The Tornadoes, Cyclones, Hurricanes & Typhoons Thread.

Geoff.D

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#1
Started this thread as a place to discuss extreme weather conditions. The other province and location based threads are not really suitable, as the above weather conditions seldom occur within the borders of SA.

Tornadoes do occur. Tropical Cyclones affect the weather over SA in the summer months.
 

Moosedrool

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#3
Regions called tornado belts have been identified in South Africa although I think it might be interesting to have an actual in depth study done on this.

The regions below shows clear indication that population count an spotters might skew the data especially in the Gauteng region.

Tornado Map.jpg

KZN is interesting since dry air is lifted blowing east from the drakensberg so when the humidity at the surface is right it doesn't surprise me at all that there's a hotspot right there.
 

Geoff.D

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#4
A tropical cyclone has moved into the Southern Indian basin from the Australian basin. Kenanga, a category 2 tropical cyclone is intensifying but too far away to affect us.
A mild depression about 485 km NE of Agalega has started to intensify and is now rated as a tropical disturbance.
 
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Geoff.D

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#5
Kenanga now rated as a category 4 cyclone, moving slowly south west. Not a place to be at sea!
The tropical depression has been upgrade to a tropical storm.
 

Gordon_R

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#6

Gordon_R

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#7
Cyclone Cilida has intensified strongly during the last 24 hours, and is now an extremely destructive storm. The track prediction has been consistent, and is likely to pass just north-east of Mauritius late on Sat 22nd into early Sun 23rd. Effects on land will be somewhat limited by the relatively compact size of the core.

sh0719[Cilida_20181221_1200].gif
 

Geoff.D

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#8
Kenanga has now dissipated to a tropical disturbance still moving Southwest.
Tropical Cyclone Cilida passed East of Mauritius is dissipating but has picked up speed and is now moving at 25 km/h Southeast.
Another area of disturbance is forming in the basin which has some potential.
 
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eg2505

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#9
so no chance any of these storms will ever make landfall this far south?

or is it a scientific impossibility for a typhoon to hit SA?
 

Gordon_R

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#10
so no chance any of these storms will ever make landfall this far south?

or is it a scientific impossibility for a typhoon to hit SA?
You can never say never, but the probability over mainland Southern Africa is very low, except for the coast of Mozambique.

This chart shows the cumulative tracks of all tropical cyclones worldwide during the 30 year period from 1985 to 2015. Clear bands of high probability are visible over some ocean basins, and nothing over others: https://en.wikipedia.org/wiki/Tropi...File:Global_tropical_cyclone_tracks-edit2.jpg

Global_tropical_cyclone_tracks-edit2.jpg
 
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Geoff.D

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#11
Once again, we have seen after some severe damage in Gauteng, a challenge arising when the word "tornado" is used to describe a storm that does extensive damage in SA.
Here is a link to a description of tornadoes which has all the main facts for everyone to see and read.
https://en.wikipedia.org/wiki/Tornado

In that link, there is a World map showing which areas are generally considered to be "tornado" prone. Suffice to say South Africa features on the map!
So let us try and stop these endless debates about whether we get tornadoes in South Africa.
SAWS describes how they interpret the F-scale here: http://www.weathersa.co.za/learning/educational-questions/56-what-is-the-fujita-scale
The grammar and spelling is not of the best, but the message is clear.

tornado.jpg
 

Gordon_R

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#13
http://www.metoc.navy.mil/jtwc/products/sh9219web.txt

THE AREA OF CONVECTION (INVEST 92S) PREVIOUSLY LOCATED
NEAR 22.7S 34.6E, IS NOW LOCATED NEAR 21.8S 36.7E, APPROXIMATELY 160
NM SOUTHEAST OF BEIRA, MOZAMBIQUE. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY SHOWS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER
(LLCC) WITH CONVECTION DISPLACED TO THE EAST OF THE LLCC. A 181349Z
MHS 89GHZ MICROWAVE IMAGE EMPHASIZES THAT THE DEEP CONVECTION IS
DISPLACED TO THE EAST AND IS ASSOCIATED MORE WITH THE MID-LEVEL
TURNING. THE SYSTEM IS LOCATED IN AN AREA FAVORABLE FOR DEVELOPMENT
WITH GOOD POLEWARD OUTFLOW, LOW VERTICAL WIND SHEAR (5-10KTS),
AND WARM SEA SURFACE TEMPERATURES (28-30 CELSIUS). GLOBAL MODELS
DEPICT DEVELOPMENT WITHIN THE NEXT 48 HOURS AS THE SYSTEM DEVELOPS
OFF THE COAST OF MOZAMBIQUE AND TRACKS NORTHWARD BEFORE LAND
INTERACTION LIMITS FURTHER INTENSIFICATION. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS UPGRADED TO MEDIUM.

