These storms include the hurricane with sustained winds of 65 knots or more, the tropical storm with 35- to 64knot winds, the tropical depression with winds 20 to 34 knots, and the tropical wave or easterly wave
with winds less than 20 knots.
Russell, North Carolina State University, "The Role of Convection in African Easterly Wave
Ferreira, "Case studies of easterly wave
disturbances over Northeast Brazil using the Eta Model," Weather and Forecasting, vol.
Weather systems likely to influence the country are the tail end of the cold front, intertropical convergence zone, easterly wave
, ridge of high pressure area, the easterlies and three to five tropical cyclone occurrences.
An official of PMD told that this rain would not be a part of monsoonal activity which is caused by easterly wave
but it would be the result of westerly trough present in the upper air.
When an easterly wave
is over an area of high sea-surface temperature, there is potential for tropical cycles, although only some of easterly waves
develop into tropical cyclones.
The synoptic situation says that the easterly wave
is penetrating into upper areas of the country.
The easterly waves
in this region have become active.
Replying a query regarding pre-monsoon, she said now the westerly waves are bringing rains in the upper parts however, monsoon is due to easterly waves
which would develop after subsiding these systems.
Mindanao, meanwhile, will experience scattered rainshowers and thunderstorms due to the northward migration of intertropical convergence zone or passage of easterly waves
, Pagasa said.
The application to the Caribbean region indicates a corridor of favorable conditions in the central Caribbean, possibly promoted by the presence of easterly waves
, and a southern unfavorable zone that shelters the Venezuelan coast from hurricane impact.
A series of disturbances in the atmosphere, known as `African easterly waves
', move towards the west in the trade winds that blow across the Atlantic Ocean.