2015 SummerWeather Outlook

Temperatures, Precipitation,

Drought, and Hurricanes

Visit www.ercot.com/about/weather for daily and seasonalweather updates.

The past two springs (2013 and 2014) have averaged at slightly cooler than

normal. That’s certainly possible for 2015 as well, though I believe there will be enough warmer potential mid-to-late

spring that this season may average a bit warmer than the past couple of

springs. But not to the very warm levels of 2011 and 2012.

Introduction

Today’s weather outlook is intended to offer a preliminary look at the summer temperature and precipitation potential. We’ll learn how this may impact the current drought in Texas. And we’ll see if the hurricane season can offer any assistance.

Objectives

At the completion of this course of instruction you will:

Be familiar with the hottest summer on record for the state of Texas Know which ocean the ERCOT meteorologist monitors most for potential influence of

the Texas weather pattern Be able to identify the historical year that is being applied as the primary historical

match (analog) for the summer of 2015 Know the probability of summer 2015 being hotter than normal Recognize the total combined number of tropical storms and hurricanes (named

storms) expected in the Gulf of Mexico in 2015

TEMPERATURE OUTLOOKSummer 2015

Summer 201186.8°

Summer 199884.2°

Repeat of 2011?

Same difference as 2nd to 55th (1998 to 1929)

2.6 degree difference

(Jun-Aug)

Past Six Summers

2013: 21st hottest, 81.2° 2012: 13th hottest, 81.5° 2010: 11th hottest, 81.6° 2009: 29th hottest, 80.8°

2014: 50th hottest, 80.4°2011: 1st hottest, 84.6°

(POR 1895-current, Jun-Sep; all of Texas)

Warming trend from the West over the past several seasons

Positive (warm) phase of the Pacific Decadal Oscillation(PDO) has played a significant role. The Pacific Oceanis the primary driver of Texas weather patterns.

Building the Forecast1. Winter temperature and precipitation patterns2. Winter upper level steering currents3. Winter sea surface temperature pattern4. El Niño Southern Oscillation (ENSO)5. PDO, AMO, PNA, WPO, EPO6. Drought

Winter of 2014-1569th Coldest Winter on Record in Texas (1895-current)

69th Driest Winter on Record in Texas

ENSO

200mb

SST

All 2/12/15ENSO/200/SST

2003, 1994,20051987, 19771978, 1959

PDO

Building the forecast

PDO-AMO(was best for winter 2014-15)

Building the forecast

Top Historical Matches

2003 1994 1977

200519591988

Summer 2015

Summer Temperatures

2003 is being applied as the best historical match

Latest set of historical years(as of 3/26/15)

Summer TemperaturesLast Year

(for review)

10yr 30yr

Summer Temperatures

Summer 2015Preliminary temperatures(2/27/15)

Summer 2014 TemperaturesLast Year

(for review)

10yr

Summer 2015 Temperatures

Continue to rely on a pattern, which has set up long-term. Hot West,mild East.

Probabilities of an overall:Hotter than normal summer: 20%Near normal summer: 35%Cooler than normal summer: 45%

Unlikely to rank with the summers of 2010-2013 for heat

Summer TemperaturesBy month

Best opportunityto break into ahotter pattern will be in September

What Others Are Saying

PRECIPITATION OUTLOOKSummer 2014

Past Six Summers

2013: 64th driest, 10.89” 2012: 52nd driest, 10.35” 2010: 105th driest, 13.49” 2009: 60th driest, 10.78”

2014: 65th driest, 10.93”2011: 1st driest, 3.60”

(POR 1895-current, Jun-Sep; all of Texas)

Top Historical Matches

2003 1994 1977

200519591988

Summer Precipitation

2003 is preferred

Summer Precipitation

Summer Precip2015

(2/27/15)

Summer Precipitation

80-120%Near normal

Similar to last summer; Possibly a bit wetter

DROUGHT OUTLOOKSummer 2014

Drought

Texas Reservoirs at 70.5% (Apr 14)

Drought

35.5% 2014-04-0736.4%, 2015-04-14

628.5 of 681ft

Drought

Drought

Drought

Drought

Drought

80-120%Near normal

HURRICANE OUTLOOKSummer (and Fall) 2014

Hurricane Forecast

Historical Averages

Named Storms: 12Hurricanes: 6Major Hurricanes: 3

Hurricane Forecast

Hurricane ForecastENSO is a strong factor in determiningthe Hurricane season (number and intensities).

Will the current weak El Niño continueInto the hurricane season?

Hurricane Forecast

Factors in DeterminingNumbers and Intensities

ENSOSaharan DustDry AirVertical Wind ShearOcean Temperatures

Hurricane ForecastWhat happened last year?

MDA/EarthSat: 12/6/2

NOAA: 8-13/3-6/1-2

Colorado State University: 9/3/1*

WSI/TWC: 11/5/2

ERCOT: 9/5/2

2014 Actual: 8/6/2

Normal: 12/6/3

*increased with a July update

Hurricane Forecast

12 6 3

Hurricane Forecast

Total Named Storms: 11Total Hurricanes: 6Major Hurricanes: 2

Named Storms in Gulf: 4-5Named Storms in Western Gulf: 2-3Hurricane in Gulf: 1-2Major Hurricane in Gulf: 0-1Named Storms with Texas Landfall: 0 or 1Hurricanes with Texas Landfall: 0 or 1

Near normal but a bit more active than 2014 –Especially in the Gulf of Mexico

TRENDSLong-Term Historical

2014 2011

6 of the hottest 21summers on record (1895-current)in Texas have occurredsince 2000.

•2011 (1)•2012 (9)•2009 (13)•2001 (15)•2010 (18)•2006 (21)

However …

5 of the hottest 21(6 of 22, and 5 of the top 12)summers on recordin Texas occurred in the 1950s.

19 of the 30 hottest summerson record occurredprior to 1960.

2015 2011

Of the driest one-third of years since 1895, 15 of them have occurred since 1955. 25 occurred prior to 1955.

The 1950s had the most dry years (6) followed by the 1930s, 20s, and 10s.

Of the wettest one-third of years since 1895, 23 of them have occurred since 1955. 17 occurred prior to 1955.

Between 1998 and 2013 (PDO-), an average of 16/8/3.

Between 1976 and 1997 (PDO+), an average of 10/5/2.

Between 1943 and 1975 (PDO-), an average of 10/6/3.

2013 and 2014 combined had fewer hurricanes and tropical storms than 2012.Quietest back-to-back yearssince 1993-1994.

Summary

80% likelihood of either normal or below normal temperatures for the summer as a whole, continuing a trend that began in the autumn of 2013

Improvements to the drought may be limited. Likely still an issue for portions of Texas following the summer season, but not expecting deteriorating conditions

Hurricane season holds a bit more potential than the previous two years – but should El Niño hold, that could hamper the potential

QuestionsQuestions

????

51

1. ______ was the hottest summer on record for Texas.

a) 2009b) 2010c) 2011d) 2012

52

2. Which ocean has shown the best correlation to Texas weather patterns?

a) Atlanticb) Indianc) Pacificd) Saturn

53

3. The historical year that is being applied as the primary historical match for the Summer 2015 is______?

a) 2002b) 2003c) 2004d) 2005

54

4. Percentage probability for the summer of 2015 to be hotter than normal: ____?

a) 10%b) 20%c) 35%d) 45%

55

5. The number of named storms forecasted in the Gulf of Mexico for 2015 are _______?

a) 0-1b) 2-3c) 4-5