Dangerous Cyclone Mahasen gathering strength in the Bay of Bengal

By: Dr. Jeff Masters , 4:25 PM GMT on May 11, 2013

Dangerous Tropical Cyclone Mahasen is gathering strength over the Indian Ocean's Bay of Bengal, and is a potential major threat to Bangladesh and Myanmar. The 11 am EDT Saturday advisory from the Joint Typhoon Warning Center put Mahasen's top sustained winds at 55 mph, with a motion northwest at 19 mph into the center of the Bay of Bengal. 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. However, the cyclone has developed respectable upper-level outflow channels to the north and east, which are ventilating the storm by carrying away air converging to the center near the surface. High wind shear of 20 - 25 knots is affecting the storm, which is keeping the system disorganized. However, wind shear has declined about 5 knots since Friday, and is predicted to fall to the moderate range, 10 - 20 knots, by Sunday. This should allow organization into a Category 1 storm on Sunday. Aiding this process will be Mahasen's motion away from the Equator, which will help the cyclone leverage the Earth's spin to get itself spinning faster. Also aiding the intensification process will be ocean waters that are an exceptionally warm 31°C (88°F). This is about 1°C warmer than average for this time of year.


Figure 1. Latest satellite image of Tropical Cyclone Mahasen gathering strength over the Indian Ocean's Bay of Bengal.

Forecast for Mahasen
The official forecast brings Mahasen to Category 1 strength before landfall occurs in Bangladesh near the Myanmar border on Wednesday. Comparative model forecasts of Mahasen from the GFS, ECMWF, UKMET, GEM, NAVGEM, and FIM models show wide disagreement on the future intensity and speed of the storm, though. It is possible that wind shear will keep the storm disorganized and below hurricane strength until landfall, as suggested by the GFS and ECMWF models. The 06 UTC forecast from the HWRF model brings Mahasen to Category 3 strength on Monday, but weakens the storm to tropical storm strength at landfall. The model predicts that the storm will dump a significant area of heavy rains of 32 cm (12.6") over Maynmar and Bangladesh. The storm surge, high winds, and heavy rains of Mahasen are a huge concern for the thousands of Myanmar refugees living near the coast in makeshift camps, as reported by the New York Times.


Figure 2. Double trouble: Tropical Cyclone Jamala (lower) and Tropical Cyclone Mahasen (upper storm) spin on opposite sides of the Equator in this in this MODIS image taken at 04:25 UTC May 10, 2013. Mahasen is the name of a King of Sri Lanka from the 3rd century. Image credit: NASA.

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 sometime May 22 - 26, 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.

There is a small disturbance a few hundred miles north of Puerto Rico today that has developed some spin and a bit of heavy thunderstorm activity. This system is over cool waters of 77 - 79°F, and will likely be torn apart by high wind shear on Sunday.

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

India Meteorological Department's tropical cyclone page

Bangladesh Meteorological Department Warning

Myanmar Dept. of Meteorology and Hydrology Warning

Tutorial on Equatorial Waves in the COMET program's Introduction to Tropical Meteorology, plus their case exercise built around the May 2002 "twin twins" case, for use in a tropical synoptic course.

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.

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hey wash looky here

Member Since: December 31, 1969 Posts: Comments:
Quoting TheChart:
As much as any TC development is a near-miracle, given the multitude of conditions that must align to allow for it ... early-season (and thus pre-season) development is that much more unlikely.

So many moving parts to consider. and while models may very well be correct in the long-range solution of TC development, I am always inclined to favor the idea of a "last-minute" change in synoptics that mitigates or even prohibits such development.

Patterns in climatology are simply a reflection of past occurrences. It is for this reason that I continue to suspect that the GFS system we see now will in fact not come to fruition.

TC


In about 2 weeks time we will see whether or not the GFS scored on the early season development.

Yes many moving parts, and things will change. It is simply a prediction based on dynamically changing atmospheric conditions.

