Saturday, April 20, 2024

20th April 

Understanding the Pacific - the process of formation of the upcoming La Nina has begun!


We had put up an article in Weather Knowledge last year (Weather Knowledge - 48), which had described the El Nino and La Nina phases of the Pacific. 

Now, let us look at the conditions in the equatorial waters of the Pacific to see the situation this year.

El Nino or La Nina usually starts forming in the middle of the year and peaks during the period December-February. 

El Nino - A condition wherein the water in the eastern equatorial Pacific is warmer than normal i.e., the sea surface temperature anomalies are positive (anomalously warm). 

La Nina - A condition wherein the water in the eastern equatorial Pacific is cooler than normal i.e., the sea surface temperature anomalies are negative (anomalously cool). 

Below images show the snapshots from October 2022 to March 2024, which show

  • The ending of La Nina of 2022-2023 (which was actually a 3-year event, from 2020 onwards!)
  • Formation and peaking of El Nino of 2023-2024 
  • Now the decline of the 2023-2024 El Nino conditions over the equatorial Pacific.






The ending of the recent El Nino is also seen in the 90-day animation of sea surface temperature (SST) anomalies below:


     (credits: Climate Prediction Center, NOAA).


In the Pacific Ocean, the surface water is pushed from east to west along the equatorial region due to easterly winds at the surface across the ocean.

Below the surface, water slowly travels west to east, and rises to the surface near the coast of Peru (a process called upwelling).

The sub-surface water in the equatorial Pacific at present is abnormally cool, with a peak cool anomaly of greater than 4°C (i.e., more than 4°C below normal). 

This water is now seen rising up to the surface at the eastern boundary of the Pacific, near the equator (see the animation below). 

And although the sun heats the surface waters, this cold pool of water is cold enough to withstand the warming upon exposure to sunshine, and so is likely to remain cooler than normal, thereby resulting into a La Nina event.

The x-axis covers the extent of the Pacific Ocean and the y-axis is the depth below the surface (credits: Climate Prediction Center, NOAA).


We can also see this cold anomaly off the coast of Peru in the below image of sea surface temperatures :

     (credits: Climate Prediction Center, NOAA).


Therefore, the process of formation of La Nina has begun. As this cold water keeps rising up to the surface, the surface winds will help it spread westwards along the equator. 

Presently, the conditions are neutral over the Pacific. They will gradually shift from neutral to La Nina in the coming months, with La Nina establishing probably from/after August.
 
Below is the outlook from NOAA's Climate Prediction Center for the 3 monthly phase of ENSO (El Nino Southern Oscillation)

I




La Nina is known to be beneficial for the Southwest Monsoon over India. So, this development is one favourable factor for this year's Monsoon!

By Vagarian Shreyas 

Friday, April 19, 2024

Weekend outlook; 20th/21st/22nd April

Mumbai:

Dry heat gone...warm stuffy discomfort coming !

After seeing blistering heat last week at 38/39°, the next three days will witness a drop in day temperatures to 34/35°. But, with the humidity going high to almost 80%  the actual feel ( 38°c) will be more sweaty and uncomfortable. 

Warm stuffy nights at 26°c.

Pune

Possibility of patchy thundershowers in some areas.

Days around 39/40°c. But humidity around 55% may make it stuffy.

Above Normal nights at 23°c.

Mahabaleshwar:

At 33°c, Hot and warm by this hill station standards, resulting in a thundershower on Saturday/Sunday. 


Thursday, April 18, 2024

Reasons for heavy rainfall over UAE and parts of Oman 

Clarification of some doubts, Vagaries briefly explains the reasons behind the recent heavy rains and thunderstorms which lashed UAE and Oman. 

The main reason - a strong trough in the jet stream (strong Western Disturbance, as we call these systems over India) which was strong enough to generate a low-pressure system near the surface close to the warm waters of the Persian Gulf. 
This system had typical characteristics which are seen in weather systems in the midlatitudes, and so strong thunderstorms and rainbands formed near the boundary between winds from opposite directions (see below image from National Center for Meteorology, UAE).



Also, this event was well forecasted by various Global weather forecast models well in advance, therefore signifying that the natural processes were most likely governing this weather system. 

Such high-intensity extreme rainfall in this part of the world is rare but not unheard of.


Clarification on some confusion on common meteorological features over the Arabian Sea:

  • A high-pressure system (anticyclone) is present in the lower levels of the atmosphere over the Arabian Sea, usually from March to May-end, till Monsoon onset. 

