Обледенение началось после сильного ветра.

The subject is обледенение.

You can tell because обледенение is in the nominative singular, which is the normal case for the subject of a sentence. The phrase после сильного ветра cannot be the subject, because it is introduced by the preposition после, and that preposition requires the genitive case.

So the structure is:

• Обледенение = subject
• началось = verb
• после сильного ветра = time phrase, after a strong wind

Because it agrees with обледенение, which is a neuter singular noun.

In the past tense, Russian verbs usually agree with the subject in gender and number:

• masculine: начался
• feminine: началась
• neuter: началось
• plural: начались

Since обледенение ends in -ие and is neuter, the verb must be началось.

The dictionary form here is начаться, meaning to begin / to start.

Russian often uses the reflexive form for events or processes that begin on their own:

• Концерт начался. = The concert began.
• Дождь начался. = The rain began.
• Обледенение началось. = The icing began.

The non-reflexive verb начать usually means to begin something:

• Он начал работу. = He began the work.

So in your sentence, началось is correct because обледенение is the thing that began.

Because после always takes the genitive case.

So:

• nominative: сильный ветер
• genitive after после: после сильного ветра

This is something you simply have to learn with the preposition:

• после урока = after the lesson
• после дождя = after the rain
• после сильного ветра = after a strong wind

Сильного ветра is genitive singular masculine.

Breakdown:

• ветер → ветра
• сильный → сильного

Why?

• ветер is a masculine singular noun.
• сильный is an adjective modifying ветер, so it must match it in gender, number, and case.
• After после, both go into the genitive.

So:

• nominative: сильный ветер
• genitive: сильного ветра

Because this sentence uses the singular, not the plural.

• ветра = genitive singular of ветер
• ветров = genitive plural

So:

• после сильного ветра = after a strong wind
• после сильных ветров = after strong winds

Russian often uses the singular where English might also use singular, but sometimes English could use plural depending on context. Here the Russian sentence presents it as one wind event.

Началось is from the perfective verb начаться, and it focuses on the fact that the event started.

That is the normal choice when you mean a single beginning:

• Обледенение началось... = The icing began...

If you used начиналось instead, that would be imperfective, and it would sound more like:

• it was beginning
• it used to begin
• it began repeatedly
• background description, depending on context

So in a simple statement about when the icing started, началось is the natural form.

Grammatically, после means after, so the phrase is primarily temporal.

However, in real life, listeners may also understand a loose causal connection from the context:

• first there was strong wind
• then icing began

So the grammar gives you sequence in time, while the situation may suggest cause as well. But if you wanted to express cause more directly, Russian would usually use a different construction.

Yes. Russian word order is flexible.

The original sentence is:

• Обледенение началось после сильного ветра.

You could also say:

• После сильного ветра началось обледенение.

Both are grammatical. The difference is mostly emphasis:

• Обледенение началось... starts by highlighting the event itself.
• После сильного ветра... starts by highlighting the time/background.

The original order is perfectly natural and neutral.

Not exactly.

Обледенение usually means icing or ice formation, often as a process or technical phenomenon. It can refer to ice forming on surfaces, wires, aircraft, roads, and so on.

Гололёд usually refers more specifically to icy conditions, especially a slippery layer of ice on roads or sidewalks.

So обледенение is the better word if you want the broader idea of icing beginning.

A useful word-by-word breakdown is:

• Обледенение = icing / ice formation
• началось = began / started
• после = after
• сильного = of a strong
• ветра = wind

A more natural English grouping is:

• Обледенение = icing
• началось = began
• после сильного ветра = after a strong wind

This is a good example of how Russian case endings show relationships that English often shows with word order and prepositions.