A severe cyclone has recently struck the east coast of India. What is it that make cyclones a frequent phenomena of the Bay of Bengal and at same time quite rare at Arabian sea?
The key differnece appears in ocean surface temperatures of BOB (Warm) and AS (cool) during pre-monsoon and post-monsoon periods. The warm temperatures in BOB causes more cyclonic activity during this period.
Another difference is related to ocean-atmosphere interactions that control tropical cyclone intensity. The BOB is generally more stratified than the AS because 1) the upper-ocean is warmer and 2) the much higher rainfall creates barrier layers in the near surface (haline stratification). Thus cyclones in the AS generally produce stronger surface cooling than in the BOB due to enhanced vertical mixing, which limits cyclone intensification. Some of these ideas are detailed in a paper that might be of interest:
Neetu, S., M. Lengaigne, E. M. Vincent, J. Vialard, G. Madec, G. Samson, M. R. Ramesh Kumar, and F. Durand (2012), Influence of upper-ocean stratification on tropical cyclone-induced surface cooling in the Bay of Bengal, J. Geophys. Res., 117, C12020, doi:10.1029/2012JC008433.
There is about a 4:1 split in terms of number of cyclones between the Bay of Bengal and the Arabian Sea - see below papers. However Cyclone Gonu in the Arabian Sea happens to be the strongest (in terms of wind speed only) named cyclone in the North Indian Ocean, while all the events with huge death tolls all occurred in the Bay of Bengal. The Cyclone Nargis paper below and the supplementary material contain details on that.
Prior to 1985, cyclones were exceedingly rare around Arabia due to a 5,500 year old Pakistan-Arabia Dust Cloud that has kept those storms from forming, but since then torrential rain in Arabia has become at least an annual event.
The Dust Cloud acted as a shield and kept the monsoonal moisture from creating cyclones or torrential rainfall. From 1200 CE and 1889, only two torrential rainfall events occurred in Arabia, then from 1890 to 1958, there were two more events.
Since the 1980s the increase in monsoonal moisture caused by Global Warming, is overwhelming the Dust Cloud, and so far in 2014 torrential rains in Arabia occurred on Jan. 5-7, Feb. 12-13, March 10-27, April 22, May 9-12 so far.
The Dust Cloud is stronger than a Category-5 cyclone like GONU, and modern remote imaging allows us to see the strength of the Dust Cloud. We can watch the Dust Cloud surround and extinguished GONU, at http://www.ecoseeds.com/GONU.html and http://www.ecoseeds.com/newGONU.html and http://www.ecoseeds.com/GONU3.html
A list of the unusual torrential rain events hitting Arabia since 1200 CE can be seen at http://www.ecoseeds.com/cool.html and http://www.ecoseeds.com/cool2.html
The BoB is potentially a very energetic region for development of cyclones, though only 5% of the total global tropical cyclones occur here. Cyclones are formed over this region mainly during the pre-monsoon and post-monsoon season among which the later are more devastating in nature.
Genesis of cyclonic systems depends upon many Oceanic and Atmospheric parameters. But in this context, more significant role is played by the atmospheric conditions (Grey (1968) ) over the warm oceanic region. Few such atmospheric situations for cyclone development are:
1. Low level relative vorticity (should be high)
2. Vertical wind shear (should be low)
3. Relative humidity of middle troposphere (should be high)
4. Middle tropospheric thermal instability (should be high)
etc..
A seasonal comparison of these parameters over BoB and AS may clear the point, why cyclones are frequent phenomena of bay of Bengal and are rare in the Arabian sea.
References may be useful:
Gray, W. M., (1968): Global view of the origin of tropical disturbances and storms. Mon. Wea. Rev., 96, 669-700.
Gray, W. M. (1975): Tropical cyclone genesis. Dept of Atmos Sc Paper No. 232, Colorado State University, Port Collins Co, USA, p 121.
Generally, one of the necessary conditions for having a cyclone is sea surface water vapor evaporation that mostly depends on SST (Sea Surface Temperature) to produce saturated bulk of humidity for moist-convection, the other alternative is having a low-centered pressure (low atmospheric pressure at sea level) as a disturbance or other configurations to have a convergent zone and then moist-convection and low level high-vorticity. These conditions between those two regions are not the same. Furthermore, there are some studies represent the effects of pre-monsoon and post-monsoon activities upon BOB's cyclone production.
