Oct 18, 2011

"Check back in 5 years" - Notes from the TX State Climatologist

I got to hear John Neilsen-Gammon, the State of Texas's Climatologist, speak about the "Basic mechanisms of the 2011 TX Drought" and our "Outlook for the future: short & long terms" last Friday. His presentation, loosely, was titled, "Texas Drought: Why You Should Get Used to It." His closing point, "If you want a better forecast, check back in five years."
 So, with that in mind, here are some highlight notes from the presentation.

Historical Data
  • For past 6 months, State of TX as a whole has recv’d an avg of 6” of rain, compared to a 110 yr historical avg of 18 inches (spring/summer months).
  • This is clearly the worst one-year drought on record. Nearest competitor 1956. Note 2007 also the wettest year on record. Note that 1980’s & 90’s were anomalously wet decades, averaging far more precipitation than historical weather and tree ring records show.
>> Gammon says: a) current drought is somewhat of a natural cycle, and b) current drought is somewhat of a correction in relation to wetter than usual decades, and c) current drought appears to be markedly exacerbated by global warming. <<
  • From a short-term perspective: this has been a top 10 drought for almost every location in TX.
  • Next most widespread drought was 1925. Longest term drought was 1956. 2011 is worst 9-month cumulative dryness of any single year on record.
  • Last major precipitation system across Texas was 9/27/2010. (Note that parts of far East Texas had already slipped into drought at the that time.) By March 2011 the drought had started statewide. By August, the coloration of the US Drought Monitor drought chart no longer did justice to showing the severity of Texas’s 2011 drought.

Current Data
  • 10/10/11 things are improving slightly, however most of the state at less than 50% of normal for 12 month precipitation accumulation period.
  • In addition to the drought, heat in 2011 is exceptional. TX temps are running neck & neck w Oklahoma’s as to which will have the hottest summer on record for the US, 2011. 

Projections Data
  • A confluence of climatological, meterological, and hydrological factors all implies that future droughts will be HOTTER. Dryness in the system drives heat increases. Evaporation management to become incredibly important.
>> Gammon says: It is not yet fully understood the value of trees and vegetation in helping to manage evaporation, hydrological systems, and high heat. It is believed that less moisture in the system means more intense heat. <<  
  • Will this continue? What can we expect?
  • Ocean temps say yes will continue. La Nina strengthens that possibility.
  • Climate models say we’re looking at a weak to moderate La Nina rest of this year, this means: below normal rainfall, above normal temperatures.
  • Global studies indicate that rainfall should increase everywhere except TX, next 20 years.
  • The evidence seems to be expanding that the worst possible conditions (a cold tropical pacific and a warm Atlantic Ocean) are increasing. However, and as always in climate science: It’s not clear which factors are going to win.

Drought outlook
> Returning to La Nina
o   Drought likely to continue
> Period of drought susceptibility
o   Ocean temps favor drought
o   Period will last 5 to 15 years
o   “Come back in 5 years for a better forecast”

This is the time for water planning.
What if we have 4 more years of 70-80% below normal precipitation?
Time to change our response to drought. Some ideas:
            > Take actions according to months of the year
            > Take actions according to whether we’re in an El Nino or La Nina

More Info
Office of the State Climatologist: http://atmo.tamu.edu/osc/
John’s blog: http://blog.chron.com/climateabyss/

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