weather trends

Weather TrendsWeather Trends

July 25, 2001

presentspresents

““Past, Present, and Future”Past, Present, and Future”

Ed KieserEd Kieser

Global UpdateGlobal Update

Recent PastRecent Past

Total Precipitation in InchesMarch through May 2001

Total Precipitation in InchesMarch through May 2001

Midwestern Regional Climate CenterIllinois State Water Survey

Champaign, IL

Total Rainfall in InchesJune 2001

Total Rainfall in InchesJune 2001


Champaign, IL

Total Rainfall Departure in inchesJune 2001

Total Rainfall Departure in inchesJune 2001


Champaign, IL

Total Rainfall in InchesJuly 1-24, 2001



Champaign, IL

Total Rainfall Percent of MeanJuly 1-24, 2001

Total Rainfall Percent of MeanJuly 1-24, 2001


Champaign, IL




Champaign, IL

Total Rainfall Departure in InchesJuly 18-24, 2001

Total Rainfall Departure in InchesJuly 18-24, 2001


Champaign, IL

Current SituationCurrent Situation

Current SituationCurrent Situation ExtremeExtreme

Variability!Variability!

Palmer Drought Severity IndexPalmer Drought Severity Index

Crop Moisture IndexCrop Moisture Index

Current Drought AssessmentCurrent Drought Assessment

National Weather Service PredictionNational Weather Service Prediction

Soil MoistureSoil Moisture

0

10

20

30

40

50

60

Surplus Adequate Short Very Short

Statewide

Northeast

Central

Corn ConditionsCorn Conditions

0

10

20

30

40

50

60

70

Good/Excellent

Fair Poor/ VeryPoor

Illinois

U.S.

U.S. Prev.

Soybean ConditionsSoybean Conditions

0

10

20

30

40

50

60

Good/Excellent

Fair Poor/ VeryPoor

Illinois

U.S.

U.S. Prev.

The Future?The Future?

Temperature OutlookJuly 31-August 4, 2001Temperature Outlook

July 31-August 4, 2001

Precipitation OutlookJuly 31-August 4, 2001Precipitation Outlook

July 31-August 4, 2001

Temperature OutlookAugust 2-8, 2001

Temperature OutlookAugust 2-8, 2001

Precipitation OutlookAugust 2-8, 2001

Precipitation OutlookAugust 2-8, 2001

Long-Lead OutlooksLong-Lead OutlooksLong-Lead OutlooksLong-Lead Outlooks

CL – Climatology – Chances are 1/3 CL – Climatology – Chances are 1/3 A, 1/3 N, 1/3 B.A, 1/3 N, 1/3 B.

A – Above Average.A – Above Average.N – Near Average.N – Near Average.B – Below Average.B – Below Average.

How to read them:

Long-Lead OutlooksLong-Lead OutlooksLong-Lead OutlooksLong-Lead Outlooks

Chance for “Above Average” Chance for “Above Average” increases from climatology by 10%.increases from climatology by 10%.

A – Odds for Above Average: 43 A – Odds for Above Average: 43 1/3%.1/3%.

N – Odds for Near Average: 33 N – Odds for Near Average: 33 1/3%.1/3%.

B – Odds for Below Average: 23 B – Odds for Below Average: 23 1/3%.1/3%.

Example: “10” around “A”:

Temperature OutlookAugust 2001

Temperature OutlookAugust 2001

Precipitation OutlookAugust 2001

Precipitation OutlookAugust 2001

Climate OutlookAugust-October 2001 Temperature

Climate OutlookAugust-October 2001 Temperature

Climate OutlookAugust-October Precipitation

Climate OutlookAugust-October Precipitation

Climate OutlooksTemperature

Climate OutlooksTemperature

Climate OutlooksPrecipitation

Climate OutlooksPrecipitation

Climate InfluencesClimate Influences

El Niño/La NiñaEl Niño/La NiñaEl Niño/La NiñaEl Niño/La Niña

ENSO: El Niño/Southern Oscillation.ENSO: El Niño/Southern Oscillation.El Niño: unusually warm water in El Niño: unusually warm water in

the eastern Pacific Ocean near the the eastern Pacific Ocean near the Equator.Equator.

