Sunday, May 20, 2018

Monsoon Watch --4 ...Quantum Analysis...20th May 2018

Quantum Analysis is evaluated for the amount of summer monsoon rainfall over Indian monsoon region during June- July....

Forecasting Methods adopted for the Indian Monsoons:

Gowarikar(1989) developed parametric and multiple power regression (MPR) models with 15 predictors for LRF of AISMR, which were later modified in 1991 to include 16 predictor parameters. The parametric model is qualitative and indicates the likelihood of the monsoon rainfall to be excess or deficient.
Thapliyal (1990) evaluated the relative performance of multiple regression, and Navone and Ceccatto (1994) have used 'feed-forward' neural network technique for the prediction of Indian monsoon rainfall with two predictors (500 hPa ridge location and Darwin SLP tendency from January to April).
The results of a recent work by Krishna Kumar (1997) indicate that a single component accounts for about half of the total variance in the predictors

Most of the studies on LRF of Indian monsoon rainfall were based on empirical or statistical techniques till 2010. IITM, Pune has recently implemented the state-of-the-art coupled climate model, the Coupled Forecasting System (CFS) developed by the National Centers for Environmental Prediction (NCEP), USA. These statistical techniques range from simple correlation analysis to advanced procedures.

Vagaries' View Point:

Vagaries leans on, and believes in the "Gowarikar Method" with 16 parameters. The results of this old but proven method has been successful. For Vagaries' forecast and analysis made in the "Arrival and quantum Monsoon Watch" series, I combine a few of them along with Dynamical models for a personal analysis and estimate.
15 initial parameters from the months March, April and May are used to analysis and forecast the simulation of Indian monsoon rainfall during June to October. These initial conditions were carefully selected  to span the evolution of both the atmosphere and ocean.

We have to take into consideration most of the 15 parameters (Gowarikar Method) before making an assessment, and these have to be analysed one by one. The prominent among the 15 are , ENSO, March temperatures of North India and East Coast, Himalayan Snow cover till March and SOI to name a few.
Of-course, I am not going to take each and every one of the 15 here, but, derive at an estimate on these basis and on the new model developed. I hope readers of vagaries trust that I have tried my best to estimate as accurately as possible.

Calculating the amount of rainfall, region wise, is of utmost importance, as SWM contributes to almost 80% of the annual total rainfall over India.
In this article, Quantum Analysis is evaluated for the amount of summer monsoon rainfall over Indian monsoon region during June and July.

The 500 hpa parameter is of importance in April. The mean latitudinal location of the 500 hPa ridge along 75°E in April over India, first identified by Banerjee (1978), is considered to be one of the most important predictors. The mid-tropospheric anticyclone over southern India migrates from 11.5°N in January to its northern most position of 28.5°N during July.
From October, the ridge starts shifting back southward. A more Northward location indicates better performance of the monsoon and vice versa. It also showed that the negative correlation of the March ridge was more dominant with the monsoon rainfall of the peninsular India, while the positive correlation of the April ridge was more dominant with the monsoon rainfall of Northern India.

ENSO factor in arriving at the rainfall amount is also of importance. The interface is the sea surface: that is where the transfers of water (evaporation/precipitation)
and momentum occur. An accurate coupling of the fast atmosphere to the slow ocean is essential to simulate the ENSO, which in turn can simulate the interannual
variability of Indian monsoon. Unfortunately, getting an accurate, or near to accurate forecast of the ENSO for the next 2 months is difficult, with no guarantee of accuracy or performance surety.

Currently we see neutral ENSO conditions persisting. But, there is a possibility of  Neutral event persisting till October. Now, this would result in normal Monsoon condition from June thru  October.( "Break Monsoon" conditions apart). 
After August, a 50-50 chance of neutral conditions continuing.

We depend also on other parameters.
Normally, Pulses from the Eastern Pacific area, that is S.China sea, would mean depressions and systems originating from the Bay. 'In Situ" systems and systems from the Far east would contribute to the rainfall to the east Coast thru Central India and into Gujarat and even into Sindh (Pakistan). No El-Nino, would mean no stopping  these pulses, and in fact not encourage WDs into coming down south, (more South than normal).
This may persist till  June, and then rapidly the flow of systems should increase from Bay in July.

