The National Center for Hydro-Meteorological Forecasting informed that this afternoon, July 18, storm No. 1, after moving deep into the mainland of the southern region of Guangxi province (China), weakened into a tropical depression.
Tonight, the tropical depression will move westward at about 20km per hour and continue to weaken into a low pressure area and gradually dissipate. By 4am tomorrow morning, July 19, the low pressure area will be at about 22.4 degrees North latitude - 104.3 degrees East longitude, in the Viet Bac region.
Due to the influence of storm No. 1, from the evening of July 18 to July 19, in the Northeast and Viet Bac regions, there will be heavy to very heavy rain with common rainfall of 70-150mm, locally over 250mm; the Northwest region will have heavy rain with rainfall of 50-150mm, the Northern Delta region will have moderate rain, heavy rain with common rainfall of 30-60mm.
Explaining the reason why storm number 1 deviated
Explaining the reason why storm No. 1 deviated further north than previously forecast, Mr. Hoang Phuc Lam, Deputy Director of the National Center for Hydro-Meteorological Forecasting, said that storm No. 1 was a storm that formed on the tropical convergence zone, then moved relatively steadily, mainly in the West-Northwest direction.
The maximum intensity of storm No. 1 reached level 13, gusting to level 17 before making landfall in the Leizhou Peninsula (China). After making landfall in the northern part of the Leizhou Peninsula, the storm gradually weakened, and on the morning of July 18, the storm crossed the Leizhou Peninsula and traveled along the southern part of Guangxi Province (China).
"The trajectory of a storm/tropical low pressure system is often controlled by the flow field in the atmosphere. Accordingly, the direction of movement of storm No. 1 is mainly controlled by the subtropical high pressure at about 5km level. Depending on the level of development and expansion of the subtropical high pressure to the west, storm No. 1 will have different directions and speeds of movement.
If the subtropical high pressure moves westward with moderate intensity, the storm will move west-northwest and directly affect the Quang Ninh and Hai Phong areas. If the subtropical high pressure moves westward strongly, the storm will move more southward and enter the southern area of the Northern Delta.
In the case of a weak subtropical high, the storm will move more to the North and enter the south of Guangxi province (China). In this scenario, storm No. 1 weakens quickly due to friction with the terrain, so the storm's winds are weaker and there is not much rain. The impact of the storm is also the lightest," said Mr. Lam.
According to Mr. Lam, one of the three scenarios is most likely to happen and is also the scenario that will have the worst impact: "In reality, storm No. 1 will occur according to scenario 3, this is the scenario that will have the least impact on Vietnam," Mr. Lam informed.
Mr. Lam said that from the afternoon of July 18 to July 19, in the Northeast and Viet Bac regions, there will be heavy to very heavy rain with common rainfall of 100-200mm, locally over 300mm; in the Northwest region, there will be heavy rain with rainfall of 50-150mm. Beware of heavy rain causing urban flooding. Warning of high risk of flash floods and landslides in the provinces of Quang Ninh, Lang Son, Cao Bang, Ha Giang, Lao Cai, Yen Bai.
"The Hanoi area and the provinces in the Northern Delta are only affected by the southern edge of the circulation after storm No. 1, with the Southeast wind zone after the storm carrying moisture from the Gulf of Tonkin to the mainland, so on the night of July 18, in the delta area and the capital Hanoi, there will still be rain, moderate rain, sometimes heavy rain with rainfall on the night of July 18 and July 19 of about 30-50mm," said Mr. Lam.
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