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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

Hurricane

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

1001. LargoFl
Guess the freezing temps will be the story tonight huh....
Quoting TropicalAnalystwx13:
Welcome to the United States, tornado season. You're late.





No. It's absent. And no where to be found.
Quoting LargoFl:
Guess the freezing temps will be the story tonight huh....

Global Warming, Largo. Global Warming.
the 1st tropical wave of the 2013 atlantic hurricane season is expected to e off the African coast in the next 72 hrs. a low latitude and low amplitude tropical wave.
1005. VR46L
Quoting stoormfury:
the 1st tropical wave of the 2013 atlantic hurricane season is expected to e off the African coast in the next 72 hrs. a low latitude and low amplitude tropical wave.


Is that what is off the horn of Africa?

06Z GFS Total Accumulated Precipitation out to the entire run, which is 384 Hours. Note the axis of the heaviest rain from the next potent Midwest system has shifted a bit south. Also note the heavy influx of tropical moisture from the tropical storm expected to develop in the Caribbean. The GFS has been pretty consistent with showing development. Cyclogenesis should only be taken seriously within the 3-5 day range, however.

240HR
Good Morning. Very nice day across Conus today and crystal clear. Most interesting feature to me this morning on the loops is that large area of convection, with a little bit of rotation, in the E-Pac due West of Central America. Gonna keep an eye on that one to see if we might get our first storm there on kick-off day on May 15th.
144HR
pottery it has been sometime that T&T has been impacted by a tropical cyclone. The last time I remember is Alma of august 1970 and Flora of sept 1963 which raked tobago
Here is the rainbow loop for that E-Pac area. Impressive.............

Link
Today SST
Quoting weathermanwannabe:
Here is the rainbow loop for that E-Pac area. Impressive.............

Link


If it persists for the next 6-12 hours it may be invest 90E.
384HR GFS 6Z
Quoting SFLWeatherman:
384HR GFS 6Z


For sure a wet Caribbean.
1017. Grothar
1018. ncstorm


00Z it was not wet in the Caribbean but 6Z it is wet
Quoting Tropicsweatherpr:


For sure a wet Caribbean.
1020. ncstorm
NavGem (nogaps)
06z
1021. VR46L
Quoting SFLWeatherman:
Today SST


SST anomaly I think....

Big difference

SST

Quoting SFLWeatherman:
00Z it was not wet in the Caribbean but 6Z it is wet


Hang on. What is this "Z" thing I keep hearing about?
Very Cold night for the Mid Atlantic and New England states. Hard to believe freezing temps 2 weeks prior to Memorial Day.

1024. Grothar
Loop Current west of FL is really heating up into the mid 80's now.

Morning/Evening.

Is there any room for development over the bay of Campeche? Small wave over toasty water?
1027. VR46L
Quoting FunnelVortex:


Hang on. What is this "Z" thing I keep hearing about?


Zulu Time ...Same as GMT and UTC

wiki Explaination
Quoting biff4ugo:
Morning/Evening.

Is there any room for development over the bay of Campeche? Small wave over toasty water?

Doubt it.
Because it is the only TC in the world right now, heeeeres MAHASEN



1030. ncstorm
very long range..6z GFS

but interesting to note vorticity associated with the area of moisture near the islands.



Here some storm pics from over the weekend in East Central Florida.




The GFS solution has changed a lot over the past day, with several severe weather outbreak days as opposed to isolated severe weather. The SPC seems to have taken an interest in the weekend, stating a multiday outbreak is likely.
1033. VR46L
Quoting ncstorm:
very long range..6z GFS

but interesting to note vorticity associated with the area of moisture near the islands.





What I found interesting in the 06Z was a High building in the Gulf !

Quoting VR46L:


What I found interesting in the 06Z was a High building in the Gulf !



What does that do to benefit storms?
Ensembles getting aggressive in the East Pacific



Quoting TropicalAnalystwx13:
The GFS solution has changed a lot over th past day, with several severe weather outbreak days as opposed to isolated severe weather. The SPC seems to have taken an interest in the weekend, stating a multiday out
break is likely.


Don't count on it. Very low QPF here likely means a capping inversion will be an issue.


Quoting StormTrackerScott:


Don't count on it. Very low QPF here likely means a capping inversion will be an issue.



I would be hard pressed to see anything significant in the way of severe weather.
1039. VR46L
Quoting FunnelVortex:


What does that do to benefit storms?


It would prevent storms getting into one of the most hurricane prone area in the Atlantic.. ... but could also lead to a drought as that's rainy season ....

I like tracking sea storms that die in the middle of the ocean ... not landfallers
Quoting nrtiwlnvragn:
Ensembles getting aggressive in the East Pacific





Hi nrt. Did TAFB eliminate the black surface map and now has this one?

Quoting Tropicsweatherpr:


Hi nrt. Did TAFB eliminate the black surface map and now has this one?



Ya, just did it without any notification or anything. The previous surface map had always been a subset of that one (Unified Surface Analysis).
Quoting VR46L:


It would prevent storms getting into one of the most hurricane prone area in the Atlantic.. ... but could also lead to a drought as that's rainy season ....

I like tracking sea storms that die in the middle of the ocean ... not landfallers


I like tracking all storms.
I was outside working in a freezing squall of heavy sleet this morning, here in S. Scotland. It would have bad enough in January, but it's mid May!

Crazy weather.
1044. VR46L
Quoting yonzabam:
I was outside working in a freezing squall of heavy sleet this morning, here in S. Scotland. It would have bad enough in January, but it's mid May!