The performance of Vagaries' Monsoon Watch Quantum Analysis is evaluated for the amount of summer monsoon rainfall over Indian monsoon region during June to SWM withdrawal in 2 phases. (June/July and August/September).

Why in 2 phases ? Because, I believe it is impossible to give actual Quantum forecast now (In May) for sometime in September...that is 120 days ahead !). I am not competent to give a forecast 90 - 120 days in advance, 
so Monsoon forecast will be 
1)...For June and July and
2)... August and September ..this is tentative and will be published in 2nd week July.

A) First 15 days of June 2018 sees 
i) Monsoon advancing from Kerala thru upto Central India, and into NE States and West Bengal.
ii) Heat ( Normal to above Normal) in Northern India, and Pakistan.
Monsoon advances into Central India and North India between 20th - 30th June.
iii) Monsoon moves into Pakistan around 1st - 10th of July in phases.

B) Mid June to July end, we can see normal rainfall and progress of the SWM in all of  Sub-Continent regions. Neutral conditions in the Pacific Oceans will send a few "pulses" to create "in situ" systems in the Bay, and the first 2 months could see around 3/4 noteworthy systems traversing the Sub continent. WDs will be few, hence, we can expect a few systems from Bay to track towards Central and Northern India, resulting in good rains in the plains of N.India and Northern Pakistan regions..and fairly good above normal rains in Nepal.

Slightly above normal rains likely along West Coast of India and A.P. coast and Odisha.
Weaker rains possible in June in Marathwada and parts of Telengana.

Thus, except for the above patch, June and July rains should be normal for the rest of the regions.

This estimate is based absolutely on the situation as it shows and stands today. 
Things, if and when they change (drastically) will be posted and Vagaries readers will be kept well informed, of any variation in the forecast. 
These are my personal views, and should not be depended upon commercially or otherwise.  They may differ from other models.

5 comments:

Unknown said...

Will West MP will get normal rain or above normal rain?

ANOOP RAWAT said...

Sir please tell when HEAT WAVES will hit NW India?

Hrishikesh said...

It seems that almost full india has got rainfall but not even a drop in Mumbai when do we expect rain around 29-31st??? If yes then which system will bring it?

NilaY Rajnikant Wankawala said...

CREDIT AUSTRALIAN GOVERNMENT BUREAU OF METEREOLOGY

Issued 22 May 2018

The latest ENSO Wrap-Up and Climate Model Summary are now available on the Bureau's website.

Tropical Pacific still El Niño–Southern Oscillation neutral

The El Niño–Southern Oscillation (ENSO) remains neutral—neither in an El Niño nor La Niña phase. Climate models favour ongoing neutral conditions for the southern hemisphere winter, despite continued warming of the tropical Pacific Ocean.

Key indicators of ENSO are mostly near average. Sea surface temperatures (SSTs) are close to the long-term average across the tropical Pacific Ocean, with Nino3.4 positive for the first time since mid-August 2017. Waters beneath the surface are slightly warmer than average. In the atmosphere, the Southern Oscillation Index (SOI) and trade winds are both within the neutral range.

Models suggest further warming of the tropical Pacific Ocean is possible over the coming months, with two of eight models indicating an El Niño could develop after the southern winter. However other models fall well short of El Niño thresholds, resulting in a broad range of possible scenarios for spring.

When ENSO is neutral it has limited influence on Australian and global climate. During an El Niño, eastern Australia typically sees less rainfall than usual during winter and spring.

The Indian Ocean Dipole (IOD) is currently neutral, with most climate models indicating a neutral pattern is likely to persist through the southern winter. However, there is a lot of variation amongst models in their outlooks, with one (of six models) forecasting a positive IOD to develop in winter, and another predicting a negative IOD during spring. The accuracy of IOD event forecasts is lower at this time of the year.

More information

Media enquiries: (03) 9669 4057 media@bom.gov.au

Natasha Fernandes said...

Mumbai...it will start raining soon then It will not stop... ..
So lets not worry abt pre monsoon.
When monsoon starts. Mumbai will leave behind all these cities which get excess pre monsoon. ..😁

Posted Saturday Night:( 23rd June) Mumbai City received good rainfall on Saturday, with Colaba measuring 127 mms in last 12 hours. Howev...