Winter 07-08 Winter 07-08

Steve Todd

Meteorologist In Charge

National Weather Service

Portland, OR

Steve Todd

Meteorologist In Charge

National Weather Service

Portland, OR

OverviewOverview

• Winter Weather Outlook

• How to stay informed

• Winter Weather Outlook

• How to stay informed

Winter OutlookWinter Outlook

LaNina conditions are present across the tropical Pacific basin.

Model forecasts indicate a weak to moderate LaNina will continue well into 2008.

Recent data and model forecasts indicate LaNina conditions will likely strengthen during the next several months.

Current ConditionsSea Surface Temperature Departures (oC)

Current ConditionsSea Surface Temperature Departures (oC)

Equatorial Pacific SSTs are -2ºC to -3ºC below average between 120ºW and the South American coast, and -0.5ºC to -1.0ºC below average near the Dateline.

Sea Surface Temperature Anomalies (Oct 7 – Nov 3)

Recent Evolution of Equatorial Pacific SST Departures (oC)

Recent Evolution of Equatorial Pacific SST Departures (oC)

Longitude

Time Negative SST anomalies now extend from the Date Line to the west coast of South America.

El Niño disappeared rapidly in January 2007.

DEC 2006

Oct 2007

Niño Region SST Departures (oC)Recent Evolution

Niño Region SST Departures (oC)Recent Evolution

The latest weekly SST departures are -1.6ºC in the Niño 3 region and -2.2ºC in the Niño 1+2 region. SST departures are -1.2ºC in the Niño 3.4 region and -0.5ºC in the Niño 4 region.

Tropical Circulation during LaNinaTropical Circulation during LaNina

The Effects of La NiñaThe Effects of La Niña

• La Niña episodes are associated with three prominent changes in the wintertime atmospheric flow across the eastern North Pacific and North America.

– An amplification of the climatological mean wave pattern and increased meridional flow across the continent and the eastern North Pacific.

– Increased blocking activity over the high latitudes of the eastern North Pacific.

– A highly variable strength of the jet stream over the eastern North Pacific, with the mean jet position entering North America in the northwestern United States/ southwestern Canada.

• La Niña episodes are associated with three prominent changes in the wintertime atmospheric flow across the eastern North Pacific and North America.

– An amplification of the climatological mean wave pattern and increased meridional flow across the continent and the eastern North Pacific.

– Increased blocking activity over the high latitudes of the eastern North Pacific.

– A highly variable strength of the jet stream over the eastern North Pacific, with the mean jet position entering North America in the northwestern United States/ southwestern Canada.

Global Effects of La NiñaGlobal Effects of La Niña

• The effects of La Nina are most evident in each hemisphere’s cold season when the jet stream is strongest.

• Some of the most reliable effects are suppressed rainfall and drought over the central Pacific, Peru, Ecuador, and the southern United States and enhanced rainfall in northwestern U.S., Indonesia, Australia, southern Africa, and northeastern Brazil.

• These effects, while looking to be the mirror image of those associated with El Niño, do have some slight differences.

• The effects of La Nina are most evident in each hemisphere’s cold season when the jet stream is strongest.

• Some of the most reliable effects are suppressed rainfall and drought over the central Pacific, Peru, Ecuador, and the southern United States and enhanced rainfall in northwestern U.S., Indonesia, Australia, southern Africa, and northeastern Brazil.

• These effects, while looking to be the mirror image of those associated with El Niño, do have some slight differences.

Historical El Niño and La Niña episodesHistorical El Niño and La Niña episodes

AMJ 1997 – MAM 1998 2.5

AMJ 2002 – FMA 2003 1.5

JJA 2004 – JFM 2005 0.9

SON 2000 – JFM 2001 -0.7MAM 1994 – FMA 1995 1.3

JJA 1998 – MJJ 2000 -1.6FMA 1993 – JJA 1993 0.8

ASO 1995 – FMA 1996 -0.8AMJ 1991 – MJJ 1992 1.8

AMJ 1988 – AMJ 1989 -1.9JAS 1986 – JFM 1988 1.6

SON 1984 – MJJ 1985 -1.1AMJ 1982 – MJJ 1983 2.3

ASO 1983 – DJF 1983/84 -0.9ASO 1977 - DJF 1977/78 0.8

ASO 1974 – AMJ 1976 -1.8ASO 1976 – JFM 1977 0.8

AMJ 1973 – JJA 1974 -2.0AMJ 1972 – FMA 1973 2.1

JJA 1970 – DJF 1971/72 -1.4ASO 1969 – DJF 1969/70 0.7

SON 1967 – MAM 1968 -0.9OND 1968 – AMJ 1969 1.0

MAM 1964 – JFM 1965 -1.1MJJ 1965 – MAM 1966 1.6

ASO 1961 – MAM 1962 -0.6JJA 1963 – DJF 1963/64 1.0

ASO 1949 – FMA 1951 -1.8

MAM 1954 – DJF 1956/57 -2.1

JAS 1951 - NDJ 1951/52 0.7

MAM 1957 – MJJ 1958 1.6

Cold Episodes minWarm Episodes max

Pacific NWLaNina Events (1950-2002)

Pacific NWLaNina Events (1950-2002)

Precipitation

Percentage of:

• above normal • normal • below normal

Temperature

U.S. Precipitation Departures for Oct-Dec and Dec-Feb

U.S. Precipitation Departures for Oct-Dec and Dec-Feb

La Niña

All episodes

Moderate/Strong

Weak

Oct-Dec Dec-Feb

So, What’s the Forecast?So, What’s the Forecast?

