INDIA METEOROLOGICAL DEPARTMENT
August 5, 2002
SOUTH-WEST MONSOON 2002 - A MID SEASON REVIEW
A mid-season assessment of the performance of southwest monsoon during the period 1 June to 31 July, 2002 is given below :
This year, the South-west monsoon arrived over Kerala on 29 May, 3 days prior to its normal date 1 June. It covered south Peninsula and northeastern states by 10 June and Konkan & Goa, western parts of interior Maharashtra, Andhra Pradesh, Orissa, West Bengal & Sikkim, parts of Bihar and Jharkhand around its normal date of 12 June. Subsequently, it was sluggish for about a week. With the formation of a well marked low pressure area on 20 June over northwest Bay of Bengal, the monsoon activity was revived. The system moved across central parts of the country bringing the monsoon to remaining parts of Jharkhand, Bihar, Chhattisgarh, Maharashtra, Madhya Pradesh, Gujarat, Uttaranchal and parts of Himachal Pradesh, Jammu & Kashmir, East Uttar Pradesh and south Rajasthan by 27 June. On 4 July it covered more parts of west Uttar Pradesh, entire Uttaranchal, Himachal Pradesh, Jammu & Kashmir, Punjab and Haryana.
The first half of July was characterised by a dry spell which resulted in prolonged summer conditions over north and northwest India. A low pressure area formed in the head Bay of Bengal on 15 July. In association with this low pressure area the dry spell was broken and many parts of the country received monsoon rains. On 19 July, the monsoon advanced into West Uttar Pradesh, Delhi, Haryana and some more parts of Rajasthan as a weak current. However, the monsoon activity was not sustained after the low pressure area became diffused and merged with the monsoon trough. On 22 July, the monsoon trough shifted to the foothills resulting in weak monsoon conditions again. As of 31 July, the monsoon is yet to cover remaining parts of West Rajasthan and adjoining Punjab and Haryana. The advance of southwest monsoon 2002 is shown graphically in Fig.1.
2. Synoptic features and associated rainfall activity
On 20 June a well marked low pressure area developed over north-west Bay of Bengal. The system moved initially in a northerly direction and then took a westward course through central parts of the country. The system weakened over southeast Rajasthan on 28 June. It caused widespread rainfall in Madhya Pradesh, Gujarat and Maharashtra. Very heavy rains were experienced in Gujarat and Maharashtra leading to floods affecting rail and road services. The cumulative rainfall for the period 1 to 26 June was 7 % above normal.
There was a lull in the monsoon activity during the first half and last week of July when on most of the days monsoon trough was located close to the foothills of the Himalayas. Rainfall activity was mainly confined to northeastern region , Bihar and adjoining areas leading to flood conditions. Peninsular India experienced scattered rainfall on some days during the second fortnight of July. Overall the monsoon activity was much subdued over most parts of the country in July.
3. Cumulative rainfall distribution (1 June to 31 July, 2002)
The progress of the monsoon rainfall over the country is monitored by evaluating the departures from the normal rainfall for each meteorological sub-division and district. These departures are classified as:
Excess (20% of normal or more)
Normal (+19% to –19%)
Deficient (-20% to –59%)
Scanty (-60% or less)
The cumulative rainfall from 1 June to 31 July 2002 (Fig.2) was excess in 1 meteorological sub-division, normal in 9 sub-divisions, deficient in 21 and scanty in 5. At the end of July, the following five meteorological sub-divisions were in scanty category:
Sub-division
% Departure from normalWest Uttar Pradesh -76 %
Haryana, Chandigarh & Delhi -74%
West Rajasthan -73%
East Rajasthan -71%
East Madhya Pradesh -61%
The following five meteorological sub-divisions , which are not in the scanty category , have received highly deficient rainfall:
East Uttar Pradesh -54%
Punjab -52%
West Madhya Pradesh -50%
South Interior Karnataka -49%
Himachal Pradesh -48%
The cumulative rainfall during the period 1 June to 31 July for the country as a whole and three meteorologically homogeneous regions has been deficient. The area weighted rainfall for the period 1 June to 31 July is as follows:
|
Area |
Rainfall in June- July 2002 |
|
|
Actual (Normal) (mm) |
% Departure from normal |
|
|
Country as a whole |
329.8 (470.8) |
-30% |
|
Northwest India |
131.7 (272.8) |
-52% |
|
Northeast India |
716.5 (800.8) |
-11% |
|
Peninsular India |
287.8 (453.1) |
-36% |
Out of 523 meteorological districts, 6% received excess rainfall, 19% normal, 41% deficient and 34% scanty.
A comparative analysis of the rainfall over the 35 meteorological sub-divisions for the months of June-July in the last ten years is presented in Fig.3 and percentage of districts with excess/normal and deficient/scanty rainfall for the same period is shown in Fig.4.
*******