I am going to have to agree with TheChart until we see:
a. more model consensus
b. The timeline move to within a week (168 hours) of development
c. Alvin in the Pacific - The MJO must move over the East Pacific before it gets to the Caribbean, therefore a tropical storm must form to confirm that conditions are ripe for development in the tropics pre-seasonally.
Member Since: December 31, 1969 Posts: Comments:
You Gotta be Kidding Me






Member Since: Posts: Comments:
Quoting TheChart:
As much as any TC development is a near-miracle, given the multitude of conditions that must align to allow for it ... early-season (and thus pre-season) development is that much more unlikely.

So many moving parts to consider. and while models may very well be correct in the long-range solution of TC development, I am always inclined to favor the idea of a "last-minute" change in synoptics that mitigates or even prohibits such development.

Patterns in climatology are simply a reflection of past occurrences. It is for this reason that I continue to suspect that the GFS system we see now will in fact not come to fruition.

TC


yes but our climate is changing
therefore climatology will also change along with it
but dew tell more of this opinion to deflect conversation from the model dipictions currently being shown seems maybe you just don't want it discuss at all but ruled out
Member Since: December 31, 1969 Posts: Comments:
oops must have read it wrong sry
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Hey I'm just being realistic here so I won't be up for future dissapointmemt.I have seen the GFS have storms and then at the last minute drop it.As we get closer to the time frame that's when I'll be keeping a eye out not trying to be a downer.
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Quoting psetas23:
but man the 18 is now like the 12 in strength dont want to see the 12 model tomorrow in strength maybe cat 2

It's a low-end tropical storm.
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As someone who went through with over 20 inches of rain in my area from ex Nicole in 2010 as this same storm will develop from a moonsoonal trough, the GFS kept showing it in long range and a lot of bloggers said the same thing like now about it being long range, it took a while to materialize but when it did, it caused a lot of damage..

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but man the 18 is now like the 12 in strength dont want to see the 12 model tomorrow in strength maybe cat 2
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how about the 18 run gfs i think its going to wobble more a little left and north maybe first starts right but then go left kinda of the Yucatan peninsula then go northeast not trying to be a troll but everybody knows the models move more and more
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Quoting stormpetrol:
Don't know what to think bro.! Do you know when our (Cayman Islands) radar is scheduled to go online?

Well you know I work with them guys and I told the blog that when it comes out I'll let them know

Btw you do know it up and operational it's just the guys want to update the website and add link to radar to it

But it's supposed to be sometime during first half of this month

I'll go and check back on Monday

If this GFS storm materialise then it will be great to have the radar up for that
Member Since: December 31, 1969 Posts: Comments:
360. SLU
Quoting bigwes6844:
I know of one at least and glad it didnt get its act together,Isaac


If Isaac formed in 2010 it would have been a cat 4 tracking through the Caribbean and entering the Gulf. Expect in 2013 that the storms which died midway across the Atlantic and those which barely strengthened will probably be in with a good chance of some serious development.
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I could see if the operational was only showing a storm in long range but the GFS has both the operational and the ensembles showing a storm in long range..dont get much better agreement than that..

GFS 18z Ensembles is running now..
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Quoting wunderkidcayman:

Hey stormpetrol what's up long time we have not talked what do you tink of the Storm GFS predicting
Don't know what to think bro.! Do you know when our (Cayman Islands) radar is scheduled to go online?
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Quoting washingtonian115:
I can't believe people are getting execited for a 200hr+ storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.


true and in most times it goes puff as the time nears...
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Quoting washingtonian115:
I can't believe people are getting execited for a 200hr+ storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.
Hey give them a break! We are just uber excited for the season to start. What else are we desperate weather bloggers to do?!
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Quoting TheChart:
I am doubtful of the long-range solution we see with the GFS. Unsettled weather, or a pronounced region of disturbed weather, may indeed be likely in that time-frame. However, climatology generally trumps all which is prohibitive to TC development (although it wouldn't be unprecedented).

