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05-12-2019, 16:58   #1
YanSno
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Technical / Discussion Tropical Cyclones 2019-2020

First system for the south Indian ocean.
Cyclone Ambali formed yesterday southwest of Diego Garcia, and is currently rapidly intensifying. So far, the storm has estimated winds of 100mph (160kph) with higher gusts, and the intensification phase isn't yet complete. The storm is likely to continue towards the southwest but rapidly weaken this weekend into early next week.

Land impacts are unlikely, but up to 100mm of rain could fall on St Brandon, and a 5% chance of tropical storm conditions in Mauritius.

There another system north or Madagascar likely to be name Belna probably this evening or tomorrow.

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06-12-2019, 07:19   #2
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Explosive intensification of Ambali overnight is now Very intense tropical cyclone Ambali with gusts reaching 330km/hr.
Still moving south south west at a speed of 13km/hr. Further intensification may occur during the day and Ambali is still forecasted to weaken rapidly as from tomorrow.
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06-12-2019, 09:47   #3
M.T. Cranium
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330 km/hr must be close to a global record.

Can you post any links to official tracking of south Indian tropical cyclones? I assume maybe it's Meteo France in charge?
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06-12-2019, 14:16   #4
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Meteo France, Mauritius Meteorological Station with the help of the Base in Diego Garcia monitors all cyclones in the south Indian basin.

Well Ambali has suffered, travelling into dry air has caused the system to rapidly weaken.

Official report from https://www.m-r.li/cyclone/hist_point_mf_3.html

Earlier this morning at 0400 Ambali reached it's peak as follows :
Cyclone Tropical Very Intense AMBALI 930 hPa.
Maximum average wind speed over 10 minutes: 222 km / h (120 kt)
Maximum gusting at sea: 313 km / h
Position on Friday, December 6, 2019 at 4:00 am (meeting time): 10.5 South / 62.2 East.
Distance from the Reunion coast: 1355 km north-northeast.
Displacement: South-South-West 13 km / h.
No alert on the meeting.

It has now be classed as a Tropical disturbance.

Link to follow cyclone tracking:
http://www.meteofrance.re/

https://www.meteo-reunion.com/cyclone/index.php

http://metservice.intnet.mu/
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06-12-2019, 19:42   #5
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AMBALI OFFICIALLY BREAKS THE RECORD.

Cyclone Ambali put on quite a show for us Thursday with it’s extreme rapid intensification phase. The system was upgraded to a tropical storm at 18:00 UTC Wednesday with winds of 35 knots (40 mph), and likely attained Category 5 intensity with winds of 140 knots (160 mph) 24 hours later – A 120 mph increase in 24 hours, the 2nd quickest intensification phase ever recorded behind Hurricane Patricia in 2015, and the quickest intensification rate ever recorded in the Southern Hemisphere.

Ambali’s 120 mph increase in 24 hours is extraordinarily rare. While rapidly intensifying storms do happen every year, a storm increasing 120 mph in 24 hours does not. Conditions were nearly perfect for rapid intensification of Ambali. 30C waters were in the storm’s path shortly after formation for at least 2 days, along with wind shear less than 5 knots near the storm’s peak intensity. The storm’s record peak intensity makes it the first Very Intense Tropical Cyclone on the local scale since Fantala in 2016, and the only A name in the basin to reach that status.

As Ambali continues to weaken, Belna is intensifying – and is a significant threat to Madagascar.

Last edited by YanSno; 06-12-2019 at 19:51.
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08-12-2019, 07:44   #6
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Cyclone Tropical BELNA 977 hPa.
10-minute mean maximum wind: 130 km / h (70 kt)
Maximum gusting at sea: 183 km / h
Position Sunday, December 8, 2019 at 10:00 (Meeting time): 11.9 South / 46.5 East.
Distance from the Reunion coast: 1370 km northwest.
Displacement: South-South-West 11 km / h.
Serious threat for Madagascar.
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08-12-2019, 10:14   #7
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This activity was due to a quick burst in the MJO in the western Indian Ocean, but all activ8ty should die down now as the MJO becomes indiscernible.

From the BOM's weekly update, issued Dec 3rd.

Quote:
Weak Madden–Julian Oscillation to have minimal influence on Australian rainfall

The Madden–Julian Oscillation (MJO) was indiscernible during the past week. While most climate models indicate the MJO will remain indiscernible for the next fortnight, some models indicate it might strengthen over the western Indian Ocean in the coming days, before rapidly weakening in about a week or two as it encounters the influence of the positive IOD over the eastern Indian Ocean. This region presents a hostile environment to a pulse of enhanced weather, such as the MJO, due to cooler than average sea surface temperatures, dry easterly winds and widespread, descending air which inhibits deep cloud formation.

