Weather Pattern Forecast Remainder of 2022 for Baltimore Gas & Electric Friday September 16, 2022 Executive Summary: The weather/climate outlook for the remainder of 2022 is most-focused on possible effects from “Fiona” during later September in an otherwise very quiet second half of September. The Mid-Atlantic drought condition is likely to continue as precipitation is generally below normal for Q4/2022. After a warmer-than-normal October, a chilly November is projected for the Mid-Atlantic. December is normally cold. A chilly start to the 2022-23 cold season turns warmer-than-normal in January and especially February. Forecast methodology: To provide Baltimore Gas and Electric an assessment of weather patterns for the remainder of 2022, operational forecasts utilizing GFS and ECMWF (models) out to 15 days are reviewed. Forecasts out to 5 weeks are based primarily on the ECMWF “weeklies” model issued every Monday and Thursday. Monthly assessments for October, November and December are based primarily on the Climate Impact Company constructed analog (CIC-CA) forecast. Expectations for winter 2022-23 are also based on the CIC-CA forecasts. Report access: This report and a plethora of supporting documents including the U.S. winter 2022-23 outlook, updated seasonal tropical cyclone outlook, week 2-4 U.S. outlook, week 2-5 tropical outlook plus the latest monthly ENSO forecast are available on the Baltimore Gas and Electric website… Baltimore Gas and Electric – Climate Impact Company User: bge2 Pass: climate2 Report format: Addressed in this report are expectations for the remainder of tropical cyclone season, whether the Mid-Atlantic drought persists, the ENSO outlook and sensible weather forecast for the remainder of September plus weekly breakdown of what to expect in October followed by the climate outlooks for November and December. The report finishes with a summary of what to expect for winter 2022-23. A plethora of graphics supporting the forecasts issued in this document are on the BGE web site. In this report, an attempt at the “bottom line” expectation and keeping the document relatively short was a priority. Tropical cyclone forecast: Earlier this week, Climate Impact Company issued a rare September seasonal tropical cyclone outlook update. The new forecast lowered seasonal tropical cyclone totals for 2022 based on the limited activity (5 tropical storms and 2 hurricanes) through mid-September and operational models which extend to early October offering little additional activity other than Fiona. The adjusted forecast calls for an additional 7 tropical storms, 3 hurricanes and 1 intense hurricane making the seasonal total 12 tropical storms, 5 hurricanes and 1 intense hurricane. The seasonal forecast is far below expectations issued by lead forecasters earlier this summer season (Table 1). The reason for the weaker than forecast seasonal activity is persistence of a tropical upper tropospheric trough (TUTT) in the Caribbean Sea and atmospheric subsidence leading to lower-than-normal relative humidity (RH) in the middle atmosphere of the central North Atlantic tropics. The TUTT and RH regime are likely to improve for late season but too late for the previously issued buoyant seasonal totals to verify. The upper air pattern through the next 15 days is generally not favorable to allow a tropical cyclone to approach the Mid-Atlantic coast although close attention to Fiona is required once that storm moves past Hispaniola in 5 days. In October, both the ECMWF and CFS V2 models indicate above normal high-pressure across the Northeast U.S. which implies steering currents to allow a tropical cyclone to approach the East Coast is possible. July Forecasts Tropical Storms Hurricanes Intense Hurricanes ACE Index Climate Impact Co. 18 8 3 130 Colorado State Univ. 20 10 5 180 T. S. Risk U.K. 18 9 4 150 NOAA 14-20 6-10 3-5 N/A 30-Yr NML 14.8 7.3 3.3 126.3 CIC SEP Update 12 5 1 93 2022 So far 6 2 0 29 Table 1: July forecasts of seasonal tropical cyclone activity by leading providers. The Mid-Atlantic drought: Despite lack of recognition by the NOAA U.S. Drought Monitor of locally dry conditions, soil moisture deficit is present and substantial rain to ease the dryness is required. As of September 10, the Palmer Drought Severity Index (PDSI) across the Baltimore area was -2.24 which is in the “moderate drought” classification. To neutralize the -PDSI value, a total of 7.31 in. of rain is required. Operational models are dry through the end of September (Fig. 1) across the Mid-Atlantic region and the CIC-CA precipitation climate outlook for Q4/2022 is also drier than normal across Maryland (Fig. 2). Consequently, the moderate drought in much of the BGE Service Area continues through 2022. Note that the climate forecast is based on synoptic-scale generated precipitation and does not include tropical cyclone risk. Fig. 1-2: The GFS ENS percent of normal precipitation forecast for the remainder of September is dry in the Mid-Atlantic region while the CIC-CA precipitation anomaly forecast for Q4/2022 is also dry for Maryland. Does La Nina continue? La Nina has entered a 3rd consecutive year for the 4th time since 1950. Previous 3-year La Nina regimes were observed in 1954-56, 1973-75 and 1998-00. The general influence of La Nina 2020-22 on the BGE Service Area was warmer and drier than normal. La Nina 2022 