Cyclogenisis of Tropical Cyclones are common and regular in the two basins of NIO I.e. the Bay of Bengal and Arbian Sea. The number occurrence of cyclonic storms in BOB are more than the Arabian Sea. It is due to higher sea surface temperature, weak vertical mixing in BOB, huge perennial fresh water influx from Himalayan Rivers, basin rainfall and sluggish wind in comparison to the Arabian Sea,. The frequency of Arbian Sea storms are less due to very large basin, cold region due to westerlies.The intensity is governed by formation time, orientation , the place of origin, associated climatic condition for intensification or dissipation, the SST and allied energy, the trajectory, the wind vector within the domain, cloud pattern, UACYCIR, positioning of ITCZ , and the inland climate, enthalpy flux exchanges, and place of landfall based on status the then ENSO, MJO, POID, El Nino Modoki and BSISO events. .
And this week, after about 5,000 years of the storms being blocked each summer, the monsoonal rain clouds from India are tracking past the southern edges of Arabia, over Oman and Yemen, as it did before the Dust Cloud blocked that movement.
The Dust Cloud images are at https://www.nrlmry.navy.mil/shared-bin/display_image.cgi?URL=/aerosol_web/globaer/ops_01/india/current.gif
You can see from today's image, that the rain clouds are interacting with the Dust Cloud in eastern Oman, and the rain clouds have become strong enough via Global Warming, to keep the Dust Cloud confined on land. The new Global Warming-powered rain cloud strength, allows the rain clouds to pass east to west along the coast of Arabia, over the open dust-free ocean waters now.
I was predicting about a decade ago, that rain cloud movement past Arabia could resume as it has this week, in two studies at http://www.ecoseeds.com/cool.html and http://www.ecoseeds.com/cool2.html . And you can see my paintings of the Dust Cloud and tropical cyclone battles at http://www.ecoseeds.com/art3.html in paintings #48 and #52-60.
All kinds of interesting things happening today. The Pseudomonas rain clouds are begin formed off the west coast of India, and the Pakistan-Arabia Dust Cloud is getting strong off the coast of Arabia, so let the battle begin!
Something very interesting going on in western coast of Arabia today, the Pseudomonas host plants are forming rain clouds over the Red Sea and into Africa. Out of the untamed mountain forests, rain clouds are forming from the little remnants of the forests, that is still not been farmed and terraced.
Plus the moisture that you see in the picture, covering half of Arabia and part of Egypt is flowing by every hour, that could be harvested to produce rain clouds, if Pseudomonas host plants were planted to produce those clouds.
>>Four very important things are happening today - in India, southern Iran and Oman. 1.) Floods in India -- Maharashtra floods: 29 dead in Pune division so far, caused by the monsoon moisture being blocked by the Pakistan-Arabia Dust Cloud. 2.) West coast of India forest trees, producing more Pseudomonas rain clouds, 3.) Moisture from monsoon going over the three southern provinces of Iran and over Oman where 12 million Iranis and 4 million Omani will NOT get a single drop of rain, because they have not replanted the Pseudomonas host plants, or replanted the native perennial grasses to harvest that moisture and produce the rain clouds for them, and 4.) The Dust Clouds are getting stronger over Pakistan and Arabia, because the animal-grazers are not leaving any vegetation on the surface, to keep the soil from not getting airborne.
>>If every person in southern Iran and Oman, planted one native tree and ten native perennial grass plant around those trees each year, that would mean about 16 million trees could get planted along with 160 million native grass plants, and covering about 150 square kilometers.
>>Then when you add the 300X raincloud multiplier-effect, that means rain clouds could be produced to rain on about 45,000 square kilometers of those two countries, with about one meter of annual rainfall?
>>Just need to redirect a tiny bit of those country's military budgets, and form a new "Department for Ecological Security" and fund the "Native Tree and Native Grass Ecological Restoration Rainfall Project" ?
Today there is a spin getting started for the storm between India and Oman, but the strength of the Pakistan-Arabia Dust Cloud will probably keep it off shore and weaken it over time. The other possibility is that the storm just gets trapped spinning for a week around the Straits of Hormuz? The other interesting part of the picture, is what is usually considered the "India Monsoon" rain clouds, is 100% Pseudomonas clouds coming off the SE Asia forests--they have a distinctive satellite image pattern.
Potential floods this week in the Thar desert of India, or northern Pakistan? Massive amounts of Pseudomonas clouds are crossing the ocean, south of India, and going towards Africa.
The Pakistan-Arabia Dust Cloud is forming a pocket that may stall that circular storm in northern India, and may force the torrential rainfall to go north of the Thar and cause floods in northern Pakistan instead?
Another flood today in India, due to the Pakistan-Arabia Dust Cloud forming a pocket and stopping the westward movement of the monsoon rain clouds. Just a little forest replanted in western India, Pakistan, Iran, Iraq, Arabia, could keep that moisture moving instead of getting blocked and causing floods.
