A critical fire risk has been put in place for south-western parts of the US this week. An upper-level trough of low pressure will deepen across the Rocky Mountains on Tuesday, which will cause surface pressure to fall. That means surface winds across Arizona and New Mexico will pick up even more. These areas are currently experiencing a mere 5-15% relative humidity, which the National Oceanic and Atmospheric Administration has deemed critical in exacerbating wildfire risk. Yet more dry, westerly winds will continue to affect these areas through this week, bringing further fire concern.
This is not the first time these areas have been affected by wildfires recently. New Mexico has already seen fires cover more than 39,000 hectares (97,000 acres) since mid-April, with thousands of people evacuated. As a result, more than 950 firefighters have been deployed in these regions.
Furthermore, convective hazards are forecast further east in the US. As the trough mentioned previously moves eastwards, it will advect moisture and increase atmospheric instability. Hazards such as thunderstorms, strong winds, hail, heavy rain and even a few tornadoes are expected to form in the mid-to-late afternoons across the southern plains this week. Daily rainfall totals could exceed 70-80mm across parts of Texas, Oklahoma and Arkansas.
Tornadoes have already been affecting parts of Texas, Kansas and Oklahoma in recent days, and 6,500 people have been left without power. More than 100 buildings have been damaged.
Meanwhile, a deepening but fairly stationary low-pressure system will feed persistent rainfall to south-eastern Brazil through Tuesday until Thursday. This feature will draw moist, tropical air from the central Atlantic before south-easterly winds take that moisture onshore to the states of Rio Grande and Santa Catarina, where 72-hour rainfall totals could exceed 150-200mm.
Elsewhere, Australia will experience huge differences in temperature across the country through this week. Northern Australia will experience maximum temperatures exceeding 30C, whereas New South Wales will see a chilly spell develop thanks to cold winds from Antarctica. Temperatures will barely reach double digits, which will be a shock after a mild autumn.