The number of migrants and refugees arriving on Greece's shores has fallen this week due to poor weather but the flow will pick up again if the weather improves, the U.N. refugee agency UNHCR said on Friday. "Nevertheless, any improvement in the weather could be expected to bring another surge in sea arrivals," UNHCR spokesman Adrian Edwards told a regular U.N. briefing in Geneva. "The current cooler, windy weather has made the crossing from Turkey to Greece even more perilous.