August 2024 saw a mix of above and below-normal temperatures in the East. The biggest weather story was Hurricane Debby, which brought heavy rain and flooding throughout the East Coast, as well as tornadoes. Debby contributed to many locations seeing above-normal precipitation in August, although a few areas still saw normal to below-normal precipitation.

September will see the start of cooler weather return to the East with a mix of normal, below-normal, and above-normal temperatures. Precipitation has a 30-50% chance of being above-normal for the southern half of the East and normal to below-normal (30% near the Great Lakes) for the northern half of the East. Read on to learn more about the weather in August and the forecast for September.

August 2024 Review:

August started on the active side and slowly became less active throughout the month. There were several short heat waves in August with above-normal temperatures reaching the upper 90s and low 100s. Dew points were high throughout the month, making it feel very humid.

August was another active severe weather month across the Eastern US. Hurricane Debby and its remnants contributed to many severe weather reports, including tornadoes, which occurred from August 5 - 9. New England saw a few additional days of strong storms, which brought several severe hail reports.

Below is a look at the preliminary severe weather reports from the Storm Prediction Center (SPC) in August 2024.

Hurricane Debby also brought flooding to much of the East. Florida, Georgia, South Carolina, and North Carolina were hit hardest with 10-20 inches of rain as Debby became semi-stationary.

Check out the rainfall reports from August 4-8.

Another unique event in August was a severe weather day on August 17 and 18, which brought very heavy rain to New England. A line of storms brought 8-12+ inches of rain to Connecticut and Long Island, with 16.31 inches reported in Oxford, Connecticut!

All of this rain caused normal to above-normal precipitation in August for many locations. Coastal areas in the Southeast saw the most rain due to Debby, but other areas in the East saw more than 2 inches above-normal.

There were a few areas of the East in the central and southern Appalachian mountains and around the Chesapeake Bay that dodged a majority of Debby's rainfall and other precipitation events, which caused below-normal precipitation in August. 

September 2024 Outlook:

The outlook for September shows a mix of below, normal, and above-normal temperatures. Coastal areas near the Chesapeake Bay have a 30-50% chance of seeing below-normal temperatures. New England and the southeast have a 30-50+% chance of above-normal temperatures. Areas in between have equal chances of above and below-normal temperatures in September.

The precipitation forecast for September shows above-normal precipitation chances (30-50%) in the southern half of the East, south of Maryland. This will primarily be associated with an increased chance of tropical systems impacting the East. The Great Lakes will see a 30% chance of below-normal precipitation while New England has an equal chance of above and below-normal precipitation in September.

 

Tropical Outlook:

As of September 2, there have been only five named tropical cyclones. August was a very quiet month for tropical cyclones after Hurricane Debby. Despite well above-normal sea surface temperatures in the Atlantic Ocean, there has been a lack of storms moving off of Africa to develop into tropical cyclones.

Additionally, the few disturbances that have moved off of Africa, have encountered unfavorable atmospheric conditions in the Atlantic Ocean. This is primarily caused by high wind shear and dry air, which inhibit tropical cyclone development.

• Wind shear is how the wind changes speed and direction with height.
• High wind shear is when there are strong changes in wind speed and direction with height, which are unfavorable for tropical cyclone's development and strengthening.

These unfavorable conditions are expected to weaken in September, which is the peak for tropical cyclone development and activity. This will lead to increased chances of tropical cyclones in September.

Check out the 7-day forecast for tropical disturbances from Monday, September 2 through Sunday, September 8. 

Despite this improvement, it is still unclear how favorable the second half of September will be for tropical cyclones. If storms move over the very warm Atlantic Ocean with favorable atmospheric conditions, strong hurricanes could develop.

Fire and Smoke Outlook:

The Western US and Canada have seen wildfire season become very active in August with several wildfires sending smoke into the atmosphere and affecting air quality throughout the US and Canada. We saw a few days of wildfire smoke transport into the Eastern US in August, degrading air quality and making skies hazy for a couple of days.

Below is a look at the wildfire potential across the US in September 2024.

Additional wildfire concerns have developed in West Virginia and nearby areas due to a very dry and warm August. This has led to increased chances of above-normal fire activity in these areas.

The wildfires in the Western US and Canada will continue to grow and strengthen for the first half of September. This will cause the East to continue to see opportunities for smoke transport in September as wildfires continue to burn in the Western US and Canada. 

Below is a look at the wildfire forecast across Canada in September 2024.

Toward the end of September, there are increasing signs of more favorable wildfire suppression with cooler temperatures and increased chances of precipitation.

Make sure to keep an eye on the sky and the OpenSnow smoke transport map. 

Happy September and enjoy the end of summer, cooler weather is on its way! I will continue the monthly reviews and forecasts at the start of each month into the fall.

Zach Butler