TC 06S weakly active in the Mozambique Channel: http://www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/index.html

https://www.mtotec.com/public/images/sat.png

Edit: These images are updated in real-time, so the current situation does not reflect the previous storms.
 
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Geoff.D

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#14
TC06S drifted around gaining strength and is now graded as a Moderate Tropical Storm, heading West North Northwest towards Mocambique. Heavy rains are expected in Moz, even spilling over into the eastern areas of SA (Kruger Park).
Meanwhile North of Desmond, there is another system developing, also moving towards the northern part of Moz.
Both these systems could affect us in the next few days, firstly, complete disrupting our normal TS activity, and then if the storms do not dissipate too quickly, by bringing lots of rain to the east of SA.
1024px-Desmond_2019_track.png

800px-Desmond_2019-01-20_1115Z.jpg
By National Aeronautics and Space Administration (NASA) - https://worldview.earthdata.nasa.gov/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=75981513
By Meow - Created by Meow using WikiProject Tropical cyclones/Tracks. The background image is from NASA. Tracking data is from NOAA, Public Domain, https://commons.wikimedia.org/w/index.php?curid=75930527
 

Gordon_R

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#15
https://www.dailymaverick.co.za/art...e-as-tropical-cyclone-desmond-makes-landfall/

Biera, the fourth largest city in Mozambique, was badly hit.

Some 277 millimetres of rain was reported in Biera in the 24 hours until 06:00GMT on Tuesday, more than the 250mm expected in the entire month of January. And the rain continues to fall.

Large waves smashed over the top of sea defences and the torrential rain transformed roads into rivers.

Cars were submerged up to their windows and dirty floodwater rushed into people’s homes and businesses.

The remnants of Tropical Cyclone Desmond are expected to bring more flooding to central Mozambique and southern Malawi as it disintegrates above the region.
 

Geoff.D

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#16
Tropical Storm Desmond dissipated quite quickly overland, turned north and the east and the remnant is now moving offshore again. At this time it is anyone's guess if the storm is going to completely dissipate or pick up strength again. Very unusual for Tropical Cyclones to form in the channel like this and move northwards.
1024px-Desmond_2019_track.png
 

Geoff.D

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#17
It seems there is a gap in the coverage of tropical cyclones in this region. Mauritius is not too interested because the storms are too far away. Reunion also seems not too bothered, and neither Mozambique or Madagascar has a weather service. So, it would be left to SAWS to take an interest but presumably because the formation of Tropical Cyclones in the channel are so rare, they are also not interested.
 

Gordon_R

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#18
It seems there is a gap in the coverage of tropical cyclones in this region. Mauritius is not too interested because the storms are too far away. Reunion also seems not too bothered, and neither Mozambique or Madagascar has a weather service. So, it would be left to SAWS to take an interest but presumably because the formation of Tropical Cyclones in the channel are so rare, they are also not interested.
Meteo.fr La Reunion puts out daily alerts for the entire Western Indian Ocean (including the Mozambique Channel). See: www.meteo.fr/temps/domtom/La_Reunion/webcmrs9.0/anglais/activiteope/bulletins/zcit/liste.html

Today's discussion (12Z on Wed 23rd) includes the following:

West of 55E, the monsoon flow feeds convective activity and the zone of disturbed weather in the
southern Mozambique Channel.

Zone of Disturbed weather north of Europa during the last 24 hours, deep convection hasn't shown any signs of organization. Micro-wave imagery confirms the wide structure without well-defined center. Ground level observations from Europa island show maximum wind about 10/15 kt. Minimal pressure is estimated at 1000 hPa.Low level equatorward feeding remains very good but with the eastward shift of the subtropical high cell, polerward convergence has decreased progressively today. The circulation is located beneath the upper level ridge.

Tonight, the low is forecast to accelerate south-south-eastward toward a low level trough between 2 subtropical high cells. Tomorrow, the northwestern vertical windshear should progressively strengthen ahead of a wide upper level trough. Deterministic models show a slight deepening ahead of the trough probably due to more baroclinic processes. Thus, from Friday, frontal characteristics should appear as it evacuates southeastward.

The risk that this system becomes a moderate tropical storm becomes moderate [30-50% probability].
Basically its a tropical depression that is unlikely to intensify much, and will rapidly become extra-tropical. Nothing to write home about...

Edit: The NCEP GFS animation shows the sequence clearly: http://www.cpc.ncep.noaa.gov/products/international/cpci/data/00/gfs_mslp_precip_safrica.html
 
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