Tropical Cyclone Danilo Forms South of Diego Garcia

Tropical Cyclone Danilo formed south of Diego Garcia on Friday. At 7:00 a.m. EST on Friday the center of Tropical Cyclone Danilo was located at latitude 11.6°S and longitude 72.3°E which put it about 290 miles (465 km) south of Diego Garcia. Danilo was nearly stationary. The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 996 mb.

The circulation around a low pressure system strengthened on Friday and Meteo France La Reunion designated the system as Tropical Cyclone Danilo. There was a well defined low level center of circulation evident on satellite images. Bands of showers and thunderstorms were revolving around the center of Danilo. The strongest thunderstorms were occurring in bands south and west of the center. Bands north and east of the center consisted primarily of showers and lower clouds. Storms near the center generated upper level divergence which pumped mass away to the west of the tropical cyclone.

There was also a tropical depression located east-southeast of Tropical Cyclone Danilo. At 7:00 a.m. EST on Friday the center of the tropical depression was located at latitude 14.4°S and longitude 81.4°E which put it about 770 miles (1240 km) east-southeast of Diego Garcia. The depression was moving toward the west at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 999 mb.

Tropical Cyclone Danilo will be in an environment favorable for intensification during the next few days. Danilo will move over water where the Sea Surface Temperature is near 28°C. It will move under the northern part of an upper level ridge over the South Indian Ocean. The ridge will produce easterly winds which will blow toward the top of the tropical cyclone. Those winds will cause moderate vertical wind shear, but the shear will not be strong enough to prevent intensification. However, the circulation around Tropical Cyclone Danilo will interact with the circulation around the tropical depression to its east-southeast. The interaction of the two circulations will disrupt the circulation on the eastern side of Danilo and that could prevent intensification during the next several days. Eventually,the two circulations are forecast to merge next week.

Tropical Cyclone Danilo will remain nearly stationary during the next day or so. Danilo could move slowly toward the southeast when the the tropical depression approaches it during the weekend. On its anticipated track Tropical Cyclone Danilo is forecast to remain south of Diego Garcia. Danilo could eventually move west toward Rodrigues next week.

12 thoughts on “Tropical Cyclone Danilo Forms South of Diego Garcia


    Good day. Thank you so much for the info. Im living in SA, which scale is used for Cyclones in the south Indian basin? We had cyclone Chalane here last week. It reach Tropical Storm Status before it hit mosambique, but when it just formed it was clasified as a Cyclone when it was still a depression? Im confused. Please assist.

    1. jay_hobgood Post author

      The term tropical cyclone is a more general term that applies to all warm core low pressure systems in the tropics. Tropical depressions, tropical storms, hurricanes, and typhoons are all tropical cyclones with different intensities. A tropical depression is a tropical cyclone that is usually given a numerical designation (e.g. SH07 for the seventh tropical cyclone in the southern hemisphere). A tropical cyclone is usually given a name when it intensifies into a tropical storm. That is when Chalane was given its name. Different nations’ meteorological agencies use different scales to rate tropical cyclones. It appears that Meteo France La Reunion uses one scale and Mozambique uses a different scale. That is one reason why I use the more general term “tropical cyclone” for the Indian Ocean and provide the maximum sustained wind speed.


            Good day. What happens to the air subsiding in the eye of the Tropical Cyclone? Is the subsiding air in the eye pulled back into the updraughts in the eyewall at all (entrained)? Or is there so little subsiding air that it does not alter pressure in the eye?

          2. jay_hobgood Post author


            That is an excellent question. Some of the subsiding air in the eye sinks to approximately 1000 meters above the surface. It forms an effective cap over a moister boundary layer just above the surface. You are correct in thinking that some of the subsiding air around the perimeter of the eye gets entrained into the updrafts in the eyewall.

    1. jay_hobgood Post author

      In hurricanes in the northern hemisphere tornadoes occur most frequently in the right front quadrant. Generally there is less CAPE in the circulation around a tropical cyclone. One hypothesis is that friction increases when rainbands move inland. Increased friction slows the wind and alters its direction. A change in wind speed and direction near the surface increases the vertical wind shear in the lower levels. Increased shear (or helicity) contributes to rotation in storms in a band moving inland and may cause a tornado to develop. The front right quadrant in the northern hemisphere is often a part of the circulation where the wind blows toward land and it is where the winds speed are often stronger. Since tropical cyclones rotate in the opposite direction in the southern hemisphere, one might expect tornadoes to be most frequent in the left front quadrant in regions like the South Indian Ocean.


    Good morning. Any updates on Danilo and 99S please? Why is its name 99S. I do understand the setup with Name giving in the North Atlantic totally, but in SWIO is diffirent due to the diffirent scale their using. Have a nice day🙋🏽‍♂️

    1. jay_hobgood Post author

      The circulation around Danilo dissipated north of La Reunion. There is no longer any deep convection and the remnants no longer meet the criteria to be a tropical cyclone. Invest 99S is southeast of Diego Garcia. It is still disorganized. It is forecast to move toward the west and to develop into a tropical cyclone. U.S. weather agencies use the numbers 90-99 to designate “Invests” which are tropical or non-tropical disturbances with the potential to develop into tropical cyclones. When a system is designated as an Invest additional products are generated which can be used by forecasters. The “S” indicates the system is over the South Indian Ocean. After they reach “99”, the agencies start over with “90” and there is also a new Invest 90S which is east of Invest 99S. If Invest 99S becomes the next tropical cyclone in the southern hemisphere, the designation will change to 10S.

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