Vòi rồng hình thành như thế nào?

 

Vòi rồng hay lốc xoáy là một cột khí xoáy dữ dội, hút từ bề mặt đất lên đám mây đối lưu, tạo thành hình phễu hoặc hình xoáy lủng lẳng từ một đám mây trông giống như cái vòi.

Có 2 loại vòi rồng chính: Vòi rồng thời tiết tốt và vòi rồng trong cơn dông. 

Ngày Quốc tế Giảm nhẹ thiên tai 2019

Bài phát biểu của Bà Akiko Fujii, Phó trưởng Ban giảm thiểu rủi ro tăng cường chống chịu thiên tai, Phó Giám đốc Quốc gia UNDP, Việt Nam, tại Cần Thơ

Theo Chỉ số Rủi ro Thiên tai Toàn cầu 2018, Việt Nam là một trong 10 nước phải chịu tác động nhiều nhất của các sự kiện thời tiết cực đoan gây tổn thất.

The Beaufort Wind Scale (extended)

The Beaufort Wind Force Scale currently in use was developed by Admiral Francis Beaufort in 1805. The initial scale was from 0 to 12 only and they described qualitatively the sea conditions without defining quantitatively the wind speed. It was extended in 1946 to include Forces 13 to 17, and they are normally used in adverse weather conditions, e.g. tropical cyclones.

Beaufort Number	Description used by HKO	General Description	Wind Speed			TC strength	Land conditions	Sea conditions	Wave Height		Image
			knots	km/h	m/s				m	ft
0	Calm (無風)	Calm	0	0-1	0-0.2	(N/A)	Calm. Smoke rises vertically.	Flat.	0	0
1	Light (輕微)	Light air	1-3	2-6	0.3-1.5		Wind motion visible in smoke.	Ripples without crests.	0.1	0.33
2		Light breeze	4-6	7-11	1.6-3.3		Wind felt on exposed skin. Leaves rustle.	Small wavelets. Crests of glassy appearance, not breaking.	0.2	0.66
3	Moderate (和緩)	Gentle breeze	7-10	12-19	3.4-5.4		Leaves and smaller twigs in constant motion.	Large wavelets. Crests begin to break; scattered whitecaps.	0.6	2
4		Moderate breeze	11-15	20-29	5.5-7.9		Dust and loose paper raised. Small branches begin to move.	Small waves.	1	3.3
5	Fresh (清勁)	Fresh breeze	16-21	30-39	8.0-10.7	LPA	Smaller trees sway.	Moderate (1.2 m) longer waves. Some foam and spray.	2	6.6
6	Strong (強風)	Strong breeze	22-27	40-50	10.8-13.8	TD	Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult.	Large waves with foam crests and some spray.	3	9.9
7		Near gale	28-33	51-62	13.9-17.1		Whole trees in motion. Effort needed to walk against the wind.	Sea heaps up and foam begins to streak.	4	13.1
8	Gale (烈風)	Gale	34-40	63-75	17.2-20.7	TS	Twigs broken from trees. Cars veer on road.	Moderately high waves with breaking crests forming spindrift. Streaks of foam.	5.5	18
9		Severe gale	41-47	76-87	20.8-24.4		Light structure damage.	High waves (2.75 m) with dense foam. Wave crests start to roll over. Considerable spray.	7	23
10	Storm (暴風)	Storm	48-55	88-103	24.5-28.4	STS	Trees uprooted. Considerable structural damage.	Very high waves. The sea surface is white and there is considerable tumbling. Visibility is reduced.	9	29.5
11		Violent storm	56-63	104-117	28.5-32.5		Widespread structural damage.	Exceptionally high waves.	11.5	37.7
12	Hurricane (颶風)	Hurricane	64-71/ 64+	118-132/ 118+	32.6-36.6/ 32.6+	TY CAT. 1	Considerable and widespread damage to structures.	Huge waves. Air filled with foam and spray. Sea completely white with driving spray. Visibility greatly reduced.	14+	46+
13	(Not used by HKO)	(Not used except Taiwan and China)	72-80	133-149	36.7-41.3		Not generally seen on land. Catastrophic damage otherwise.
14			81-89	150-166	41.4-46.1	TY CAT. 2
15			90-99	167-183	46.2-50.8
16			100-108	184-201	50.9-55.8	TY CAT. 3 & above
17			109+	202+	55.9+

