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Bay of Bengal Tropical Storm Mahasen remains a dangerous threat

By: Dr. Jeff Masters , 2:39 PM GMT on May 13, 2013

It's always a nervous time when a tropical cyclone with the potential to intensify marches through the Indian Ocean's Bay of Bengal. That's because fifteen of the twenty deadliest tropical cyclones in world history have been Bay of Bengal storms that have hit Bangladesh, India, or Myanmar. The most recent of these horrifying storms was 2008's Cyclone Nargis, which killed 146,000 people in Myanmar. The Bay of Bengal's notorious history is why hurricane forecasters are watching Tropical Cyclone Mahasen a little nervously today. Even though there has been little change to the 55 mph tropical storm over the past two days, the storm remains a potential threat to undergo rapid intensification into a dangerous major hurricane. The 11 am EDT Monday advisory from the Joint Typhoon Warning Center put Mahasen's top sustained winds at 55 mph, with a motion northwest at 11 mph towards India. Satellite loops show that Mahasen has a large area of intense thunderstorms with very cold cloud tops that reach high into the atmosphere. The cloud pattern is not well-organized, with little spiral banding. This lack of organization is also apparent on radar out of Chennai. However, the cyclone has developed a respectable upper-level outflow channel to the northwest. Wind shear has decreased to a moderate 10 - 20 knots, and is continuing to decrease. Ocean waters that are an exceptionally warm 31°C (88°F), about 1°C warmer than average for this time of year. The warm ocean waters extend to great depth, and the Tropical Cyclone Heat Potential (TCHP) is over 90 J/kg/cm^2, which is favorable for rapid intensification.


Figure 1. MODIS image of Tropical Cyclone Mahasen taken at 07:55 UTC Monday May 13, 2013. At the time, Mahasen was a tropical storm with 55 mph winds. Image credit: NASA.


Figure 2. Storm-total rainfall from Tropical Cyclone Mahasen as predicted by the 00 UTC May 13, 2013 run of the HWRF model. Rainfall amounts of 16 - 30 cm (6 - 12") are expected along a wide swath just to the right of where the storm makes landfall. Bangladesh's two largest cities, Dhaka and Chittagong, are shown. If Mahasen's track occurs farther to the left, as suggested by some models, these two cities will receive Mahasen's heaviest rains. Image credit: India Meteorological Department.

Forecast for Mahasen
The official forecast brings Mahasen to Category 1 strength before landfall occurs in Bangladesh near the Myanmar border on Thursday near 18 UTC. However, the model forecasts of Mahasen from the GFS, ECMWF, UKMET, GEM, NAVGEM, and FIM models continue to show wide disagreement on the future intensity, speed, and landfall location of the storm. It is possible that wind shear will keep the storm disorganized and below hurricane strength until landfall, as suggested by the ECMWF model. However, other model guidance, such as the 00 UTC May 13 forecast from the HWRF model, bring Mahasen to Category 2 strength by Tuesday. Mahasen is currently approaching a trough of low pressure to its northwest that is expected to recurve the storm to the northeast into Bangladesh. As the recurvature process progresses today through Tuesday, wind shear should relax to a low to moderate 5 - 15 knots, and a strong upper-level outflow channel will intensify to the storm's north, aiding intensification. There is a lot of hot, dry air to the storm's northwest over India, and if this dry air gets wrapped into Mahasen's circulation, it could put the brakes on rapid intensification, though. Considering all these factors, I give a 30% chance that Mahasen will undergo rapid intensification to a Category 3 or stronger storm by Wednesday. The storm should experience higher wind shear and less oceanic heat content in the waters beneath it in the 12 hours before landfall, which should cause some weakening. But even a weakening Category 1 storm has the potential to bring a devastating storm surge to the coast of Bangladesh, and torrential rainfall will be a major flooding threat regardless of the storm's final intensity at landfall. The 00Z May 13 run of the HWRF model predicts that the Mahasen will dump a significant area of heavy rains of 16 - 30 cm (6 - 12") over Maynmar and Bangladesh. The storm surge, high winds, and heavy rains of Mahasen are a particular concern for the thousands of Myanmar refugees living near the coast in makeshift camps, as reported by the New York Times.

