2004 Regional Climate Highlights By Gerald Bell Climate Prediction Center NOAA/NWS/NCEP Contributors: Vernon Kousky, Craig Long, Rich Tinker, Wasilla Thiaw, Song Yang

Outline Temperature and precipitation anomalies Indian and African monsoon seasons Active Atlantic, suppressed East Pacific hurricane seasons Evolution to early stages of El Niño, MJO influence Anomalous conditions over North America (Apr-Aug) Stratosphere: Antarctic ozone January stratospheric warming

Temperature and Precipitation Anomalies

Regional Temperature Anomalies during 2004 Cool Summer Hot and Dry, Wildfires Warm El Niño Develops

Jan.-Sep Temperature Rankings 1 is the coldest since is warmest since 1950

Regional Anomalies during landfalling TC’s (Jan-Mar) Cool Summer Hot and Dry, Wildfires Warm El Niño Develops Drought Continues Suppressed rainfall Inactive East Pac. hurricanes Active Atlantic Hurricanes 7 U.S. landfalling TC’s

Monsoon Rains India West Africa Southern Africa

June-August India Monsoon Rainfall Figure Courtesy: Song Yang See Yang and Yoo Poster 1.26 Total 2004 rainfall: 13% below average Above average Below average

West Africa and Southern Africa Monsoon Rainfall Anomalies (mm) Posters: Thiaw and Mo, P. 1.2 Nicholson, P Thiaw, P Posters: Thiaw, P. 1.28

Anomalous 200-hPa VPOT and Divergent Wind Vectors Enhanced West African monsoon system and suppressed rainfall over Central America/ Amazon Basin predominant since 1995.

Anomalous 200-hPa STRM and Rotational Wind Vectors Inter-hemispheric symmetry to anticyclonic streamfunction anomalies Stronger subtropical ridges reflect enhanced West African monsoon system and suppressed Amazonian rainfall system (Chelliah and Bell 2004), Classic for above-normal Atlantic hurricane seasons (Bell and Chelliah 2005) Anticyclonic

Atlantic and East Pacific Hurricane Seasons See poster: Chelliah, Bell and Mo, P. 1.24

Very Active Atlantic hurricane Season 2004 Normals Tropical Storms Hurricanes Major Hurricanes landfalling systems in 2004, 18 landfalls during of these systems made landfall along the Gulf Coast

Suppressed East Pacific hurricane Season 2004 Normals Tropical Storms Hurricanes 6 9 Major Hurricanes East Pacific hurricane seasons generally below normal since 1995

2004 Atlantic Tropical Cyclone Tracks Figure Courtesy Unisys Weather.com Above-normal seasons have large number of systems forming in Main Development Region (MDR). During 2004, 8 /14 TS, 7/8 H and 5/6 MH formed in MDR (9 o N-21.5 o N). MDR

Aug-Sep 2004: Total Precipitation (mm) during the periods in which the six landfalling tropical systems were producing precipitation in U.S., and % of 2-month total

Since 1995, 8 of 10 Atlantic hurricane seasons were above normal. On average 2-3 hurricanes hit the U.S. in above-normal seasons.

Warmer SSTs Amplified subtropical ridge (200-hPa) Stronger Tropical Easterly Jet Favorable AEJ Enhanced Cyclonic RELV These conditions have prevailed since of 10 hurricane seasons have been above-normal. Also characterized the active decades of the 1950s-1960s Primary Conditions associated with Active 2004 Atlantic Hurricane Season Weaker easterly trades 850-hPa westerlies Very low vertical wind shear (200 – 850 hPa)

Standardized SST Departures in Main Development Region Above normal 2004 Atlantic hurricane season associated with ongoing anomalous warmth across tropical Atlantic that began in 1995—reflects warm phase of Atlantic multi-decadal mode (Goldenberg et al. 2001)

Less cyclonic More cyclonic Stronger Easterlies Weaker easterlies Lower Shear Higher Shear Recent Decade of Favorable Conditions Anomalies are relative to Inactive Period Averaging Regions Vertical Wind Shear: hPa 700-hPa Zonal Wind 700-hPa Relative Vorticity Bell et al., BAMS, May 2004

Evolution to Early Stages of El Niño See poster: Kousky, P. 1.15

Latest SST Anomalies (C): 4-10 October 2004 Latest SST Anomalies ( o C): 4-10 October 2004

Evolution of SST Anomalies Averaged 5 o N - 5 o S Largest positive SST anomalies were west of date line until July Since July, anomalous warmth has persisted and expanded eastward. Negative anomalies in eastern Pac. disappearing

Strong MJO during hPa Velocity Potential Anomalies averaged 5N-5S MJO has produced significant variability in the atmosphere and in Pacific Ocean temperatures. No El Niño signature yet. See poster: Weickmann and Berry, P Anomalous Divergence Anomalous Convergence

Area-Averaged SST Anomalies in Niño-4 and Niño 3 Regions Intraseasonal SST fluctuations are associated with oceanic Kelvin waves triggered by MJO In September, the anomalous warmth expanded eastward to cover Niño-3 region

Extratropics

Persistent April-July Circulation over North America Hot and Dry Alaska Cooler Canada, cooler summer in U.S. Below-average Southwest U.S. monsoon

April-July 2004 Precipitation Percentiles 300-hPa Heights and Temperatures

June-August Mean Temperature Rankings 1 is the coldest since is warmest since 1950

June-August Mean Maximum Temperature Anomalies (C)

Some Summertime Cold-air Outbreaks

Stratosphere Antarctic Ozone hole January N.H. Stratospheric Warming

Antarctic Ozone Hole (Concentrations <220 DU) NOAA SBUV/2 Satellite Estimate Figure Courtesy of Craig Long, poster P 1.23

January 2004 Stratospheric Warming Daily Temperature Departures (C) Figure Courtesy of Craig Long, poster P 1.22

Height Anomalies (m) associated with 2004 Stratospheric Warming Stratospheric warming contributes to strong negative phase of the Arctic Oscillation

Summary Many temperature and precipitation anomalies associated with multi-decadal fluctuations: Chelliah and Bell 2004, Goldenberg et al. 2001) Precipitation:Temperature Enhanced West African monsoon Warm N. Atl Drier Amazon Basin Active Atl. hurricanes, summertime eastern U.S. rainfall, Evolution to early stages of El Niño No single cause of N.A. circulation anoms. during Apr-Aug., hemispheric-scale pattern of anomalies, extended into middle strat. January negative AO also linked to stratosphere—warming event Antarctic ozone hole near mean size