global variable is not accessible in firebase function

I declared a global array in index.js (firebase function). Once the code is deployed, this array is filled from firebase data. I have two functions, in the first one (onTW) i made some changes to the array, and i'm just displaying it in the other function(onRemoveTW). The problem is I'm getting an empty array in the second function. Here's my code.

    var TWArray = [];
    TWRef.once('value', function (snapshot) {
snapshot.forEach(function(childSnapshot) {
    var name=childSnapshot.key;
    var users = {};
    var userNbr = 0;
    TWRef.child(name).child('rm').once('value', function (snapshot2) {
        snapshot2.forEach(function(childSnapshot2) {
            userNbr++;
            if(childSnapshot2.key=='a'){
                users.a = childSnapshot2.val();
            }
            if(childSnapshot2.key=='b'){
                users.b = childSnapshot2.val();
            }
            if(childSnapshot2.key=='c'){
                users.c = childSnapshot2.val();
            }
            if(childSnapshot2.key=='d'){
                users.d = childSnapshot2.val();
            }
        })
        TWArray.push({
            rmName:name,
            users:users,
            userNbr:userNbr
        });
    })

})
    })
    exports.onTW = functions.database
    .ref('/Orders/TW/{requestId}')
    .onWrite(event => {
const userKey = event.data.key;
const post = event.data.val();
 if (post != null) {
    var users={};
            users.a=userKey;
            TWArray.push({
                rmName:userKey,
                users:users,
                userNbr:1
            });
            console.log(TWArray);
            console.log("TWArray.length : "+TWArray.length);
     }
    });
     exports.onRemoveTW = functions.database
     .ref('/Orders/RemoveTW/{requestId}')
    .onWrite(event => {
const userKey = event.data.key;
const post = event.data.val();
if (post != null) {

    console.log("TWArray.length : "+TWArray.length);
}
    })

Thanks in advance!