north indian ocean Severe Tropical Cyclone Helen

[Somerset Squall]

The fourth tropical cyclone of the season has formed in the northwest Bay of Bengal. Winds are at 35kts. The cyclone has curved banding features wrapping around a well defined LLCC. Shear is moderate, but waters are warm and outflow is good, which should allow some strengthening before 04B makes landfall on the east coast of India in around 48hrs time. Based on the structure of 04B, I suspect JTWC's forecast peak of 45kts could be a little low.

 

Edited November 19, 2013 by Somerset Squall

[Somerset Squall]

Winds have risen to 45kts. 04B has quite a tight inner core, so I think 04B has the chance to ramp up quickly, unless shear rises further. JTWC now forecasting a peak of 60kts.

[Coast]

Tropical Storm FOUR: Probability of Cat 1 or above winds to 72 hours lead

 

[Coast]

 

 

International weather models have declared the emergence of a ‘numbered tropical cyclone 04B’ in the Bay of Bengal. This takes last night’s depression to a tropical storm, just below the status of a ‘named tropical cyclone’, or a deep depression in India Met Department parlance.

 

There is, however, significant divergence in the forecast among various models over the exact location for a landfall. Some take it even north of Nellore in Andhra Pradesh coast. India Meteorological Department has suggested the coast between Chennai in Tamil Nadu and Ongole in Andhra Pradesh (its morning update is awaited). The landfall is expected to take place by tomorrow night, as per consensus forecasts. A heavy rain alert has been mounted for the north Tamil Nadu and adjoining south coastal Andhra Pradesh coasts.

 

http://www.thehindubusinessline.com/industry-and-economy/agri-biz/global-models-declare-tropical-storm-in-bay/article5370845.ece

 

[Somerset Squall]

04B has been upgraded to Cyclonic Storm status by IMD, and has been given the name Helen. Winds are up to 50kts according to JTWC. Helen has barely moved today in a weak steering environment, but should move west soon as ridging builds to the north. Helen has the opportunity to strengthen a little more before landfall.

[Coast]

 

 

Tropical Cyclone 04B has strengthened and been renamed "Helen" as it slowly nears landfall in southeastern India.

 

On Nov. 20 at 1200 UTC/7 a.m. EST, Tropical Cyclone Helen had maximum sustained winds near 50 knots/57.5 mph/92.6 kph. It was centered near 15.5 north and 83.9 east, about 499 nautical miles/574.2 miles/924.1 km south-southwest of Calcutta, India. Helen was crawling to the northwest at 1 knot/1.1 mph/1.8 kph. A mid-level subtropical ridge (elongated area) of high pressure is expected to slowly build east of Helen and steer the storm on a more western track in the next day.

 

Current warnings are in effect for fishermen along the coasts of Andhra Pradesh, who are advised to return to shore. Animated multispectral satellite showed a resurgence of deep convection over the low-level center of circulation. Satellite data also showed that the band of thunderstorms that appeared strong to the north has weakened and become fragmented. Visible/short wave infrared data from ESA's METEO-7 satellite and rainfall data from NASA's Tropical Rainfall Measuring Mission or TRMM satellite was combined at the Naval Research Laboratory to create a composite image of the storm on Nov. 20. The image showed the clouds associated with Helen were mostly still over the open waters of the Arabian Sea, and that south of the center, light rainfall was occurring.

 

Helen is expected to intensify to 60 knots/69.0 mph/111.1 kph over the next two days and weaken before landfall. Helen is forecast to pass just south of the Yelichetladibba Palem and Nachugunta Reserved Forests in Andhra Pradesh, located in the coastal plain of Krishna Delta. Helen is expected to make landfall in the vicinity of Chinnaganjam in southeastern India.

 

 

 

http://phys.org/news/2013-11-tropical-cyclone-helen-landfall-india.html#jCp

[Su Campu]

"...over the Arabian Sea..."?! I think they mean the Bay of Bengal!

[Somerset Squall]

Helen has strengthened a little more, to 60kts according to JTWC. Helen has been upgraded to a severe cyclonic storm by IMD. Helen has finally made some westward progress towards the coast. JTWC note that Helen as upwelled some colder water due to the slow motion of the system, but Helen has left this behind now. Helen has about another 24hrs over water, but shear seems to be increasing and there is another tongue of cooler water near the coast. This means that Helen has probably just about peaked ad should weaken some prior to landfall.

[Coast]

Tropical Storm HELEN: Probability of tropical storm winds to 48 hours lead

[Vorticity0123]

Helen is about to make its landfall in mainland India. The landfall location has shifted somewhat to the north, because of unexpected continued northwestward movement according to the JTWC:

 

 

BASED ON A REINTERPRETATION OF PREVIOUS
0600Z DATA IN LIGHT OF THE MORE DEFINITIVE 1200Z DATA, THE 0600Z
BEST TRACK POSITION WAS MOVED TO PORTRAY THE CONTINUED NORTHWESTWARD
MOVEMENT. THE CURRENT FORECAST DIFFERS FROM PREVIOUS WITH REGARDS TO
LANDFALL POSITION DUE TO THIS REANALYSIS.

