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128

You were right to question whether the atmosphere really held that much water. It comes nowhere close! We use precipitable water to track this, which is the measure of all moisture in the entire column of air in the troposphere. We can get good widespread estimates from remote observations. This animation shows current amounts of precipitable water ...


64

Improbable. It is well known that the Coriolis force is needed to form a hurricane, and the figure of 5oN/S as the minimum for formation is widely publicized. You can also find record of tropical storm formation near India as far south as 1.4oN. The problem of crossing the Equator isn't one of hurricane formation though, it is one of hurricane motion. ...


24

Tornadoes are the result of small-scale effects such as the convergence of updraft/downdraft regions in a single thunderstorm, the stretching or entrainment of vertical vorticity, wind shear profiles, and even friction with the ground. Hurricanes rely on massive amounts of latent heat release from an atmosphere moistened by warm ocean waters causing rising ...


23

I invite correction if I missed any details, the column of air above you, at any one time, at 100% humidity can hold maybe 3-6 inches (75-150 mm) of water depending on temperature and it's likey to rain only a percentage of that, not all of it. If air remained stationary, which, of-course it doesn't, then we'd get much less downpours. The hurricane is ...


14

The equation of motion for a fluid parcel in the atmosphere (in Cartesian space) is $$\dfrac{D\mathbf u}{Dt} = -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F,$$ where $\mathbf u$ is the wind, $\rho$ is density, $p$ is pressure, $\mathbf\Omega$ is the angular velocity of the Earth, $\mathbf g$ is gravity and $\mathbf F$ ...


13

Harvey is almost stationary and is rotating new gulf moisture up the "dirty" side (east of the center). I am outside the main path and have 10+ inches (250 mm) in 30 hours (emptied the rain gauge twice). It has been reported that affected areas have exceeded the "500 year" rainfall level. I guess they need a 1000 year level. The atmosphere is pretty big and ...


12

Hurricanes can be viewed as having primary and secondary circulations. The primary circulation is what we see in satellite photos, comprising the winds and clouds that circle the low pressure zone at the center of the hurricane. The secondary circulation is a vast heat engine that provides the energy needed to sustain the primary circulation. The low ...


11

Yes two hurricanes/tropical cyclones/typhoons can merge with each other and the effect is known as Fujiwhara effect- Fujiwhara effect. The National Weather Service defines the Fujiwhara effect as "Binary Interaction where tropical cyclones within a certain distance(300-375 nautical miles depending on the size of the cyclones) of each other begin to rotate ...


11

The short answer is no. Tropical cyclones (TC) develop and persist in conditions favorable to them: 1) Low Coriolis parameter $f = 2\Omega \sin{\theta}$, where $\Omega$ is the angular velocity of Earth and $\theta$ is latitude. If $f$ is small, the centripetal force balances the pressure gradient force in the gradient wind balance, and the radius of ...


10

The winds in a hurricane move cyclonic and inward at the surface and anti-cyclonic and outward in the upper troposphere. Cyclonic winds are counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere. Anti-cyclonic is the opposite of cyclonic. See this answer for a more detailed discussion of the winds within a tropical cyclone.


10

Since you don't seem interested in Atlantic-Pacific crossovers, of which there are several good examples..... 2004's Hurricane Ivan made landfall on the Gulf Coast, degraded into a tropical depression and was eventually declassified while crossing the southeast US. After coming back into the Atlantic, Ivan tracked back south, re-formed into a tropical ...


9

Let us state the obvious reasons first: Warm SSTs along the Timor Sea as well along the Queensland coast favour the formation of Tropical Cyclones - The following two URLs show the SSTs along the Northern as well as Eastern Coast of Australia for the referenced periods. a) http://earth.nullschool.net/#2015/02/15/2100Z/ocean/primary/waves/overlay=...


9

As suggested by Kossin et al., "The poleward migration of the location of tropical cyclone maximum intensity," (Nature, 2014, dx.doi.org/10.1038/nature13278), the answer could be "maybe". As the tropical region increases in size (tropical expansion: the increasing area of the world where tropical phenomena is observed has expanded in time) due in part to ...


9

It does occasionally happen. Not often, because to kick-start a hurricane there has to be some rotation to start with, from the Coriolis effect, together with a sea surface temperature of >27 °C (+ some other requirements such as lack of horizontal shear). This combination is best met during summer when one or other hemisphere is tilted towards the sun, ...


9

The formation of twin cyclones does occur in both the Indian Ocean as well as the Western Pacific with the Indian Ocean twins being weaker . Schubert et al Symmetric Twin Tropical Cyclones report that the October through May is the period of formation of twin tropical cyclones with December through February being the maximum frequency. The original ...


