Bay of Bengal Tropical Storm Mahasen remains a dangerous threat

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

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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

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This TCFP has been so consistant with the potential formation of a TD for so long now above south america...


Member Since: April 30, 2013 Posts: 5 Comments: 4316
Member Since: April 30, 2013 Posts: 5 Comments: 4316
Good morning.2013 is sure making up for the cold 2012 lacked..
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Member Since: April 30, 2013 Posts: 5 Comments: 4316
Member Since: April 30, 2013 Posts: 5 Comments: 4316
Quoting VR46L:


Maybe but I doubt it ... it looked better yesterday !


90E going POOF? Could this be the first POOF of the season?
Member Since: February 28, 2013 Posts: 6 Comments: 3294
Quoting FunnelVortex:


LAWL
Member Since: April 30, 2013 Posts: 5 Comments: 4316
659. VR46L
Quoting TropicalAnalystwx13:

That's not at all true. Disturbances -- especially weaker ones (though I wouldn't necessarily consider 90E a weak one) -- take quite a while, usually a day or two, to detach from the monsoon trough/ITCZ. Give it time.


Maybe but I doubt it ... it looked better yesterday !
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Quoting Torito:


you need to link videos, not put them as an image, just letting you know :]
Thank's!
Member Since: October 27, 2012 Posts: 0 Comments: 2026
It's too cold this morning. Almost broke a century old record.
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Quoting Luisport:


you need to link videos, not put them as an image, just letting you know :]
Never mind, you fixed it :P
Member Since: April 30, 2013 Posts: 5 Comments: 4316
Triple X-Class Solar Flares - May 14, 2013 Link
Member Since: October 27, 2012 Posts: 0 Comments: 2026
Quoting VR46L:
See 90E is still embedded,Its losing its chance of making it ..



That's not at all true. Disturbances -- especially weaker ones (though I wouldn't necessarily consider 90E a weak one) -- take quite a while, usually a day or two, to detach from the monsoon trough/ITCZ. Give it time.
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Speaking of songs on your mind..
Tuesdays allways makes me think of this one.. :)

Tuesday Afternoon..Moody Blues..Enjoy
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Quoting no1der:
And here in western New England, I came very close to losing all my peaches, pears and cherries last night, with trees in bloom and a freeze warning.

Meanwhile it's 46 and raining in W. Greenland:

Link



It was a chilly 29 here in the southern Apps this morning. I'm not sure how the local orchards fared, but luckily the trees were a lot further behind this year than last. Orchards are big business here, hopefully they didn't lose the whole crop.
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Good Morning All..
Got down to 51 degrees this am ..
Broke record low set in 2001..
Currently 57 degrees 93%rh and dew at 55..
Winds calm and partly cloudy skies..

Beautiful sunrise coming..



Looks inviting this am..

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The Columbia Glacier descends from an ice field 3,050 meters (10,000 feet) above sea level, down the flanks of the Chugach Mountains, and into a narrow inlet that leads into Prince William Sound in southeastern Alaska. It is one of the most rapidly changing glaciers in the world.

The Columbia is a large tidewater glacier, flowing directly into the sea. When British explorers first surveyed it in 1794, its nose%u2014or terminus extended south to the northern edge of Heather Island, a small island near the mouth of Columbia Bay. The glacier held that position until 1980, when it began a rapid retreat that continues today.

These false-color images, captured by Landsat satellites, show how the glacier and the surrounding landscape has changed since 1986. The images were collected by similar sensors the Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM on three different Landsat satellites (4, 5, and 7).

The Landsat sensors detect light reflecting off the Earth in the short wave-infrared, near-infrared, and green portions of the electromagnetic spectrum. With this combination of wavelengths, snow and ice appears bright cyan, vegetation is green, clouds are white or light orange, and the open ocean is dark blue. Exposed bedrock is brown, while rocky debris on the glaciers surface is gray.

By 2011, the terminus had retreated more than 20 kilometers (12 miles) to the north, moving past Terentiev Lake and Great Nunatak Peak. In some years, the terminus retreated more than a kilometer, though the pace has been uneven. The movement of the terminus stalled between 2000 and 2006, for example, because the Great Nunatak Peak and Kadin Peak (directly to the west) constricted the glacier%u2019s movement and held the ice in place.