Source of the images (last column): http://www.stormfax.com/beaufort.htm

Wildweather with Rich Hammond - Part 2: Water - Documentary

Wildweather with Richard Hammond - Part 1: Wind: The Invisible Force

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

Understanding ENSO

Improve your understanding of the El Niño and La Niña and their impacts on our climate and weather with BoM's new Understanding ENSO video
This video explains what El Niño–Southern Oscillation (ENSO) is, how the cycle works including the science behind the phases, and the potential impacts on Australia’s climate and weather.

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.

Kalmaegi track's probability forecast 06Z 15Sep

Typhoon Rammasun hits the Philippines

Authorities said at least 10 people had been killed by the storm.

Strong winds knocked out power and forced thousands of people to evacuate as Typhoon Rammasun hit the central Philippines.
The typhoon, also known as Glenda, struck the main island of Luzon with gusts of up to 185km/h (115 mph).

Millions without power
Town halls had been converted into shelters and evacuees had also been taken to schools and gymnasiums.
"Trees are starting to fall down and everything is just rain and wind," eyewitness Zhey Anzures told the BBC from a Manila suburb.
"We are also just beside a construction site and the cranes are really rotating because of the strong winds."
Manila Electric Company said 2.3 million of its customers were without electricity.

The Philippines is hit by around 20 major storms a year. Typhoon Rammasun is the first to make landfall this year after the rainy season began in June.
Typhoon Haiyan, which devastated the country last year, killed more than 6,000 people and was said to be one of the worst storms on record.

Which Tropical Cyclones Are Similar to Typhoon Rammasun

Here is the two candidates:
1. Typhoon Elsie, October 1989.
Formed higher, also gained typhoon intensity (Vmax >= 64kts) when made landfall in Luzon island, Philippine but after passing longitude of 115E, Elsie has weaken and made landfall about 17-18N of Vietnam with tropical depression intensity.

Typh. Elsie is similar to typh. Rammasun but seem to get weaker after passing 115 degree East

2. Typhoon Angela, October 1995
Formed lower and further to 145 degree East, gained typhoon intensity when passing 135E and kept intensifying and begin to degrade after longitude of 113E. Angela was downgraded and completely dissipated when moving into Bac Bo gulf.

3. What's my forecast for typh. Rammasun?
- Rammasun will continue its way straight forward into Bac Bo gulf after passing Hainnan island while keep its intensity at severe tropical storm or weak typhoon. It means that Rammasun will move further north and stronger than its two cousins.
- The difference in month between Rammasun and its cousins also suggest that Rammasun will go further north.
... much more information need to be justified but impossible with those two track maps.

TY. Rammasun Track Probability Forecast

Track probability forecast of typh. Rammasun 21 UTC 16/7/2014

IPCC aims for clarity and relevance in new report

 Thomas Stocker argued local climate models have not been user-friendly

Providing information that policymakers can use is key to the Intergovernmental Panel on Climate Change (IPCC) as work begins on its next global assessment.

The report, known as AR5, will focus on factors that materially affect people's lives, such as the Asian monsoon.

Bão lửa hiếm hoi ở Brazil

Cột lửa cao tới vài mét nhảy múa trên những cánh đồng ở vùng Aracatuba, Brazil, hôm qua thiêu đốt hàng nghìn mẫu đất.

Cơn lốc xoáy hiếm hoi này gây ra tình trạng tắc nghẽn giao thông ở đường cao tốc tại Aracatuba, BBC đưa tin. Nguyên nhân là do những cơn gió khô, nóng khiến các đám cháy rừng lan rộng.

