The intertropical convergence zone or “ITCZ” roughly forms a band that circumnavigates the Earth near the Equator where the northeast trade winds in the Northern Hemisphere converge with the southeast trade winds in the Southern Hemisphere. Sailors have often referred to it as the “doldrums” due to its generally light winds. Yet, the ITCZ is an important part of the global circulation as it forms the ascending branch of the Hadley circulation. This is ultimately driven by incoming solar radiation, which peaks near the Equator.
Heavy precipitation has been falling in areas of California that were recently devastated by deadly wildfires. This flooding rainfall has resulted in evacuations in burn scarred areas such as Butte County where the deadly Camp Fire hit this month. Flash floods, debris flows and mudslides are now predicted in areas where deadly wildfires stripped away vegetation. On a positive note these Pacific storms are expected to dampen wildfires and replenish the Sierra Nevada snowpack. This snowpack is an important source of water for California's streams and rivers.
Usagi strengthened to hurricane intensity as it approached Vietnam from the South China Sea but weakened to tropical storm intensity when coming ashore. Very heavy rainfall and damaging winds accompanied tropical storm Usagi when it hit Vietnam's southern coast. More than 350 mm (14 inches) of rainfall was reported causing widespread flooding around Ho Chi Minh City.
During the past week a strong low-pressure system moving through southern Europe battered, drenched and flooded Italy. It caused flooding, landslides and other damage to large areas of the country. The deaths of at least 11 people have been attributed to this stormy weather. High winds knocked down many trees and heavy rainfall from these storms contributed to flooding in large areas of Italy. Venice was inundated when heavy rain fell and a surge of water from the Adriatic Sea was pushed into the city by the storm's very high winds.
At least eleven deaths have now been attributed to deadly hurricane Micheal. Some casualties resulted not only from Micheal's destructive winds and storm surges but also from the blinding rain that Micheal produced as it battered states from Florida northeastward through Virginia. Today tropical storm Micheal is moving out over the Atlantic Ocean and has transitioned into a powerful extratropical storm.
For the period 03Z August 21 to 16Z August 22, the IMERG real time system experienced an outage of CPC 4-km IR data. Despite the outage, IMERG EARLY and LATE products continued to be produced but users should be aware that the quality of these products during this period may be suspect and should be used judiciously. Furthermore, the products for the first few hours after the outage are less than optimal due to IMERG restart but should be acceptable for most users.
The summer monsoon is a regular feature this time of year in India, and it can bring heavy rains to the region. However, periodically areas of low pressure can form within the general monsoon trough and bring even more rain.
Most of the Eastern half of the United States had rainfall during the past week. Some parts of the country experienced heavy rainfall that resulted in flash floods and various other problems. Slow-moving storm systems and nearly stationary fronts were the cause of heavy rainfall over Virginia this past weekend. Several trees were brought down by a severe storm that hit Fredericksburg, Virginia Sunday Afternoon. Fallen trees blocked several roads, flash flooding occurred and electrical power was lost in that area.