--Withdrawal Has Begun About Three Weeks Later than Average
The rain-giving summer Monsoon has begun its belated withdrawal from the Indian Sub-continent.
The India Meteorological Department (IMD) began to track the southeastward withdrawal of the mega weather system as of Monday, the IMD website showed.
The IMD have a set of objective guidelines to determine withdrawal from a given area. Among these is the cessation of significant rainfall for a period of at least five days. Such a shutting off of significant rain has indeed happened in the north west of the Subcontinent beginning last week.
The average onset date of the South West Monsoon is about Sept. 1 along the Pakistan border. By the end of the month, the Monsoon has normally ended from Delhi to Mumbai.
The swath of black on this water vapor satellite image, taken Sept. 26, 2012, shows very dry air that has settled over the north west of the Indian Subcontinent. (Indian Meteorological Department-IMD)
Wednesday, Monsoon withdrawal had progressed east of Delhi to a line from western Nepal to the Kathiawar Peninsula of Gujarat state, the IMD indicated.
Thus, having lingered over the northwest of the Subcontinent about three weeks later than usual, the Monsoon has quickly retreated, catching up with its average position for the last week of September.
The late withdrawal from Pakistan and western India was significant, as it allowed much of the region to recover from earlier shortfalls in seasonal rainfall.
By Sept. 19, seasonal rainfall (June-Sept.) in India, for instance, was only 5 percent below normal. It had been short by more than 10 percent earlier in the season, being the cause of some concern with respect to agriculture and water supply.
However, before leaving Pakistan, the summer Monsoon unleashed abnormally late, excessive rainfall and flooding that killed scores of people.
About 120,000 homes were destroyed, leaving tens of thousands of people homeless, the BBC News website said on Tuesday.
Vast areas of crops were damaged or destroyed.
In at least one location, Jacababad, rainfall was unprecedented in the historical record, the Pakistan Meteorological Department (PMD) said.
Going forward, October, historically a month of major weather transition across the Subcontinent, will bring further withdrawal of the South West Monsoon. By the middle of the month, only parts of southern and eastern India, together with Sri Lanka, normally remain within the fold of the Monsoon.
Meanwhile, a new weather phenomenon, the North East Monsoon, begins to show itself. The onset of the North East Monsoon heralds dry weather for most of the Subcontinent, but it also ushers in the rainy season for southeastern India and eastern Sri Lanka.
The rainy phase of the North East Monsoon typically ends before the end of the year.
The plum rains are known as "meiyu" in China, the "baiyu" or "tsuyu" in Japan, and the "jangma" in the Koreas. The heart of the plum rain season stretches from early June to mid-July, with a tendency to shift south to north across the affected area.
In the wake of the mid-June cloudbursts, most of Pakistan to northwestern India last week saw a return to dry, hot weather typical of the weeks leading up to the Monsoon onset. It was as if the Monsoon withdrew to its "normal" position for the latter half of June.
The 38.5 degree C (101 degrees F) reading Tuesday in Ajaccio, Corsica, may have been tops in Europe.
Monsoon Onset was June 13th, 2013, in Delhi, almost two weeks earlier than average. The June 15th onset at Karachi and Islamabad was more like three week ahead of schedule.
In Pakistan, hit-or-miss downpours missed the Sindh capital, Karachi. One did hit Pad Idan, where it left 60 mm of rain Wednesday. This was more than 20 times greater than the normal June rainfall.
It is still possible that this scenario is over wrought as to the intensity and spread of rain in Pakistan and northwestern India. However, it is the hunch of the present forecaster that some very unusual weather is going to unfold in the Subcontinent during the next week!