Hiện tượng này xảy ra sau nhiều tuần khô hạn, gây cháy rừng khắp cả nước này. 

"Big Nothing" weather pattern

The "Big Nothing" weather pattern that has taken over the western
North Pacific for the past several years is about to create a modern-day record for typhoon season delay. If the 5th TC of the year is not numbered by the JTWC by the 6th of August, this year will be the most delayed typhoon season in the historical record. It seems that in these warmer times, tropical cyclone activity is going out not with a bang, but with a whimper.

(Mark Lander)

Không có chuyện cảnh báo vống bão số 1

TP - Ông Hoàng Phúc Lâm, Phó phòng Dự báo Hạn ngắn, Trung tâm Dự báo Khí tượng Thủy văn T.Ư cho rằng, Trung tâm đã đưa ra những bản tin về cơn bão cập nhật dự báo đúng về hướng đi, thời gian đổ bộ của bão số 1, không có chuyện cảnh báo vống cường độ của bão.

Tuy nhiên, lượng mưa thực tế có ít hơn so với dự báo của trung tâm.

Sóng biển ập vào Đồ Sơn (Hải Phòng). Ảnh: TTXVN.

Texas on alert as Hurricane Alex sweeps in

US President Barack Obama has declared a state of emergency in Texas as Hurricane Alex bears down on the coast with 80mph (130km/h) winds.

Alex, which has now strengthened to a category two hurricane, is expected to make landfall near the Texas-Mexico border.

France's Flood in pictures

Deadly flash floods hit southern France

At least 19 people have been killed by flash floods in south-eastern France, officials say.

Several others have been reported missing after torrential rain hit the mountains above the Cote D'Azur region on Tuesday.
A number of towns in the department of Var were affected, with hundreds of homes flooded.
Meteo France, the national weather service, said up to 40cm (15.7in) of rain had fallen since Tuesday.
Meterologists say the floods are the worst in the region since 1827.
About 2,000 rescue workers have been drafted into affected regions around Draguignan - the worst-hit area - near the Mediterranean coast to help those trapped in their vehicles or houses.
'Devastated' Water levels were said to be falling slightly in Draguignan on Wednesday, though the rain was continuing in nearby Roquebrune and Frejus.
Meteo France has warned of further storms on Wednesday night.
"We have never seen so much rain in the month of June," Patrick Galois of Meteo France told the AFP news agency.
At least 1,000 people had to leave their homes and spend the night in schools or other temporary shelters, and some 175,000 houses were estimated to have been left without electricity.
Some reportedly sought shelter on the roofs of their homes, while helicopters were brought in to rescue people.
Rescue teams had to moved 436 inmates from a prison in Draguignan after two floors flooded.
The force of the water swept empty cars and other vehicles down streets in Draguignan.
"This morning, we woke up to find a town centre that was devastated, extremely battered with overturned cars floating in the streets, collapsed roads and gutted houses," said Corinne Orzechowski, the official leading the emergency operation.
Condolences The floods are believed to be the worst since 1827 The BBC's Hugh Schofield in Paris says that many of those who died were caught in their cars.
Rail and air services in the region were interrupted, and about 300 passengers travelling on a high-speed train between Nice and Lille had been trapped by the flood waters, the AFP news agency reported.
The railway line between Toulon and Frejus will be closed until Thursday morning.
President Nicolas Sarkozy offered condolences to the families of the victims, and pledged his support to rescue workers "mobilising non-stop to provide aid and find those still missing".
He plans to visit the area early next week.

'Much more water' found in lunar rocks

The Moon might be much wetter than previously thought, say scientists.

A US-led team analysed the mineral apatite in lunar rocks picked up by the Apollo space missions and in a lunar meteorite found in North Africa.

The scientists found that there is at least 100 times more water in the Moon's minerals than they had previously believed.

The new study has been published in the journal PNAS.

