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12/05/2023, 2:48 pm EST
Executive Summary: The Climate Impact Company constructed analog month 1-3 outlook for the U.S. valid for January through March 2024 is updated. The outlook has increased influence from the developing El Nino climate. The outlook has minor adjustments and continues to emphasize a colder Southeast U.S. regime in January followed by widespread chill in February. A snowy regime is implied for the Mid-south to the Northeast Corridor. In March, a mature El Nino climate fades. Fig. 1: The Climate Impact Company ENSO phase constructed analog forecast for 2024 utilizing southern oscillation index. Climate discussion: The atmosphere is steadily beginning to respond to the oceanic warming in the tropics caused by El Nino. Consequently, added emphasis on the atmospheric component to ENSO utilizing southern oscillation index (SOI) is heavily considered in the updated month 1-3 outlook (Fig. 1). The constructed analog forecast of ENSO phase for 2024 utilizing SOI indicates peak intensity of El Nino over the next 1-2 months followed by a steady decay to neutral ENSO phase by Q2/2024 and potential La Nina for the second half of 2024. The influence of the SOI-based ENSO forecast on the winter 2023-24 climate offers only minor changes. The January forecast is slightly warmer while the East-central U.S. is dry maintaining water level concern on the Mississippi River. The February forecast remains chilly although slightly warmer in New England. February looks quite snowy in the East and Mid-south States. In March the Northeast is very warm and Southwest cold and stormy as the mature phase of El Nino fades. January 2024 outlook: The mid-winter outlook breaks the streak of very warm months across the U.S. The southeast quadrant shifts colder than normal due to an energetic subtropical jet stream generating locally chilly polar air masses while causing wintery precipitation risk in the Mid-Atlantic States. The Northwest Coast to Northern California is in the face of a Pacific storm track bringing above normal precipitation and mild climate. The cold/snowy risk in the East is reliant on the Northwest Pacific storm track easing. Fig. 2-3: The Climate Impact Company January 2024 temperature and precipitation anomaly outlook. February 2024 outlook: Late meteorological winter remains cold. The CIC-CA forecast is adjusted for a stronger atmospheric El Nino climate but influence on the previous forecast is minor. Other forecast models such as CFS V2 and ECM also support colder risk. The East Coast storm track is impressive and could feature significant snow away from the coast. Snow can also occur in the Tennessee Valley. A low latitude storm track also brings wet weather and mountain snow to California. Fig. 4-5: The Climate Impact Company February 2024 temperature and precipitation anomaly outlook. March 2024 outlook: Early meteorological spring turns stormy across the Great Plains featuring both rain and snow events. The Great Lakes are stormy and mild while the entire Northeast U.S. is warmer than normal. The chilly region is across the Central Rockies to the Southwest U.S. Fig. 6-7: The Climate Impact Company March 2024 temperature and precipitation anomaly outlook. U.S. gas population weight HDD outlook: Early meteorological spring turns stormy across the Great Plains featuring both rain and snow events. The Great Lakes are stormy and mild while the entire Northeast U.S. is warmer than normal. The chilly region is across the Central Rockies to the Southwest U.S. Fig. 8: The Climate Impact Company U.S. population weight HDD forecast for each month of the 2023-24 cold season. The November value is observed.
12/05/2023, 2:32 pm EST
Discussion: The ongoing Panama Canal drought continues. About 40% of worldwide cargo ship traffic is affected. Long-term rainfall deficits have worsened due to El Nino. The El Nino episode is strengthening and expected to peak over the next 1-2 months. During this time, dry climate continues as the DEC/JAN/FEB 2023-24 rainfall anomalies for the Panama Canal vicinity indicate sparse amount (Fig. 1). The MAR/APR/MAY 2024 rainfall anomaly forecast maintains the drought as marginal dry conditions linger (Fig. 2) and El Nino is weakening. Once El Nino ends and neutral ENSO generates (with a slight chance of a La Nina reversal), the JUN/JUL/AUG 2024 outlook promises above normal rainfall (Fig. 3). Fig. 1: Climate Impact Company constructed analog forecast for rainfall anomalies in the Panama Canal region for DEC/JAN/FEB 2023-24. Fig. 2: Climate Impact Company constructed analog forecast for rainfall anomalies in the Panama Canal region for MAR/APR/MAY 2024. Fig. 3: Climate Impact Company constructed analog forecast for rainfall anomalies in the Panama Canal region for JUN/JUL/AUG 2024.
12/04/2023, 11:40 am EST
Fig. 1-4: The 12-week Nino SSTA observations, daily upper ocean heat east of the Dateline, equatorial Pacific upper ocean heat monthly values for the past year, and the IRI/LDEO Nino34 SSTA forecast into Q3/2024. Discussion: Today’s ENSO update reveals that Nino34 SSTA remains robustly warm but slightly cooler than last week which was the warmest signature of El Nino 2023-24 thus far (Fig. 1). The daily upper ocean heat east of the Dateline across the equatorial Pacific indicates significant warming in recent days (Fig. 2). Monthly values dating back one year also indicate the subsurface equatorial Pacific warming fueling the El Nino episode shifting intensity to the east of the Dateline (Fig. 3). A collection of all dynamic and statistical forecast models of the Nino34 SSTA reveals peaking El Nino during the next 1-2 months followed by weakening to neutral phase middle of 2024 (Fig. 4). The NCEP CFS V2 forecast continues to indicate La Nina for the second half of 2024.
