There are a few of these street trees around Waikiki, Tabebuia with smallish leaves, maybe 3.5 to 5 cm or a bit more, quite a bit smaller than usual for this genus. Leaves are glaucous. I've only seen the odd flower on them, so they probably don't really bloom in the winter. The only all-white-flowered one I can find now is T. alba; the leaves and habit are more convincing for T. bahamensis. For my reference, several species are listed on this page: Tabebuia roseoalba, White Trumpet tree -
possibly T. cassinoides (syn. T. uliginosa)? It apparently has a small white flower and somewhat small leaf (for Tabebuias) but I'm not sure if it's single or compound (as in you plant). The comparative sketch is from A. H. Gentry Taxon Vol. 18, No. 6 (Dec., 1969), pp. 635-642 see also: Tabebuia cassinoides | Wikiwand
I don't think it can be, with those simple leaves. The way I recognized the tree here was by the palmately compound leaves, and the leaf colouring on T. cassinoides seems too green, my second photo not-withstanding. Thanks for the comparative sketch, though! The leaf shape is similar to T. rosea. I'm going to edit my original posting - a leaf I picked up this morning is only 3.5cm and there seemed to be a lot at that size.
I found another young tree today, with three flowers total. I don't know what's with my camera and the colour grey - the leaves were very grey - that was how I noticed the tree. And the flower petals were lightly tinged with areas of pink.