As the glacier terminus has retreated, the Columbia has thinned substantially, as shown by the expansion of brown bedrock areas in the Landsat images. Since the 1980s, the glacier has lost about half of its total thickness and volume. Rings of freshly exposed rock, known as trimlines, become especially prominent around the inlet throughout the 2000s.

Just south of the terminus, a layer of floating ice is dimpled with chunks of icebergs that have broken off, or calved, from the glacier and rafted together. The area and thickness of this layer, varies depending on recent calving rates and ocean conditions. In most of the images in the series (particularly 1989 and 1995) the lange extends south to Heather Island, marking the point at which the glacier reached its greatest extent.

Like bulldozers, glaciers lift, carry, and deposit sediment, rock, and other debris from Earths surface. This mass accumulates on leading edges in piles called moraines. The Columbia's moraine created a shallow underwater ridge, or shoal, that prevents the lange from drifting beyond it.

The structure of Columbia's moraine played a large role in the stability of the glacier before 1980. Like other tidewater glaciers, the Columbia built up a moraine over time, and the mixture of ice and rock functioned like a dam keeping out the sea. It was supported on one end by the shoreline and by the underwater terminal moraine at the other. When the glacier retreated off the moraine around 1980, the terminus lost a key source of support. Once freed from this anchoring point, the grinding and dragging between the sea floor and the massive block of ice was reduced, increasing the rate at which ice flowed forward and icebergs calved from the glacier.

Between 2007 and 2010, part of the terminus began to float as it passed through deep water between the Great Nunatak Peak and Kadin Peak. This changed the way icebergs calved significantly. When the Columbia was grounded, calving occurred at a fairly steady rate, and the bergs that broke off were small. When the glacier began to float, larger chunks of ice tended to break off, as seen in the image from 2009. The terminus has reached shallower waters and is grounded again, but rapid calving is expected to continue until the terminus reaches the shoreline, a point about 15 kilometers (9 miles) from the current terminus that the Columbia will likely reach by 2030

Link

Member Since: February 28, 2013 Posts: 6 Comments: 3294
644. VR46L
Quoting SouthernIllinois:

Oh, no! Not at all! Just a song in my head that brings back many memories. All good here! Feeling great.


Good to hear!!
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643. VR46L
See 90E is still embedded,Its losing its chance of making it ..


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Quoting FunnelVortex:
Anything on 90E?


A mess!


Member Since: February 28, 2013 Posts: 6 Comments: 3294
Another little EPAC system ready to ramp up.


Member Since: July 17, 2009 Posts: 71 Comments: 26452
Quoting SouthernIllinois:

Yeah. I hear ya. The EURO is much more patient. The MJO getting into the Atlantic Basin very soon might spell some early tropical trouble.


MJO is almost here.


Member Since: February 28, 2013 Posts: 6 Comments: 3294
638. VR46L
Quoting SouthernIllinois:
I've been downhearted baby,
I've been downhearted baby,
Ever since the day we met
Ever since the day we met

I've been downhearted baby,
I've been down--I've been downhearted baby,
Ever since the day we met
Ever since the day we met


Feeling a little blue this Morning ?

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636. VR46L
BTW Good Morning Folks!!
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This was from Melbourne this past weekend.

Member Since: February 28, 2013 Posts: 6 Comments: 3294
633. VR46L
Quoting AussieStorm:
Evening all. I would like to share a link
European Severe Weather Database





Thanks Aussie !! Appreciate the link !

Thankfully I dont see the severe weather to the extent that Australia and the United States does.
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It's funny how all the cool air drains down the westside of FL instead of the eastern side of the state. Almost a 20 degree difference from orlando to just north of Tampa.

Member Since: February 28, 2013 Posts: 6 Comments: 3294
Quoting AussieStorm:
Not sure if this was posted. This was from May 7.
Awesome Lightning Photo.


@Interior US Dept of Interior 7 May
One of the most spectacular #lightning strikes we have ever seen. Near the South Rim @GrandCanyonNPS.


Cyberteddy I believe posted it last week.
Member Since: February 28, 2013 Posts: 6 Comments: 3294
Anything on 90E?
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Not sure if this was posted. This was from May 7.
Awesome Lightning Photo.


@Interior US Dept of Interior 7 May
One of the most spectacular #lightning strikes we have ever seen. Near the South Rim @GrandCanyonNPS.
Member Since: September 30, 2007 Posts: 9 Comments: 15937
Quoting SouthernIllinois:

You know, I've noticed that sometimes. The GFS is a bit behind when it comes to latching on to solutions the other models already have. Almost like a game of Follow The Leader.


