Learn Hardcore Indonesian: Kereta baru berangkat, sudah ada pengumuman perubahan jadwal. - The train had just departed when there was already an announcement of a schedule change.

Here baru is an adverb meaning “just (now).” It modifies the verb berangkat (to depart), so kereta baru berangkat = “the train has just departed.”

As an adjective meaning “new,” baru would modify a noun: kereta baru = “a new train.”
To avoid ambiguity in writing:
- “The new train departed”: Kereta baru itu berangkat.
- “The train just departed”: Kereta baru saja berangkat or Kereta barusan berangkat.

What nuance does the baru … sudah … pairing convey?

It highlights quick succession and often a mild sense of surprise or complaint: “No sooner had X happened than Y already happened.”

Example pattern: Baru mulai, sudah capek. (Just started, already tired.)
In your sentence, it suggests “The train just left, and there’s already an announcement of a schedule change,” with a slightly incredulous tone.

Is it okay to join the two clauses with just a comma in Indonesian?

Yes. Indonesian often uses a comma to place two closely related independent clauses side by side. You could also:

Use a semicolon: Kereta baru berangkat; sudah ada pengumuman…
Make two sentences: Kereta baru berangkat. Sudah ada pengumuman…
Add a connector for a different nuance:
- dan/lalu/terus (and/then) for simple sequence
- padahal (even though) to stress contrast/surprise

Could I say Kereta sudah berangkat instead of Kereta baru berangkat?

You can, but the nuance changes:

Kereta sudah berangkat = the train has already departed (focus on completion).
Kereta baru (saja/barusan) berangkat = the train just departed (focus on recency).
If you want both ideas: Kereta baru saja berangkat; sudah ada pengumuman… keeps the “just” + “already” contrast.

What exactly does sudah ada mean here? How is it different from ada or telah ada?

sudah ada = “there is already” (existential + “already”).
ada = “there is/are” (no aspect).
telah ada = same meaning as sudah ada, but more formal/literary.
Colloquial: udah ada.
Negative counterpart: belum ada = “there isn’t yet.”

Why is there no tentang before perubahan jadwal? Should it be pengumuman tentang perubahan jadwal?

Both are correct:

pengumuman perubahan jadwal is a compact noun-noun chain (“announcement [of] schedule changes”).
pengumuman tentang perubahan jadwal is slightly more explicit/formal. Use whichever suits the register; the version without tentang is very common.

What is the structure and meaning of perubahan?

Perubahan is a noun formed from the verb ubah (to change) with the circumfix per-…-an, meaning “change” (the event/result).

Related nouns:
- pergantian (from ganti) = replacement/switch (often implies one thing replacing another)
- pergeseran (from geser) = shift
Here perubahan jadwal = a change to the schedule.

Why use berangkat and not pergi?

Berangkat = depart/set off (commonly used for vehicles, trips, scheduled departures).
Pergi = go/leave (more general).
For trains, buses, planes, etc., berangkat is the natural verb.

What does ada do in sudah ada pengumuman…?

Ada is the existential “there is/are.” Sudah ada pengumuman… = “There is already an announcement…”

If you mean a specific known announcement, you can topicalize/mark it: Pengumumannya sudah ada (“The announcement is already out”) or Pengumumannya sudah keluar.

How would I make the sentence more formal or more casual?

More formal: Kereta baru saja berangkat; telah ada pengumuman perubahan jadwal.
More casual: Keretanya baru berangkat, udah ada pengumuman perubahan jadwal.
- Note -nya in Keretanya can mark a topical “the train (as for the train).”
- udah is the colloquial form of sudah.

Can I switch the clause order?

Yes, depending on what you want to emphasize:

Sudah ada pengumuman perubahan jadwal, kereta baru berangkat. (Emphasis on the early announcement.)
You can also make the temporal link explicit:
- Begitu kereta berangkat, langsung ada pengumuman perubahan jadwal. (As soon as the train departed, there was immediately an announcement.)

Do I need kereta api instead of kereta?

Both are fine. Kereta api is the full term (“fire train,” i.e., locomotive-powered), but in modern usage kereta alone commonly means “train,” especially in speech and headlines.

Could Kereta baru berangkat be misread as “The new train left”? How do I avoid that?

In speech, intonation usually disambiguates. In writing, to be clear:

“The new train left”: Kereta baru itu berangkat.
“The train just left”: Kereta baru saja/barusan berangkat or Kereta sudah berangkat barusan (colloquial). Placing baru (saja/barusan) right before the verb makes the “just” reading explicit.