Striae angled or curved away from the central nodule are termed convergent striae. Striae may be convergent in a specific part of the diatom valve. For example, the striae may be convergent throughout the valve, convergent only at the center valve, convergent only at the ends, etc. Convergent striae are opposite of radiate (divergent) striae.
Barber, H.G. and Hayworth, E.Y. (1981). Guide to the Morphology of the Diatom Frustule. Freshwater Biological Association, 112 pp.