This group is one of several different teams of researchers hunting for evidence of water on the Moon - and clues to how it got there.

Lead author Francis McCubbin from the Carnegie Institution for Science in Washington DC told BBC News that the water content on the Moon ranges from 64 parts per billion to five parts per million.

"It would be about 2.5 times the volume of the Great Lakes," he said.

"Or another way of looking at it - if you took all of the water that was locked up inside the rocks of the Moon and put them on the surface, it would make a metre-thick layer covering the Moon."

The scientist explained that the Moon most probably formed after a Mars-sized space body collided with the young Earth, some 4.5 billion years ago.

The high-energy impact produced molten debris, which eventually cooled to form our planet's only natural satellite.

Back then, he said, there was a magma ocean on the Moon. Magma contained water, which eventually erupted via "fire fountains" on to the lunar surface.

Most of this water evaporated during the volcanic activity - but some of it stayed, said Dr McCubbin.

"I like to use the analogy of someone who's trying to make non-alcoholic beer, there's always going to be some alcohol left," he explained.

Quest for water

After the US Apollo space missions of the late 1960s and early 1970s returned to Earth with numerous samples of lunar rocks, scientists spent years examining them in search of water.

Continue reading the main story

So maybe there was a lot of cometary debris going by and as these 'dirty icebergs' hit the Moon, they provided a lot of water input

Lawrence TaylorUniversity of Tennessee in Knoxville

At first, they declared that the Moon was dry - but this theory was challenged in 2008, when a US team used the method of secondary ion mass spectrometry (SIMS) and found evidence of water in lunar volcanic glasses - pebble-like rocks that ended up on the Moon's surface after the volcanic outpouring.

It was a breakthrough discovery, even though the quantity of water was only of the order of 46 parts per million.

Nevertheless, the scientists said that their research shed light on the origins of lunar water, asserting that it was "native" to the Moon.

Earlier in 2010, a radar experiment aboard India's Chandrayaan-1 lunar spacecraft found thick deposits of water-ice near the Moon's north pole.

In the recent study, Dr McCubbin and his colleagues used SIMS to look at the Apollo samples once more - but this time, they analysed the only water-bearing mineral of the rocks - apatite.

Apollo missions brought many lunar rocks back to Earth

This mineral happens to be a major component of tooth enamel and bones and, as Dr McCubbin explained, "has a better chance of retaining water than volcanic glass".

The team specifically studied hydroxyl (OH) - a chemical compound in apatite that contains one atom of oxygen and one atom of hydrogen.

The researchers combined their measurements with models that analyse how the material crystallised as the Moon cooled.

The team found that the Moon's interior contains at least 100 times more water than was previously believed, stored in lunar minerals.

Other researchers have called the results important for future studies.

"It is gratifying to see this proof of the OH contents in lunar apatite," commented lunar scientist Bradley Jolliff from Washington University in St. Louis, Missouri.

"The concentrations are very low and, accordingly, they have been until recently nearly impossible to detect. We can now finally begin to consider the implications—and the origin - of water in the interior of the Moon."

Other theories

Dr Lawrence Taylor from the University of Tennessee in Knoxville, US has been involved in a separate, but similar research.

He told BBC News that besides finding water in the apatite, he and Jim Greenwood from Wesleyan University in Connecticut have come up with an additional theory about the origins of lunar water.

"We're thinking now that there might have been a cometary input as well," said Dr Taylor.

He explained that there were a lot of comets flying around at the time of the Moon's formation, "hitting the little, nascent, early Moon some 4.5 billion years ago".

Some scientists call comets "dirty icebergs" as they mostly contain ice, as well as other rocky material, soil and gases.

"So maybe there was a lot of cometary debris going by and as these 'dirty icebergs' hit the Moon, they provided a lot of water input," Dr Taylor said.

"Back then, the outer portion of the Moon was molten, it was all a lunar magma ocean, so the comets were incorporated into the chemistry of the [Earth's satellite]".