“Easterly waves” are areas of low air pressure in the tropics that move westward and may become tropical cyclones. The most well-known type of easterly wave is the “African easterly wave,” which moves from West Africa north of the equator into the Atlantic Ocean and sometimes into the Pacific. Although almost all Northeast Pacific tropical cyclones develop from easterly waves, it is unclear how important the African waves are to this region. Most previous studies indicate that Northeast Pacific easterly waves are actually African easterly waves that cross Central America. However, it is difficult to observe an African easterly wave moving from the Atlantic to the Northeast Pacific. The authors were curious if easterly waves could develop in the Northeast Pacific. They used the Weather Research and Forecasting (WRF) model to study if strong daily thunderstorms near the Gulf of Panama (i.e., Panama Bight) could produce enough wind to form easterly waves in the Northeast Pacific.
Important Conclusions:
- Daily thunderstorms near the Gulf of Panama (i.e., Panama Bight) can create easterly waves locally or strengthen African easterly waves that cross over Central America. Either way, these easterly waves may form into tropical cyclones in the Northeast Pacific Ocean.
- When Central American mountains were removed in the model, there was less wind produced by thunderstorms near the Gulf of Panama and easterly waves were much weaker in the Northeast Pacific Ocean.
- When African easterly waves were blocked from entering the Northeast Pacific Ocean in the model, easterly waves there were weaker than they were if they moved in from the Atlantic.
http://journals.ametsoc.org/doi/full/10.1175/JAS-D-16-0124.1