North American Impacts of El Nino

Jon M Schrage

r(-SOI3mrm,OLR’), r(-SOI3mrm,’@200), r(-SOI3mrm,winds@ 200)

40N

20N

0

20S

40S

140E 180 140W 100W

Rossby Wave Source

• Conservation of Absolute Vorticity

• The twin anticyclones aloft are what initially displaces the air parcels.

• Results in a pattern of troughs and ridges far downstream.

PNA PATTERN

PNA PATTERN

The following slides are composites from January 1998.

http://www.cdc.noaa.gov/cgi-bin/Composites/printpage.pl

500mb heights

1000mb T

1000mb T

OLR

OLR

Precip

Precip

Sea Level Pressure

Sea Level Pressure

Changnon

• What counted as an impact of El Nino?– The general monthly and seasonal

temperature and precipitation conditions– The lack of Atlantic hurricanes– Snowstorms?– An event attributed to El Nino by a NOAA

employee speaking in an official capacity

Changnon

• Losses during El Nino:– Rain in the southeast (including Florida)

• Unusual tornadoes• Crop damage by rain• Reduced tourism• Direct damage from storms

Changnon

• Losses during El Nino:– Storms:

• October, 1997 in Midwest• January, 1998 in New England• April, 1998 in Ohio Valley

Changnon

• Losses during El Nino:– Drought in Hawaii– Ski resorts in Midwest– Producers of salt, natural gas, snowmobiles,

etc.– Fires in Florida

Changnon

• Benefits during El Nino:– Mild Winter in Midwest:

• Few lives lost (13 vs. 757!)• Lower fuel costs (10% nationally!)• Fewer airline and shipping delays• Longer construction season• Snow removal costs

Changnon

• Benefits of El Nino:– No landfalling hurricanes

• 13 lives, $5 billion, saved

Changnon

• Benefits of El Nino:– Difficult to quantify:

• Improvement in lifestyle• Recharging reservoirs

Changnon

• Losses:– Human lives lost: 189– Economic costs: $4.2 billion

• Benefits:– Human lives saved: 850– Economic gains: $19.6 billion

Changnon

• Lessons:

• “…the need to focus on both the good and bad impacts of predicted weather conditions. The media tends to focus only on the negative outcomes.”

Changnon

• Lessons:– “News… writers tend to approach “local”

experts for interpretations of the events… [resulting] in widely different interpretations…”

Changnon

• Lessons:– “…all weather conditions produce winners and

losers”

Changnon

• Lessons:– “…predicting future impacts on lives and the

economy due to expected weather is likely as difficult as making accurate long range weather predictions.”