Several seasons have seen May storms, which is not a harbinger for the remainder of the season.

TC


I don't care about Climatology joking
Look it seem that some stuff don't follow Climatology anymore !

Climatology is not everything yeah Climatology is good sometimes but please stop going on and on about it

Yeah GFS has this thing with forecasting long range stuff but not all the time it wrong plus the storm that its Forecasting is starting to come out of that la la land call long range so don't go on the down side and say its not gonna and I am not saying it is gonna but what I am saying it that it could just keep watching it when it does start to form/ or does not then we can say with 100% in our hearts yes or no

Now I am not singling you out TheChat I'm also talking to the rest of the guys who say yes and no with 100% this is not the time to say yes or no at least wait for another 177 hours or the 19th before we can say yes/no
Member Since: December 31, 1969 Posts: Comments:
Quoting stormchaser19:


I don't remember see the GFS so consistent with the formation of a TC at this time frame....



its done it plenty of times...but it's not dependable.
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Fuzzy Likelihood high after 192 hours in the Carribean :)


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Quoting washingtonian115:
I can't believe people are getting execited for a 200hr storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.


I don't remember see the GFS so consistent with the formation of a TC at this time frame....
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Quoting washingtonian115:
I can't believe people are getting execited for a 200hr+ storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.


120 hrs is a little short... a storm at 240 hrs is believable...getting past there is getting towards fantasy land....

The GFS shows some accuracy even around 252 to 264 hrs especially with troughs etc..but tropical storms are harder to pin down with their unpredictability, and with their changing local weather patterns rather than being the local weather patterns.
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350. VR46L
Quoting washingtonian115:
I can't believe people are getting execited for a 200hr+ storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.


I dont know Wash ! I remember Sandy Issac and even Debby last year all showed in that 384 time frame . As every day goes by that, this one is showing I am buying into it ... the track will probably change but the GFS is now really seeing something .
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Quoting TomTaylor:
Yeah. Is the CFSv2 also interpolated to some extent? I believe I read it's native res is around T126 which works out to 56km as well, correct me if I'm wrong though.

And sorry for pestering you with all the questions but I find this whole topic interesting. Previously I just assumed plots were showing me exactly what the equations in the model were solving. But clearly there's a bit more going on behind the scenes.


Well they are. The equations are integrated at each grid point, but sometimes the data is scaled up a bit because often people don't really need to see the full resolution data, and the file size is smaller.

Yeah CFS is T126 and disseminated by NOMADS on a 1.0° lat/lon grid, which is a very slight interpolation from the T126 grid but essentially the same resolution.
Member Since: December 31, 1969 Posts: Comments:
Quoting TomTaylor:
I do think this will get pulled out in Florida's direction. Impossible to pinpoint Florida right now but at the moment pattern favors it getting pulled out of the Carib.


Lol. Who knows. It has to develop first, but every run seems to have a trough to the north of it so far.
Member Since: December 31, 1969 Posts: Comments:
Quoting MississippiWx:
I definitely see the future system in the Caribbean moving more west. For sure. It's gonna miss the trough and the banana ridge is going to shoot it west into the Central Gulf over the Gulf Stream. Gah, all you Florida-casters. Get a GRIP.

;-)
lol, I do think this will get pulled out in Florida's direction. Impossible to pinpoint Florida right now but at the moment pattern favors it getting pulled out of the Carib.
Member Since: December 31, 1969 Posts: Comments:
I definitely see the future system in the Caribbean moving more west. For sure. It's gonna miss the trough and the banana ridge is going to shoot it west into the Central Gulf over the Gulf Stream. Gah, all you Florida-casters. Get a GRIP.

