The 850mb winds in the Pacific Ocean which are a measure of the intensity of the Easterly Trade Winds are consistently showing anomalies ( westerly anomalies) across North Indonesia area. Easterly trade winds otherwise seem to be showing no anomaly and thus reducing the chance of an El Nino forming for a few more months.
The CPC considers a three month group SSTA in the ONI plots. So it can be expected that the ONI for August- Sept-Oct settles to around +0.40C
Above is the IRI Probabilistic ENSO Forecast. The forecast still calls for a 50% + chance for El Nino formation till DJF 2012-2013 period.
So according to our estimates, The ONI will be in the Neutral Range in the ASO period and shall hit the El Nino threshold of +0.5C in the SON period i.e El Nino Conditions may emerge around November end to December 2012 with a very weak amplitude.
So for those forecasters forecasting using the ENSO, it appears that more or less a ENSO Neutral will persists through the Northern Hemisphere winter with a slight El Nino conditions emerging in the year end.
The tendency of ENSO will depend on whether El Nino gets established this year end or not.
However, in this forecast we are least bothered about the ENSO
----------------------------------------------------------------------------------------------------------------------------------
3) Introduction to the Arctic Oscillation -
AO- Arctic Oscillation is not much known to the people of India as the parameter is not used for making any forecast ( Long Range/Short Range) relating to India. However, in this study we observed that the AO seems to have some association with the Indian Winters. Before we get into the observational part, lets understand the basics of the AO
AO is an oscillatory phenomena characterised by dipolar natured air pressure across the High Latitudes and the Mid Latitudes simultaneously. AO is Characterised by two prominent modes-
1) The Positive
2) The Negative
The Positive Mode of the AO is characterised by the formation of low pressure in the Polar Regions and subsequent higher pressure in the Mid latitudes refraining the cool air from the higher latitudes to spread in the mid latitudes. Vice versa conditions are observed during the Negative Mode
(all jet streams mentioned below are the subtropical jet streams)
The most important feature of the AO is that it influences the subtropical jet stream. In the case of the positive AO, the jet streams have a zonal flow from the usual west-east direction. Whereas in the case of the Negative AO, the jet streams don't have a zonal flow rather they have a wave shaped ( comprised of crest and troughs) as seen in the below figure-
In the above figure, one can clearly see how the cold air enters the mid latitudes during the Negative phase.
Arctic Oscillation is given by the Arctic Oscillation Index ( AOI). The AOI is one of the most unpredictable index and one can't predict how the AO will behave as it varies stochastically.
----------------------------------------------------------------------------------------------------------------------------------
4) Relation between the Arctic Oscillation and minimum temperatures during winter
Since the volume of investigated data is large, we use the SAMPLING method from statistics.
Hypothesis-
1) It has been observed from the data that the minimum temperatures in a region stretching southwards from the Maharashtra-Madhya Pradesh have a inverse relation with the AOI
i.e the higher the AOI (MORE POSITIVE), the lower the temperatures during the Winter ( as compared to the previous years).
2) Minimum temperatures in a region stretching northwards from the Maharashtra-Madhya Pradesh border are directly proportional to the AOI
i.e the lower the AOI ( MORE NEGATIVE IN MAGNITUDE) min temperature VS previous year's temperature.
3) The geographical boundary at the Maharashtra-Madhya Pradesh region across which the AOI varies directly/inversely is being coined as the Deoras limit.
The result prominently applies for the December month so we shall investigate the relation for December month only
*** South of Deoras Limit***
Data set for Nagpur,Maharashtra
Average Monthly min temperature (1950-2002)
http://indiawaterportal.org/met_data/
AOI Historical ( 1950-2012)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/monthly.ao.index.b50.current.ascii.table
YEAR MONTH AOI AVG MIN TEMP(C)
1950 DEC -1.928 13.028
1951 DEC 1.987 12.765
1951 DEC 1.987 12.765
1952 " -1.827 14.991
1969 " -1.856 13.232
1970 " -0.399 11.944
1994 " 0.894 13.044
1995 " -2.127 15.403
1995 " -2.127 15.403
1996 " -1.721 13.101
One infers that for a period say 1951 the min avg temp for december was lesser than 1950 when the AOI had opposite relation
Thus through sampling, the probability of the above relation holding good is high though there are some cases where the relation doesn't hold good.
*** NORTH OF DEORAS LIMIT***
For simplicity and to reduce the length of this forecast, we shall consider the case for Ludhiana,Punjab. However from the given links, one can verify that the relation holds good for all the areas North of Deoras Limit
YEAR MONTH AOI AVG MIN TEMP(C)
1950 DEC -1.928 5.457
1951 DEC 1.987 8.439
1951 DEC 1.987 8.439
1952 " -1.827 7.523
1997 " -0.071 5.676
1998 " 1.353 8.113
1972 " 1.238 8.349
1973 " -0.181 5.475
Thus through sampling, the probability of the above relation holding good is high though there are some cases where the relation doesn't hold good.