peaks in November and weakening follows in early 2023. Long-range forecasts indicate El Nino risk for later 2023. The latest 15-day outlook: Only one issue of concern for the BGE Service Area the second half of September: Fiona. Currently, the NOAA/NHC 5-day forecast track takes Fiona directly across the Hispaniola mountains next Monday (Fig. 3). Very few tropical systems can survive this trek. However, all operational models redevelop Fiona once well north-northwest of Hispaniola and a hurricane by mid-next week is possible. In 10 days, ECM has Fiona approaching the East Coast (Fig. 4) while GFS keeps Fiona offshore and traveling northward (Fig. 5). Both models indicate a major hurricane. Other than the Fiona risk, the mid-to-late September forecast is unusually quiet. Expect a warm-up next week with middle 80’s common each day (Fig. 6). The last week of September cools to normal. The influence of Fiona could elongate the warm weather pattern and once Fiona is out of the picture make the late September forecast cooler than indicated. Fig. 3: NOAA/NHC 5-day forecast track for Tropical Storm Fiona takes the system across Hispaniola early next week. Fig. 4-5: The ECM and GFS projection for Fiona in 10 days. Both models indicate a major hurricane. Weekly assessments for October: The October Outlook, including tropical risks is based on the ECMWF “weeklies”. Climate forecasts for October are warmer than normal with near normal rainfall. The ECMWF projection indicates some wet weather for the first full week of October, mainly due to a cold front passage not likely to feature thunderstorms (Table 2). Both week-2 and week-3 forecasts indicate potential for 1 in. of rain caused by generally weak cold fronts. October is moderately warmer than normal cooling to near normal the last full week of October which is a dry week. In the tropics, Florida and the Southeast Coast are at risk of tropical cyclone impacts for the first half of October. The BGE Service Area is at minimal risk. However, until mid-October has passed, BGE should maintain hurricane awareness. Precipitation Temperature Oct. 3-9 1-1.5 in. of rain. Mainly showers. (No T-storms) 1-3F above normal Oct. 10-16 1 in. of rain possible. Mainly showers. 1-2F above normal Oct. 17-23 1 in. of rain possible. Mainly showers. 1-2F above normal Oct. 24-30 Mostly dry. Near normal Table 2: Weekly forecasts for the BGE Service Area based primarily on the ECMWF model. The November/December 2022 outlook: The BGE Service Area forecast for November and December 2022 is based on the most recent constructed analog forecasts. During October, the tropics are more active than normal. Tropical cyclones moving across much warmer than normal waters in the central/northern latitudes of the North Atlantic are likely to carry significant latent heat into the far northern latitudes. This type of pattern can lead to high-latitude high-pressure blocking and force a cool trough to develop in the East U.S. The evolution described is forecast for November. Consequently, November is cooler and drier than normal in the Mid-Atlantic region (Fig. 6-7) during late autumn with a vigorous storm track staying off the East U.S. Coast. In November, the BGE Service Area can expect above normal heating demand due to a monthly average temperature around -1F. Expect 6 days with morning low temperatures <32F. The projected heating degree days for November is 555 (30-year normal 539/10-year normal 544). In November, about 1/2 to 2/3 of normal rainfall is expected. The December 2022 forecast in the Mid-Atlantic region is near normal temperature and precipitation (Fig. 8-9). Early winter is colder and snowier than normal across the North-central U.S. Some of the chilly air masses in that region emit eastward and reach the BGE Service Area. In-between cool air visits, local temperature is quite mild. Near normal rainfall and no snow is expected. About 20 days in December feature morning low temperatures <32F. The projected HDD in December is about 778 (30-year normal 813/10-year normal 748). Fig. 6-7: Climate Impact Company constructed analog temperature and precipitation anomaly forecast for November 2022. Fig. 8-9: Climate Impact Company constructed analog temperature and precipitation anomaly forecast for December 2022. Expectations for Winter 2022-23: After a normally cold start to meteorological winter, the mid-to-late winter forecast is mild (Fig. 10-11). In fact, a major January thaw takes place across the Central U.S. In February, a “polar vortex” pattern generates although the attendant cold is likely to strike the Great Plains to Texas and moderate before reaching the East Coast. In January, the BGE Service Area can expect slightly above normal temperature with the drier than normal pattern continuing and about average snowfall (Table 3). In February, the Mid-Atlantic region is on the warm side of a cold Central U.S. pattern. The precipitation forecast could easily be higher than indicated but with minimal snow and quite mild temperatures. Fig. 10-11: Climate Impact Company constructed analog temperature and precipitation anomaly forecast for DEC/JAN/FEB 2022-23. Precipitation Temperature Snowfall December 2022 60% of normal -0.2 <1 in. January 2023 75% of normal +1.3 3-6 in. February 2023 Near Normal +3.5 1-3 in. Table 3: Monthly precipitation/temperature projections for the BGE Service Area.