Dự báo tốt, Thiệt hại lớn. Do đâu? - phần 1

Hàng năm, tác động của các thiên tai khí tượng thuỷ văn nguy hiểm trên thế giới nói chung và Việt Nam nói riêng vẫn gây ra những thiệt hại ngày càng tăng về người, phá huỷ các công trình xây dựng, sản xuất nông nghiệp, dẫn đến những thiệt hại lớn về kinh tế. Tất cả những điều này vẫn xảy ra dù có một thực tế là những thiên tai này đều đã được dự báo sớm, dự báo tốt, thậm chí còn có độ chính xác cao, thông tin được truyền phát kịp thời, đầy đủ đến người dân như với cơn bão số 10 năm 2017. 

Hình ảnh về trận lũ tháng 10/2017

Vậy nguyên nhân nào dẫn đến những thiệt hại vẫn không ngừng tăng và chưa bao giờ là con số 0 trong các lần có thiên tai này?
Trước khi đi vào thảo luận ký kiến cá nhân. Xin được chia sẻ những cách làm của các nước tiên tiến trong khu vực.

Vì sao nắng nóng?

Đầu tháng 6/2017, các tỉnh Bắc Bộ và Trung Bộ đang hứng chịu đợt nắng nóng gay gắt với nền nhiệt độ cao, có nơi thậm chí tới trên 40 độ C. Vậy đâu là nguyên nhân gây ra nắng nóng và đợt nắng nóng kỷ lục này khi nào chấm dứt?

Ngay từ ngày đầu tháng 6, các tỉnh Bắc Bộ và Trung Bộ chịu ảnh hưởng của rìa phía đông nam vùng áp thấp phía tây với đới gió tây nam mạnh gây ra thời tiết ít mưa, nắng mạnh ở hầu khắp các tỉnh phía đông Bắc Bộ, khu vực các tỉnh Sơn La, Hòa Bình và các tỉnh Trung Bộ từ Thanh Hóa đến Phú Yên duy trì trạng thái thời tiết ít mưa, ban ngày nắng nóng diện rộng với nhiệt độ phổ biến 36 – 39 độ C, có nơi trên 39 độ C như tại Kim Bôi (Hòa Bình) 39.3 độ, Hà Đông 39.2 độ.

Địa hình và gió chính là nguyên nhân gây ra hiệu ứng phơn và nắng nóng ở khu vực Bắc và Trung Bộ trong mùa hè

Nguyên nhân nào gây ra nắng nóng

Climate and Water Outlook, April–June 2017

Which scenario for TY. Hagupit after entering East Vietnam sea?

This post will summary some of the scenarios  of TY. Hagupit track after entering East Vietnam Sea. In 114 TCs in the IBTraCS data set lies within 1.5 degrees of TY. Hagupit location, there are 18 TCs that are active between 23th November to 23th December, and 15 TCs that have similar intensity with current intensity of TY. Hagupit (55kts). Especially, there are only two tropical cyclones which are active in the same period and similar intensity with Hagupit. They are TY. Manny (1993) and TY. Axel (1994).
Let's have a look on the best tracks of Manny and Axel below

Best track of TY. Axel (December 1994)

Best track of TY. Manny (December 1993)

Both Typhoons downgraded quickly after making landfall and crossing Phillipines and entering East Vietnam sea.
As we are now at the end of the TC season, there is not many chance for a TC to intensify when moving over East Vietnam sea. Hapupit is not an exemption. It should dissipate very soon and very likely to dissipate over the water area.

Nepartak (1601) - Scatterometer wind estimation

This is the latest picture of scatterometer winds of Typhoon Nepartak at 1830 UTC 05 July 2016.

The scatterometer winds (in arrows or flags), with an infrared satellite image (from METEOSAT, GOES or Himawari) and numerical weather prediction model forecast winds from ECMWF in green arrows or flags. These model winds are valid at the time of observation.

A calm indicator circle is plotted if the wind speed is less than 0.5 m/s. The scatterometer winds are coloured according to the Beaufort scale, winds up to 5 Bft. (10.7 m/s) are in red, winds as of 6 Bft. are coloured as shown in the legend below the picture.

