Google SearchLiaison announced on their Twitter feed: "Later today, we are releasing a broad core algorithm update, as we do several times per year. It is called the September 2019 Core Update. Our guidance about such updates remains as we’ve covered before. Please see this blog for more about that: webmasters.googleblog.com/2019/08/core-updates.html"
Danny Sullivan from the Google development team said the update started rolling out within hours and may be completed in a few days' time.
He said on Twitter: "I expect it to begin in a few hours; these typically take a few days to fully roll out. Yes, we'll post when the rollout begins. We don't post when it ends because there are typically other updates that are always happening, too. But after a few days, as said."
This is not the first time Google informed the community about a broad core algorithm update days before rolling it out. Marked progress, according to webmasters, who commend the company for seriously considering their outreach.
The guidelines with regard to the new Google update remains the same. Search Engine Journal offers a quick run-through of Google's guidance (or disclaimers) concerning core updates:
Effects are widescale. Your website ranking could drastically shoot up or drop.
These are called “broad” core updates because there is no specific target in mind. Their goal is to simply improve Google systems as a whole.
If your page ranking drops, do not panic. You are not being penalised. Google is just reassessing your web content against other contents published before the new update rolled out.
Focus on generating quality content. Make that your priority and every SEO specialist recommends this method as the best way to deal with the aftermath of a core algorithm update.
Broad core updates normally occur on a quarterly basis (or every after few months). Warning: some websites might not recover until after a new update is rolled out.
You may improve your website but recovery may or may not happen. However, doing something to improve your website gives you a better chance of recovery than not doing anything at all.