Crazy weather.


Tell me about it .. Last tuesday got up to a beautiful 68°F now its 45°F

Its a cool looking storm though..

1045. pcola57
1046. LargoFl
Stay Alert today south and east coast florida.................CHANCE OF THUNDERSTORMS EASTERN AREAS OF SOUTH FLORIDA...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS: THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON ACROSS
EASTERN AREAS OF SOUTH FLORIDA...ESPECIALLY THE EASTERN PORTIONS
OF PALM BEACH...BROWARD...AND MIAMI-DADE COUNTIES. A FEW
THUNDERSTORMS MAY BE STRONG.

WATERSPOUTS: A FEW WATERSPOUTS CANT BE RULED OUT ALONG THE
ATLANTIC COAST.

WIND: WINDS GUSTS COULD EXCEED 50 MPH IN THE STRONGEST
THUNDERSTORMS THIS AFTERNOON...MAINLY OVER THE EASTERN
METROPOLITAN AREAS.

FLOODING: VERY HIGH RAINFALL RATES COULD LEAD TO LOCALIZED
1047. Thrawst
Quoting TropicalAnalystwx13:
The GFS solution has changed a lot over the past day, with several severe weather outbreak days as opposed to isolated severe weather. The SPC seems to have taken an interest in the weekend, stating a multiday outbreak is likely.


I saw it 1st :p
1048. Thrawst
Quoting StormTrackerScott:


Don't count on it. Very low QPF here likely means a capping inversion will be an issue.




Capping inversion will allow less storm interactions; more discrete supercells; more potential for tornadoes.
1049. pcola57
Worldwide SST..

1050. pcola57
Quoting Thrawst:


Capping inversion will allow less storm interactions; more discrete supercells; more potential for tornadoes.


Capping inversion will actually limit the tornado potential from an outbreak to more of an isolated tornado event. Now large hail and severe wind gusts will likely be the rule.
May will likely go down as the lowest number of tornadoes during the month of May in recorded history!
Quoting Thrawst:


I saw it 1st :p




you seen nothing 1st
This is Saturday evening on the GFS and as you can see there isn't much QPF across Tornado Alley. If I were a storm chaser I would be in central Kansas late in the day on Saturday for any chance of seeing a tornado.



1055. Thrawst
Wow one week from 06z GFS today

1056. Dakster
Quoting LargoFl:
Stay Alert today south and east coast florida.................CHANCE OF THUNDERSTORMS EASTERN AREAS OF SOUTH FLORIDA...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS: THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON ACROSS
EASTERN AREAS OF SOUTH FLORIDA...ESPECIALLY THE EASTERN PORTIONS
OF PALM BEACH...BROWARD...AND MIAMI-DADE COUNTIES. A FEW
THUNDERSTORMS MAY BE STRONG.

WATERSPOUTS: A FEW WATERSPOUTS CANT BE RULED OUT ALONG THE
ATLANTIC COAST.

WIND: WINDS GUSTS COULD EXCEED 50 MPH IN THE STRONGEST
THUNDERSTORMS THIS AFTERNOON...MAINLY OVER THE EASTERN
METROPOLITAN AREAS.

FLOODING: VERY HIGH RAINFALL RATES COULD LEAD TO LOCALIZED


Nice. I will beo n my way to work when this hits and I have computers to move...
1057. Thrawst
Quoting Tazmanian:




you seen nothing 1st


Saw it before you.
1058. pcola57
Good Morning All..
Expecting a new blog post by Dr. Masters..

Here you go VR46L..



Quoting Thrawst:


Saw it before you.





you seen nothing 1st
Quoting Thrawst:


Saw it before you.


It's May and atleast some severe weather can be expected across the Plains and everybody on here has seen this increase of severe weather potential later this week on the models but don't get your hopes up on a outbreak.
1061. Thrawst
The severe weather event is still 6 days out and the models will change in terms of dynamics and potential capping inversion. However, it is safe to say that the tornado season MAY finally (ha get the pun?) rearing its ugly face.
1062. Thrawst
Quoting StormTrackerScott:


It's May and atleast some severe weather can be expected across the Plains and everybody on here has seen this increase of severe weather potential later this week on the models but don't get your hopes up on a outbreak.


I'm kidding man. It's just been a horrible season. You just have a feeling mother nature will come back with a bang in the wake of this weak season.
Brrrr, it's cold this morning. Detroit Metro Airport tied its record low temp of 30° this morning. Today's high temp should be in the low 50s. Of course, since this is Michigan, the high on Wednesday should be in the low to mid 80s.
1064. Dakster
wxchaser97 - Sounds like fun. (NOT!)
1065. VR46L
Quoting pcola57:
Good Morning All..
Expecting a new blog post by Dr. Masters..

Here you go VR46L..





Thanks PCOLA but the temp here is a bit colder than that .. Only 48°F and rather windy..Gusting 36 Knots ...
From freezing temps to extreme heat across the Midwest.

42 in Tallahassee tonight. WOW!

disturbance in the Epac showing signs of organization. this is soon to be invest 90Eand would be surprise to see the first storm of the Epac season form on the official opening date 15th may
Temps right now.

1070. Grothar
Quoting Tazmanian:




you seen nothing 1st


You tell him, Taz!!!!
JeffMasters has created a new entry.
1072. Thrawst
Quoting Grothar:


You tell him, Taz!!!!


I am the victim. Rarely happens. Damn.