Like the GFS being to quick to bring in the MJO to our part of the world when the Euro was much slower in bringing the MJO to the Caribbean and E-Pac.
Member Since: February 28, 2013 Posts: 6 Comments: 3294
The dreaded CAP!


DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0355 AM CDT TUE MAY 14 2013

VALID 171200Z - 221200Z

...DISCUSSION...
MEDIUM-RANGE MODELS CONTINUE TO GENERALLY AGREE WITH THE ADVANCE OF
A WRN U.S. TROUGH ACROSS THE ROCKIES EARLY IN THE PERIOD...WITH
ASSOCIATED CONVECTIVE/SEVERE POTENTIAL RAMPING UP ACROSS THE PLAINS
AS THE TROUGH APPROACHES DAY 5 /SAT. 5-18/. DETAILS REMAIN
UNCLEAR...BUT CURRENT INDICATIONS ARE THAT THE GREATEST THREAT MAY
OCCUR A BIT FARTHER N ON DAY 5 THAN PREVIOUSLY FORECAST -- I.E. FROM
NRN KS NWD INTO SD. CAPPING SUGGESTS THAT INITIATION MAY BE
HINDERED UNTIL LATE AFTERNOON.
..AFTER WHICH SUPERCELLS SHOULD
INITIATE INVOF A DRYLINE/PRE-FRONTAL TROUGH AND THEN SHIFT EWD
THROUGH THE EVENING HOURS. LARGE HAIL AND DAMAGING WINDS WILL
LIKELY BE THE PRIMARY THREATS...ALONG WITH ISOLATED TORNADOES.

AS THE UPPER TROUGH AND ASSOCIATED SURFACE SYSTEM CONTINUES EWD DAY
6 /SUN. 5-19/...SEVERE POTENTIAL APPEARS LIKELY TO CONTINUE -- FROM
IA SSWWD ACROSS WRN MO/ERN KS AND INTO THE NWRN OK VICINITY. STORMS
-- POSSIBLY ONGOING IN SOME AREAS EARLY IN THE PERIOD -- SHOULD
INCREASE DURING THE AFTERNOON...BRINGING CONTINUED THREAT FOR LARGE
HAIL AND DAMAGING WINDS ALONG WITH ISOLATED TORNADOES.

MODELS BEGIN MORE SUBSTANTIAL DISAGREEMENT THROUGH DAY 7 AND
BEYOND....AND THUS WILL RESTRICT AREAL OUTLINE OF SEVERE POTENTIAL
TO DAYS 5-6 ATTM.
Member Since: February 28, 2013 Posts: 6 Comments: 3294
Quoting SouthernIllinois:
Scott,

The 06Z GFS out to 384 hours isn't so gung-ho on the idea of heavy rain for you guys. But that obviously can and may change. We'll have to see.



The GFS isn't agreeing the the CMC or Euro on amything right now but it is starting to trend in their direction.
Member Since: February 28, 2013 Posts: 6 Comments: 3294
Accuweather.com is showing the rainy season kicking into full gear by next Monday across the FL Penisula. I guess it is agreeing with the Euro and CMC. Accuweather is also showing some very impressive rain totals in Orlando next week.

Member Since: February 28, 2013 Posts: 6 Comments: 3294
Quoting biff4ugo:
P.S.
at 8:32 UTC, did is that the exposed surface circulation on Mahasen, to the east?

Looks like it to me.

Watch the long loop but slow it down and you'll see it.
Link
Member Since: September 30, 2007 Posts: 9 Comments: 15937
P.S.
at 8:32 UTC, did is that the exposed surface circulation on Mahasen, to the east?
Doh! Aussie beat me to it.
I like the blue shaddow of the circulation on Aussies polarised temp animation (middle of post #617)
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A pretty amazing loop of TC Mahasen. CoC pops out then convection gets back over it.

Member Since: September 30, 2007 Posts: 9 Comments: 15937
Nice Waffels!

Europe's sever weather looks like the US's but arcing SE instead of NE.
Different part of the Sine wave?
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Member Since: September 30, 2007 Posts: 9 Comments: 15937
GGEM as well as the Euro is bringing a flood threat to FL come next week as deep tropical moisture moves across the Bahamas and into FL.


Member Since: February 28, 2013 Posts: 6 Comments: 3294

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.