NEW DELHI: In line with India Meteorological Department forecast, the southwest monsoon rains arrived at southern Kerala coast and Northeast India simultaneously on Tuesday, the earliest since 2011 and setting India up for higher farm output and robust economic growth.Monsoon's early arrival in North East, where the rains normally arrives a few days after its onset over Kerala, is being aided by cyclone Mora, currently moving north from the Bay of Bengal."All the required conditions have been met," a weather office source who did not wish to be named, told Reuters. The official announcement is expected shortly, the source said.Andaman and Nicobar that are usually the first areas to receive the monsoon rains, received rainfall six days ahead of schedule earlier this month.Heavy rains have lashed northeastern states of Tripura, Mizoram, Manipur, Nagaland and Arunachal Pradesh as Mora moved further up the Bay of Bengal. A heavy rain alert has been issued for many parts of the northeast in the wake of the storm for Tuesday and Wednesday.Officials said monsoon is likely to advance into most of Kerala and some parts of Tamil Nadu in the next 24 hours.The normal date for monsoon's onset over the Indian mainland, usually the Kerala coast, is June 1. This year, IMD had forecast a May 30 onset, which is within the normal range of monsoon's arrival.There are also indications of monsoon progressing well on the western coast and the southern peninsula, including some interior parts of Karnataka and Maharashtra during the first week of June.“We are expecting Madden-Julian Oscillation (MJO) activity over the Indian Ocean which will aid the advance of the monsoon,“ said D Sivananda Pai, IMD's lead monsoon forecaster.MJO is a weather disturbance in the equatorial Indian Ocean that travels like a pulse from west to east. Depending on its position at that time, MJOs can depress the monsoon or activate it for a few days.It's rather rare for monsoon to arrive over Kerala and the northeast simultaneously, but not unheard of, said officials. “There have even been years when monsoon has hit northeast India before arriving over Kerala,“ said Pai.IMD on April 18 forecast this year's monsoon rains at 96 percent of the 50-year average of 89 cm.IMD earlier this month had said that the country is likely to receive higher rainfall than forecast in April as concerns about the weather phenomenon El Nino eased.