The exact data acquisition time is plotted in red next to the satellite swath.

The coloured dots give the value of the Maximum Likelihood Estimator (MLE) which indicates how well an observation fits to the Geophysical Model Function. High MLE values usually indicate high spatial wind variability or rain presence in the Wind Vector Cell.

BoM's tropical cyclone track forecast

This graphical product provides information about the movement and intensity of a tropical cyclone, as well as showing the areas likely to experience its effects.

This version of the video uses an example from Queensland

Typhoon LINFA on Microwave images

LINFA is the third tropical cyclone active over Western North Pacific and it's the second times that Vietnam issued the Tropical Cyclone Warning.
Forecast from 12UTC 19 June 2009 for different warning centers - Good agreement
LINFA are moving northward and going to make landfall on south China.

Here are some images of LINFA from MI

(LINFA from MI on 10Z 19 June, 2009)

North Vietnam - Hot weather of 39 degree C

(tcforecast) 8th June, National Center for Hydro-Meteorological forecasting, hot weather will be in most provinces of North and Central Vietnam. The highest temperature since popular 34-37°C, particularly exceed 39°C.
In the North, hot weather still continue about 1-2 days, on 9th June, will be the dog days, the highest temperature since popular 36-38°C. However, hot sunshine in the North has so far none of the central regions when the temperature is at 38-39 ° C and outdoor temperature can be up to 45 ° C.
Causes of the temperature rise is due to air humidity is low (40% -60%). Urban areas such as Hanoi or limestone mountainous as Hoa Binh, hot and dry conditions are more severe than elsewhere. Low humidity make the temperature at night, maintained at high levels, approximately 30°C.

Pagasa warns of flash floods, landslides in west Luzon

MANILA, Philippines — Monsoon rains enhanced by a prevailing low-pressure area could spawn flash floods and landslides in the western part of Luzon, state eather forecasters said Friday afternoon.

The Philippine Atmospheric Geophysical and Astronomical Services Administration said the LPA was estimated at 800 km east of Luzon as of 2 p.m.

In its 5 p.m. bulletin, Pagasa said the southwest monsoon is also affecting Luzon.

"Luzon will experience monsoon rains which may trigger flashfloods and landslides over the western section. The rest of the country will be partly cloudy to cloudy with isolated rainshowers or thunderstorms," it said.

Moderate to strong winds blowing from the southwest will prevail over central and southern Luzon and Visayas and the coastal waters along these areas will be moderate to rough.

Light to moderate winds coming from the sSouthwest will prevail over Mindanao and coming from the Northeast to west over the rest of the country.

Coastal waters along these areas will be slight to moderate except during thunderstorms.

Meanwhile, Pagasa warned fishing boats and other small seacraft against venturing out to the sea, and larger seacraft to watch out for big waves

Hot weather in North Vietnam

For the next two weekend days, the weather in northern provinces of Vietnam will be hot and dry!

First reason is prolonged rainfall in the North recently, including rainy days, even some provinces had heavy rain accompanied by thunderstorm, has ended. 

From 23th to 28th May, in the North western part, it's mostly cloudy, light Showers and thunderstorm in the afternoon, sunny on day-time, teperature in some provinces might be hotter than 35 degree Celcius.

The provinces in north-eastern part, it's cloudy at night and early morning. There are scattered rain but just mild. The other regions, it's local shower and thunderstorm. The temperature about 22 to 34 degree C. 

For longer forecast, it might be rainy again on 29th may.

Tropical Storm No1 over Western Pacific is expected to be on 3 May

(tcforecast) Tropical depression One is forecast to strike the Philippines as a tropical storm at about 18:00 GMT on 3 May (01:00 on 4May - Vietnam local Time). Data supplied by the US Navy and Air Force Joint Typhoon Warning Center suggest that the point of landfall will be near 14.4 N, 124.6 E. One is expected to bring 1-minute maximum sustained winds to the region of around 64 km/h (40 mph). Wind gusts in the area may be considerably higher. The information above is provided for guidance only and should not be used to make life or death decisions or decisions relating to property. Anyone in the region who is concerned for their personal safety or property should contact their official national weather agency or warning centre for advice.