VAGARIES OF NELLORE DISTRICT-
NELLORE District, a place Located in Coastal Andhra Region is a well known center of Trade and Education. Even though the district is small and compact,the vagaries of Rainfall varies every Kilometer. Practically speaking, the North-west of District, there lies a dry-rain shadow region. Where as a much greener Paddy fields to the South-east and East of the District. Nellore district gets 60-65% of Rains in North-East and Remaining 35-40% Rains in South West Monsoon. Some Areas of Nellore remain Bone dry during South-West Monsoon. Nellore district typically falls under the rain shadow region of South West Monsoon due to Eastern Ghats of Height 900 meters just 70 kms running parellel to the Coast. The thunderstorms forming over Kadapa area pounds well in Eastern ghat area with Kodur, Rajampeta section getting more than 20-35% excess rain than the Normal rain received by Nellore district.
South West Monsoon Of Nellore District-
Nellore distrct gets a normalized quantum of South West Monsoon. Kavali Mandal gets lowest rain during South-West Monsoon period, while the Tada Mandal gets the Highest Rainfall during the same time. The main reason behind lack of South West Monsoon is the Ghats to the west of district not allowing proper flow of Monsoonal winds at the surface levels. So less often the Sea breeze front interacts with the Clouds and make Thunderstorms. Further, the Winds from South-SouthWest at Mid-levels has Shown a good improvement in Thunderstorms.
During South-West Monsoon, the Upper air Circulation gives rains above Bapatla Latitude. In the mean while the August and September seasons, witness heavy Thunderstorms in Tada and Gudur Mandal, Flanking from Tirupathi or Bordering Tamilnadu.
Pics of Nellore During South West Monsoon. One can see Many dry days with almost less Number of Thunderstorms in June and July Month. When the winds turn South-Southwest, during Break Period, the Monsoon gets bountiful giving some rains to Nellore Town.
Some times, the rains get influenced by Systems Forming in Bay of Bengal. Suddenly the Thunderstorms make their way into the district.
AVAILABLE READINGS OF ATMOSPHERE 100kms South of Nellore....
Lifted index: -3.37
LIFT computed using virtual temperature: -4.03
SWEAT index: 219.00
K index: 37.80
Cross totals index: 19.30
Vertical totals index: 24.30
Totals totals index: 43.60
Convective Available Potential Energy: 1883.71
CAPE using virtual temperature: 2050.02
Convective Inhibition: -69.93
CINS using virtual temperature: -43.65
Equilibrum Level: 136.86
Equilibrum Level using virtual temperature: 136.83
Level of Free Convection: 810.39
LFCT using virtual temperature: 832.96
Bulk Richardson Number: 357.93
Bulk Richardson Number using CAPV: 389.53
Temp [K] of the Lifted Condensation Level: 295.09
Pres [hPa] of the Lifted Condensation Level: 905.84
Mean mixed layer potential temperature: 303.56
Mean mixed layer mixing ratio: 18.74
1000 hPa to 500 hPa thickness: 5824.00
Precipitable water [mm] for entire sounding: 61.12
INFERENCE-
In general, the Storms form in a place where the K-index is Very High and moisture availability there in Mid-levels. An article by NOAA shows, the development of Storms take place heavily if Convective inhibition is very less and the K-index is more than 40C. In nellore District, the storms arising from Kadapa district will cause heavy rainfall provided the Parameters like Vorticity, CAPE(Convective Available Potential Energy), K-index, PWAT (Preciptable Water Vapour) or a Trough or Circulation provided with Good dip of Winds over the District. Sea Breeze interaction is the Key factor for the Storms to Develop suddenly as the Moisture gets provided by Sea breeze font.