Today, there is a very clear line and wall stopping the westward movement of the monsoon rain clouds by the Pakistan-Arabia Dust cloud. The rain clouds are trying to bring lot of rain westward to Iran, Iraq, Egypt, Jordan, Arabia, Kuwait Qatar, UAE, and some investment by those countries to revegetate the native trees and local native grasses, and stop the dust from getting airborne, would help bring a lot of rain to those countries every summer.
Today there is a un-named tropical storm in the Arabian sea, but the Pakistan-Arabia Dust Cloud is getting ready to block it, so let the battle begin! Dust storm is the orange in Arabia.
for the daily Pakistan-Arabia Dust Cloud map, then when a cyclone potentially is present, then check and for the current Arabian sea storm HIKAA , to view this new Dust Cloud battle, see and click on one of the "Loop" links to watch a movie of the fight.
Even though HIKAA is very small, it seems to be making some headway against the Dust Cloud in Oman, so expect some flash floods along the coast there, wherever the Dust Cloud stalls HIKAA. If you read my website at http://www.ecoseeds.com/cool2.html prior to the 1950s, how rare that Arabia torrential rainfall evens were.
Between 1200 CE and 1889 only two events, then two more between 1890 and 1958. Now they occur several times a year.
THIS LAST WEEK of October 2019--you can watch the Cyclone Kyarr that is headed towards Oman across the Arabian Sea!! The predicted path is from http://tropic.ssec.wisc.edu -- The battle has already begun, with the Pakistan-Arabia Dust Cloud, at the Monterey NAAPS website, with only 20-40 micrograms of atmospheric dust per cubic meter starting to slow Kyarr down and blocking the cyclone like a wall, that you can see in the Colorado State RAMMB.CIRA Metrosat 8 in their "Storm Relative 16 km Geostationary Water Vapor Imagery"
The research gate system is not showing when files have been added to answers, so added one file three times, and have attached the missing Kyarr file here, with the RAAMB Dust Cloud battle image.
Cyclone KYARR is really trying to get to Arabia to rain on the native grassland there, but the man-made Dust Cloud is forming a wall. The cyclone will either stall and be eaten by the Dust Cloud, or be pushed towards the Horn of Africa?
Right now, Sunday afternoon October 27, 2019, the Cyclone KYARR is making an attack on the Pakistan-Arabia Dust Cloud, and it is eating into the wall, and the Dust Cloud is having a difficult time recovering because the attack is out at sea. Kyarr might bring some significant rain and flash floods to the Empty Quarter, if the Dust Cloud keeps weakening--and make the rivers flow and the grasses grow again?
http://tropic.ssec.wisc.edu/ is still predicting that Cyclone Kyarr is going to lose its battle with the Dust Cloud, and glance off it the Dust Cloud and get pushed towards the Horn of Africa? But if I was going to put a bet on the battle right now, it is straight for the Empty quarter, because it is gaining strength and predicted to become a Category 3 soon.
For the next 100 hours of so, this might be one of the most interesting Arabia Sea Cyclone battles with the Pakistan-Arabian Dust Cloud! Why? Because there is the minimum amount of atmospheric dust that can be detected--only 20-40 micrograms per cubic meter--and that tiny amount of dust is pushing around a Category 3 cyclone!
The NAAPS dust image right now, is showing the Dust Cloud wrapping around the cyclone, which is a pattern that keeps an Arabian Sea cyclone from moving inland, and watering the lands wherever it normally would beach itself.
GONU was a perfect example, where the Dust Cloud caught it, like Kyarr is being caught right now, and Gonu was caught in the Straits of Hormuz and squeezed like a grape, until all of the life was squeezed out, and then it was released and flicked to the northeast to die over Iran--a unique end of a cyclone for the last 100 years or so.
The CIMSS imagery from SSEC-UW-Madison is showing the wall of the Dust Cloud, instead of the cyclone moving along 18-20 degrees longitude like it wants to, CIMSS is predicting that it is going keep bouncing off the Dust Cloud wall, and running in a line parallel to the coast of Arabia towards the Horn of Africa. The prediction is that Kyarr will still be a Category 1 cyclone after 96 hours and will end up about 55 deg. west latitude and 15 deg.north longitude.
However, because of the weakness of the Dust Cloud, Cyclone Kyarr may be able to keep going towards and dump a lot of water to fill the empty wadis of the Empty Quarter along the 18-20 deg. longitude line.
For today, October 29, 2019, the cyclone is now Category Three and has been trapped by the minimum amount of atmospheric dust possible, only 20-40 micrograms per cubic meter! The cyclone is still trying to stay on course in a straight east to west track, but the Pakistan-Arabian Dust Cloud will probably keep it in its tight grip until it runs out of moisture, and never be able to move to the southwest, as is still being predicted by the CIMSS models.