;-)
Member Since: December 31, 1969 Posts: Comments:
I can't believe people are getting execited for a 200hr+ storm that may not even materialize..Sure it's something to watch but I'll wait until its 120hrs out to really be like "mmmmm" and "what the??!?" until then this is for entertainment purposes.
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Quoting TropicalAnalystwx13:

You missed a system north of Puerto Rico. Cool little disturbance that acquired a weak surface low down from an elongated upper-level trough. As a whole, it managed to become marginally warm core. If it had more time over water without the presence of this trough...I'd say it had a good chance of development. However, because the upper-level low is to the east and the lower-level flow is to the west, the disturbance is expected to be sheared and die, especially once it reaches the backside of this upper-level trough which promotes lowered divergence and sinking air.

There's a good chance of tropical development in the western Caribbean towards the end of May and early June as a strong MJO pulse makes its way to Octants 8 and 1. Though the GFS is alone in showing an actual tropical cyclone, the CMC and others have much above-average precipitation across the region towards the end of the month, with high pressure farther north. That's always a sign of mischief. Still long way out. Could be a 'no storm' or 'Hispaniola' storm for all we know.


next to nothing....LOL
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:

You missed a system north of Puerto Rico. Cool little disturbance that acquired a weak surface low down from an elongated upper-level trough. As a whole, it managed to become marginally warm core. If it had more time over water without the presence of this trough...I'd say it had a good chance of development. However, because the upper-level low is to the east and the lower-level flow is to the west, the disturbance is expected to be sheared and die, especially once it reaches the backside of this upper-level trough which promotes lowered divergence and sinking air.

There's a good chance of tropical development in the western Caribbean towards the end of May and early June as a strong MJO pulse makes its way to Octants 8 and 1. Though the GFS is alone in showing an actual tropical cyclone, the CMC and others have much above-average precipitation across the region towards the end of the month, with high pressure farther north. That's always a sign of mischief. Still long way out. Could be a 'no storm' or 'Hispaniola' storm for all we know.



Oh.... I never fall over myself for disturbances and lows....wouldnt have developed regardless.

But I do agree that development is possible with the MJO pulse...but i dont trust the models about it past 300 hrs.
Hoping it brings rain to the SE so we dont fall back into a dry pattern
Member Since: Posts: Comments:
Quoting GeorgiaStormz:
wait did i miss something? AOI?

south floria storm??

You missed a system north of Puerto Rico. Cool little disturbance that acquired a weak surface low down from an elongated upper-level trough. As a whole, it managed to become marginally warm core. If it had more time over water without the presence of this trough...I'd say it had a good chance of development. However, because the upper-level low is to the east and the lower-level flow is to the west, the disturbance is expected to be sheared and die, especially once it reaches the backside of this upper-level trough which promotes lowered divergence and sinking air.

There's a good chance of tropical development in the western Caribbean towards the end of May and early June as a strong MJO pulse makes its way to Octants 8 and 1. Though the GFS is alone in showing an actual tropical cyclone, the CMC and others have much above-average precipitation across the region towards the end of the month, with high pressure farther north. That's always a sign of mischief. Still long way out. Could be a 'no storm' or 'Hispaniola' storm for all we know.
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Quoting SLU:


And it also remained that way through mid-July which caused the convection to be highly suppressed in the MDR last year early in the season. Yet still it was able to produce an active Cape Verde season by August but most of the storms struggled to develop for the same reasons: low 400mb temps and dry air.
I know of one at least and glad it didnt get its act together,Isaac
Member Since: December 31, 1969 Posts: Comments:
Quoting Levi32:


Yeah I meant GFS for 0.205. I goofed up my English. CMC is not T574, just so that's clear.
Yeah. Is the CFSv2 also interpolated to some extent? I believe I read it's native res is around T126 which works out to 56km as well, correct me if I'm wrong though. Is there any extended range resolution drop?