8

Apart from the fact that only a few tropical cyclones follow a more southerly route (a list bellow) after going around the North Atlantic, I think the main problem is that tropical cyclones would weaken significantly after landfall in the Iberian Peninsula. An example of this is Hurricane Raphael in 2012. Source Weather.unisys.com. There is no "easy" path ...


8

During the Indian Summer Monsoon, a low level jet covers the Arabian Sea. This causes vertical wind shear to increase over the Arabian Sea and inhibits cyclogenesis in the region. Hence, less tropical cyclone activity compared to the Bay of Bengal. http://www.meted.ucar.edu/tropical/textbook_2nd_edition/print_3.htm#page_5.3.0 (Need account to login) http://...


8

The hurricane season is set by the National Hurricane Center. They use statistics to determine the dates. Specifically: The Atlantic hurricane season is officially from 1 June to 30 November. There is nothing magical in these dates, and hurricanes have occurred outside of these six months, but these dates were selected to encompass over 97% of tropical ...


7

Hurricanes form over tropical waters (between 8 and 20 degrees latitude) in areas of high humidity, light winds, and warm sea surface temperatures [typically 26.5 degrees Celsius (80 Fahrenheit) or greater]. These conditions usually prevail in the summer and early fall months of the tropical North Atlantic and North Pacific Oceans, and for this ...


7

The direction of the vertical shear plays a large role in cyclogenesis, where easterly shear tends to enhance the formation of cylones and westerly shear tends to suppress it (Tuleya and Kurihara, 1981). Internal waves are responsible for large transfers of energy across vast distances. Therefore, they play important roles in a wide array of atmospherical (...


7

Hurricanes backtracking and looping seem to be quite common in the Atlantic (Nadine, Jeanne, Alberto, Dennis), and West Pacific (Ernie, Nari, Fung Wong, Parma, Roke) but not so much in the East Pacific (where the tracks are way more linear, with much less latitudinal change). In general, tropical cyclones are steered by the global wind field. The ...


7

The paths of cyclones in the Australian Basin are no more erratic than cyclones, hurricanes or typhoons elsewhere. Conditions at the time of a cyclone's existence determine its path. Sinuosity of Cyclone Tracks - SW Indian Ocean states that over the past three decades the sinuosity of cyclone paths in the SW Indian Ocean has a high degree of variability. It ...


7

Alex was an out of season freak event that bucked the trend and broke all the rules. As hurricanes go, it was somewhat weak, and could never have strengthened beyond category 1. Three conditions made it happen (i) there was an unusually strong vortex over Cuba which kick-started the rotation, (ii) the high level atmospheric shear, which usually kills off ...


7

To summarize David's great answer for folks perhaps looking for an answer more approachable to a wider audience: the answer is a thorough yes to the main question. Hurricanes do have a cooling impact. Hurricanes take warm air near sea level (and evaporated moisture, which is also a form of energy) and release it higher in the atmosphere where it is cooler (...


6

Japanese legend claims that typhoons twice save Japan from attempted invasions by Kublai Khan, once in 1274 and seven years later 1281. These divine winds ("kamikaze") are mixed in Japanese mysticism and are perhaps apocryphal. The Chinese were meticulous record keepers and recorded disasters of all kinds. Liu et al. scoured written Chinese history for ...


6

The original question asked why there were no hurricanes in the southern hemisphere. The answer given: It really is just a naming convention based on location. You can see in the wikipedia article here: http://en.wikipedia.org/wiki/Tropical_cyclone#Classifications.2C_terminology.2C_and_naming , it says: Tropical cyclones are classified into three main ...


6

The Coriolis effect is necessary for FORMATION but NOT for MAINTENANCE of a tropical cyclone. Once formed, in a full-fledged tropical cyclone of hurricane intensity the wind balance is cyclostrophic, between the pressure-gradient and centrifugal force, with the Coriolis effect negligible by comparison. This is especially true if the tropical cyclone is ...


6

Alex was a weird development, being only the second ever recorded in any month to form north of 30°N and east of 30°W, the only other being Hurricane Vince in 2005. It developed over waters cooler than normally required for tropical development at 20-22°C, however upper level air was remarkably cold for the latitude above where Alex developed, giving a ...


6

The atmosphere can "hold" only maximum 75mm worth of precipitation at any given locality, this is true. However, this particular hurricane Harvey was a very slowly moving structure. The vortex would carry the warm water-saturated masses from Gulf of Mexico, which essentially collided with colder air from the North, generating rainfall. It is the continuous ...


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