REFERENCE MAP OF MANDALS IN NELLORE DISTRICT-
North-East Monsoon Of Nellore District-
As the Sun comes down from the tropic of Cancer, the Inter-Tropical Convergence Zone moves Downwards, Dipping Along the Peninsular India. This will cause the Winds to Flow from the evolving Siberian High to the Location of ITCZ. This forms a Weaker Wind pattern which flows from North-east. The winds while crossing Bay of Bengal, picks up some Moisture and dumps along the coasts of South-Coastal Andhra and Tamilnadu. The Active Phase of North-east Monsoon Corresponds to a System. The System may be a Trough, Low pressure, Cyclone, Depression. It is also seen that there is no year wiithout any system forming in the seas of Indian Ocean. For NELLORE DISTRICT, the Major part of Rains are due to North-East Monsoon.
BRIEF SUMMARY OF CYCLONES IN NELLORE DISTRICT-
CYCLONE PRONE AREAS OF INDIA-
CYCLONE PRONE MANDALS OF NELLORE DISTRICT-
NEM CYCLONE TRACKS HITTING NELLORE DISTRICT (1979-2016) -
INFERENCE OF CYCLONIC ACTIVITY IN NELLORE DISTRICT-
"Positive Indian Ocean Dipole makes a possible Genesis of Lower Level Cyclonic Systems over Bay of Bengal, suppressing the formation of Tropical cyclones. But an exceptional case might arise, if Cyclone forms it will be confined to Lower latitudes during Postive IOD". We can expect a Bountiful Rainfall in Nellore District during the Positive IOD peiod in 70% of cases.
"Negative Indian Ocean Dipole makes a possible Genesis of Strong Cyclonic Systems over Bay of Bengal, Improving the possible formation of Tropical Cyclones". In one or Two cases, it Moves towards Nellore district. Its almost a Hit or Miss type. If System moves towards Nellore District then there comes the Rainfall.
POSITIVE IOD-
Active Period of North East Monsoon over Nellore District-
The increase in rainfall activity over Andhra-Tamilnadu coasts which takes place sometime around middle of October is generally considered as the "setting in of Northeast Monsoon". Normal date of onset of the northeast monsoon is around 20 October with a deviation of about a week on either side.
The rainfall over south peninsula towards the end of southwest monsoon season is mainly in the interior districts and it generally occurs in the afternoon , evening or early part of the night. As the season advances the rainfall is mainly in the coastal districts with the interior districts getting less rain. It generally occurs during night and early morning hours . Maximum rainfall mostly occurs between 2100 and 0300 hrs IST. Along the east coast rainfall during late night and morning hours (2400 to 0900 hrs) is an usual feature of northeast monsoon. When there is a low, depression or cyclone close by the rainfall occurs throughout the day.
Rains in NELLORE District during 97B system, 2015
Rains Pelting the Coast of Mallamu, NELLORE under the influence of Deep Depression, 2015
Rain Fury in Nellore District, November-2015
Andhra Pradesh Witness the Loss to the District due to Rains, November-2015
Cyclone Roanu, Stationery near Nellore Coast, May-2016
Industrialization of Nellore District-
Nellore has shown a good growth in Literacy, Marketing, Industrialization these days due to good governance of the Political Leaders. Industrial effulents making the atmosphere pollute the District natural trends of Weather.
Climate Change perspective leading for the slight increase in Rainfall over Nellore District year by Year. There will slight change of Strength of Monsoons from now.
PULICAT LAKE BIOLOGICAL ECO-SYSTEMS GETTING AFFECT BY CLIMATE CHANGE-
PENCHALAKONDA ECO-SYSTEM LOSING ITS GREENERY IN NELLORE DISTRICT-
CONCLUSION-
Nellore district is one of the best place for Tourism and Wondering Ecosystems. Monsoon of Nellore district adds more importance. The core ap Website measures and displays the Monsoon status of All districts of Andhra Pradesh. We can visit them at http://core.ap.gov.in/CMDashBoard/Index.aspx
Andhra Government acted in a right way and initiated many Afforestation acts between 2010-2015 period, which improved the status of Nellore District eco-systems.
BY
B.SAI PRANEETH
