WRAL WeatherCenter Blog

Watching the weather ahead of today's SpaceX launch

Posted May 27, 2020 12:21 p.m. EDT

A SpaceX Falcon 9 rocket with the company's Crew Dragon spacecraft onboard is seen on the launch pad at Launch Complex 39A at sunrise as preparations continue for the Demo-2 mission (Photo Credit: (NASA/Joel Kowsky)

Forecasters at the US Air Force's 45th Weather Squadron issued their L-0 (launch day) for today's launch attempt of astronauts aboard the Crew Dragon capsule atop a SpaceX Falcon 9 rocket with a prediction of a 50/50 chance of conditions violating launch criteria.

Weather conditions are monitored not just around the launch site, but also along 50+ locations across the Atlantic Ocean extending to Northern Ireland to ensure safe landing conditions should the crew need to abort during ascent.

Launch Weather forecast for May 27

Should the launch be postponed for weather, technical or any other reason, additional launch opportunities are available on Saturday at 3:22 pm and Sunday at 3:00 pm. The weather looks slightly better on those days but with similar concerns.

Launch weather forecast for backup launch days

Concerns on all days around rain, and thick clouds in the area as well as the formation of anvil clouds.  These cumulonimbus incus, Latin for anvil rain cloud get their shape from rising air bumping into and spreading out across the lower portion of the stratosphere.  They are an indication of a mature storm, one that can cause dangerous lightning.

cumulonimbus incus or "anvil cloud" seen from the International  Space Station

Launch Weather Criteria

  • Do not launch if the sustained wind at the 162-foot level of the launch pad exceeds 30 mph.
  • Do not launch through upper-level conditions containing wind shear that could lead to control problems for the launch vehicle.
  • Do not launch for 30 minutes after lightning is observed within 10 nautical miles of the launch pad or the flight path, unless specified conditions can be met.
  • Do not launch within 10 nautical miles of an attached thunderstorm anvil cloud, unless temperature and time-associated distance criteria can be met.
  • Do not launch within 10 nautical miles of a detached thunderstorm anvil cloud.
  • Do not launch within 3 nautical miles of a thunderstorm debris cloud, unless specific time- associated distance criteria can be met.
  • Do not launch within 5 nautical miles of disturbed weather
  • clouds that extend into freezing temperatures and contain moderate or greater precipitation, unless specific time-associated distance criteria can be met.
  • Do not launch for 15 minutes if field mill instrument readings within five nautical miles of the launch pad exceed +/- 1,500 volts per meter, or +/- 1,000 volts per meter if specified criteria can be met.
  • Do not launch through a cloud layer greater than 4,500 feet
  • thick that extends into freezing temperatures, unless other specific criteria can be met.
  • Do not launch within 10 nautical miles of cumulus clouds with
  • tops that extend into freezing temperatures, unless specific height-associated distance criteria can be met.
  • Do not launch within 10 nautical miles of the edge of a thunderstorm that is producing lightning within
  • 30 minutes after the last lightning is observed.
  • Do not launch through cumulus clouds formed as the result of or directly attached to a smoke plume, unless time-associated criteria can be met.
  • Do not launch if downrange weather indicates violation of limits at splashdown in case of Dragon launch escape.
  • Do not launch if downrange weather shows high probability of violating limits at splashdown in case of Dragon launch escape.

Downrange weather is monitored at more than 50 locations along the ascent track along the North American eastern seaboard and across the North Atlantic. Probability of violation is calculated for each location including limit conditions for wind, waves, lightning, and precipitation.

Source: Crew Dragon Launch Weather Criteria Fact Sheet

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