Official Forecast Has Low Confidence In A Clean Range Weatherwise

After Saturday’s scrub, SpaceX stated it would attempt to launch Falcon 9 and the Northrup Grumman Cygnuns NG-21 mission towards the International Space Station Sunday morning.

“SpaceX is targeting Sunday, August 4 for Falcon 9’s launch of Northrop Grumman’s 21st Cygnus mission (NG-21) to the International Space Station from Space Launch Complex 40 (SLC-40) at Cape Canaveral Space Force Station in Florida. The instantaneous launch window is at 11:02 a.m. ET.”

Why Saturday’s Attempt Was Scrubbed

About 90 minutes before Saturday’s planned liftoff at 11:21 AM EDT, a line of heavy thundershowers brushed over Cape Canaveral Space Force Station and Launch Complex 40. Another squall line with anvil clounds with potential lightning was heading towards the Cape when mission managers made the call to waive off the attempt for the day.

The launch window was instantaneous, meaning SpaceX could not delay the launch time to let the storms pass.

Weather Forecasters Not Confident For Sunday

The 45th Weather Squadron is pessimistically rating Sunday’s chances at only 10% GO:

Their discussion is nearly as dismal as the launch chances: “The Space Coast will remain on the eastern side of the system upon its slow approach Sunday, with fast moving squalls bringing numerous rounds of heavy rain and strong winds. As a result, the Probability of Violation (POV) is very high for the initial launch window Sunday morning,” says the 45th.

“For the backup launch window Monday morning, the weather will remain poor with a similar POV as deep tropical moisture lingering as the Tropical System slides into the Florida Big Bend and Northeast Florida. Winds will remain strong with tropical squalls moving through Central Florida.”

But, it’s Florida, and a one in ten chance can end being all that SpaceX needs to successfully launch and land Falcon 9 at Cape Canaveral Space Force Station.

Stay tuned.

Launch Preview

Here’s yesterday’s full preview of the NG-21 mission. All information is still accurate, except for the launch times and weather forecast (those have been updated here).