Skymet weather

Aviation weather hazards during post Monsoon season

Indian-Airlines CroppedAs monsoon starts to retreat from Northwest India in second fortnight of September, the weather starts changing for better. From uncomfortable warm sultry days of Monsoon, it becomes comfortable in the day with mornings & evenings becoming pleasantly cool, with slight nip in the air. This is mainly because Cool dry air starts ushering a season of azure blue skies, mild sun, good visibility & no rain over entire country except Tamil Nadu & Kerala, which experience retreating Monsoon or Northeast Monsoon.

This is the most awaited period by aviators, as weather conditions are just ideal, Hang-gliding, Para-sailing & Hot-air Ballooning. This period is known as Post-Monsoon period in meteorological parlance which is equivalent to Spring in USA & Fall in UK. It covers months of October & November.

According to Skymet Meteorology Division in India, the highlight is that the season has almost no aviation weather hazards mainly in Nortwest & Central India.

Mild Temperatures: Surface temperature is the single most important and decisive factor for the `all up weight` for the airplane to lift off but with temperatures ranging from a high 32 to 340C , aircrafts are able to carry more passengers/load than what are able to carry in summer monsoon.

Maximum temperatures drop below 30°C by late October and there is a gradual fall in average temperature. Minimum temperatures drop below 20°C. During Autumn, the wind direction begins changing from Southwesterly to Northwesterly.

Wind Shear:  As airflow streamline steadies to moderate westerly flow, the threat of wind shear becomes negligible. However, Clear Air Turbulence (CAT) is a cause for concern over mountainous terrain as it can lead to uncontrolled swaying and bumpiness leading to anxiety among the air travellers. Aviators need to exercise extreme caution while flying in Hilly areas or in the vicinity of hills.

Humidity: With the advent of Dry cool air from the North, the humidity drop is dramatic. From about 70-80% in Monsoon, humidity comes down to 30%-40% by end of Oct, rendering days & nights pleasantly comfortable.

Weather Systems: This period is excellent for flying because there are no major weather systems affecting this period as WDs have yet to make their presence felt, Westerly Jet is not very strong to cause concern. Temperatures are not low & humidity is not high enough for mist/fog to form. The only jarring note is provided by formation of a cyclone in Bay of Bengal, Which can cause loss of lives & damage to property due to high winds, heavy rains, tidal waves & Storm surges. During the life-cycle (3-4 days) of a cyclone, the weather within 500 km radius of its centre is highly hazardous for any kind of flying & is best avoided.

Hence, Oct-Nov is the period when flying conditions are their best, & weather is ideal for outdoor activities like Golf, Cricket & picnics. So, enjoy till sun shines.!!

Philippines faces threat of typhoon

TyphoonWest Pacific ocean has an active stormy season commencing from September and lasting till December. The intensity of these systems vary largely from a tropical depression to super typhoon. The West Pacific was struck by four CAT-5 typhoons last year during the period between September and December 2013. A vast stretch of coastline of Philippines, Vietnam, Laos, China, Japan and Korea remains under threat of strong tropical storms, frequently achieving typhoon status. These systems have devastating potential and are punched with a deadly combination of gale winds and torrential rains.

Presently, tropical depression ‘Fifteen` (LUIS) is marked in the open seas of western pacific, centered around 14°N and 132°E, having a wind speed of about 55 kmph. The system is likely to become a tropical storm and also rapidly upgrade to a typhoon in the next 36 hours. The tropical system seems to be heading for northern parts of Philippines and likely to make a landfall in 48- 72 hours. While crossing the coast, the wind speed may exceed 130 kmph and rainfall amounts of the order of 20 cm or more in 24 hr at many places. Disaster risk reduction and management council has already been advised to take appropriate action for safety and security of life and property.

After crossing Philippines, the storm is likely to emerge in the South China Sea and strengthen further.

Rainfall decreasing across the country

Monsoon rainAfter some very good spell of rain during the first nine days of September, rainfall is on a declining trend in the country now. For instance, 7.3 mm of rain was recorded on the 9th of September against the daily average of 6.8 mm, which slipped to record 5.1 mm on the 10th of September against the daily average of 6.5 mm. On the 11th the rainfall figure was 6 mm against the average of 6.7 mm, which clearly shows that rainfall is decreasing across the country.

However, on the two days (10th and 11th Sept) when rain has been below normal there have been cases of spot heavy rain. Bhira and Dahanu in Maharashtra recorded 112 mm and 121 mm of rain respectively on the 10th of September.

