Weather outlook from Thursday 25th to Sunday 28th April. 

Mumbai: Typical Mumbai Summer with hot and humid weather expected till Friday 26th April, with days around 34°C, nights around 25-26°C with high humidity. Days will get hotter over the weekend, with max temperatures going upto 37-38°C in western parts, and 38-40°C in eastern suburbs due to hot northerly breeze. 

Thane district and parts of Navi Mumbai can see above 40°C max temperatures over the weekend. 

Pune: Similar weather pattern to continue, no major change is expected. Days can be hot around 39°C, maybe touching 40°C over the weekend. Some localized thunderstorms may pop up around the city, but no major relief is expected from the hot weather. Nights can remain slightly better around 22-23°C. 

Parts of north Madhya Maharashtra (Jalgaon), Marathwada (Ch. Sambhajinagar, Jalna) and Vidarbha (Buldhana, Akola, Amravati, Washim, Nagpur, Bhandara, Chandrapur, Yavatmal) to get thunderstorms for next 2-3 days. 

Nagpur region max temperature may remain around 39-40°C (and not much beyond 40°C) due to some rain/thunderstorms.

Thunderstorms due to line of wind discontinuity (LWD) will develop in few areas near and east of the Western Ghats of Maharashtra, Goa, Karnataka and Kerala. 

Maharashtra districts of Pune, Raigad, Satara, Ratnagiri, Sindhudurg, Kolhapur, Ahilyanagar and places like Belgaum, Dharwad/Hubli may get some thunderstorms during the next 4 days. Rain will not be uniformly spread. 

Gujarat: Usual hot summer weather is expected across the state. Mainly dry weather with maximum temperatures around 40-41°C in most parts of Saurashtra, Kutch and Ahmedabad/Vadodara regions. Surat/Valsad regions can see max temperatures of 36-38°C. 

Weather to get hotter over eastern states of India with above 42°C temperatures and heatwave conditions in parts of Odisha, West Bengal, Bihar, Jharkhand, eastern Uttar Pradesh and some parts of Telangana and Chhattisgarh🔥.

Himalayan regions of Jammu, Kashmir, Ladakh, Himachal Pradesh and Uttarakhand will get some rain/thunderstorms from Friday-Sunday due to an approaching Western Disturbance. Some snow expected in high elevations as well. 

Parts of Punjab/Haryana can get some dust storms followed by thunderstorms. 

 Monsoon Watch -2 ...2024....21st April.

1.Mascrene Highs...

This is a series of Very High Pressure areas. The power house of the S.W. Monsoon forming down South. 

Formations below the Normal requirement.

Indicator: Negative

2. Seasonal Pre Monsoon Heat...well,  there is complaint of "Heat", but observe the real scene.

The squares show the "below normal" anomaly. The Monsoon parameters see this....reality 

Indicator : Normal

3. Seasonal Low

Core between 1006 mb...Should normally be 1004/1006.......As mentioned, by end May/early June it normally should reach a low nadir of 994 mb in June in the Thar Desert, and with 1008mb in the South Arabian Sea, a perfect gradient is created to attract the south -west winds towards the coast.

Indictor: Neutral.

4. The Line of Wind Discontinuity in Peninsula India, should normally stabilise around Central India perpendicular down into the Southern Peninsula by mid April. 

But this year it has been active first half of April, and continuing into latter half of April

Indicator: Neutral

5. ENSO;

An ENSO event is not active in the tropical Pacific Ocean and there are no signs of an El Niño or La Niña developing. Possible with signs of La Nina developing.

But La Nina is not the only parameter for estimating our Monsoon.

Indicator: Positive

6. Bay Low:

The Bay has yet to host a pre monsoon low during  April. 
As discussed, we should normally see a low sometime after the 15th of April. 

Another factor, which helps the winds gain strength, and bring more moisture into the Indian landmass, is the sea temperatures on both sides of the Peninsula. 

C

0

1

3

5

7

9

11

13

15

17

19

21

24

27

30

35

Indicator: Positive

After 2007, this is the first time when both +IOD and La Nina may develop and exist simultaneously during the core SWM months (July/August).

Overall Summary: Parameters 

1. Negative

2. Normal 

3. Neutral 

4. Neutral 

5. Positive 

6. Positive

Seems (without commitment today)..SWM onset could be on time

But, situations can change fast, and by the time we discuss the next MW, some factors can suddenly become +ve or -ve. So, MW discusses and follows the developments as they emerge, and discuss the parameters as is where is. 

No model can commit  today when the Monsoon can arrive. 

Also, Quantum of rain forecasting in April for June right through September is an impossible task. Things get clearer by last week of April. 

Vagaries' (in MW) normally remains true to estimates around early May. 

 Monsoon Watch  -2 coming up at 11 pm IST Today.

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):

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 

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. 

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

 

 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