Current cyclones and Watching

Translations are automated.

Invest 92L # 7 - July 29, 2020 - 19H00 UTC

Home » Weather analysis » Analysis of weather systems » Invest 92L # 7 - July 29, 2020 - 19H00 UTC

Le 29 juillet 2020 à 17:00

By Olivier Tisserant

4.96/5 (135)

Reminder: the information and illustrations on this site are NOT INTENDED to protect property and people from cyclonic risks. For this, you must follow the information and recommendations of your prefecture for France and the competent authorities for other territories.

THEInvest 92L, which became Cyclone Potentiel # 9 for reasons essentially linked to the implementation of warning procedures in the West Indies, has almost completely crossed the arc. A convective zone continues to interest the north of the arc this afternoon and some convective hearths may still give some good squalls locally tonight.

Despite the many missions of the Hurricane Hunters it is still not possible to classify it as a cyclone (depression or storm) due to the fact that its organization is not yet sufficient to maintain a closed circulation of winds around its minimum pressure. On the other hand, since 36 hours we have noticed a slow but constant strengthening of the convection which should allow it to organize itself before its passage over the Dominican Republic.

The forecast for the next few days remains very delicate since it depends a lot on the interaction with the lands that will be crossed. The more the system interacts with the earth, the more it will weaken. As a result, its trajectory and speed, which have been quite variable in recent hours, will determine the evolution of its intensity.

In any case, the Dominican Republic and Haiti must prepare to receive a system a little more powerful than the one that has crossed the Caribbean arc since yesterday. The increased convection will give more rain and the better organization more wind.

Then, the interaction or not with Cuba will be decisive for the state of this system when it enters Florida. If it passes far enough north of Cuba to maintain contact with hot water, it will maintain its intensity at a minimum and could even strengthen a little (the models are on a strong consensus for a maintenance and tropical storm, more or less strong. , at 120h). If it spends too much on Cuba it could suffer a lot from the lack of water and its convection could quickly collapse.

What lessons can we learn from this eventful and somewhat strange episode?

The first of course is that nothing is ever played out in terms of hurricane weather. For more than 5 days the digital models and the nhc predict between a good storm and a category 3 on the arc and in the end it is a big disturbance (with certainly good gusts and rainfalls) which passed. This science is still very far from perfect, and many parameters still escape both machines and forecasters. It must make us extremely humble and cautious and prevent us from making sweeping claims on these matters.

The second is that the Euro model (ECMWF extension) was extremely relevant to this episode. He was the first to identify this system almost 8 days ago in this form (wide, powerful but without vortex with a passage over the center of the arc) and he maintained this forecast over the entire period while the others models have gone in all directions both in terms of trajectory and intensity. For several seasons theECMWF extension regularly performs better than the GFS on complex systems and this is an element to take into account. The only other models that held up the shock and were also relevant are Arôme and Arpège, the 2 models from Météo France which perfectly anticipated and planned this system (and as a result Météo France has perfectly managed the Watching phases).

The third is that the use of raw model outputs (whether in graphics or on sites such as Windy) by people who do not know how to analyze them and cross-check the data, poses significant prevention problems on time. social networks. How many people have published or shared alarmist news that is totally irrelevant because it has been taken out of context and not analyzed? it must be taken into account that part of the population is extremely fearful of these systems and that the multiplication of anxiety-inducing publications not expertized participates in a collective paranoia which quickly assumes enormous proportions. I repeat it again, even if it means taking a series of stupid comments from me: stop sharing everything you read on these subjects !! just share the publications of official organizations (nhc, Météo France, Prefectures, etc.) which are always assessed. This is probably the most important lesson to be learned.

The fourth and last for me is to remain humble also in the designation of the conditions that we observe. When someone says “There is nothing in Guadeloupe” he suggests that it is the whole island while he only has visuals on his town or even his neighborhood. There may be 10 kts and wind and no rain in Basse-Terre and 70 kts and the deluge on the Pointe des Châteaux… or the reverse. Giving information like this can be problematic because people may think they are safe even though their area is very exposed. So be careful and precise in your feeling information, because it will be read and will potentially be the basis of behavioral choices of other people away from you, with therefore other conditions.

We must all, and me the first, use these experiences to try to better apprehend the next episodes, with more serenity and collective conscience.

To follow the live quantified evolution of # 09, it is HERE.

Image credits; Tropical tidbits, NHC / Noaa, UW-CIMSS