La Niña: unusually cool water in La Niña: unusually cool water in the eastern Pacific Ocean near the the eastern Pacific Ocean near the Equator.Equator.

Some terms:

La NiñaLa NiñaLa NiñaLa Niña

Easterly trade winds strengthen, Easterly trade winds strengthen, causing more upwelling of cold causing more upwelling of cold water in the eastern Pacific Ocean.water in the eastern Pacific Ocean.

The reasons for the strengthening The reasons for the strengthening of the trade winds are still not fully of the trade winds are still not fully known. El Niño and La Niña are known. El Niño and La Niña are extreme phases of a naturally extreme phases of a naturally occurring climate cycle.occurring climate cycle.

Why does it occur?

Normal ConditionsNormal Conditions

Convective LoopConvective Loop

EquatorEquator

120ºE120ºE 80ºW80ºW


Every 2-7 years. The interval Every 2-7 years. The interval between events is irregular.between events is irregular.

Maximum cooling of the Pacific Maximum cooling of the Pacific waters is generally observed waters is generally observed between December and February, between December and February, the same time period as the the same time period as the maximum warming during El maximum warming during El Niño.Niño.

When does it occur?

00

180180OO 150150OOWW 120120OO

WW 090090OOWW

00OO

55OOSS

1010OOSS

NIÑO - 4NIÑO - 4 NIÑO - 3NIÑO - 3

160160OOEE

NIÑO - 2NIÑO - 2

NIÑO - 1NIÑO - 1

Sea Surface Temperature AnomaliesSea Surface Temperature AnomaliesNiño 3

00

180180OO 150150OOWW 120120OO

WW 090090OOWW

00OO

55OOSS

1010OOSS


160160OOEE

NIÑO - 2NIÑO - 2

NIÑO - 1NIÑO - 1

Sea Surface Temperature AnomaliesSea Surface Temperature AnomaliesNiño 3El Niño El Niño El Niño El Niño

La Niña ImpactsLa Niña ImpactsLa Niña ImpactsLa Niña Impacts

Bottom Line: There is little Bottom Line: There is little correlation between La Niña and correlation between La Niña and weather in Illinois, especially in weather in Illinois, especially in summer. summer.

There is a slight tilt in the odds There is a slight tilt in the odds toward a wetter than average spring toward a wetter than average spring (April through June).(April through June).

There is a slight tilt in the odds There is a slight tilt in the odds toward a cooler than average spring.toward a cooler than average spring.

Illinois:

El Niño ImpactsEl Niño ImpactsEl Niño ImpactsEl Niño Impacts

Bottom Line: There is little Bottom Line: There is little correlation between El Niño and correlation between El Niño and weather in Illinois, especially in weather in Illinois, especially in summer. summer.

Winters are often milder than Winters are often milder than average during a average during a strongstrong El Niño. El Niño.

There is a good chance of less There is a good chance of less snowfall than average during a snowfall than average during a strongstrong El Niño. El Niño.

Illinois:

Pacific Decadal OscillationPacific Decadal OscillationPacific Decadal OscillationPacific Decadal Oscillation

Know as the “PDO.” It’s a long-Know as the “PDO.” It’s a long-term ocean fluctuation of the term ocean fluctuation of the Pacific Ocean, with a cycle of Pacific Ocean, with a cycle of about 20 to 30 years.about 20 to 30 years.

What is it?


Evidence suggests that the PDO Evidence suggests that the PDO switched to the “cool” or “negative” switched to the “cool” or “negative” phase in the eastern Pacific Ocean in phase in the eastern Pacific Ocean in 1999. 1999.

It appears that this will act to steer the It appears that this will act to steer the jet stream farther north over the jet stream farther north over the western U.S.western U.S.

The “warm” or “positive” phase appears The “warm” or “positive” phase appears to have lasted from 1977-1998.to have lasted from 1977-1998.

What is happening?