MJO pulse that spawned Mahasen headed towards the Atlantic
Mahasen spun up in response to an active phase of the Madden Julian Oscillation (MJO) that has been moving through the Indian Ocean during the past week. The MJO is a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days. The strong MJO pulse coincided with a convectively coupled atmospheric Kelvin wave (CCKW), a wave of increased heat and moisture propagating along the Equator, which helped increase thunderstorm activity. The active pulse of the Madden Julian Oscillation is expected to reach the Western Caribbean (in a somewhat weakened state) May 21 - 25, and there will be a heightened chance of an early-season tropical storm forming in the Eastern Pacific and Western Caribbean during that time period.

Resources
Comparative model forecasts of Mahasen from the GFS, ECMWF, UKMET, GEM, NAVGEM, and FIM models

India Meteorological Department's tropical cyclone page

Radar out of Chennai, India

Bangladesh Meteorological Department Warning

Myanmar Dept. of Meteorology and Hydrology Warning

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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Quoting wunderkidcayman:

the caribbean and their radars
One is needed near Nicaragua.
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the caribbean and their radars
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According to Reuters, a boat that was evacuating refugees from Myanmar ahead of the storm struck rocks and sank. 100 on the boat, most feared drowned. Very, very sad.

Link
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For all of the other regulars on here I have a question of odds for you: What do you guys think are the percentage odds of a hurricane (major or otherwise) hitting the east coast of central Florida this year?
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Put all of these together with the cayman radar and what you get full Caribbean coverage

Link

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Link
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correcting:
Peak seems to be at 93 hours...........



I'M DONE ,GOOD NIGHT FOR EVERYONE!!!!!
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I made a short blog entry on 90E for those who are interested.

First East Pacific Invest (90E) has a potential to develop
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Quoting Saltydogbwi1:


Hey Levi, Yes it's a new installation been in the works for a few years now just undergone testing and training in the past few months. It was funded by the EU in part and installed to "fill the gap" in radar coverage in the NW Caribbean.
Quoting wunderkidcayman:




First time cayman has a Doppler radar and is now up and operational however is not up on the CINWS website because they are revamping the site


Great news! It will be invaluable.
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Quoting KoritheMan:


Awesome. This should prove immensely helpful when tracking tropical cyclones in this area.

Yep
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Quoting wunderkidcayman:




First time cayman has a Doppler radar and is now up and operational however is not up on the CINWS website because they are revamping the site


Awesome. This should prove immensely helpful when tracking tropical cyclones in this area.
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Recent ASCAT pass of 90E (top right):



Not much in the way of strong winds yet, and the circulation is still not well-defined. The system is embedded within a uniform southerly flow regime in the monsoon trough, and there are no indications or hints of westerly wind barbs along the south side of that center. At this point, most of the rotation is mid-level, and the pass also suggests that the center is a little farther south than I had it earlier (my best estimate was closer to 10N).
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Quoting KoritheMan:
.


Quoting Levi32:


Is this a new installation? I don't remember there being a Cayman radar station before. If it gets up and running I can't wait to use it this season.


First time cayman has a Doppler radar and is now up and operational however is not up on the CINWS website because they are revamping the site
Member Since: December 31, 1969 Posts: Comments:
Quoting Levi32:


Is this a new installation? I don't remember there being a Cayman radar station before. If it gets up and running I can't wait to use it this season.


Hey Levi, Yes it's a new installation been in the works for a few years now just undergone testing and training in the past few months. It was funded by the EU in part and installed to "fill the gap" in radar coverage in the NW Caribbean.
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Quoting wunderkidcayman:
hey guys just in case you missed it earlier here is a sample of cayman radar this just to show how the new Cayman Radar will look once the new website is created new website maybe up by the end of the month



Is this a new installation? I don't remember there being a Cayman radar station before. If it gets up and running I can't wait to use it this season.
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hey guys just in case you missed it earlier here is a sample of cayman radar this just to show how the new Cayman Radar will look once the new website is created new website maybe up by the end of the month

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surface heat real feel

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Quoting Tropicsweatherpr:
This is the new Surface Map from TAFB that goes from Hawaii to West Africa. The black graphic was eliminated.



Link
I actually prefer this map to be honest.
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0z full-resolution GFS - "Alvin" at maximum intensity: barely a hurricane (purple colors indicate >64kt)

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Quoting Levi32:


The fact that it can is not under debate. The point is that we almost always look for the disturbance to separate from the monsoon trough before saying it will now develop, because the large majority of the time it must do so before forming a coherent circulation. 90E is an example of that because it is in a completely favorable environment. What's preventing it from taking off? Answer: the fact that it's embedded within the monsoon trough.


