It is this time of the year. Winter is coming as Christmas is coming. It seems like Christmas comes sooner and sooner each year. One huge factor for this winter is the strong El Nino. It is one of the strongest El Nino since 1997-1998 if we go back to 1950. There were strong El Nino before 1950. 1877-1878, 1888-1889, 1896-1897, 1902-1903, 1904-1905, and 1940-1941 had strong El Nino.
Other factors to consider are Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and now Northeast Pacific Warm Pool (NEPWP). However, since this El Nino is large and strong and has significant impact, it will weigh in more than other factors listed. Since, we have a strong El Nino, here are my analog winters.
I choose these analog years because they are strong El Nino regardless of Eastern Equatorial or Modoki or Central Pacific. I did not include 1904-1905, 1987-1987, and 1992-1993 because the peak happened in Spring, unlike right now. Since, I go by divisional climate data, there is nothing before 1895, but there are local climate data before 1895, but it would be tedious to look at. However, I can look at upper air pattern and temperature anomaly in those analog years thanks to 20th Century Reanalysis Monthly Composites, which has 20CRV2c.
It shows troughing south of Alaska, which is a positive East Pacific Oscillation (EPO). A positive EPO is less favorable for freezes. Now, that does not mean the EPO will always be positive because it can go negative. A negative EPO would have ridging over Alaska, which means a better chance for cold blasts in the winter. There is also ridging off the east coast of Japan and surrounding Antartica.
So, how does it affect temperature and rainfall? Let’s start with temperature.
The Northern part of America is warm as the jet stream travels further south than normal. It is also warm throughout South America as El Nino is off the coast of South America. It is cold in the Arctic and Antartica region. El Nino also effects rain.
In terms of rainfall, Southern and Western US, West Coast of South America, Central Africa, Northern Pakisan/Afghanistan, and Southeast China is wetter than normal. The wettest is the area over where El Nino is. Meanwhile, most of Eastern South America, Philpppines, Indonesia, Northern Australia, Southeast Africa, Madagascar, and Central America are going to be dry. Droughts are usually a huge problem during El Nino for those areas.
Keep in mind temperature and rainfall records often do not go back to the 19th Century in many parts of the world. Let’s take a look at divisional climate in America. The data goes back to 1895, so there will be no data available prior to 1894, which means no data for 1877-1878 and 1888-1889. Let’s start with rainfall.
Rainfall is heavier to the south as mentioned previously due to jet stream. The jet steam carries more storm systems over the Southern US. Meanwhile, the Northern US is drier as a result. Generally it is wetter, but not always. Here is the wettest and driest analog years.
Driest: 1896-1897 6.68
Wettest: 1997-1998 8.99
Analog Mean: 7.61
Analog Standard Deviation: 0.87
Overall Mean (1895-2015): 6.74
Overall Standard Deviation (1895-2015): 0.88
Driest: 1896-1897 3.49
Wettest: 1991-1992 12.72
Analog Mean: 7.09
Analog Standard Deviation: 2.63
Overall Mean (1895-2015): 4.82
Overall Standard Deviation (1895-2015): 1.83
Upper Texas Coast
Driest: 1896-1897 5.30
Wettest: 1991-1992 23.54
Analog Mean: 13.18
Analog Standard Deviation: 5.24
Overall Mean (1895-2015): 10.24
Overall Standard Deviation (1895-2015): 3.53
1896-1897 was dry overall for America including Texas and Upper Texas Coast. The wettest is 1991-1992 and 1997-1998. Overall, analog years are wetter than normal. How does temperature fare?
The Southern US is cooler than normal. It is due to the perpetual cloud coverage and rain, which keeps things cooler than normal. There can also be cold blasts during a strong El Nino. Up north is warmer than normal in the winter. Some people would like it as those areas are cold in the winter. Here is the warmest and coolest analog years.
Coolest: 1902-1903 30.03°F
Warmest: 1991-1992 36.35°F
Analog Mean: 33.55°F
Analog Standard Deviation: 2.29
Overall Mean (1895-2015): 32.31°F
Overall Standard Deviation (1895-2015): 2.01
Coolest: 1972-1973 43.83°F
Warmest: 1991-1992 46.90°F
Analog Mean: 46.90°F
Analog Standard Deviation: 1.89
Overall Mean (1895-2015): 47.28°F
Overall Standard Deviation (1895-2015): 2.31
Upper Texas Coast
Coolest: 1972-1973 50.13°F
Warmest: 1997-1998 55.93°F
Analog Mean: 53.47°F
Analog Standard Deviation: 1.09
Overall Mean (1895-2015): 53.97°F
Overall Standard Deviation (1895-2015): 2.63
America is warmer overall in those analog years. That is due to the Northern US being warmer than normal. Texas and Upper Texas Coast is cooler than normal due to all the rain and clouds over the Lone Star State. The combination and cooler and wetter weather increases the chance for winter weather for Southeast Texas. What about snow?
In Southeast Texas, snow has occurred in these analog years.
The data record from Houston Weather Bureau (WB) in January 1897 has handwriting I cannot read too well. It says that snow and a blizzard happened in Houston on January 25, 1897. There was a hard freeze from January 25-29. It did not go above freezing between January 26-29. It is a freeze in par with other huge freezes in January/February 1951 and February 1989 freezes! February 12, 1958 saw a snow flurry. The Winter of 1972-1973 had three snowfall events of over one inches. That is unheard in Houston area! It is also one of the coldest winters on record for Upper Texas Coast on par with 1977-1978 and 2009-2010. There is no weather record from 1877-1878 in Southeast Texas, so I do not know what the weather was like that time. 1888-1889 had no snowfall recorded. There were some freezes in January and February of 1889. It was more of a wet winter that time. This is from Houston WB records.
Another thing to consider is severe weather. I created a GIS heat map of tornado, hail, and strong wind for those analog years. The tornado, hail, and strong wind is from the 1950s and later. They are all within 300 miles. Let’s start with tornadoes.
Tornadoes are generally rare in the Winter, but they can happen. In analog winters, tornadoes are most common from Southeast Texas, Louisiana, Arkansas, and Missouri. The second hot spot is Central Florida. El Nino causes the jet stream to go further south, allowing storms to track over. These storms dump heavy rain and can produce severe weather. Let’s look at strong winds from storms.
The entire Eastern US is most at risk for strong winds. Also, Central California is at most risk for strong winds. Strong winds can from severe thunderstorms and storm systems, a tight pressure gradient of low and high pressure, or a cold front passes. So, what effect does El Nino have on hail in the winter?
The highest risk for hail is Texas, Oklahoma, Arkansas, Louisiana, Southern Kansas, and Southern Missouri. There is also a higher risk in Alabama and Georgia and Southern Florida. Not a good thing as severe weather is generally more common in an El Nino winter in the Southern US.
The heat map could give us a good idea where severe weather events could happen this winter. Frankly, I would be just as concerned about severe weather, especially in the Southern US. I would not be surprised if this winter will be known as the winter of severe weather besides winter weather.
Past El Nino does not guarantee that this El Nino will be similar. All El Nino’s are different. Regardless, I expect an interesting winter coming. So fasten your seatbelt tightly. It will be a rough ride for sure.