This week, the US has declared a critical fire danger in the south-western US. On Tuesday, an upper level trough of low-pressure will form in the Rocky Mountains. This will cause the surface pressure to drop. This means that New Mexico and Arizona will see an increase in surface winds. These areas are currently experiencing 5-15% relative humidity. This is critical for reducing wildfire risk, according to the National Oceanic and Atmospheric Administration. These areas will be subject to more fire danger from the west winds and dry weather throughout the week.
These areas have been affected by wildfires in the past. New Mexico has seen wildfires that have ravaged more than 39,000 hectares (97,000 acres), since mid-April. Thousands of people have been evacuated. These fires have already displaced more than 950 firefighters.
Convective dangers are also forecast to be more east in the US. As the trough mentioned above moves eastwards, it will advect humidity and increase atmospheric instability. This week, thunderstorms, strong winds and hail, heavy rain, and even tornadoes are possible across the southern plains. In parts of Texas and Oklahoma, daily rainfall could exceed 70-80mm in some areas.
Recent tornadoes have already impacted parts of Texas and Kansas in recent days. In Oklahoma, 6,500 people were left without power. More than 100 buildings were destroyed.
A deepening, but relatively stationary low-pressure system will bring rain to south-eastern Brazil from Tuesday through Thursday. This feature will draw humid, tropical air from central Atlantic before southerly winds bring that moisture onshore to the state of Rio Grande and Santa Catarina. 72-hour rainfall totals may exceed 150-200mm.
Australia will experience large temperature swings across the country during this week. Northern Australia will see temperatures of 30C and New South Wales will experience colder weather due to the Antarctica winds. After a mild autumn, temperatures will barely reach the double digits. This will be quite a shock.