METD WEATHER
AKSHAY DEORAS
SEVERE WEATHER FORECASTER
In the IndiMO II, METD WEATHER had issued 19th June 2012 as the monsoon onset date for Nagpur and a general of 14th-19th June 2012 for the Central India. The monsoon however as mentioned in the previous posts is very slow and almost stalled which is making this decision difficult
METD WEATHER CONDITIONS for Monsoon onset--
AKSHAY DEORAS
SEVERE WEATHER FORECASTER
In the IndiMO II, METD WEATHER had issued 19th June 2012 as the monsoon onset date for Nagpur and a general of 14th-19th June 2012 for the Central India. The monsoon however as mentioned in the previous posts is very slow and almost stalled which is making this decision difficult
METD WEATHER CONDITIONS for Monsoon onset--
1] MONSOON
A) - HEAVY RAINS
THE MONSOON RAINFALL OR THE ONSET OF MONSOON IS CONSIDERED ON THAT DAY WHEN THERE ARE HEAVY RAINS ( *** NOT APPLICABLE FOR RAINFALL DUE TO ANY CYCLONE LANDFALL***).
RAINFALL ACCUMULATION MUST BE MORE THAN 5mm
*** CONVECTIVE RAIN AFTER SUNNY MORNING SHALL NOT BE CONSIDERED AS MONSOON RAINS***
B)- WINDS
THE WINDS ( SURFACE-500MB) MUST BE FROM SOUTH-WEST ATLEAST FOR 48HRS AND HAVING INTENSITY OF MORE THAN 10KT IN ALL LEVEL.
( WINDS FROM SOUTHWEST FOR A DAY ARE NOT TO BE CONSIDERED AS MONSOON WINDS)
C) MOISTURE
***SURFACE RELATIVE HUMIDITY MUST BE GREATER THAN 60% ATLEAST FOR 48HRS
*** THERE MUST BE A DEEP LAYER MOISTURE IN ATMOSPHERE IN LAYERS 500MB-900MB ATLEAST FOR 48HRS WITH SATURATION ***
D) AIR PRESSURE
*** SURFACE AIR PRESSURE IN A REGION ( NOT APPLICABLE FOR HILLY REGION) SHALL BE BELOW 1006 MB CONSECUTIVELY FOR 2-3 DAYS. SINCE LESS PRESSURE REGION INDICATES LOCALITY OF THE MONSOON TROUGH.
*** ANY PERIOD WHEN SURFACE AIR PRESSURE GOES ABOVE THE LIMIT SHALL NOT BE CONSIDERED FOR MONSOON ONSET***
E) TEMPERATURE
*** SURFACE AIR TEMPERATURE MUST DROP TO 35C OR BELOW AFTER PRECIPITATION
*** TEMPERATURE SHALL BE MAINTAINED IN THE MAXIMUM LIMIT AS 35C ( MAX TEMP) ATLEAST FOR 48-72HRS.
*** TEMPERATURE ABOVE THE LIMIT SHALL NOT BE CONSIDERED FOR MONSOON ONSET***
F) CLOUDING
*** DUE TO DEEP LAYER MOISTURE,CLOUDING SHALL BE PRESENT IN THE REGION
*** OVERCAST CONDITION ATLEAST FOR 24HRS CONTINUOUSLY
ANY CLEAR WEATHER DAY WITH ALL THE ABOVE CONDITION POSITIVE ( EXCLUDING RAINFALL) SHALL NOT BE CONSIDERED FOR MONSOON ONSET
G) 850MB MOISTURE TRACK FOR NORTHERN LIMITS OF MONSOON
THE NORTHERN LIMITS OF MONSOON SHALL BE ADVANCED ONLY WHEN 850MB MAP SHOWS MOISTURE OF RELATIVE HUMIDITY GREATER THAN 60% AND BEING MAINTAINED FOR 2-3 DAYS
THE ABOVE ARE THE CONDITIONS WHICH METD WEATHER HAS BEEN CONSIDERING SINCE LAST 3 YEARS AND REGARD AS THE CORRECT MEASURES TO DETERMINE MONSOON ONSET.
THE INDIAN METEOROLOGICAL DEPT NORMS ARE DIFFERENT AND HAVE NO CONNECTION TO THE DATES FORECASTED BY METD WEATHER
Present conditions in Central India-
1) Rains ( IMD Nagpur)
As can be seen from the rainfall on 16th June evening till 1000hrs of 17th June, Jabalpur in M.P has got the heaviest rainfall of 75.7mm followed by Chadrapur in Maharashtra of 44mm and Nagpur getting 11.8mm rainfall.
Still heavy rains weren't reported for more than half of the stations above.
2) Winds-
The peak winds in Nagpur since 16th June were around 20km/hr mostly from West. The upper air winds also are satisfying the conditions.
3) Moisture-
The Surface Relative Humidity (lowest) was 35% at Nagpur at 0530PM on 16th June. This definitely doesn't fit into the criteria of the monsoon onset.
4) Air Pressure at the surface
The mean air pressure was around 1002mb since 16th May. The pressure is being maintained since 24hrs.
5) Clouding-
The overall cloud cover falls in the Mostly Cloudy with today being the same in Nagpur.
6) SFC temperature
The surface air temp of Nagpur on 16th June was around 38.2C which violates the norms
The 850mb shows some moisture in the region.
If these conditions ( except temp,moisture) are favorable then why isn't METD WEATHER declaring the onset???
Here is the latest (00z,17th June) GFS Nagpur Meteogram. The topmost profile shows the atmospheric moisture till 25th June. As can be seen that the amount of moisture in the region is strongly decreasing from around 18th-19th June. The 2m RH plot also shows a strong decrease in the moisture amounts with absolutely no rainfall expected from 20th June onwards.
If METD WEATHER declares the onset of Monsoon in the region then the immediate dry phase will take over with no rains. The parameters also aren't expected to remain consistent as a result the change of monsoon onset on 19th June is very low......
Abhijit Modak from Badlapur city,Maharashtra sends these photos taken today (17th June 2012). Badlapur is an Extended Central Line Suburb of Mumbai in Thane District. . These photos clearly show the heavy rains in the region.
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