An MJO pulse over the western Indian Ocean at this time of the year typically decreases the chance of above-average rainfall across northern Australia and the Maritime Continent. However, if the MJO pulse remains weak or indiscernible, its influence on rainfall patterns over northern Australia is likely to be insignificant.
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27-12-2019, 10:00   #8
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Conditions are favorable

The tropical disturbance is almost stationary in the Inter Tropical Convergence Zone (ZCIT).

The environmental conditions are favorable for its intensification and a movement towards the South. Therefore, it will approach and influence the weather on the Mascarene Islands for the next few days.

Weather deterioration is expected from Sunday in Mauritius.

The evolution of this system is closely monitored by the Mauritius Meteorological Service.
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28-12-2019, 17:35   #9
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Tropical disturbance 96S located north northeast of Saint Brandon.

Conditions are generally favorable and should allow this system to gradually intensify in the coming days. It could reach the stage of tropical depression in the next 12 to 24 hours. At 4 p.m. it was analyzed at the tropical disturbance stage by the Navy, bordering on the tropical depression stage. We can see on the that convection has intensified for a few hours even if the satellite presentation remains elongated and still poorly defined.


➡️ The models direct this system in the general direction of the area located just to the south-east of Mauritius.
However, there has been a slight shift towards the east of the average trajectory of the models since this morning, which means that if these simulations were verified the system could pass a little further off Mauritius than envisaged yesterday.

But nothing is less certain. The models are fluctuating which is normal because the exact positioning of the center which currently remains wide and still poorly defined is not yet precise. This can distort the simulations of trajectories upon arrival.

Once the system is better organized, probably tomorrow, confidence in the forecast should increase considerably.

Last edited by YanSno; 28-12-2019 at 17:40.
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29-12-2019, 10:49   #10
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Tropical Disturbance has continued to intensify and is now a Moderate Tropical Storm. It will be name Calvinia in the next few hours by Mauritius Meteorological Service. It's currently gusting at sea at 95kmph, it will countinue to intensify as conditions are favorable. Some wind sheer to the north west of the center but it's likely to drop on approach to Mauritius. Gfs has the centre stall doing a loop on Mauritius while continue to intensify. Most active bands are to the South East of the the system. A cyclone warning class 2 is currently in force in Mauritius. The possibility of cyclonic conditions on Mauritius and Réunion Island has now increased.
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30-12-2019, 08:40   #11
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A cyclone warning class 3 is in force in Mauritius.

Over the last few hours, the severe tropical storm has remained almost stationary at about 120 km to the east of Mahebourg near the point 20.7 degrees south and 58.5 degrees east. It continues to intensify and a movement towards the west will bring the centre closer to mauritius.

Cyclonic conditions, that is wind gusts of the order of 120 km/h, may occur over Mauritius by the early afternoon.
Active cloud bands associated with CALVINIA will continue to influence the weather over Mauritius.
Weather will be rainy. The rain will be moderate to heavy at times with thunderstorms. There will be localised accumulation of water and flooding.

The new radar on Trou Aux Cerf has finally had its first storm within the 450km radius. Image below (copyright mms)
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30-12-2019, 10:11   #12
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The observations during the last hours indicate that the severe tropical storm CALVINIA has started to undertake a loop to the East-South-East of Mauritius and continues to intensify. At 1300 hours,it was centered near the point 20.5 degrees South and 58.3 degrees East, at about 90 km off the coast of Mahebourg. While making this loop, the centre of CALVINIA may come dangerously close or over Mauritius. Wind sheer has considerably dropped,looks like Clavinia will looping around Mauritius for at least 12-24hr this is due to HP to the south . It may also reach Tropical Cyclone status while exiting the region. The center on the storm is starting to define and can be clearly seen below.
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30-12-2019, 11:12   #13
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Even Calvinia is a rather small system but should pack quite a punch. The outer bands are starting to wrap around the centre. Landfall is expected tonight around 10pm local time in Mauritius as per Meteo France. Some structural damage has already started on the island except the weather to deteriorate in the next few hours and simulation are going for over 200mm of rain.
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30-12-2019, 17:40   #14
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Well Calvinia has pretty much stayed stationary for the last 12 hours. It has been looping around but last radar shows it's been drifting towards the north west thus landfall on the south of Mauritius is highly likely . Winds over 150kmph are packed around the centre those gusts are around a 50km radius from the centre. It's a small diameter system any shift can make big impacts on the island. It will be a though night for the Mauritian population as the situation is very uncertain.


Last edited by YanSno; 30-12-2019 at 18:02.
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31-12-2019, 08:40   #15
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After 24hr Calvinia has started to move south eastward.It's the first time that a storm stalled in that region for that long. Mauritius was spared as it didn't intensify any further than a strong tropical storm while being stationary and the active quadrant was along the south east side of Calvinia. Now that the Hp to the south is moving away Calvinia will accelerate while intensifying further it's now has a pressure of 980mb with gusts of 150kmph. Calvinia has no threat to land and is expected to become extra tropical in the next 2 days. I will post some of the damage caused on the island later.

Last edited by YanSno; 31-12-2019 at 16:25.
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