Hazardous Weather Ahead and Outlook for Winter 2009-2010
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Transcript of Hazardous Weather Ahead and Outlook for Winter 2009-2010
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Hazardous Weather Ahead and
Outlook for Winter 2009-2010
Dave Reynolds -MTRDan Keeton - STOMeteorologists in
Charge
weather.gov/SanFrancisco
or /Sacramento
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Your NWS Weather Forecast Office
San Francisco Lightning
• Our goal:Provide forecasts and warnings so people can make informed decisions.
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WFO Product Timeline7-Day Forecast
3-5 Day Outlook
Special Weather StatementHazardous Weather OutlookMarine Weather Statement
Hydrologic Outlook
Hazard Watch12 to 48 hours ahead
Hazard Advisory Hazard Warning
potential
imminent
Nuisance Life and/or property threatening
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• This weather pattern, which features strong zonal flow aimed at portions of the west coast, is likely to last up to a week and maybe longer.
• The pattern may be related to ongoing activity in the tropics associated with the Madden-Julian Oscillation.
• This weather pattern is likely to be more transient in nature than that typically observed with El Nino.
• El Nino does favor additional events of this type – but typically they occur later in the winter (January-February timeframe), and are associated with an amplified wave pattern, eastward extension of the Pacific Jetstream, and persistent pattern of storminess somewhat farther to the south.
Developing Stormy Pattern for California
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MJO Index -- Recent Evolution
The MJO has continued to propagate eastward.
The axes (RMM1 and RMM2) represent daily values of the principal components from the two leading modes
The triangular areas indicate the location of the enhanced phase of the MJO
Counter-clockwise motion is indicative of eastward propagation. Large dot most recent observation.
Distance from the origin is proportional to MJO strength
Line colors distinguish different months
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Storm track and moisture source often associated with the MJO
Setup for Atmospheric River
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SSMI shows AR stretching across Pacific to Central California
Central CA>15 inches rain
Atmospheric River
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Series of Storms Starting Sunday Night
First Storm: Sunday Night – Monday NightMore Storms: Tuesday – Next Week Week
Remnants of Typhoon NIDA
MJO driven thunderstorms
Enhanced Jet
Cold arctic air to move south and west Sunday
H
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(knots)
ECMWF 156-hr forecast 250 mb winds valid 12Z Wed 09 Dec
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In general there is widespreadagreement on strong zonal flow into California next week. MaybeCentered south of Bay Area.
Valid 4pm Wednesday Dec 09
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Details still to be determined on timing and location of impacts
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Drought Relief is Coming
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Winter Outlook
• Expect possible moderate strength El Nino to persist through spring.
• Could bring recurrence to weather we will see next week.
• May not see influence until January• Impacts still not certain
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Sea Surface Temperature Anomalies – El Niño
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Thunderstorm Activity TropicsLocated over SSTs > 28C
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Mass of warm water under surface should maintain or enhance El Nino
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Animation of subsurface tropical ocean temperatures
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SST Outlook: NCEP CFS Forecast Issued 8 November 2009
The CFS ensemble mean (heavy blue line) predicts El Niño will last at least through Northern Hemisphere spring 2010.
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El Niño
El Niños feature a strong jet stream and storm track across the southern part of the United States, and less storminess and milder-than-average conditions across the North.
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ENSO strength vs SFD WY rainfall and sign of PDO Sept-Nov.
Strong El Nino
Weak/ModEl Nino
NeutralWeak/ModLa Nina
Strong La Nina
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Where are we now? Years with closest fit
DECJAN
JANFEB
FEBMAR
MARAPR
APRMAY
MAYJUN
JUNJU
L
JULA
UG
AUGSEP
SEPOCT
OCTNOV
NOVDEC0
10
20
30
40
50
60
70
MEI Ranking
1972-73
2009-10
1965-66
1957-58
Monthly Pairs
Rank
ing
1-60
72-73 WY = +.5965-66 WY = -.2557-58 WY = +.67
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U.S. Precipitation Tends Forecast for El Niño 09-10
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weather.gov/SanFrancisco
Hazard map – clickableSatelliteRadarRiver ForecastsForecast Discussion
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Media Briefing
• Any Questions??