On the 11th, Ratnagiri in Maharashtra recorded 134 mm of rain, while Gwalior in Madhya Pradesh observed 101 mm of rain. This indicates that rain has not dercreased completely but the overall distribution has taken a dip. The last 24 hours suggest that rain will remain below normal in most parts of the country.

Meanwhile, there are some pockets which are absolutely dry. For example Jodhpur, Jaisalmer, Bikaner and Barmer in Rajasthan have not witnessed any rain in the last couple of days. Rayalaseema and interior Karnataka are also experiencing similar conditions with Kurnool, Ananthpur, Gadag, Chitradurga and Bangalore observing nil rain.

Tamil Nadu has been absolutely dry. Even the oceanic stations of Minicow, Aminidivi and Port Blair have been recording nil rain. Thiruvananthapuram, Cochi and Kozhikode in Kerala have also been experiencing minimal rain.

The situation in East India isn’t good either with places like Kolkata and Bankura in West Bengal observing nil rain.

Rainiest state Kerala may experience rain deficit in September

Usually known to be a month of heavy rains in Kerala, this year September exhibits symptoms of withdrawal from the beginning. With zero rain over cities like Kochi, Kozhikode and Kottayam in the past week, rain indicates to be scanty in this last month of Monsoon for God’s own country.

The lush green Kerala that never witnesses a lull in heavy rains is now on the threshold of withdrawal of southwest monsoon. During the last week, Kochi received just 28 mm of rain which is 51% deficit as compared to the rain received last year in the same period. The position is worse for Thiruvananthapuram which remained 94% deficit by receiving mere 5 mm in the last seven days.

While the starting few days of the week observed light to moderate rain showers, it became nil in the last few days . There was hardly any rain in cities like Kochi, Kozhikode, Kottayam and Thiruvananthapuram.

The monthly rainfall for most of the cities in Kerala is above 200 mm for September but witnessing the situation, Skymet meteorology Division in India anticipate a rain deficit for this month in Kerala.

So while the past week has been quiet for this South state of India, the upcoming week may bring slight respite from this quiet spell.

Rain for the Week 6th Sep -12th Sep

Dates Kochi Kozhikode Kottayam Thiruvananthapuram
6th Sep 19 9 12 1
7th Sep 5 12 12 0.3
8th Sep 2 10 14 2
9th Sep 2 20 5.8 2
10th Sep Trace 2 6 Trace
11th Sep Trace 0 0 Trace
12th Sep 0 0 0 0

Rain comparison for the week 6th Sep- 12th Sep

City 2013 2014
Kochi 58 mm 28 mm
Kozhikode 35 mm 53 mm
Thiruvananthapuram 89 mm 5.3 mm

 

Rain in Delhi brings pleasant weather conditions

Rain in DelhiThe month of August had largely been hot, humid and gruelling for Delhiites. The city hardly observed any good showers after the 10th of August, when the Safdarjung Observatory had recorded 82.2 mm of rain. Till the 27th, the national capital received only 120 mm against the monthly average of 253.4 mm of rain.

A sudden development of thunder clouds on the 28th afternoon brought good showers in Central, East and south Delhi. Showers were the heaviest in Central Delhi that include Connaught Place and the Lutyens zone.

September came as a big relief and the city has been enjoying some lovely weather conditions since the beginning of the month. The first day itself recorded 36 mm of rain. There was a relative lull after the 6th but rain once again picked up pace since the 10th of September.

On Thursday, the city began receiving rain since morning and intermittent showers continued for the entire day. As reiterated by Skymet Meteorology Division in India, rain in Delhi was once again patchy in nature. While Noida received 20 mm of rain, Indrapuram remained dry. Ridge received heaviest rainfall of 50.4 mm, Faridabad followed with 26 mm, Hindon 25.2 mm, Lodhi Road 18.3 mm, Safdarjung 15.2 mm, Delhi University 14 mm, Pusa 6 mm and Yamuna Sports Complex 4 mm. Mangeshpur and Najafgarh did not receive any rain.

The day remained overcast, keeping maximum temperature low at 29.1°C at Safdarjung.  Though, Palam received just 0.3 mm of rain, proximity of rain patches did not let maximum here rise above 30.4°C. Yesterday’s spell gave rise to humidity content in the air, suppressing the quick rise of day temperatures. With forecast of light rain on Friday as well, temperatures will hover in the mid-thirties.

 

 







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