Duly noted. I mean that sincerely.
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Quoting KoritheMan:


It's definitely slower, I was just saying it can happen. Looks like we agree here. :P


The fact that it can is not under debate. The point is that we almost always look for the disturbance to separate from the monsoon trough before saying it will now develop, because the large majority of the time it must do so before forming a coherent circulation. 90E is an example of that because it is in a completely favorable environment. What's preventing it from taking off? Answer: the fact that it's embedded within the monsoon trough.
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Time to Bail - Stay Safe - Stay Warm/Cool/Dry - GO EPAC
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Quoting BaltimoreBrian:
Pedley now you've done it. I promised yesterday not to post Alvin and the Chipmunks vids.



photo re moved
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Quoting Levi32:


It is impossible to develop a mature circulation without inevitably contorting the monsoon trough and eventually breaking it. Sometimes the circulation begins to develop and close off before the wave (within the monsoon trough / ITCZ) has broken, but from my personal observation this seems to usually be a more difficult and slower process for cyclogenesis than if the monsoon trough breaks first, allowing the disturbance to quickly acquire a closed circulation.


It's definitely slower, I was just saying it can happen. Looks like we agree here. :P
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Quoting TropicalAnalystwx13:
Bordering on hurricane intensity by Thursday afternoon.



That would actually be a hurricane, since the global models tend to struggle with accurate wind/pressure relationships insofar as exhibiting a low bias. At least, from what I've read on here.

That said, I'm not really too familiar with model specifications and mechanics. I understand them enough to furnish an accurate forecast, I know the difference between a statistical and dynamical model, and I know some of the weaknesses of specific models, but overall, Levi is probably better suited to answer things in that field than I am.
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But I didn't... That will be the end of the Chipmunk videos. Hard to find a good one.

98.1 here today. Glad it was dry. No AC used either day. Should be only low 90's tomorrow.



Hmmm, maybe they don't see it that way. Thought they said 93. WU is showing 92. I'll hope for that....lol

Airport was 102 not a record (1927-109f)
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539. beell
Quoting BaltimoreBrian:
Beel's satellite pic must have been taken before the fires east of Austin.


The Bastrop fire started on the 4th of September. Pic is from the 3rd.

Link
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POSS T.C.F.A.
90E/INV/XX

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Beel's satellite pic must have been taken before the fires east of Austin.
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Quoting TropicalAnalystwx13:
Bordering on hurricane intensity by Thursday afternoon.


Will peak at 72 hours!!!!!
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535. beell
Quoting HurricaneDean07:

The state of Texas in 2011 was in such a rain deficit that year, that literally the climate had became a desert where the dry air was so arid that it prevented any type of moisture from reaching the state.
Texas was to blame in the death of Tropical Storm Don and Hurricane Nate, as well as prevent Tropical Storm Lee from getting any kind of convection to blow up on its West side... Depressing year that was. Glad weve rebounded to a degree.


Most, if not all the dry air associated with the northerly winds on the west side of TS Lee originated N of Texas. End result was still the same. Strong, dry, northerly winds drove every bit of remaining moisture out of the fire fuels and brought a rash of wildfires to the eastern part of the state. The Bastrop fire was along the western edge of this dry swath.

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Pedley now you've done it. I promised yesterday not to post Alvin and the Chipmunks vids.
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Bordering on hurricane intensity by Thursday afternoon.

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Quoting ProgressivePulse:


Typically Southern FL landfalls and Gulf landfalls go hand in hand. Just the nature of things.


Betsy, Andrew, Katrina being good examples.
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The Chipmunks- Pretty Woman

ALVIN
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New Hurricane Season. New Portrait :D
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I hope this has already been posted. If not, here it is.

Space Oddity as sung by Commander Chris Hadfield, ISS
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Quoting stormchaser19:
GFS TD at 48 Hours


Looks like we might have Alvin. May arrive just in time for the start of there Hurricane season.15TH
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GFS TD at 48 Hours
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Quoting TropicalAnalystwx13:

Ah, I remember Don.

