Beckoning gesture
 

I had noticed in Costa Rica that people signal others to approach by holding their palm down, holding the fingers together and moving the whole hand as though scratching the surface of a table or something.
Yet last night I saw a program from the hospital La Mascota - in Nicaragua - where a mother called to her family to come greet her son who was emerging from surgery, by doing the above with palm up, as is the US custom.
Was she just excited by the moment or is it a regional custom?

It's done both ways, but with the palm up, if the context and gesture is not very clear and friendly, it may feel like a challenge or another kind of invitation. With the palm down, it's mostly understood that you want to tell them something. Women usually accompany it with a movement of the head like nodding fast. All this, obviously, may change from region to region. :)