Surprisingly, the cyclone is winning the Dust Cloud battle--The Dust Cloud was at minimal strength, only 20-40 micrograms of dust per cubic meter vs a Category 3 cyclone, but a little dust is coming to the Dust Cloud's aid from the coast of Oman, but probably not enough to stop the cyclone from its direct east-west trajectory, into Oman and the Empty Quarter.
All of the cyclone track predictions, and all of the tropical cyclone and monsoon computer models, have never included the effects of the Pakistan-Arabia Dust Cloud into their models so far?
Like Gonu, Kyarr is trapped in the same spot near the Straits of Hormuz, and is getting eating by the increased 40-80 micrograms per cubic meter of the atmospheric dust.
And like Gonu will probably be shot in the opposite direction as the current RAMMB and SSEC predicted tracks, towards Iran and/or Northern India, if you watch the loop, you can see that process getting started at:
Without adding the Dust Cloud impacts to our computer models, they will be blind and keep producing incorrect track forecasts.
For example, I am predicting a quicker death for Kyarr and in the opposite direction: 12 hours=Lat 25, Long 70, intensity 50. 24 hours=Lat 28, Long 80, intensity 0.
Today, Cyclone Maha is rushing to the aid of Cyclone Kyarr, and that extra moisture may help keep Kyarr stay alive until they meet in a few days, to continue the battle with the Pakistan-Arabia Dust Cloud?
Today, November 1, 2019, the new Cyclone Maha is predicted to bounce off the Pakistan-Arabia Dust Cloud wall, which in the middle of the Arabia Sea, is a nearly unique direction change?
Both Cyclones have lost against the Pakistan-Arabia Dust Cloud, and KYARR got pushed down to the Horn of Africa where it is still alive today with 20 mph winds, and MAHA looks like it is going to increase to a Category 3, but is being held in place in the middle of the Arabia Sea, until it loses all of its power, centered about Lat 19 N and Long. 64 E, according to the predicted track at tropic.ssec.wisc.edu
Today, there is an unnamed (so far) uncoordinated block of moisture in the Arabian Sea, about the size of India, maybe the largest I have seen in 20 years, with a weather front to the northeast, and very little atmospheric dust from the Pakistan-Arabia Dust cloud to interact with today. If the moisture pulls together to form a storm, that may change, and the battle may begin.
Today, December 1, 2019, there is a very strange storm in the Arabian Sea, with wind speeds only 20-25 mph so far, but that could change? You can see how the Dust Cloud over Arabia is very strong right now, so the only direction would be towards the Horn of Africa?
What is now known as "Storm 6" is gaining ground, and is probably going to be joined by another batch of moisture from India, and it is trying to go north and rain on Arabia, but the predicted path is still the Horn of Africa.
As I predicted, today December 3, both storms are trying to move due north, the westward one trying to rain on Arabia, and the eastward one to run parallel to the coast of India, but the Pakistan-Arabia Dust Cloud is going to start its battle now and is already breaking up Storm 6. Unusual we have two storms in the Arabian Sea at the same time this year, twice so far?
Let the battle begin!--The Tropical Cyclone Six is trying to move north, and it is grinding against the Pakistan-Arabia Dust Cloud right now, the night of December 3, 2019. The storm is predicted to only get about 35-40 mph but it is also predicted to continue the battle against the Dust Cloud for the next 96 hours.
Today, December 4, 2019, now four storms in the Indian Ocean may merge together, to try and battle the Pakistan-Arabia Dust Cloud, and Storm Six is still trying to make its way northward to rain on Arabia, instead of the predicted path towards the Horn of Africa. NEVER seen four tropical storms at the same time in the Indian Ocean?
There seem to be 5 potential storms lined up, headed straight for the Arabia Sea today, one after the other? Maybe potential contenders, to see if they can break through the Pakistan-Arabia Dust Cloud barrier, and get the rivers to flow and the grass to grow in the Empty Quarter of Arabia, in the next couple of weeks?
Today, the Storm-6, that is now officially Cyclone PAWAN, is starting another attack against the Pakistan-Arabia Dust Cloud today, December 5, 2019, and the Dust Cloud can clearly be seen in one of the http://rammb.cira.colostate.edu/products/tc_realtime/ site images.
Every day some exciting storm or cyclone visiting the Arabia Sea this month? A new storm forming behind the cyclone that is stuck near the Horn of Africa still battling the Dust Cloud, image attached. The two storms to the south not moving anywhere, so will not go north to merge to fight the Dust.
Today December 23, 2019, at least two storms forming in the Arabian sea, maybe will combine forces and try to fight against the Pakistan-Arabia Dust Cloud?
Today December 27, 2019 a new but very small storm in the Arabian Sea, headed towards Oman. In 2019 never saw as many storms in that sea in the last 20 years.