 

The biggest threat with this system will be anomalous rainfall with the system.

 

Currently the Indian basin is quite active. The image below (MIMIC TPW) shows the total precipitable water (a measure for humidity).

 

Helen can be seen rotating just to the west of India. 30W (Yes, it stubbornly continues to hold on) can be seen moving westward to the west of India while slowly weakening. There is a lot of dry air behind 30W (low TPW values), which is probably impeding with development.

 

However, the main area of interest lies over Thailand. One can see a slowly rotating column with very high TPW values near that area. That area is probably the next area developing in a TC in the Bay of Bengal.

 

The JTWC notes about the AOI in Thailand that: 

 

THE DISTURBANCE IS CURRENTLY IN AN EXTREMELY FAVORABLE
ENVIRONMENT LOCATED SOUTH OF THE SUBTROPICAL RIDGE AXIS WITH
EASTERLY DIFFLUENCE ALOFT, AND IS UNDER LOW TO MODERATE (10-15
KNOTS) VERTICAL WIND SHEAR.

Chances of development are currently in the medium category for the next 48h.

 

The GFS forecasts this system to become a potent and potentially destructive cyclone making landfall at almost exactly the same area as Helen is about to do (though it is still 5 days away, exact landfall position may shift somewhat.)

 

At T48, the cyclone can be seen as a still weak entity to the west of Thailand:

 

 

However, at T120h, the system can be seen as a strong TS/weak hurricane about to make landfall at almost the same spot as Helen.

 

 

Usually, the GFS has a bias to underestimate the minimum pressure (too low grid level). This means that the next area will be an area worth watching.

 

 

Sources:

http://www.usno.navy.mil/JTWC/

http://tropic.ssec.wisc.edu/#

http://en.wikipedia.org/wiki/Precipitable_water

http://www.wetterzentrale.de/topkarten/fsavneur.html

Edited November 21, 2013 by Vorticity0123

[Somerset Squall]

Slow moving Helen is about to make landfall. Winds have decreased to 35kts. The observed weakening is mainly down to shear, as convection has been sheared to the northeast of the LLCC, leaving it exposed, just off the coast. Helen will make landfall in the next few hours and dissipate quickly over land.

[Coast]

 

 

NASA’s Aqua satellite captured visible and infrared imagery of slow-moving Tropical Storm Helen as it was spreading its western clouds over parts of southeastern India on November 21.

 

On Nov. 21 at 07:55 UTC/2:55 a.m. EDT the MODIS or Moderate Resolution Imaging Spectroradiometer instrument that flies aboard NASA’s Aqua satellite captured a visible image of Tropical Cyclone Helen that showed clouds in the storm’s western quadrant had already spread over eastern India. Two minutes before the MODIS instrument captured the visible image of Helen’s clouds, the infrared instrument aboard Aqua called the Atmospheric Infrared Sounder or AIRS instrument used infrared light to gather data from the storm. The infrared data showed that the strongest thunderstorms with the coldest cloud top temperatures were still off-shore. The stretched around the center from northwest to southwest and wrapped around to the east. Only the bands of thunderstorms in the northern quadrant appeared to be fragmented, which could be a result of that area’s interaction with land.

 

On Nov. 21 at 1500 UTC/10 a.m. EST, Tropical Cyclone Helen was located about 495 nautical miles/569.6 miles/ 916.7 km southwest of Calcutta, India, near 16.1 north and 83.0 east. Helen was moving a little faster than the previous day, now at 4 knots/4.6 mph/7.4 kph to the northwest. Helen’s maximum sustained winds had increased slightly to 55 knots/63.2 mph/101.9 kph, and those tropical storm force winds extend out 65 nautical miles/74.8 miles/120.4 km from the center. Helen was also creating maximum wave heights of up to 20 feet/6.0 meters, and causing rough seas along the southwestern coast of India.

 

As a result of the strong waves and tropical-storm force winds, warnings are in effect for Andhra Pradesh that include: A storm surge of 1 to 1.5 meters/3.2 to 4.9 feet will occur at the time of landfall, Thatched roofs and huts will sustain damage and a call for fisheries to cease operations.

 

Helen is expected to weaken as it nears the coast as it moves into cooler waters and continues to battle moderate wind shear. Helen is expected to make landfall near Tenali early on November 22. After landfall, Helen should weaken as it moves west where it is expected to dissipate in a couple of days

 

 

http://www.redorbit.com/news/space/1113010276/tropical-storm-helen-affecting-southeastern-india-112113/

 

[Beasterly]

Cyclone Helen makes landfall on India's east coast

 

 

A cyclone has made landfall on India's east coast with winds of up to 90km/h (55mph) and heavy rain, the country's meteorological department has said.

Thousands of people were evacuated from coastal areas in advance of the storm. So far there have been no immediate reports of any casualties.

Cyclone Helen is expected to trigger storm surges of up to 1.5m (5ft).

