Cold cloud top temperatures can tell forecasters if a tropical cyclone has the potential to generate heavy rainfall, and that is exactly what NASA’s Aqua satellite found on Dec. 10 over a much smaller area than was occurring on Dec. 9.

On Dec. 10 at 6:47 a.m. EST (1047 UTC) NASA’s Aqua satellite analyzed Tropical Storm Belna using the Atmospheric Infrared Sounder or AIRS instrument. AIRS found coldest cloud top temperatures (purple) as cold as or colder than minus 63 degrees Fahrenheit (minus 53 degrees Celsius) in a small area over northwestern Madagascar.

The AIRS instrument aboard NASA’s Aqua satellite captured a look at cloud top temperatures in Belna which gave insight into the storm’s strength. Cloud top temperatures provide information to forecasters about where the strongest storms are located within a tropical cyclone.

Tropical cyclones do not always have uniform strength, and some sides are stronger than others. The stronger the storms, the higher they extend into the troposphere, and the colder the cloud temperatures are.

On Dec. 10 at 6:47 a.m. EST (1047 UTC) NASA’s Aqua satellite analyzed the storm using the Atmospheric Infrared Sounder or AIRS instrument. AIRS found the strongest storms with coldest cloud top temperatures as cold as or colder than minus 63 degrees Fahrenheit (minus 53 degrees Celsius) in a small area over northwestern Madagascar. NASA research has shown that cloud top temperatures that cold indicate strong storms that have the capability to create heavy rain.

By Dec. 11 at 4 a.m. EST (0900 UTC), Belna had become devoid of all heavy rainfall, and the forecasters at the Joint Typhoon Warning Center (JTWC) issued their final bulletin on the storm.

Belna had weakened to a tropical depression and had maximum sustained winds near 30 knots (34.5 mph/55.5 kph). Belna was located near latitude 21.3 degrees south and longitude 45.4 degrees east. It was over land and just six nautical miles southwest of Antananarivo, Madagascar. Belna was moving south and is expected to dissipate in a day or two.

Tropical cyclones and hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

The AIRS instrument is one of six instruments flying on board NASA’s Aqua satellite, launched on May 4, 2002.

Rob Gutro
NASA’s Goddard Space Flight Center

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On Oct. 30, the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Terra satellite provided a visible image on Kyarr as it tracks through the Arabian Sea. The MODIS image showed that the storm maintained an eye, but it had become filled with high clouds. The eye also appeared somewhat oblong, indicating that the storm is weakening. Large feeder bands, that is, bands of powerful thunderstorms that spiral into the low-level center, extended north and south of center.

The shape of the storm is a clue to forecasters that a storm is either strengthening or weakening. If a storm takes on a more rounded shape it is getting more organized and strengthening. Conversely, if it becomes less rounded or elongated, it is a sign the storm is weakening.

After the MODIS image was taken, a microwave satellite image revealed the defined oblong microwave eye feature, but the bulk of the deep convection (strong thunderstorms) were confined to the eastern semicircle.

At 5 a.m. EDT (0900 UTC) on Oct. 30, the center of Tropical Cyclone Kyarr was located near latitude 19.2 degrees north and longitude 61.8 degrees east. That puts the center about 184 nautical miles east-southeast of Masirah Island, Oman. Maximum sustained winds were near 90 knots (104 mph/167 kph).

The Joint Typhoon Warning Center or JTWC noted that Kyarr is moving toward the southwest. JTWC noted, “The system should weaken gradually as environmental conditions degrade with more rapid weakening expected after 24 hours due to increasing easterly upper-level convergent flow [where lines of equal atmospheric pressure are pressed together between a high-pressure area to the north and the tropical cyclone or low-pressure system] and potentially dry air entrainment [dry air moving into the storm and sapping the moisture that helps create the thunderstorms the make up the storm].”

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

By Rob Gutro
NASA’s Goddard Space Flight Center

Related content

• The latest Tropical Cyclone Kyarr news and the forecast

• Update : Latest update of New Delhi RSMC. Kyarr weakened into a Cyclonic Storm. At 0300 UTC of 31 october, the center was located near 18.0°N and 60.2°E, about 1330 km west southwest of Mumbai (India), 670 KM East-northeast of Salalah (Oman) and 320 km South-southeast of Masirah (Oman). It is very likely to move southwestward across westcentral Arabian sea during next 3 Days according New Delhi. The closest approach of Socotra is expected Saturday. An other tropical storm named Maha is under surveillance in the Southeast of Arabian sea.

