A week of extremes in the US as Arctic air plunges southwards across many states, sweeping away record-breaking warmth from last weekend. With low pressure in the west drawing up warm, humid air from the Gulf of Mexico, much of the south and midwest basked in spring-like weather this weekend with temperatures widely an extraordinary 15-20C above normal for late December.
This week, however, most people will ditch their summer clothes for hats and scarves as a ridge pressure builds across the west, allowing for a polar airmass to dive southward, bringing freezing temperatures and the risk of snow.
Remarkably high temperatures have not just been confined to North America in recent days, with São Paulo in Brazil recently recording a maximum temperature of 36.2C – the highest on record for December. Further high temperatures are expected to start this week with the heat spreading to parts of Chile and Argentina later.
Across the Pacific, winter has firmly established itself in Japan with severe weather causing havoc to daily life. Heavy snow and icy conditions resulted in a deadly pileup last Friday on a motorway in Minakami, Gunma prefecture, leaving two dead and dozens injured. More heavy snow is forecast this week as bitterly-cold westerly winds from Siberia blow across the comparatively warmer Sea of Japan, picking up moisture and resulting in a phenomenon known as “sea-effect” snow that can affect much of northern and western Japan.
Summer storms have hammered parts of the South Island of New Zealand with torrential rain, large hail and lightning, which has caused severe disruption to travel in many places in recent days, with the Canterbury Plains seeing a rare and powerful “supercell” storm. Further severe weather is anticipated in the country over the coming days, with the North Island expected to experience strong winds and very high rainfall totals of 100mm in western parts, with some areas perhaps recording up to 200mm, as an area of low pressure moves through the region.