Vol-1, Issue-13, December 1-15, 2015 Geography and You Free Copy geography CLIMATEandyou.com A FORTNigHTLY ONLINE MagaZINE ON WEATHER, WATER AND HAZARDS CYCLONES ■ Tropical Cyclones ■ Tropical cyclones: fact file ■ Structure of a Cyclone ■ Cyclone Formation ■ Observational Network for Cyclones ■ Atmospheric Phenomena: Altocumulus Cloud (AC) G'nY CLIMATE December 1-15, 2015 ● Volume 1 ● Issue 13 1 Be a WEatHER Climate A fortnightly online magazine on weather, water and hazards journalist Volume 1 • Issue 13 • December 2015 FREE COPY Advisor Air Vice Marshal (Retd) Dr. Ajit Tyagi, Former Director General, No weather India Meteorological Department event is Editor too small Sulagna Chattopadhyay or too large Legal Advisor Krishnendu Datta REPORT NOW Correspondence/Editorial Office Now you can 1584, B-1, Vasant Kunj, put all the idle New Delhi-110070 weather talk Phone: 011-26122789 to good use. For G'nY subscriptions, renewals, Calling all, enquiries please contact: professionals Circulation Manager and amateurs to E-mail: [email protected] report about any Please visit our site at weather event www.geographyandyou.com for that they find further information. unusual. Weather ©IRIS Publication Pvt. Ltd. events such All rights reserved throughout the as lightning, world. Reproduction in any manner, cloud, hailstorm, part or whole, is prohibited. Printed, flooding, etc., published and owned by Sulagna are of special Chattopadhyay. interest to us. You may capture Research Credit short videos on your phone and LIGHTS (Learning in Geography, send it to us too. Humanities, Technology and Science) a not-for-profit research foundation Photographers are especially Published at welcome. IRIS Publication Pvt. Ltd. Geography and You does not take any There are PRIZES responsibility for returning unsolicited too. For the best publication material. entry in reporting, an award of Rs All disputes are subjected to the exclusive 1000 is offered. jurisdiction of competent courts and forums The report will be in Delhi/New Delhi only. published in G'nY CLIMATE. For the best photograph a cash prize of Rs 500 is offered, which will be printed in G'nY. For queries write to editor@ geographyandyou.com Advisor's Desk Dear readers, Natural disasters in the current decade are occurring nearly five times Contents as often as they were in the 1970s, with both developed and developing countries bearing the burden. The Feature frequency of geophysical disasters (earthquakes, tsunamis,volcanic eruptions and mass movements) 4 Tropical Cyclones remained broadly constant throughout this period, but a sustained rise in hydro-meteorological related 5 Tropical Cyclones: Fact File events (mainly floods and storms) pushed total 6 occurrences significantly higher. Since 2000, on an Structure of a Cyclone average of 341 hydro-meteorological related disasters 6 Cyclone Formation were recorded per annum, up 44% from the 1994- 2000 average and well over twice the level in 1980- 7 1989. Of all hydro-meteorological disasters, about Observational Network for Cyclones 89% were due to flooding and storms. But storms - Suman Goel were by far the bigger threat to life accounting for about 1.45 m of the 1.94 m global disaster deaths - Deadliest Hurricanes in History between 1971- 2010. Most of these deaths occurred - Deadliest Typhoons in History in developing and least developed countries. - Deadliest Cyclones in India However, in recent years there has been significant reduction in loss of lives because of improved - Recent Cyclones in India cyclone monitoring and warnings and disaster 11 Atmospheric Phenomena: preparedness. Indian coasts are vulnerable to cyclones. Altocumulus Cloud (AC) Awareness about the characteristic features of 12 News Updates disaster such as climatology, structure, associated hazards and warning system helps in disaster 13 Conference Alert preparedness. G'nY Climate propose to cover these topics related to cyclones in simple to understand format for the benefit of wider readership in two issues. Current issue covers nomenclature of cyclones in different oceans, structure of cyclones, conditions favourable for the formation of cyclones and observing network for monitoring of cyclones. Forecasting, Warning and mitigation will be covered in the next issue. Other stories of interest in this issue include report on Chennai Floods, El Nino update and news of Year 2015 turning out to be the hottest year on record as yet. Dr. Ajit Tyagi G'nY CLIMATE December 1-15, 2015 ● Volume 1 ● Issue 13 3 World TROPICAL CYCLONES ropical Cyclones are intense low pressure systems formed over The average annual frequency of tropical cyclones in the north the seas in tropical areas where surface wind speeds exceed IndianOcean (Bay of Bengal and Arabian Sea) is about 5 (about 33 knots (64 kmph), Winds in a cyclonic storm