A l'armari hi ha la samarreta i els texans que vull portar avui.

A l'armari means in the wardrobe / in the closet.

Here, a is the preposition used with places in many Catalan expressions, where English often uses in or at.
l'armari is the wardrobe, with el armari becoming l'armari because of elision before a vowel.

So:

• a + l'armari = in the wardrobe / in the closet

Catalan often uses a where English learners might expect something more like in.

Hi ha is the standard Catalan way to say there is or there are.

• ha comes from the verb haver
• hi is a locative particle that is part of this expression

So:

• hi ha la samarreta = there is the T-shirt
• hi ha els texans = there are the jeans

Even though hi originally has a place-related function, in modern Catalan hi ha is best learned as a fixed expression meaning there is/are.

Unlike English, Catalan does not change this expression according to number.

So both of these are correct:

• Hi ha una samarreta = There is a T-shirt
• Hi ha uns texans = There are some jeans

English changes there is / there are, but Catalan normally keeps hi ha in both cases.

Both are possible, but A l'armari hi ha... puts the location first for emphasis or topic.

It is similar to saying in English:

• In the wardrobe, there is...

This kind of word order is very natural in Catalan. The sentence begins with the place, and then hi ha introduces what is there.

Catalan uses definite articles more often than English does.

So where English might naturally say:

• the T-shirt and jeans
• or even just T-shirt and jeans

Catalan typically says:

• la samarreta i els texans

The articles make the clothes sound like specific items the speaker has in mind.

Yes, texans is plural in Catalan too.

• singular: el texà can mean a Texan man, so for clothing this form is not normally what learners need
• plural clothing form: els texans = jeans

Just like in English, this item is usually referred to in the plural.

Grammatically, que vull portar avui comes right after els texans, so it most directly modifies els texans.

That means the most literal structure is:

• the T-shirt and the jeans that I want to wear today

However, in real context, speakers may mean both items together, especially if the overall meaning is clear.

If someone wanted to make it clearer that the relative clause refers to both items, they might rephrase the sentence.

Que is the relative pronoun meaning that, which, or sometimes who depending on context.

Here it links els texans to the clause vull portar avui:

• els texans que vull portar avui = the jeans that I want to wear today

Catalan uses que very often in relative clauses, much like English that.

Vull portar means I want to wear.

• vull = I want
• portar = to wear / to carry / to take, depending on context

For clothes, portar is a very common verb meaning to wear.

About the alternatives:

• porto would mean I wear / I am wearing / I carry
• vull vestir is less natural here for most everyday contexts

A useful distinction is:

• portar roba = to wear clothes
• vestir-se = to get dressed

So vull portar avui means I want to wear today, not I want to get dressed today.

Avui means today, and Catalan often places time expressions at the end of the clause, especially when they modify the verb phrase naturally.

So:

• que vull portar avui = that I want to wear today

Other positions are sometimes possible, but the final position is very normal and natural here.

Armari is a general word for a cupboard, cabinet, wardrobe, or closet, depending on context.

So in this sentence, a l'armari could be understood as:

• in the wardrobe
• in the closet

The exact English word depends on what kind of storage furniture or space is meant.

Normally, with haver in the sense of there is/there are, you use hi ha.

So:

• A l'armari hi ha... is correct
• A l'armari ha... is not correct in standard Catalan

For learners, it is best to memorize hi ha as one unit.

Catalan often drops the vowel of the article before a word beginning with a vowel or silent h.

So:

• el + armari becomes l'armari

This is called elision. It is very common:

• l'amic
• l'escola
• l'home
• l'armari

Yes. Starting with A l'armari can highlight the location.

It can feel like:

• In the wardrobe, there are the T-shirt and the jeans...

This is a common discourse pattern in Catalan: first mention the setting or location, then say what is there. It does not necessarily sound strongly dramatic, but it does make the place the starting point of the sentence.