Texas Drought: June 2011 Stats - July 6, 2011
I'll finish up the weather modification story later, but first the National Climatic Data Center has posted the average precipitation numbers for June in Texas. I'll have those numbers, and the rankings, below. The records go back to 1895.
Meanwhile, NCDC also computes the most common and widely accepted drought index, the Palmer Drought Severity Index. When I'm asked how the current drought ranks historically, I turn to these numbers. Alas, they have not adjusted the early precipitation total to reflect the historical values we calculated, so it's almost certain that the droughts prior to the mid-1940s were a little bit more severe than the numbers indicate. Nonetheless, it's a nice index because it takes into account the effect of temperature on evaporation.
Last month, I reported that the drought was the third-worst on record for that time of year. That message often got truncated to third-worst, period. That's not what I meant. But I'm unhappy to report that the continued dry weather have made the mis-interpretation correct. The present Texas drought is the now third most severe statewide on record, going back to 1895. The severity is surpassed only by the 1950-1957 drought and the 1916-1918 drought.
Here are the peak PDSI drought intensities for some historical droughts, and the month in which peak intensity was achieved:
1950-1957 -7.80 September 1956
1916-1918 -7.09 August 1918
2011-? -6.37 June 2011 (so far)
1924-1925 -6.10 July 1925
1999-2000 -5.51 September 2000
2005-2006 -5.48 July 2006
1909-1911 -5.31 January 1911
If you're looking for the Dust Bowl, you won't find it here. The Dust Bowl drought was mainly in the central Plains, and in Texas only the northern Panhandle suffered the worst.
It has been so dry and hot that the PDSI has been declining at the unprecedented rate of over 1.00 per month. At that rate, we would continue to move up the list. It's sobering to note that we're in a virtual tie with the other really bad droughts at this point in the summer:
June 1956 -6.54
June 1918 -6.41
June 2011 -6.37
June 1925 -5.80
How hot is it? NCDC reports that the statewide average temperature was 85.2 F. That's a new record for June:
June 2011 85.2
June 1953 84.9
June 1998 83.9
June 1990 83.6
June 1980 83.3
June 1934 83.2
I don't know to what extent these numbers have been adjusted by NCDC for station moves, urban heating, etc., but even the most liberal allowance for artificial heating would place June 2011 as at least the second hottest June on record.
It's also on the list of warmest months, period:
July 1998 86.5
July 1980 86.3
August 1952 85.7
June 2011, July 2001, July 1969, July 1954, August 1902 85.2
Finally, as promised, here are our precipitation rankings. Note that all these numbers are subject to minor adjustments as late-reporting stations come in:
June: 0.99″ Fifth driest (tie). Record: 0.73″ June 1933.
May-June: 2.53″ Third driest. Record: 1.97″ May-June 1998.
April-June: 3.33″ Second driest. Record: 2.68″ April-June 1998.
March-June: 3.60″. Driest ever. Previous record: 5.04″ March-June 1896.
Note: March, April, May, and June were all among the ten-driest for their respective months.
February-June: 4.26″. Driest ever. Previous record: 6.45″ February-June 1917.
January-June: 5.81″. Driest ever. Previous record: 7.35″ January-June 1917.
December-June: 6.55″. Driest ever. Previous record: 7.89″ December-June 1916-17.
November-June: 7.58″. Driest ever. Previous record: 8.58″ November-June 1970-71.
October-June: 8.40″. Driest ever. Previous record: 10.38″ October-June 1924-25.
Note: October-June were the driest nine consecutive months ever. Previous record: 9.36″ June-February 1917-18. November-June was almost the driest eight consecutive months ever, but October-May was drier.
September-June: 13.17″. Third driest. Record: 12.96″ September-June 1924-25.
August-June: 14.44″. Second driest. Record: 14.37″ August-June 1924-25.
July-June: 19.49″. Seventh driest. Record: 15.50″ July-June 1924-25.
Final note: if Texas receives 2.00″ or less precipitation in July, it will break the August-July 12-month record.
From the Houston Chronicle, July 6, 2011.
John Nielson-Gammon, Climate Abyss