Unfortunately, the COVID-19 pandemic continues to cause race cancellations deep into the Fall 2020 racing season. As a demonstration of the product I can deliver to improve a race director’s situational awareness of weather factors potentially hazardous to volunteers and participants alike, I will post a series of forecasts, assuming a 5k will take place this Saturday August 22, 2020 starting at 9 AM. The location of the race will be in Three Bridges, like for the annual Three Bridges 5 miler race that we time.
I will provide a 5-day forecast on Monday morning with a big picture forecast of the general conditions to be expected for that morning. On Wednesday I will provide a 3-day forecast with more explicit timing of any potential weather hazards along with temperature, winds, and dewpoint, and any other variable necessary to assess racer comfort levels to inform the quantity of things the race often provides such as ice, water, shade, or on the other hand, cover from rain or shelter from cold. Finally, on Friday I will send out a 1-day forecast. A day-of forecast (0-day lead time) will only be sent out if high uncertainty was a factor in the 1-day forecast such as thunderstorms or a mesoscale convective system moving through the midwest overnight. In 2017, Tropical Storm Cindy moved through New Jersey and spawned a tornado in Monmouth County, only miles away from a race at CBA, causing a delay in the start of the race. This would require a 0-day lead time forecast, possibly in the form of a live phone call briefing with the race director within three hours before the race. A 0-day lead time forecast is only issued in these rare circumstances.
MONDAY MORNING FORECAST [5-day lead time]
The current forecast for Monday morning is dry and warm. A 5-day forecast will require the use of global ensemble numerical weather prediction models such as the GEFS and ECMWF and signals in 24-hour precipitation are the most useful at this leadtime to detect areas of disturbed weather.
Between 2am Saturday and 2am Sunday, there is a low probability of precipitation (<10%) accumulations greater than 0.01″ across most of New Jersey. However, there is a large precipitation signal around Florida which may indicate a stalled tropical wave or depression in the area. In the upper levels, an anomalously strong digging trough into the Gulf of Mexico will favor cyclogenesis to the east of Florida and an intensification of a SW to NE oriented upper level jet along the southeast coast. This moves north towards North Carolina through Tuesday but current steering patterns prevent it from moving towards New Jersey. There does not appear to be a major rain threat for Saturday morning from this system. The ECMWF indicates lower pressure over the Great Lakes region running up against the subtropical high pressure system over the southeast, but any precipitation from this system will lift north into Canada. The red polygon in the figure below shows the area with the lowest probability of precipitation on Saturday. The green colors over the area indicate the ensemble mean value of only 0.01 to 0.05″ of precipitation in the 24 hours from 2 am Saturday to 2 am Sunday, which is negligible and indicates an extremely low probability when all of the ensembles are assessed.
In terms of temperature, there is a high confidence of above average temperatures. All ensembles suggest warm temperatures in the northeast, cool temperatures in the southeast, a dipole with a high likelihood of occurring given the upper level pattern. Dewpoints will remain consistent around 65F throughout most of the day, which isn’t as dangerous as it has been for a lot of the summer but with temperatures nearing 80F towards the end of the race, expect runners to be sweating out a lot of water and electrolytes. Above average temperatures during a morning race in August may pose heat related race hazards. Here are how temperatures will look as a function of time throughout the morning:
*** race start ***
9am: 78F , sunny with a very light wind from the southwest.
*** first runner finishes ***
9:30am: 79F, sunny with a very light wind and will feel HOT.
10am: 81F, sunny. Most runners will have finished or will be finishing and it will feel HOT. Ensure water remains to help bring runners’ body temperatures down.
Air temperatures nearing 80F, dewpoints in the mid-60s, and a negligible wind all contribute to more sweat and electrolytes that runners will lose during the race that will have to be replaced. Offering cold water and potentially cups filled with a sports drink with electrolytes at mile 3, or somewhere else near the halfway point may help combat runner lightheadedness and the need to vomit from rapid loss of fluid and/or electrolytes. Offering this at the finish line would also benefit runners and prevent post-race cramping, vomiting, and lightheadedness.
WEDNESDAY MORNING FORECAST [3-day lead time]
No update to the 3-day forecast is necessary from the 5-day forecast. All heat related hazards remain highly likely. and the likelihood of precipitation is again very low.