Extreme Events and Climate Variability

X. William Proenza, Director

National Weather Service Southern Region

Fort Worth, Texas

Issues:

Scientists are telling us that global warming

means more extreme weather.

Every year we seem to experience weather

extremes.

What is the origin of extreme events?

A Major Issue for All Countries Is Global

Warming and Its Regional Impacts

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a1880 1900 1920 1940 1960 1980 2000

1880 1900 1920 1940 1960 1980 2000 -1 .2

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S ea so n a l C lim a te Im p a c ts D ep en d o n th eS im u lta n e o u s In flu en ces o f:

E x trem e E v en ts a re M o stly R e la te d to C ircu la tio n C h a n g es , i.e . to Va r ia b ility

N a tu ra l C lim ate Va r ia b ility E l N in o /L a N in a P a c ific D e ca d a l O sc illa tio n

A rc tic O sc illa tio n (w e a k im p a c t in T ro p ics )

C lim a te C h a n g e

A tm o sp h e ric N o ise

(P D O )

The El Nino/Southern Oscillation (ENSO) is a major factor in global climate variability.

T h e P a c if ic D e ca d a l O sc illa tio n (P D O )

ty p ic a l w in te r tim e S e a S u r fa c e Tem p e ra tu re (c o lo rs ) ,S ea L ev e l P ressu re (co n to u rs) a n d su rfa ce w in d stress (a r ro w s) a n o m a ly p a ttern s d u rin g w a rm a n d c o o l p h a ses o f P D O

w a rm p h a se c o o l p h a se

L a N ina (J uly 1998-J une 1999)~

Departure from N ormal (mm)E l N ino (J uly 1997-J une 1998)~

Rainfall Changes A ssoc iated w ith EN SO are theL arges t Sourc e of Variability in the T ropic s

E N S O A ls o Impac ts H ur ric ane A c tivity

Soc ietal Impac ts from 1997/98 E l N ino

1. Crop/S toc k Damage 2. E nergy Savings 3. Famine 4. F ires 5. F isheries Dis ruption 6. Health R isks 7. Human Fata lit ies

8. P es ts Inc reased 9. P roper ty Damage10. Tourism Dec reased11. Transportation P roblems12. Soc ial Dis ruptions13. W ildlife Fata lit ies14. Water R ationing

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Colombia Gets Less Rain During El Nino

Major Weather-Related Natural Disasters

(1999 La Nina)

60 N50 N

40 N

30 N

20 N

10 N

E Q

10 S

20 S30 S

40 S

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60 S0 60 E 12 0E 18 0 12 0W 60 W 0

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FFF F

FF

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F

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F

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D

S Storm s, Hail, TornadoesF Floods, LandslidesH Hurricanes, TyphoonsD Drought

Flood 55,360 $1.3BStorm s 16,863 $17.0BDroughts 404 - Cold Waves 409 $1.3B

VictimsInsured Losses

Regional 1999 Floods Possibly Linked to La Nina

Date Event

April 9-16 Mudslides & heavy rains Columbia:

Cauca, Argelia

May 5-15 High water in Amazonas, Peru

August 15-22 Flooding in eastern Venezuela

Aug 30-Sept 11 Flooding in Columbia: Antioquia,

Cordoba, Choco

Sept 12-29 Persistent rains, floods, mudslides in

Columbia, Honduras, Nicaragua,

Guatamala

Dec 12-19 Major flooding and mudslides in

Venezuela (50,000+ victims)

Impacts of December 1999 Floods

in Venezuela

Extended Pacific Jet Stream& Amplified Storm Track

LLow Pressure

PolarJet

StreamWarm

Cold

Dry

DryWet

Pers istent

E l N in o~

H

Variable Pacific Jet Stream

BlockingHigh

Pressure

PolarJet

Stream

Cold

Dry

Dry

Wet

Warm

Wet

Variab le

L a N in a~

Typical Winter Weather Anomalies

And Atmospheric Circulation Changes

During El Nino & La Nina

L ocation s F or M a jo r Sto rm s (D a ys P e r W in te r S ea s on )

E xten s iv e Sto rm sD ec 9 7-M a r 9 8

M a ss iveIce Sto rm

Ja n 98

Stro ng “N orthe aste r”

Sto rm sJa n-F eb 9 8

To rnad o O utb re akF eb 9 8

F re qu en t Sto rm sN ov 9 7-M a r 9 8

Examples of C limate Control Over Weather Patterns.The Basis of Linking Climate and Weather

LA N ina 1998-1999~Above AverageSto rm s, H u rricane

Force W indsN ov 98 - Feb 99

A ctive H urricaneSeason

A ug-N ov 98

TornadoesJan 1999

N o M ajo r “N ortheaste rs”

Be low N orm alSto rm iness

D ec 98 -Feb 99

M a jor Ice Sto rmJan 99

M a jorSnow Sto rm

Jan 99

Extensive IceSto rm

D ec 98D rought

Spring 1999

Dim inishedHurricane

Threat

Jet Stream Shifts Associated with Clim ate Variability Produce Regional Changes In Extrem e Weather Events

T h e P a c if ic D e c a d a l O sc illa tio n (P D O )

ty p ic a l w in te r tim e S e a S u r fa c e Tem p e ra tu re (c o lo rs ) ,S ea L ev e l P ressu re (co n to u rs) a n d su rfa ce w in d stress (a rro w s) a no m a ly p a ttern s d urin g w arm a nd c oo l p h a ses o f P D O

w a rm p h a se c oo l p ha se

R e fe re n c e : N a th a n M a n tu a U n iv e rs ity o f W a sh in g to n

Tota l Trend Pacific Decadel O scilla tion

Arctic O scilla tion G lobal Warm ing

Contributions to Surface Temperature Trend from 1950-1999

S U M M A RY

E x tre m es resu lt fro m :

- m a jo r c lim a te a n o m a lie s (e .g . e sp e c ia lly E l N in o a n d L a N in a in T ro p ics )

- u n u su a l a tm o sp h er ic c irc u la tio n p a tte rn s (m o s tly re la te d to c lim a te v a ria b il ity )

- fa c to rs a c tin g to g e th e r fo r a ir te m p e ra tu re (e .g . E N S O , P D O , A O , g lo b a l w a rm in g )

T h e im p a c ts o f th e w a rm in g tre n d o n c irc u la tio n c h an g e s , i.e . a lso e x trem e s , is s t ill a re se a rc h issu e .