Explanation for why super typhoon Mangkhut did not enter Vietnam

According to Mr. Khiem, scientifically, the movement of storms depends on many factors: guiding currents (subtropical high pressure), the inertia of the storm, the impact of terrain and friction...

In particular, for strong storms, the role of guiding currents is very important. The guiding currents usually exist in cycles of about 3 days. This time, while the storm was still far from the Philippines, the subtropical high pressure developed strongly and existed in the South.

If the subtropical high pressure continues to be as strong as in the early days, based on the calculation models, the storm will deviate to the west (ie move in the west-northwest direction, towards Vietnam). However, 2-3 days later, the storm's trajectory will change because the subtropical high pressure tends to retreat to the North.

At that time, all forecast models of the US, Japan, and Europe updated the atmospheric conditions like that. According to calculations, the storm's trajectory followed the edge of the subtropical high, with a direction deviated to the North compared to the previous forecast (going more northwest than west-northwest).

Consecutive super storms

The close proximity of hurricanes in the Atlantic Ocean in 2017, including Hurricane Maria, Hurricane Irma and Hurricane Harvey, underscores the worrying link between the rise of increasingly intense and frequent storms and climate change and global warming.

Not only in the East Sea and the Northwest Pacific, storms also appear simultaneously in most of the world's oceans in mid-September.

According to statistics on September 11, there were 9 tropical cyclones (including storms, tropical depressions and low pressure areas) active globally, including super storms Florence, Helene, Isaac, storms Paul and Olivia, super storm Mangkhut...

Several studies on the relationship between global warming and hurricane activity have found that very strong hurricanes and hurricanes are occurring more frequently, particularly in the Atlantic region.

Some scientists even say that a Category 6 hurricane may have to be proposed for the Atlantic (currently the highest category is Category 5).

Difficulty in forecasting

Storm forecasting technology, especially forecasting periods of 3 days or more, is built on the basis of numerical forecasting models.

Meanwhile, although there have been significant improvements in storm trajectory prediction errors in numerical forecast models, the models still have weaknesses that have not been overcome, that is, large errors in storm location prediction.

Over the past 20 years, there has been little improvement in the ability to forecast hurricane intensity.

For the forecast track of Typhoon Mangkhut, the model predictions before the typhoon made landfall in the Philippines were quite consistent.

However, after the storm passed Ludong Island (from 7am on September 15), the model's forecasts became more scattered and different.

However, one common point among the forecast trajectories is the tendency of the trajectory adjustment to tilt gradually to the right, predicting that Typhoon Mangkhut will make landfall near Hong Kong and after making landfall will move more overland.

Due to friction with the mainland for a longer time and distance before reaching the Vietnam-China border, storm Mangkhut will weaken more before affecting northern Vietnam.

Thus, the main danger from storm Mangkhut for Vietnam will be heavy rain in the Northern region and Thanh Hoa, especially the northern mountainous provinces.

It can be seen that climate change along with technological limitations, including limitations of forecasting models for the problem of predicting storm trajectory and intensity, will continue to cause many difficulties for storm forecasting.