POST-TROPICAL CYCLONE DON DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011
400 AM CDT SAT JUL 30 2011

THE DON IS DEAD. THE CYCLONE LITERALLY EVAPORATED OVER TEXAS ABOUT
AS FAST AS I HAVE EVER SEEN WITHOUT MOUNTAINS INVOLVED. DON HAS NO
CONVECTION...MEAGER RAINFALL...AND ONLY A SLIGHT SIGNATURE IN
SURFACE OBSERVATIONS AND RADAR DATA. THEREFORE...THIS IS THE LAST
ADVISORY ON THIS SYSTEM. DON SHOULD OPEN UP INTO A TROUGH LATER
TODAY AS IT MOVES TO THE WEST-NORTHWEST AND IS NOT EXPECTED TO POSE
A RAINFALL THREAT.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 27.9N 98.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
12H 30/1800Z 28.5N 101.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 31/0600Z...DISSIPATED INLAND

$$
FORECASTER BLAKE



About as accurate as Imagine it would be. lol
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Quoting HurricaneDean07:

The state of Texas in 2011 was in such a rain deficit that year, that literally the climate had became a desert where the dry air was so arid that it prevented any type of moisture from reaching the state.
Texas was to blame in the death of Tropical Storm Don and Hurricane Nate, as well as prevent Tropical Storm Lee from getting any kind of convection to blow up on its West side... Depressing year that was. Glad weve rebounded to a degree.

Ah, I remember Don.

POST-TROPICAL CYCLONE DON DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042011
400 AM CDT SAT JUL 30 2011

THE DON IS DEAD. THE CYCLONE LITERALLY EVAPORATED OVER TEXAS ABOUT
AS FAST AS I HAVE EVER SEEN WITHOUT MOUNTAINS INVOLVED. DON HAS NO
CONVECTION...MEAGER RAINFALL...AND ONLY A SLIGHT SIGNATURE IN
SURFACE OBSERVATIONS AND RADAR DATA. THEREFORE...THIS IS THE LAST
ADVISORY ON THIS SYSTEM. DON SHOULD OPEN UP INTO A TROUGH LATER
TODAY AS IT MOVES TO THE WEST-NORTHWEST AND IS NOT EXPECTED TO POSE
A RAINFALL THREAT.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 27.9N 98.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
12H 30/1800Z 28.5N 101.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 31/0600Z...DISSIPATED INLAND

$$
FORECASTER BLAKE

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Quoting KoritheMan:


I don't know where this talk of separating from the ITCZ/monsoon trough before development can occur comes from (assuming you are making that sort of implicit leap). The system having its own inflow away from convective competition will certainly help, but there have been numerous tropical cyclones which developed within an active monsoonal flow regime/ITCZ.


It is impossible to develop a mature circulation without inevitably contorting the monsoon trough and eventually breaking it. Sometimes the circulation begins to develop and close off before the wave (within the monsoon trough / ITCZ) has broken, but from my personal observation this seems to usually be a more difficult and slower process for cyclogenesis than if the monsoon trough breaks first, allowing the disturbance to quickly acquire a closed circulation.
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00Z GFS has started now at 15H
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i like the rains down in africa
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Quoting MississippiWx:


Don performed a magic show and disappeared once it hit the Texas coastline.

The state of Texas in 2011 was in such a rain deficit that year, that literally the climate had became a desert where the dry air was so arid that it prevented any type of moisture from reaching the state.
Texas was to blame in the death of Tropical Storm Don and Hurricane Nate, as well as prevent Tropical Storm Lee from getting any kind of convection to blow up on its West side... Depressing year that was. Glad weve rebounded to a degree.
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500 feet above Aden after a long walk up stairs cut in the rock is the Dakhma. A holy place. Built by the Zoroastrians. Three concentric stone circles with ledges. The circles are 20-25 feet tall and about 7 feet thick.

The Dakhma is where the Zoroastrians brought their dead. You cannot burn them. That would pollute the fire. You cannot bury them. That would pollute the earth. They laid them on the stone, the men atop the outer circle, then the women on the next inner circle and the children on the innermost.

Yemen has white buzzards. They picked the bones clean and the sun bleached the bones dry. Then they were put in ledges in the outer circle facing out, where the wind carrying sand ground the bones to dust.
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Quoting Tropicsweatherpr:
This is the new Surface Map from TAFB that goes from Hawaii to West Africa. The black graphic was eliminated.



Link




so we noted
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This is the new Surface Map from TAFB that goes from Hawaii to West Africa. The black graphic was eliminated.



Link
Member Since: Posts: Comments:

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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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