Storm that downed Air Algerie 5017 may become a tropical storm Bertha this week

Flight path and wreckage site (source: BBC)

The path of 5017 was clearly into the mesoscale convective system.  The latest is that the pilots asked to return back to Ouaga as they probably realized that they could not fly through this storm (http://www.bbc.com/news/world-africa-28528174).  It is unclear whether they were in trouble at that point or not.

I have completed additional analysis of this storm.  Based on the analysis the storm was growing in size with the top of the clouds between -50 and -73C which going to be somewhere between 12 and 16 km (39,000-52,500 ft). For planes that fly at altitudes of 39,000 feet, typical temperatures are about -50 to -55C which means that flight 5017 would not have been able to climb above many of the storms.  

Cloud top temperatures at 0000 UTC or 1 hour 17 minutes before 5017 takeoff

As you can see in this picture at midnight (local time), there is a large area of clouds between 200 and 220 Kelvin (-73 to -53C), an hour prior to the flight taking off.  The plane should have been diverted to the west of the storm or potentially east, but the forecasters may have seen thunderstorms to the east near the Mali, Niger border and opted not to send them that direction.  Of course sending them directly into the storm makes absolutely not sense.

Cloud top temperatures at 0100 UTC 17 minutes before 5017 takeoff.

At 0100 (local time) we see that there has not been much movement in the storms position prior to takeoff, which should have definitely prompted a delay or a diversion to the west of the storm.  Given the large area of cold cloud temperatures, this was a large area of thunderstorms, which without a weather radar in the northern part of the country, could not have been easily maneuvered through  by Air Traffic Control.  While the aircraft does a radar in the nose of the plane, it only sees nearby thunderstorms.  

Cloud top temperatures at 0200, 10 minutes after contact with flight 5017 is lost

By 0200 UTC, the area of cold clouds have moved east and expanded.  This is 10 minutes after radar contact was lost.  Given where the crash site occurred, it is possible that the plane made it through much of the system, but that potentially there was some damage or maybe a buildup of super-cooled water on the pitot tubes.  The exact cause will be known by black boxes.  RIP 5017 passengers and crew.

However, the story does not end there.  Normally, such mesoscale convective systems (MCS) are long-lived and may continue for another thousand miles.  In this case, that is the story of this particular MCS.  Throughout the day, the system continue to grow and evolve.  It appeared to decay near Guinea, but really did not and the convection was regenerated as it left the coast.   

 Satellite picture of the convection linked to flight 5017 for July 24-July 27 (3 hours intervals)

The speed of the MCS suggests that it was not moving with an African Easterly wave but faster. It is possible that a mid-level circulation was generated in the organized convection.  Finally, the Guinea highlands have been known as a region where spin can be generated when organized convection is cross it over and moving over the Eastern Atlantic Ocean.


Once the convection made it to the central Atlantic, it appears it linked up with the inter-tropical convergence zone or a monsoon trough and the convection was reinvigorated.     It is possible that the convection itself may have generated spin--- in what is known as a bottom-up formation of tropical cyclones over the ocean.  The following movie shows how the convection evolved in Atlantic on July 27 and 28th.

Satellite picture of the convection linked to flight 5017 for July 24-July 27 (3 hours intervals)


This morning the system is not looking strong but there is a 70% chance of tropical cyclone formation over the next few days.

Visible Image Tropical disturbance July 30, 1445 UTC (1045 EST) 

The deep thunderstorms (convection) are scarce this morning and the low level center is exposed.  However, the overall environmental conditions are favorable for further development.   Assuming that this system survives, the current model tracks are taking the system into the Northern Caribbean by this weekend. It is too early to determine if this system will impact the US as it needs to form first.

Potential track of the current Tropical Disturbance (Invest 93) based on weather models

In summary, this was a unique tropical disturbance whose origins go back to the West Africa and is notable because of the tragic situation associated with mesoscale convective system over Burkina Faso.  The future of the system remains unclear but the genesis of tropical depression is possible over the next  day with additional development into Tropical Storm Bertha is possible later in the week.

Even though we are anticipating a lower than normal number of Atlantic tropical cyclones, it is virtually impossible to know which tropical disturbance may ultimately develop into a tropical cyclone.  Make sure that you remain aware and have your emergency preparation plan in place if you live in coastal areas.