And sorry for pestering you with all the questions but I find this whole topic interesting. Previously I just assumed plots were showing me exactly what the equations in the model were solving. But clearly there's a bit more going on behind the scenes.
Member Since: December 31, 1969 Posts: Comments:
338. 7544
Quoting KEEPEROFTHEGATE:


now that sure will bring in over 1000 comments :)
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wait did i miss something? AOI?

south floria storm??
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Quoting TomTaylor:
Sorry, 0.205 for GFS. And ok thanks for clearing that up then. So clearly some slight interpolating going on there, but I guess not nearly as bad as the GFS on NCEP's behalf.


Yeah I meant GFS for 0.205. I goofed up my English. CMC is not T574, just so that's clear.
Member Since: December 31, 1969 Posts: Comments:
Ok 18Z GFS is funny it's doing the opposite of the 12Z

12Z started disturbance on the 17 and develops into TS later than before and slows movement of track slower

18Z started disturbance later on the 18 and develops into TS earlier and the movement of the track is quicker

Both still has it becoming at TS though one is weaker than the other and both ends up in the NW Caribbean Cayman Cuba area around the 27/28 let's see what happen late tonight for the 00Z forecast
Member Since: December 31, 1969 Posts: Comments:
Member Since: December 31, 1969 Posts: Comments:
Quoting Levi32:


Well Environment Canada has me confused, because they claim 0.225 but GrADS tells me the grid is 0.24, and it is. The file doesn't lie, so I put it as 0.24. This does beat the GFS in the deep tropics I believe. ~0.205 is approximate for the mid-latitudes because it's a Gaussian T574 grid, not a lat-lon grid.

No, the GEFS and GEPS from NOMADS are disseminated at 1.0 0-384 hours.
Sorry, 0.205 for GFS. And ok thanks for clearing that up then. So clearly some slight interpolating going on there for GEM, but I guess not nearly as bad as the GFS on NCEP's behalf.
Member Since: December 31, 1969 Posts: Comments:

18Z GFS has a West Cuba Hit, then continues up towards SE Florida.
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Quoting TomTaylor:
Couple random questions

1. GEFS extended range is disseminated at 2.5 degrees like GFS extended, right?

2. I recall you saying GEM and GEM-ens are disseminated at full resolution. But on your site it says GEM is being displayed at 0.24 degrees. If it's disseminated at full res, shouldn't it be a higher resolution than that? You know, since GFS native resolution is 2.05 degrees and GEM is higher res than GFS...


Well Environment Canada has me confused, because they claim 0.225° but GrADS tells me the grid is 0.24°, and it is. The file doesn't lie, so I put it as 0.24°. This does beat the GFS in the deep tropics I believe. For the GFS, ~0.205° is approximate for the mid-latitudes because it's a Gaussian T574 grid, not a lat-lon grid.

No, the GEFS and GEPS from NOMADS are disseminated at 1.0° 0-384 hours.
Member Since: December 31, 1969 Posts: Comments:
look at the increase of moisture in Africa for each run's last frame..
06z


12z GFS


18z
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CMC continues to call for the first tropical storm in the eastern Pacific by late next week.

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327. VR46L
Oh dear!!

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AOI/XX/XXL
MARK
23.33N65.11W
Member Since: December 31, 1969 Posts: Comments:
Quoting Levi32:


He said once that he uses 400mb because the tropopause is higher in the tropics.
Couple random questions

1. GEFS extended range is disseminated at 2.5 degrees like GFS extended, right?

2. I recall you saying GEM and GEM-ens are disseminated at full resolution. But on your site it says GEM is being displayed at 0.24 degrees. If it's disseminated at full res, shouldn't it be a higher resolution than that? You know, since GFS native resolution is 0.205 degrees and GEM's native res (25km) is a higher res than the GFS' (27-28 km)...
Member Since: December 31, 1969 Posts: Comments:
South Florida watch out
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997mb over Cuba on the 18z. The incipient disturbance is now showing up on the 0-192hr high-res portion of the GFS run.

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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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