Though it has not been calculated but we do suspect that when calculated on a 3-4 month basis, the results will come better and the anomalies in the result will decrease considerably.
Reason-
----------------------------------------------------------------------------------------------------------------------------------
5) Estimated Arctic Oscillation Index during 2012 Winter
As stated above, the AO is a stochastically varying phenomena. September 2012 had AOI of 0.772
Here is the observed and forecasted value of the AOI
Thus from the models, it can be inferred that AOI will remain in the negative mode for remaining half of Oct for sure
Since its an experimental forecast, I think that the AOI will remain in the negative mode till somewhere Mid November after which it will oscillate between the negative and positive phase.
So the OND average AOI as per my estimate shall be negative considering the happening Oct negative AOI and estimated Nov AOI
----------------------------------------------------------------------------------------------------------------------------------
6) The 2012 Winter Forecast
Like said above, it will all depend on the AOI. If the net AOI turns out to be positive then areas South of Deoras Limit will experience slightly cooler than normal winter and vice versa
However considering the expected negative AOI, it appears that Northern Deoras Limit regions will experience a marginal cooler than normal winter whereas areas south of the limit shall experience a slightly warmer winter with the intensity increasing towards South India
Zone Wise-
North India-
1] Jammu and Kashmir,Himachal Pradesh,Uttaranchal
Normal winter conditions will be observed here.The temperature anomaly ( All season Average) shall be around 0.2C to 0.1c less than average temperature.
2] Punjab,Haryana,Chandigarh,New Delhi
The overall temperature anomaly in these regions depends on the western disturbance. However it does appear that these regions will witness ( 0.5C to 0.7C) less than average temperature.
After the snowfall events, temperature in the plains will drop suddenly but average will be near to the predicted value.
** We shall not estimate the number of western disturbances as its a debatable topic. However, the precipitation in the hilly areas seems NORMAL
3] Madhya Pradesh,Rajasthan,Uttar Pradesh,Gujarat
A Cooling effect is likely in these areas as the jet streams coupled with the negative AOI influence shall lead to drop of temperatures due to more cool air incursion.
** Uttar Pradesh will have NORMAL winter and hence I don't expect any anomaly in the temperature.
The Average temperatures will be ( ~0.5C) less than average normal temperature. Areas like Rajasthan-Gujarat border can experience lesser than avg temp by a factor of around ( 0.8C to 1C)
4] Northern Chattisgarh,Bihar and Jharkhand,West Bengal
Regions will witness a slightly cooler than normal winter conditions with average variation of about 0.3-0.5C ( lesser than the normal)
5] Sikkim,NE India
Though this shall not support the Deoras limit but it appears that the regions will witness warmer conditions with temperatures around ( 0.3 to 0.5C) more than normal
6) Central,Northern,Eastern Maharashtra,
These areas will be witnessing normal winter conditions but the tendency shall be a slightly warmer than normal by a factor of around 0.3C.
The expected record min temperature of Nagpur for the season shall be in the range of 7.5C ( +/- 0.5C)
7) Southern Maharashtra and remainder Southern India
Warmer than normal conditions with temperature variation of a factor of around ( 0.5C to 1C) more than Normal for Southern India
* No forecast available for Lakshadweep, Andamaan Nicobar Is.*
----------------------------------------------------------------------------------------------------------------------------------
7) References & Acknowledgements
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/
http://www.apcc21.net/eng/service/fore/lmon/japcc030101_lst.jsp
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml#forecast
http://en.wikipedia.org/wiki/Arctic_oscillation
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_mrf.shtml
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif
http://metdweather.blogspot.in/2010/11/2010-winter-forecast-for-india.html
http://metdweather.blogspot.in/2011/10/2011-winter-forecast-of-india.html
http://indiawaterportal.org/met_data/
http://ggweather.com/enso/oni.htm
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/hgt.ao.cdas.gif
http://www.apcc21.net/eng/service/fore/lmon/japcc030101_lst.jsp
http://nsidc.org/icelights/2012/02/02/the-arctic-oscillation-winter-storms-and-sea-ice/
http://weather.unisys.com/archive/sst/
Attached above is the 48hr projected base 00z,27th Nov 700mb vorticity coupled with the precipitation.. One can see that the rainfall amount will be very heavy (snowfall as well) in J&K prominently in Central,Western J&K.
.gif)