rotates in 5-6 % of the Global annual average) and in the globe is about 86. counterT clock wise manner around a low pressure centre, termed The frequency is more in the Bay of Bengal than in the Arabian the 'eye' of the storm. The eye is well known for being eerily calm Sea, the ratio being 4:1. as compared to the areas comprising the spinning 'arms' of the Average annual frequency in different basins: storm. The horizontal extent of a well developed tropical cyclone is of the order of 100 to 1000 Km and its vertical extension is about Basin Tropical Storm frequency 10 to 15 Km. The word, ‘Cyclone’ is derived from the Greek word North Atlantic 12.1 ‘Cyclos’, meaning the coil. Eastern Pacific 16.6 Western Pacific 27.0 TYPES OF CYCLONES North Indian 4.8 The term 'cyclone' actually refers to several different types of storms. Some occur over land while others occur over water. But all South-West Indian 9.3 of them are spinning storms rotating around a low-pressure centre. Australian region 11.0 Tropical cyclones occur over tropical ocean regions causing devas- Southern Pacific 7.4 Climate tation in coastal areas. These form in areas deep with convection Global 86.0 over warm waters and have warm core and derive their energy from the of release of latent heat by thunderstorms. CLASSIFICATION OF StORMS Extra tropical cyclones, as name suggest, form in higher lati- These are classified in different categories primarily based on wind tudes, have cold air at their core, and derive their energy from the speed. Intensity of cyclones are also inferred from satellite imageries release of potential energy when cold and warm air masses interact. by T- numbers based on cloud pattern. The intensity of cyclone is These storms always have one or more fronts connected to them, also related to pressure drop at the centre of the storm. The more and can occur over land or ocean. An extra tropical cyclone can the drop in pressure in the central region, the more is the severity have winds as weak as a tropical depression, or as strong as a of the storm. Cyclonic storms are generally categorized according hurricane. Examples of extra tropical cyclones include blizzards, to the maximum wind speed associated with the storm( Table). If Nor'easters, and the ordinary low pressure systems that give the the maximum wind speed is between 34 - 47 knots (about 60-90 continents at mid-latitudes much of their precipitation. kmph) it is called a Cyclonic Storm. A Severe Cyclonic Storm will Tropical cyclones moving to higher latitudes become Extra- have maximum wind speeds ranging around 48 - 63 knots (about tropical storms when they caught up in a front and change from 90-120 kmph). If the maximum wind is 64-89 knots it will be warm core to cold core. Polar cyclones are cyclones that occur in called a Very Severe Cyclonic Storm and when the wind is 90 -119 Polar Regions likeGreenland, Siberia and Antarctica. Polar cy- knots it is Extremely Severe Cyclonic Storm and 120 knots and clones can form in any time of the year, although summer polar above, it isa Super Cyclonic storm. There is very little association cyclones are usually weaker than the ones that form in the winter. between intensity (either measured by maximum sustained winds These occur in areas that aren't very populated, hence the damage or by the lowest central pressure) and size (measured by radius of they cause ispretty minimal. gale force winds). In the United States, Hurricanes are termed Category 1, 2, 3, 4 or StORMS IN DIFFERENT OcEANS The location of a storm is an System Satellite Condition Associated Wind Speed important factor since it deter- (Abbreviation) ‘T’ No. of Sea Knots (Kmph) mines what we call it. For ex- Low Pressure Area (L) 1.0 Moderate <17 (<31) ample, if the storm occurs in the Depression (D) 1.5 Moderate to Rough 17 – 27 (31 – 49) Atlantic Ocean and Northeast Deep Depression (DD) 2.0 Very Rough 28 – 33 (50 - 61) Pacific, it's called a hurricane, Cyclonic Storm (CS) 2.5 – 3.0 High 34 – 47 (62 – 88) after theCaribbean god of evil- Severe Cyclonic Storm 3.5 Very High 48 – 63 (89 - 117) Hurricane. The same type of (SCS) Very Severe Cyclonic storm in the Northwest Pacific is 4.0 – 4.5 Phenomenal 64 – 89 (118 - 166) called a Typhoon, derived from Storm (VSCS) Extremely Severe the Arabic-Toofan. The same 5.0 – 6.0 Phenomenal 90 – 119 (167 - 221) storms in the South Pacific and Cyclonic Storm (ESCS) Super Cyclonic Storm Indian Ocean are called Tropi- 6.5 – 8.0 Phenomenal ≥120 (≥222) cal Cyclones. In Australia these (SuCS) storms are called ‘Willy-Willies’. Source: www.imd.gov.in 4 December 1-15, 2015 ● Volume 1 ● Issue 13 G'nY CLIMATE 5, in rising order of intensity in keeping with increase in wind speed: November 30, the typhoon and cyclone seasons follow slightly Category 1: wind 74-95 mph (119-153 km/h) different patterns.