  • The presence of this high pressure causes some southerly winds over the Oman coast, but does not give such extreme rainfall. 
  • This high pressure is seen every year, but we do not see such rain events every year. 

The observed heavy rainfall event was due to the trough in the Jet stream as explained above.

Impacts on the western parts of India:

  • The variation in the location and intensity of this high pressure also affects the weather for the west coast of India, by sometimes delaying the sea breeze or even setting in the sea breeze early.
 High pressures create sinking air or subsidence and are often associated with clear skies and dry weather. Such high pressure areas have caused heatwave like conditions with very dry weather and low humidity for Mumbai during February end and early March in the past years.

  • There was no strong high pressure over western Maharashtra across the first few kilometers of the atmosphere, otherwise we wouldn't have witnessed thunderstorms developing over the Ghats and Madhya Maharashtra regions.
  • Explained by Vagarian Shreyas








 

Wednesday, April 17, 2024

 U.A.E. Oman and Dubai face severe W.D.

SEE WORLD WEATHER NEWS PAGE 

UAE had surpassed all the paper records in 75 years  since 1949


They recv more than enough.


Total rainfall of 3.5 years receives in just 1.5days


Highest places received rainfall between

14.04.2024 to 17.04.02024 morning 


Khatam Al shaknah in Al ain (Abu Dhabi)

259.5 mm


Kalba in sharjah 

239.5mm


Al Marmoom in Dubai Al ain road

219.4mm


Wadi Al tuwa in ras Al khaimah

205.6mm


Margham in dubai

200.6mm


Saih Al Salem in Dubai

198.6mm


Ras Al Ghanadah in Dubai

197.1mm



Al faqa in Al ain (Abu Dhabi)

189.1mm


Raknah and Al qattara in Al ain(Abu Dhabi)

186.1mm


Al jurf in Dubai 

185.9mm


Umm Al Ghar in Al ain(Abu Dhabi)

178.1mm


Al rowdah in Al ain (Abu Dhabi)

176.2mm


Dubai IA

142mm



Al ain IA

127.2mm


Sharjah  IA

123.8mm


Zayed IA(Abu Dhabi)

100.2mm


Ras al khaimah(IA)

48.5mm


Abu Dhabi city

91.1mm


Dubai Jumeirah

168mm

Tuesday, April 16, 2024

Forecast for Mumbai/Pune:

Similar weather expected for Mumbai and Pune for Wednesday 17th April. 

Mumbai: Hot daytime weather in Mumbai city and suburbs, followed by humid afternoon and evening/night. Thane district will be hotter with above 40C max.
Eastern outer townships of Thane/Raigad district may see some localized thundery buildup and rain.

Some reduction in daytime heat can be expected from Thursday/Friday with the early onset of sea breeze.

Pune: Hot daytime temperatures, followed by thunderstorms for Pune and Ghat regions.
Pune region can see similar weather even for Thursday 16th April.


Parts of Konkan can get rain/thunderstorms next 2 days in some areas (more chance for interiors near Ghats).

 16th April

Temperatures around Mumbai

Mumbai Scruz 39.7° ( April record is 42.2° on 24-4- 1952).

Colaba 35.2° ( April record 40.6° on 19 -4-1955).

Koparkhairne 43.0°, Chembur 37.7°



Pune 40.7° with hails and thundershowers 

Looking Down from Space !A Different angle of seeing the Total Solar Eclipse. Other than the one we see normally:





The Moon’s shadow swept over North America, from the Pacific coast of Mexico, through Texas, and over the Great Lakes before crossing the Atlantic coast of Newfoundland, Canada.

On April 8, 2024, millions of Americans saw day turn temporarily to night as the Moon passed between the Sun and Earth to create a total solar eclipse.

As people in the 115-mile-wide (185-kilometer-wide) path of totality looked up and saw the Moon conceal the bright orb of the Sun and obscure all but its wispy corona, Earth-observing satellites captured imagery of the Moon’s shadow as it raced eastward over North America.

About 1 million miles from Earth, NASA’s EPIC (Earth Polychromatic Imaging Camera) imager on the DSCOVR (Deep Space Climate Observatory) satellite, captured the above views of Earth.

NASA Earth Observatory

20th April  Understanding the Pacific - the process of formation of the upcoming La Nina has begun! We had put up an article in Weather Know...