How Bad Is This Drought?

It has not rained much in Southeast Texas. In fact, we have not seen over 1 inches of rain since January and it has been 4 months in a row that the Upper Texas Coast has seen less than 1 inch per a month. In fact, October to May rainfall total is the driest on record as shown on the list of top 10 driest October to May rainfall total in the Upper Texas Coast.

1.) 2010-2011 14.17
2.) 1924-1925 15.20
3.) 1955-1956 16.60
4.) 1908-1909 16.74
5.) 1950-1951 17.36
6.) 1916-1917 17.90
7.) 1917-1918 17.92
8.) 1901-1902 18.10
9.) 1939-1940 18.67
10.) 1962-1963 19.26

However, when it comes to Palmer Drought Severity Index (PDSI), it is not the worst. PDSI uses uses temperature and rainfall information in a formula to determine dryness. 0 is considered normal, while negative value is drier, while positive value is wetter. Here is the list of lowest or worst PDSI for Upper Texas Coast.

1.) 1917-1918 -4.86
2.) 1924-1925 -3.85
3.) 1955-1956 -3.68
4.) 1999-2000 -3.57
5.) 1954-1955 -3.37
6.) 1916-1917 -3.30
7.) 1950-1951 -2.98
8.) 2005-2006 -2.93
9.) 1951-1952 -2.90
10.) 1915-1916 -2.87

The drought of 1917-1918 is the worst even to this very day. It is legendary in its own right. The 1950s was the longest drought in Texas as it lasted for 7 years. October 2005 to May 2006 has a lower PDSI than right now. The winter of 2005-2006 was abnormally warm, which would have a more negative PDSI. The PDSI for October 2010 to May 2011 in the Upper Texas Coast is -1.54, which is serious. To compound it, there are more people living in Texas today than in the late 1910s and 1950s. More people use water for drinking, farming, and watering their yards. It is going to worsen the drought as water supplies are becoming more strained.

If we do not see rain any time soon this summer, the drought will only get worse and easily be in the top 10 worst droughts for Upper Texas Coast in terms of PDSI. Also, if it is dry, it will get hotter as drier grounds is more favorable for heat. Moisture moderates air temperature. It is no surprise that wetter years are cooler than compared to drier years, which are warmer.

Here is a chart of Upper Texas Coast October to May PDSI from 1895 to 2011.

Here is a chart of Upper Texas Coast October to May rainfall total from 1895 to now.

It shows that droughts come and go. It is cyclical in nature. Here is the top 10 highest October to May PDSI for Upper Texas Coast.

1.) 1919-1920 4.35
2.) 1991-1992 3.94
3.) 1941-1942 3.60
4.) 1973-1974 3.47
5.) 1992-1993 3.47
6.) 1913-1914 3.35
7.) 1979-1980 2.96
8.) 1960-1961 2.85
9.) 2006-2007 2.71
10.) 1923-1924 2.41

Top 10 wettest October to May rainfall for Upper Texas Coast.

1.) 1991-1992 46.97
2.) 1940-1941 45.29
3.) 1913-1914 44.01
4.) 1994-1995 43.40
5.) 1925-1926 42.79
6.) 1943-1944 42.41
7.) 1949-1950 42.41
8.) 1992-1993 42.26
9.) 2006-2007 42.23
10.) 1990-1991 41.82

Some of the highest PDSI and rainfall came after droughts, so there is hope in the end. I do remember the early 1990s being very wet.

Here is a NCDC of May droughts for all of Texas.

The current drought for all of Texas is one of the worst droughts in history, along side with 1918 and 1956. If Texas does not get rain, it will be a serious problem for everyone.

As for why we have a drought, it is because of La Nina cycle of El Nino Southern Oscilliation (ENSO). This past October to May was La Nina. La Nina is the opposite of El Nino, in which the Pacific Ocean water off the coast of South America is cooler than normal. The cooler water pushes the jet stream further north, which causes storm systems to go further north than usual. That means all the energy is further away from Texas. In an El Nino, the jet stream is further south, which means storm travel further south than normal, which means a wetter year. Some of the wettest years happened in El Nino years. The correlation between La Nina and rainfall and PDSI is strong.


Pearson Correlation
r = 0.41
p-value = < 0.01


Pearson Correlation
r = 0.42
p-value = < 0.01

The correlation value and p-value are strong, so there is a significant relationship between ENSO and PDSI and rainfall.

Data Source
NOAA-Divisional Data

El Nino/La Nina Data
FSU-Japan Meteorological Agency ENSO SST

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