• Update : Kyarr weakened into a Very Severe Cyclonic Storm which is the equivalent of a category 2 on the Saffir-Simpson scale. It was centered over westcentral and north Arabian Sea and lay centred at 0530 hrs IST of 30th October, 2019 near latitude 19.6°N and longitude 62.3°E, about 1100 km westnorthwest of Mumbai (Maharashtra), 930 km east-northeast of Salalah (Oman) and 370 km eastsoutheast of Masirah (Oman) according RSMC New Delhi. Kyarr should gradually change track by turning westward and then southwestward over the next 24 to 36 hours. Landfall over Arabian Peninsula now seems excluded. On this track, the system will move toward Socotra while weakening. It expected to pass near or over the island during this weekend according.

• Update: The system that has demonstrated power by becoming the first Super Cyclone observed in the Arabian Sea since Gonu (2007), begins to weaken. Latest satellite data shows signs of degradation. The eye loses in definition, the top cloud warm up and an intrusion of dry air seems visible on the water vapor data. The trend is now weakening, as confirmed by the SATCON automatic intensity estimate which suggests a decrease. Human agencies (New Delhi CMRS & JTWC) are in good agreement. The northwest track will gradually turn toward westward and finally southwestward. Landfall over the Arabian Peninsula is therefore less and less likely. On this track, the system should move closer to Socotra and the Gulf of Aden over the next few days. However, New Delhi and the Navy are at a loss for future intensity. In the RSMC scenario, Kyarr would weaken so fast that it would be nothing more than a low when approaching Socotra. On the contrary, JTWC suggest a system still sufficiently strong approaching the Yemeni island. The threat level for the regions mentioned above will depend on the intensity of the system beyond the next 48 hours which is currently very uncertain.

Previous Kyarr coverage

Kyarr became Sunday 27th an impressive Super Cyclonic Storm, which corresponds to the top of the intensity scale in the North Indian Ocean. The future of the cyclone is very uncertain.

The system took full advantage of the favorable environmental conditions to become a Super Cyclonic Storm, which represents the top of the intensity scale in the North Indian Ocean. According to the JTWC, the max sustained winds were estimated at 135 kt, which is the equivalent of a violent hurricane at the limit of the category 4/5 on the Saffir-Simpson scale.

Such intensity is rarely observed in the Arabian Sea. The last Super Cyclonic Storm to have evolved in this part of the North Indian Ocean was Gonu during the 2007 cyclone season. This 2019 hurricane season is likely to enter the category of very active. If only 4 storms were nammed (Fani, Vayu, Hikaa and Kyarr), all reach tropical cyclone intensity. The accumulated cyclonic energy of this season should be very high!

Patrick

Cyclone Chaser 2.0, I am passionate about these phenomena and I share my passion on my blog cycloneoi.com

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Kyarr formed early on Oct. 25 from a low-pressure area designated as System 97A in the northern Indian Ocean. Once the storm consolidated, it intensified quickly and became a tropical storm just off the southwest India coast.

The India Meteorological Department issued some warnings on Kyarr on Oct. 25. There is a heavy rainfall warning in effect that calls for light to moderate rainfall in most places. Heavy to very heavy falls are predicted at isolated places very likely over coastal districts of Karnataka, Goa and south Konkan and isolated heavy rainfall over north Konkan during next 24 hours. There is also a wind warning in effect calling for gale-force winds with speeds reaching 70-80 kph (43 to 50 mph) gusting to 90 kph (56 mph), prevailing around the system center over east-central Arabian Sea. It is very likely to increase gradually becoming 90-100 kph (56 to 62 mph).

On Oct. 25 at 5:10 a.m. EDT (0910 UTC), the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Aqua satellite provided a visible image of Kyarr. The image showed that there is a large band of powerful thunderstorms circling Kyarr’s low-level center of circulation. In addition, infrared satellite imagery showed that Kyarr has a solid core of strong convection – that is, rising air which forms the thunderstorms that make up a tropical cyclone, wrap around the low-level circulation center. Microwave satellite imagery revealed the storm had developed an eye, a sign of strengthening.

The shape of the storm is a clue to forecasters that a storm is either strengthening or weakening. If a storm takes on a more rounded shape it is getting more organized and strengthening. Conversely, if it becomes less rounded or elongated, it is a sign the storm is weakening.

At 11 a.m. EDT (1500 UTC) on Oct. 25, the Joint Typhoon Warning Center or JTWC noted Tropical Cyclone Kyarr was located near latitude 16.3 degrees north and longitude 71.9 degrees east, about 579 nautical miles south-southeast of Karachi, Pakistan. Maximum sustained winds were 55 knots (63 mph/102 kph).

Kyarr is drifting generally northward while located between two subtropical ridges (elongated areas of high pressure) located to the northwest and northeast of the tropical storm. As those ridges strengthen and build, Kyarr is forecast to turn to the northwest and rapidly intensify.

The JTWC expects the storm will peak after three days, but will then start to weaken on approach to the Oman coastline.