At least 27 people died when a stronger cyclone, Phailin, hit India's eastern coast last month.

The meteorological department has classed Cyclone Helen as "severe" and has warned of "extensive damage to thatched roofs and huts".

It says there will be "minor damage to power and communication lines due to uprooting of large trees" in the state of Andhra Pradesh.

Twenty rescue teams had been deployed in the flood zone, a spokeswoman for the National Disaster Management Agency, Tripti Parule, told the AFP news agency.

"Evacuations of thousands has already taken place and provision for food, water and shelter are also on track," she said, adding that the aim was for "zero casualties".

Last month Cyclone Phailin destroyed tens of thousands of homes, uprooted trees and blocked roads in the states of Orissa and Andhra Pradesh.

Hundreds of thousands of people were evacuated ahead of Phailin, which was classified as a "very severe" cyclone.

 

http://www.bbc.co.uk/news/world-asia-india-25047158

Edited November 23, 2013 by Beasterly

[Beasterly]

After Cyclone Helen, it's time for Lehar storm to hit AP?

 

Hyderabad: Even before the impact of the severe cyclonic storm Helen could be analysed, another depression, now situated 450 km south-east of Port Blair, is likely to develop and intensify into a severe cyclonic storm by November 27 midnight or November 28 morning.

If it does intensify into a severe cyclonic storm, it will be named “Leharâ€, officials at the Meteorological Department informed.

On the Asian circuit, it was India’s turn to name the cyclone from the list of assigned names.

Phailin was named by Thailand and Helen by Bangladesh.

“This depression is also very likely to intensify into a cyclonic storm. According to our preliminary report it will have the same impact as Helen and will affect the Kakinada coast,†informed S.V.S.S. Ramakrishna, head of department, Department of Meteorology and Oceanology, Andhra University.

“November is the peak month for tropical cyclones and the situation is very favourable for the formation of systems,†he said.

M. Narsimha Rao, assistant meteorologist at the Meteorological Centre, Hyderabad said that compared to the Arabian Sea, the frequency of the formation of systems is more in the Bay of Bengal.

“October to December is post monsoon period which is also one of the reasons,†he said.

 

http://www.deccanchronicle.com/131123/news-current-affairs/article/after-cyclone-helen-its-time-lehar-storm-hit-ap

[Coast]

Hyderabad: Cyclonic storm Helen hit Andhra Pradesh coast near Machilipatnam on Friday, triggering heavy rains and strong gales, killing seven people and causing massive damage to the crops in the coastal region. Trees were uprooted disrupting traffic and communication and electricity towers were damaged as strong gales with speed reaching 100-110 kmph caused havoc in the coastal districts of Krishna and two Godavari districts. The deaths were mostly caused by falling trees in the affected districts, said officials. The sea conditions were rough and the sea water at some places flushed out for a few metres over land. Cyclone Helen lashed Andhra Pradesh. PTI. According to Visakhapatnam Cyclone Warning Centre, the cyclone made the landfall near Machilipatnam in Krishna district around 2 p.m. Officials said it would take some more time for the entire system to cross the coast. Under the influence of the severe cyclonic storm, many parts of Krishna, Guntur, East Godavari, West Godavari,

 

Visakhapatnam and other districts were receiving rain. The Indian Meteorological Department (IMD) has warned that storm surge of about 1 to 1.5m height would inundate the low-lying areas of West and East Godavari, Krishna, Guntur districts and adjoining areas of Prakasham district. The IMD has warned that even after landfall the storm is likely to maintain the intensity for six hours and gradually weaken into a deep depression in subsequent six hours while moving westwards across coastal Andhra Pradesh and Telangana. With heavy rains likely to continuing in coastal districts over next 36 hours, authorities have evacuated 17,000 people from low-lying areas. C. Parthasarathi, commissioner, disaster management, said 66 relief camps were opened. The high-speed wind has damaged coconut, banana and paddy crops, and dealt another blow to farmers who are still recovering from the heavy damage caused by last month’s Cyclone Phailin and accompanying heavy rain. Rainfall at most places with heavy to very heavy rainfall at a few places and isolated extremely heavy rainfall (25cm or more) would occur over north coastal Andhra Pradesh and adjoining Guntur, Krishna, West Godavari districts of south coastal Andhra Pradesh during next 36 hours, said a bulletin by the IMD. Rainfall at most places with isolated heavy to very heavy falls would occur over remaining districts of south coastal Andhra Pradesh, Rayalseema and isolated heavy to very heavy falls over Telangana during next 48 hours.

 

Earlier, Chief Minister N. Kiran Kumar Reddy Friday reviewed the situation with the chief secretary and other officials in Hyderabad and directed them to take all precautionary measures, especially in Krishna and Guntur districts. A control room to monitor the situation has been opened at the state secretariat in Hyderabad. 

 

http://www.firstpost.com/india/cyclone-helen-strikes-andhra-pradesh-leaves-7-dead-1244927.html?utm_source=ref_article