Today we will take a look at severe weather on a global and local point of view in Nepal. Tornadoes form because of several different factors, but they start out because of strong westerly winds flowing aloft and southeasterly surface winds flowing below. This causes a vertical wind sheer, making a rotating body of air. This horizontal body of air is then lifted off of the surface by the updraft of a thunderstorm. If the horizontal air mass is lifted to a vertical position it is considered a mesocyclone. At the point of the actual tornado making contact with the ground it becomes a funnel cloud that descends through the wall cloud. Looking at the United States specifically tornados tend to travel from west to east. This is because tornados usually form in the mid-latitude hemisphere, where the westerlies blow the storms west to east. Focusing back on Nepal, we can find that Nepal lies in the area of south-eastern Asia that has an attractive climate for tornadoes. However, Nepal itself has no recorded data of experiencing a tornado they occur above and below it in India and South China. (source)
The United States experiences an average of 1,200 tornadoes annually. (source) Due to lack of meteorological equipment in Nepal, I was unable to find the average of tornadoes let alone tornadoes recorded at all.
In relation to this global map of tornado prone areas, Nepal is in the mid-latitude hemisphere of the globe. This makes it a target for severe thunderstorms, which leads to possible tornadoes. Cold, dry air tends to spill over the Himalayas, mixing with the warm moist air in the wet monsoon seasons which creates unstable air. I believe that the increased amount of tornadoes in the past 30 years is due to the climate change of the earth. The global heating that has been occurring creates more instability in the air, and warms the winds and oceans making it easier for storms to form.
Next, we're going to compare a different storm that occurs in the U.S and globally, the hurricane.
It takes three main components to strike a hurricane. First you have to have an ocean temperature of 80 degrees or more, to get a lot of evaporation happening. In addition to the warm ocean temperature it needs to go deeper than the surface, in fact try a depth of 200m. This ensures that when the strong winds are chopping up the water you still have warm water throughout no matter what. To create a hurricane you usually need to be between >5 degrees north or south. This allows coriolis to initiate the spinning of the storm, so that it can travel. Nepal happens to lie at 26.5 degrees north of the equator making it perfect for hurricanes. Hurricanes in the United States usually strike southern states like Texas, Louisiana, and Florida including the states above them, and East coast states. This is because they rest near warmer oceans closer to the equator. Hurricanes have been known to strike Hawaii as well. To look at a more global viewpoint on hurricanes, there are three main formation regions, and each zone calls them by different names. In the Atlantic and the East pacific they are called Hurricanes. In the Indian Ocean and near Australia they are called tropical cyclones. Off the coasts of China, Indonesia and Japan they are called Typhoons.
Hurricanes tend to travel in a curve along the east coast after they have done their damage due to the warm waters of the gulf stream running along the east-coast, being pushed along by the east-westerly winds and the jet stream. Annually 5-6 hurricanes strike the U.S. source Although I was not able to find a database of recorded hurricanes for Nepal it has had a couple severe ones that stood out in articles I found. The tropical cyclone "Hudhud" hit Eastern India this year and traveled over to Nepal causing blizzards in the Himalayas and flooding from all the rain. source