Factors Influencing ForecastFactors Influencing Forecast

• ENSO

• Trends (10 yr temp, 15 yr precip)

• NAO & PNA

• Tropical 30-60 Day Oscillations (i.e. Madden Julian)

• Surface Conditions (snow, wet or dry soils, etc.)

• Statistical Forecast Tools

• Dynamic Forecast Models

• ENSO

• Trends (10 yr temp, 15 yr precip)

• NAO & PNA

• Tropical 30-60 Day Oscillations (i.e. Madden Julian)

• Surface Conditions (snow, wet or dry soils, etc.)

• Statistical Forecast Tools

• Dynamic Forecast Models

Winter Outlook 2007/2008Winter Outlook 2007/2008

Probability Forecasts

-- how to use

Probability Forecasts

-- how to use

33%33%33%BelowNormalAbove

Example:40 contour for above normal precipitation = 40% probability

of above normal temperaturesEC = equal chances of any 3 categories

Seasonal Outlook (December 07- February 08)

Seasonal Outlook (December 07- February 08)

Precipitation Temperature

Seasonal Outlook (March – May 2008)Seasonal Outlook

(March – May 2008)TemperaturePrecipitation

Winter Forecast for Pacific NWWinter Forecast for Pacific NWLa-Nina conditions lasting into 2008

Wetter than normal

No clear signal on temperature departures

(equal chances of below, normal, above normal temps)

La-Nina conditions lasting into 2008

Wetter than normal

No clear signal on temperature departures

(equal chances of below, normal, above normal temps)

354822.99”2000-2001

395033.89”1999-2000

394945.93”1998-1999

385054.54”1995-1996

375036.30”Normal (PDX)

Temperature (min)

Temperature (max)

Precipitation

Staying Informed & Being PreparedNWS Weather Operations & Role

Staying Informed & Being PreparedNWS Weather Operations & Role

OUTLOOK – Weather patterns show potential for a weather event in the next 2 to 5 days

WATCH – Conditions are favorable for a severe weather event in the near future –12 hours up to 72 hours

WARNING – life or property threatening weather is occurring or imminent

ADVISORY – Weather effect is occurring or imminent that will cause significant inconvenience and if caution not taken may be life or property threatening

OUTLOOK – Weather patterns show potential for a weather event in the next 2 to 5 days

WATCH – Conditions are favorable for a severe weather event in the near future –12 hours up to 72 hours

WARNING – life or property threatening weather is occurring or imminent

ADVISORY – Weather effect is occurring or imminent that will cause significant inconvenience and if caution not taken may be life or property threatening

National Weather ServiceProduct Stream

National Weather ServiceProduct Stream

Weather/FloodOutlook

72 48 24 0

Time to onset of event (hours)

Increasing confidence that event will occur

Weather/Flood Watch

Weather/Flood

Warning

READY SET GO

Weather on the WebWeather on the Web

NWS Front Page

• Your link to real-time weather

NWS Front Page

• Your link to real-time weather

weather.gov/portland

Something New from the NWSSomething New from the NWS

Fully Localized Atmospheric Research EnvironmentFLARE

Desktop Weather Display System

Fully Localized Atmospheric Research EnvironmentFLARE

Desktop Weather Display System

Application http://www.wrh.noaa.gov/wrh/ssd/flare.msiDocumentation http://www.wrh.noaa.gov/wrh/ssd/index-flare.html

- Observational data- Zone forecasts- 5 different panels- Looping image panel-Warning display mode-Customizable-Great for EOCs,desktops, Kiosks, etc

- Observational data- Zone forecasts- 5 different panels- Looping image panel-Warning display mode-Customizable-Great for EOCs,desktops, Kiosks, etc

Available NOW!Contact Tyree for details

Available NOW!Contact Tyree for details

High-Impact Weather Briefings(GoToMeeting Technology)

High-Impact Weather Briefings(GoToMeeting Technology)

• Interactive on-line briefings

• Demo’d last winter season

• Ability for the “briefer” to display their PC desktop remotely to everyone else

• Operates best with high speed Internet

• And its Secure- End-to-end encryption, user

authentication, one-time meeting passwords, secure control over desktop sharing

• Interactive on-line briefings

• Demo’d last winter season

• Ability for the “briefer” to display their PC desktop remotely to everyone else

• Operates best with high speed Internet

• And its Secure- End-to-end encryption, user

authentication, one-time meeting passwords, secure control over desktop sharing

Any Questions?Any Questions?