Extratropical Highlights – November 2024

 

1. Northern Hemisphere

The 500-hPa circulation during November resembled a wavetrain pattern with centers of maxima over the Canadian Maritime, the United Kingdom, and the Bering Sea.  Weak to moderate below average heights were located over the North Atlantic Ocean, the Kara Sea, and off the U.S. West Coast (Fig. E9). The main land-surface temperature signals include above average temperatures across most of North America and Eurasia (Fig. E1). The main precipitation signals include above average rainfall along the U.S. Central Plains, and central Russia and below average rainfall in Europe (Fig. E3).

 

a. North America

The 500-hPa circulation during November featured an amplified ridge over the east half of North America with a strong maxima located over the Hudson Bay and weak below average heights along the U.S. West Coast (Fig. E9). Above average temperatures were recorded for the east half of North America with many areas reaching the highest 90th percentile of occurrences while the west half recorded near normal temperatures (Fig. E1). Precipitation totals were well above average for the Great Plains (>90th percentile), while the Pacific Northwest and the Inter-Mountain West recorded rainfall in the highest 80th percentile of occurrences, and Southern California and the Midwest received rainfall in the near 60th percentile of occurrences (Figs. E3, E5, E6). The Northeast, Mid-Atlantic, Southeast, and Gulf Coast received below average rainfall (Figs. E3, E5, E6).

 

b. Europe and Asia

The 500-hPa circulation during November featured an amplified ridge over the United Kingdom, Europe, and the Mediterranean (Fig. E9). This ridge was interrupted by below average heights over the Kara Sea and northern Russia (Fig. E9). Above average heights were recorded for the eastern third of Asia (Fig. E9). Temperatures were largely above normal with many regions in Southern Europe and Southern Asia reaching the highest 90th percentile of occurrences (Fig. E1). Temperatures were below normal east of the Kolyma Range and Kamchatka Peninsula (Fig. E1). Below average rainfall was recorded for Northern and Southern Europe with the latter reaching the lowest 10th percentile of occurrences. Across Eastern Europe and Northern Russia, above average rainfall was recorded with many areas near the Kara Sea receiving totals in the highest 90th percentile of occurrences (Fig. E3).

 

c. Atlantic hurricane season

The 2024 Atlantic hurricane season produced 18 named storms, with 11 becoming hurricanes and 5 of those becoming major hurricanes. The 2024 Accumulated Cyclone Energy (ACE) value was 166% percent of normal relative to the 1951-2020 median. Based on this activity, NOAA classifies the season as being above normal. An average season has 14 named storms, 7 hurricanes, and three major hurricanes. This season was the second most costly on record. Of note, Hurricane Helene brought extensive damage to infrastructure and record-breaking flooding to parts of the Appalachian Mountains in North Carolina.

 

2. Southern Hemisphere

The 500-hPa height field during November resembled a wavetrain pattern with a minima in heights located over the South Pole and west of southern Chile and above average heights in the South Pacific Ocean and the Indian Ocean (location of the maxima, Fig. E15). Temperatures were above normal in the east half of Australia, the southeastern coast of Africa, and southern Brazil (Fig. E1). Below average rainfall was recorded for SE South America, NE Brazil, and South Africa (Figs. E3, E4). Of note is the extended record of below average rainfall for Brazil, which is considered to be experiencing an extended drought (Fig. E4). The South African monsoon season runs from October to April. During November 2024, parts of this area recorded below average precipitation (Fig. E3), and area-averaged totals were in the lower 40th percentile of occurrences (Fig. E4).

The Antarctic ozone hole typically develops during August and reaches peak size in September. The ozone hole then gradually decreases during October and November, and dissipates on average in early December (Fig. S8 top). During 2024, the ozone hole was smaller than average thru August and September, and then near normal until the last half of the month of November where it increased in size to be larger than the average 2014-2023 mean size. The polar vortex has picked up speed during November and looks to be above average at the start of December (Fig. S8 middle), while polar stratospheric cloud cover remains near normal (Fig. S8 bottom).