snow in the Texas Panhandle and North Texas in February and even March. January was rather cold for the Upper Texas Coast. Despite it all, 2014-2015 was an average winter. A stark contrast from last winter for Texas, which was a cold and dry one.

So how did my forecast turn out? Let’s look at 2014-2015 temperature and precipitation.

2014-2015_WinterTemperatureAnomaly_NH

2014-2015_WinterPrecipitationAnomaly_NH

East of the Rocky Mountains was cooler, especially in the Northeast. The Western US was very warm like if Summer chose to stay in December. Also, Siberia was very warm, along with Europe. All the cold air went to the Eastern US this past winter. Many areas in the Western US had record warm winters for 2014-2015.

Most areas had near normal rainfall for Winter with the exception of British Columbia, Southern Mexico, and Mediterranean. The Western US drought situation is getting somewhat better. Better to have rain than no rain for sure.

Here’s the analog map for 2014-2015 Winter I created.

2014-2015_WinterTemperatureAnomaly_NH

2014-2015_WinterPrecipitationAnomaly_NH

The temperature anomaly for 2014-2015 looks similar to the analog temperature anomaly map, with the exception of colder winter over Siberia and Arctic. Some of those analog winters were very cold like 1972-1973, 1976-1977, and 2009-2010.

The precipitation anomaly map does not look similar in those analog winters. The exception is the Mediterranean and Southern Mexico, which had wet winters in those analog winters. The analog years for America have wet winters in the southern half of America. That was not the case for this past winter.

What could next winter be like? It could depend on how El Nino behaves. We are likely seeing a multi-year El Nino, which last happened in 1986 to 1988. A multi-year El Nino is much rarer than a strong El Nino like in 1982-1983 or 1997-1998. I should know more later this year.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s