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

Rob Gutro
NASA’s Goddard Space Flight Center

https://www.windy.com/-Satellite-satellite?satellite,3.360,62.117,5,internal

A suspect area numbered 97A over Arabian Sea is under surveillance. The global models suggest a futur cyclogenesis from this suspect area. ASCAT data shows a low level circulation centered in the north-west of Lakshadweep. Environment appear favorable for further development with low to moderate shear, strong divergence and very warm sea surface temperature.

However, 97A should approach the west coast of India. The proximity of land could hinder its development. The future of this low is therefore still uncertain. The situation will be closely monitored for the coastal regions of the Indian states of Karnataka, Maharashtra and Gujarat. It's not exclude that cyclonic storm stage could be reach during the next 48 to 72 hours. The next name on the cyclone list is Kyarr, name proposed by Myanmar.

For information, September/October/November period is usually the second peak of cyclone activity of the year in the North Indian Ocean.

Patrick

Cyclone Chaser 2.0, I am passionate about these phenomena and I share my passion on my blog cycloneoi.com

https://www.windy.com/-Satellite-satellite?satellite,-2.328,62.402,4,internal

If the six conditions, we’ve covered in previous chapter, are met, the tropical cyclone appears. Let's now learn what phases there are to grow from the tropical disturbance of the atmosphere to a huge tropical cyclone.

It starts with a tropical disturbance

At the beginning of every tropical cyclone, there is a tropical disturbance or a wave that can be caused for example by thunderstorm going from a land above an ocean. In this phase, previously mentioned six conditions play a big role to start the engine of development.

What is a tropical depression

In the next phase, the wind rises and starts to circle a centre of the disturbance due to the Coriolis force. Now it’s called tropical depression and it is a measurable and observable object in the atmosphere with clouds slightly rotating around causing low precipitation.

Almost a Hurricane

When the wind speed reaches 39 mph (63 km/h), it is called a tropical storm. Tropical storm looks like a little hurricane, but it has no eye in its centre. It is all covered in clouds spinning around an invisible centre.

In this phase, the storm gets a name. It can stop growing here and the name will be already used for only tropical storm and not for a cyclone (like was a case with recent tropical storm Ivo that weakened to tropical depression). More on tropical storm naming in following chapters. Anyway, even tropical storms can make huge damage.

When Tropical storm becomes a Hurricane

Finally, tropical cyclone is a phase with wind speed above 74 mph (119 km/h). It has a fully developed eye in the centre and its structure is quite stable above an ocean.

There are different names for tropical cyclones based on location, they are called hurricanes in the Atlantic Ocean and north-eastern Pacific Ocean, typhoons in the north-western Pacific Ocean and simply cyclones in South Pacific and Indian Ocean.

Before we get to more details in the upcoming chapters, we’ll uncover the difference between tropical and extratropical cyclone in the next one. See you next chapter.

Štěpán Šubík

Prague based student of meteorology eager for science, who likes to learn, but also wants to live to the fullest every day. Follow me on Twitter.

Next chapters:

• What is the difference between tropical and extratropical cyclone
• What’s the difference between hurricane, typhoon, cyclone

Previous chapters:

• What is a cyclone
• What is a tropical cyclone

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June 13th

June 12th
300,000 people are set to be evacuated to shelter homes, fishermen have been advised not to venture into sea along and off the Gujarat coast till June 15.

Vayu is likely to damage thatched houses, blow away rooftops and metal sheets, disrupt power and communication lines and cause major damage to roads and crops.

June 11th
Tropical Cyclone Vayu (VAYU-19, IMD's identifier ARB 01) formed 10 June 2019 in the Arabian Sea and it heads towards Gujarat and Pakistan, expected to strengten to Category 1 hurricane (or more precisely, because we are in the Indian Ocean basin, the Cyclone) later today (UTC 2019-06-11T18:00:00.000Z or 11 Jun 2019 8:00 PM local time).

Extremely heavy rains are expected across coastal India and over Pakistan.

Vayu is the 3rd named storm of the 2019 North Indian Ocean cyclone season.

The outlook

GDACS (JTWC) expects maximum wind speeds 167 km/h, estimate of the exposed population in Category 1 or higher is 6.6 million.

Vayu formed early on June 10 as a tropical depression in the Arabian Sea, northwest of the Maldives, and it gradually strengthened, becoming a Cyclonic Storm Vayu later that day.

Expected impact of the tropical storm Vayu

Unlikely to be as destructive as Fani, tropical storm Vayu will still have a huge impact on India. GDACS (JTWC) estimates Vayu will affect the popullation of 3.5 million in Category 1 or higher, with 176 km/h maximum sustained wind speed, maximum storm surge 1.4 m (13 Jun 05:00 UTC), ranked as High vulnerability for India.

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Get current forecast and stay safe

To track the path of Vayu, check out the Windy hurricane tracker at https://www.windy.com/hurricanes regularly. We'll also update this post to reflect the latest development of the Cyclone Vayu.