Artemis I Launch Attempt #2: Mostly Favorable Weather Expected

Update Saturday Morning: NASA has scrubbed the Artemis I launch on Saturday due to a liquid hydrogen leak. NASA is currently investigating and will determine a new launch time.

FastCast—Saturday, Sep. 3 to Wednesday, Sep. 7:

Smoke will make a relatively quick exit from Western Washington overnight after a very hazy evening. Parts of Eastern Washington will continue to deal with surface smoke, as some areas are downwind (east of) local wildfires. Although smoke has left the region, fire danger is still high around Washington state, especially in the mountains and Eastern Washington. With a major weekend for outdoor recreation ahead, remember to be fire-wise, follow local burn bans (check Washington DNR), and to clear your campfire area of any unnecessary brush. Labor Day Weekend will start cooler and cloudier in Western Washington, with Saturday being cloudy (with a slight chance of morning showers) and highs in the mid 70s. Sunday will be a tad warmer, with highs in the upper 70s and clouds increasing through the day. Monday will be the coolest day, starting cloudy and gradually getting sunnier, with highs in the low 70s. Clouds will dissipate for a mostly sunny day on Tuesday, with highs rebounding to the mid 70s. Wednesday will be partly cloudy with highs again in the mid 70s. Expect low temperatures throughout this entire period to be in the low to mid 50s, cooler than this past week.

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Continue reading the full blog below!

For the second time, NASA is attempting to launch Artemis I, an un-crewed mission that will orbit the Moon and return to Earth over the next 42 days. This past Monday, NASA scrubbed the planned launch due to a technical issue involving one of the engines. Later in the week, a new launch window was announced for Saturday, September 3rd, from 2:17 to 4:17 PM Eastern Time (11:17 AM to 1:17 PM Pacific Time). 

Watch the Artemis I launch at this link: Artemis I Launch to the Moon

Launch coverage begins at 9:15 AM Pacific Time, with the launch window opening 2 hours later at 11:17 AM.

So, as is usually the question at Cape Canaveral, will the weather cooperate for the launch?

NASA and US Space Force meteorologists gave the launch a 60-80% probability, which seems accurate based on the forecast models that we will take a look at below.

Let’s start with the HRRR forecast for expected thunderstorms and precipitation at 2 PM EDT, near the beginning of the launch window.

The HRRR forecast shows no precipitation in the area of Cape Canaveral (the area of land sticking out into the Atlantic Ocean between Palm Bay and Daytona Beach). This is a good sign, as showers and thunderstorms can stop a NASA launch in its tracks.

Another important variable is cloud cover, mainly when cumulus clouds (can contain lightning) are present. The HRRR cloud cover forecast for the beginning of the launch window is below.

The HRRR shows 100% cloud cover at Cape Canaveral, but as long as the clouds aren’t too thick and don’t contain lightning or freezing temperatures, the launch can still happen.

The other major high-resolution forecast model we’ll take a look at is the NAM model.

Below is the NAM forecast for precipitation at the beginning of the launch window.

The NAM shows potential thunderstorms on parts of the Florida Coast, but not near Cape Canaveral. The agreement between the HRRR and NAM for no precipitation near the launch site is good news!

Now, let’s take a look at cloud cover. The NAM forecast is below.

The NAM shows more scattered clouds than the HRRR, putting cloud cover at Cape Canaveral around 50-80%. Again, this is not a no-go unless the clouds have lightning, are too thick, or have freezing temperatures.

Overall, the biggest weather threat to launch is, as usual, the chance of thunderstorms. The Storm Prediction Center forecast through Pivotal Weather is below.

This forecast shows a chance of general thunderstorms (light green) for the entirety of the Southeast US, quite common for a late summer day.

One more variable to watch is the temperature. NASA can’t launch when temperatures between 100 and 500 feet above the surface are 94+ degrees. The surface temperature forecast from the HRRR model is below.

Temperatures at Cape Canaveral will likely be in the upper 80s to near 90, with the Atlantic Ocean cooling the area slightly more than the surrounding region. While air temperatures will likely be suitable for launch, the hundreds of thousands of spectators will be dealing with feels like temperatures in the upper 90s due to very high (and typical) Florida dewpoints…likely in the upper 70s. 

Lucky for us in Western Washington, we can watch the Artemis I launch in the comfort of a cool and cloudy late summer morning, with temperatures in the upper 60s to low 70s!