Sea Surface TemperatureAnomalies - January 8, 2000

Sea Surface TemperatureAnomalies - January 8, 2000

Pacific Decadal OscillationPacific Decadal OscillationPacific Decadal OscillationPacific Decadal OscillationPDO Index:


+- - -+


+- - -+

42 65 49 62


The average national summer The average national summer temperature ranking tends to be temperature ranking tends to be lower than average. lower than average.

Annual precipitation tends to be less Annual precipitation tends to be less in the Midwest, Tennessee Valley, in the Midwest, Tennessee Valley, southern New England, and West.southern New England, and West.

Trend toward more precipitation in Trend toward more precipitation in the northern Rockies, Oklahoma, the northern Rockies, Oklahoma, eastern Texas, and the Mid-Atlantic eastern Texas, and the Mid-Atlantic Coast.Coast.

Impacts - Negative Phase:

No Simple AnswersNo Simple AnswersNo Simple AnswersNo Simple Answers

The atmosphere operates on many The atmosphere operates on many time and space scales. They all time and space scales. They all influence the weather. influence the weather.

La Niña, El Niño, PDO, etc. do La Niña, El Niño, PDO, etc. do influence the jet stream (and the influence the jet stream (and the global scale), with the greatest global scale), with the greatest impact on weather near the Pacific impact on weather near the Pacific Ocean and in and near the tropics. Ocean and in and near the tropics. The impact is much reduced here. The impact is much reduced here.

Beware!

Time and Space ScalesTime and Space ScalesTime and Space ScalesTime and Space Scales Global Scale: More than a week. > 2000 Global Scale: More than a week. > 2000

miles. Longwaves in westerlies.miles. Longwaves in westerlies. Synoptic Scale: Days to more than a week. Synoptic Scale: Days to more than a week.

200-2000 miles. Fronts, highs, lows. 200-2000 miles. Fronts, highs, lows. Mesoscale: Minutes to hours. 2-200 miles. Mesoscale: Minutes to hours. 2-200 miles.

Thunderstorms, tornadoes, sea breezes.Thunderstorms, tornadoes, sea breezes. Microscale: Seconds to minutes. < 2 Microscale: Seconds to minutes. < 2

miles. Small turbulent eddies.miles. Small turbulent eddies.

ConclusionsConclusions

El NiñoEl NiñoEl NiñoEl Niño

It appears that an El Niño is It appears that an El Niño is forming in the Pacific Ocean for forming in the Pacific Ocean for this winter. Many will make this winter. Many will make forecasts accordingly. forecasts accordingly.

Remember, not all El Niños are Remember, not all El Niños are strong.strong. The last one was, so The last one was, so beware of hype! beware of hype!

A weak El Niño usually has little A weak El Niño usually has little direct impact on our weather. direct impact on our weather.

What to consider:

Final ThoughtsFinal ThoughtsFinal ThoughtsFinal Thoughts

All large-scale indicators heading into All large-scale indicators heading into harvest season are neutral. Shorter-harvest season are neutral. Shorter-range and smaller-scale events will range and smaller-scale events will dominate. dominate.

The hit and miss nature of rainfall this The hit and miss nature of rainfall this season will lead to high variability in season will lead to high variability in yields, even within counties.yields, even within counties.

Best decisions are still made by following Best decisions are still made by following shorter-term weather trends. There are shorter-term weather trends. There are surprises every year!surprises every year!

Looking ahead:

Tune toTune toIn-Depth Weather:In-Depth Weather: 5:35, 6:35, 7:35, 8:35, 9:35 AM5:35, 6:35, 7:35, 8:35, 9:35 AM and 12:35 PM Central Timeand 12:35 PM Central Time

Detailed Agricultural Weather:Detailed Agricultural Weather: 8:51 AM & 2:32 PM Central Time8:51 AM & 2:32 PM Central Time

Tune toTune to

www.will.uiuc.eduwww.will.uiuc.edu

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Thank You!Thank You!

Tune toTune to

Thank You!Thank You!

Questions?Questions?

weather trends

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temperature outlookaugust

near average

cool water

warm water

climate cycle

precipitation outlookaugust

iltotal rainfall departure

average conditions