12/04/2023, 8:42 am EST
Unusually active for an El Nino year; western basin was relatively quiet. The 2024 season is likely more dangerous than 2023 for the Gulf of Mexico and U.S. East Coast. Executive summary: The North Atlantic basin observed 20 tropical storms, 7 hurricanes, and 3 intense hurricanes with an ACE index of 146 in 2023. The activity level is considered moderately higher than normal and unusually active for an El Nino warm season. The much warmer than normal North Atlantic basin enabled buoyant activity although except for Idalia most activity was out-to-sea. The preliminary outlook for 2024 is a stronger season than 2023 with much greater risk of hurricanes returning to the western North Atlantic basin. The 2023 season discussion: The 2023 North Atlantic basin tropical cyclone season was unusual for several reasons. First, the number of tropical storms was 20 whereas the average number for an El Nino summer/autumn is 9.1. Second, seasonal activity reaching 20 storms is rare. This is only the 4th season on record with that achievement 3 of which are in the past 4 years. The much warmer than normal North Atlantic basin is blamed for the uptick. In fact, the 2023 SSTA across the North Atlantic basin was record warm. Third, almost all the activity (except for Major Hurricane Idalia) was out to sea. The mid-troposphere across the western North Atlantic was dry preventing most activity from developing or traveling to the Western Caribbean or Gulf of Mexico. Fourth, while oceanic El Nino was moderate-to-strong during the warm season, atmospheric El Nino (based on multi-variate ENSO index) was neutral. The neutral atmosphere/El Nino Ocean combination is unique. The 2023 seasonal activity was close to normal number of hurricanes and intense hurricanes although somewhat above normal for number of tropical storms and ACE index. Note that the various climatology is increasing as the years considered are more modern. The Climate Impact Company seasonal activity forecasts were unusually variable. Initial forecasts were on target with the number of hurricanes/intense hurricanes but too low for number of tropical storms. A significant upward adjustment was made in July due to the record warm North Atlantic SSTA but lowered slightly in August as El Nino westerly shear was developing. The preliminary hurricane tracks forecast for 2023 identified Idalia but had one more hurricane affecting the U.S. compared to verification. The other 5 hurricane tracks were forecast off the East Coast. Of the 20 events in 2023, Idalia (115 knots) ranked 3rd strongest trailing Lee (145 knots) and Franklin (130 knots) as most intense. Preliminary 2024 seasonal outlook: The 2023-24 El Nino is expected to peak in intensity over the next 1-2 months and weaken the first half of 2024. Forecast models vary but generally indicate neutral ENSO for the 2024 tropical cyclone season. Other models, such as the NCEP CFS V2 favor a strong La Nina. Consequently, the ENSO regime is likely favorable to produce above normal seasonal activity. Additionally, the recent tendency for a warmer than normal North Atlantic basin is likely to continue further enhancing the above normal seasonal risk (and intensity). Analog years with El Nino to neutral ENSO (or La Nina) transitions from the past 30 years with a warm North Atlantic basin include 2016 and 2010. The seasonal activity average for each year was 17 tropical storms, 10 hurricanes, and 4 intense hurricanes with an ACE index of 153. The entire western North Atlantic basin is at risk of impacts from hurricanes in 2024. Fig. 1: The 2023 North Atlantic basin seasonal tropical cyclone activity. Tropical Storms Hurricanes Intense Hurricanes ACE Index 2023 FINAL 20 7 3 145.6 50-Year 13.0 6.6 2.7 105.7 30-Year 15.4 7.5 3.3 129.9 10-Year 16.9 7.6 3.3 132.6 AUG FCST 17 6 2 114 JUL FCST 20 9 4 171 JUN FCST 13 7 3 136 APR FCST 12 7 3 92 Table 1: Tropical cyclone activity for 2023 compared to 30-year and short-term climatology plus the APR, JUN, JUL, and AUG seasonal forecasts by Climate Impact Company. Fig. 2: Climate Impact Company projection of hurricane tracks issued last spring. Fig. 3: The AUG/SEP/OCT 2023 global SSTA analysis from IRI/LDEO. Identified are the presence of El Nino and a very warm North Atlantic basin which helped shape the North Atlantic tropical cyclone season climate pattern. Fig. 4: July through October 2023 relative humidity anomalies at 600 MB across the tropical/subtropical North Atlantic environment. The dry western North Atlantic basin prevented most activity from forming or moving to that sector. Storm # Storm Name Dates Max Wind (knots) Pressure (MB) ACE Index 1 Unnamed 1/16-17 60 976 1.4 2 Arlene 6/2-3 35 998 0.4 3 Bret 6/19-24 60 996 4.6 4 Cindy 6/23-26 50 1001 2.5 5 Don 7/14-24 65 988 7.2 6 Gert 8/21-9/4 50 998 2.4 7 Emily 8/20-21 45 1001 0.7 8 Franklin 8/20-9/1 130 926 26.6 9 Harold 8/22 34 998 0.5 10 Idalia 8/27-31 115 940 7.4 11 Jose 8/31-9/1 50 997 1.3 12 Katia 9/2-3 50 998 1.2 13 Lee 9/5-16 145 926 36.8 14 Margot 9/7-17 80 970 12.7 15 Nigel 9/17-22 85 971 10.5 16 Ophelia 9/22-23 60 981 1.4 17 Philippe 9/23-10/6 45 998 9.4 18 Rina 9/28-10/1 45 999 1.9 19 Sean 10/11-14 40 1004 1.4 20 Tammy 10/18-29 90 965 15.2 Table 2: A list of tropical cyclone events for 2023 including dates, max wind, and low pressure plus ACE index. Data provided by Colorado State University. Fig. 5: A collection of all dynamic/statistical Nino34 SSTA forecasts by IRI/LDEO indicates neutral ENSO for the 2024 North Atlantic tropical cyclone season.