Dangerous Cyclone Mahasen gathering strength in the Bay of Bengal

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

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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

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Quoting wunderkidcayman:


I knew someone would say that and That is why I said it to see who would say that first and TAZ you is the winner




what did i win ?
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971. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Advisory #20
CYCLONIC STORM MAHASEN (BOB01-2013)
5:30 AM IST May 13 2013
==========================================

At 0:00 AM UTC, Cyclonic Storm Mahasen over southeast Bay of Bengal moved northward and now lays near 11.5N 86.5E, about 750 km northwest of Car Nicobar, 650 km northeast of Trincomalee, Sri Lanka, 700 km southeast of Chennai, India, 1330 km south southwest of Chittagong, Bangladesh.

It would move initially northward during the next 12 hours and recurve thereafter northeastwards towards Bangladesh-Myanmar.

According to satellite imagery, Satellite estimate Dvorak intensity is T2.5. Associated intense to very intense convection over Bay of Bengal and adjoining Indian Ocean between 7.0N to 14.0N west of 88.0E, adjoining Sri Lanka, Palk Strait. The lowest cloud top temperature due to convection is -70C.

3 minute sustained winds near the center is 40 knots with gusts of 50 knots. The central pressure of the system is 996 hPa. The state of the sea is high around the center of the system.

The upper tropospheric ridge runs along 15.0N and is providing poleward out flow in association with the anticyclonic circulation over southern Andaman Sea. Upper level divergence is favorable for maintaining the intensity. The low level convergence along with low level relative vorticity shows no change during past 12 hrs. The sea surface temperature is about 30-32C and ocean thermal energy is more than 100 kj/cm square over storm area. The vertical wind shear of horizontal wind continues to be about 5-10 knots (low to moderate) in the northeast sector. The MJO now lies in the border of phase 3 with amplitude greater than 2. It is favorable for intensification and northward movement of the system. Dynamical parameters show the intensification of the system after recurvature.

Most of the numerical weather prediction models suggest initial northwestward movement and then recurving northeastwards towards Bangladesh adjoining Myanmar coast. However, there is large divergence in the numerical weather prediction guidance with respect to intensification of the system. ECMWF and HWRF model maintain intensity till recurvature and weakening thereafter. UKMO maintains intensity till landfall. While JMA and GFS indicate weakening of the system. Dynamical statistical models of India Meteorological Department suggest slight weakening during next 36 hrs and then intensification further during subsequent 24 hrs.

Forecast and Intensity
======================
12 HRS: 12.7N 86.3E - 40 knots (Cyclonic Storm)
24 HRS: 14.5N 86.8E - 40 knots (Cyclonic Storm)
48 HRS: 17.4N 88.2E - 40 knots (Cyclonic Storm)
72 HRS: 20.0N 90.0E - 40 knots (Cyclonic Storm)
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Ryan Maue %u200F@RyanMaue
GFS 00z landfall location of TS Mahasen 78hrs in Bangladesh. Equiv of Cat 2 hurricane (using full-res GFS)
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Well, it's mid-May... and it's the start of the hardest part of the year for hurricane trackers... waiting for first storm to forms.
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Although there's no real organization, the EPac AOI seems to be firing off convection pretty nicely. It's sitting over 30 degree SSTs at the moment, so this may be an area to watch at the start of the EPac season.
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Good Night All - Stay Safe - Stay Cool....lol
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Quoting trHUrrIXC5MMX:
Hurricane potential risk... how does it look for you?


even if you live inland, you must keep yourself vigilant during this season...


Changes:

Moderate Risk: now including more of the Bay of Campeche area
High Risk: now including all Texas coast, Corpus Christi-Padre Is-Brownsville. CARIBBEAN ISLANDS under high risk, except for the Windward Is.
**Very high risk: Have expanded such risk much northwards up North Carolina now also for New Orleans and Galveston and coastal MS ...

Moved north the medium alert a bit in Nicaragua and Belize


click image for larger picture...

Im not joking you guys about this btw!


Well, Hurricane Hugo proved that I'm not 100% safe in Asheville this fall. Also, I might go back to Raleigh if a hurricane hits Carolinas during weekend.

Btw, can you explain why you think Florida to Carolinas and Texas is under the most risk this year?
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Quoting Tazmanian:




oh plzs



i think some of you act like little 3 years



some of you guys need too grow up



there likey not any thing fun on the gfs right now any ways


I knew someone would say that and That is why I said it to see who would say that first and TAZ you is the winner
Member Since: Posts: Comments:


Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting nigel20:
Have goodnight all....I'm off to bed!


Goodnight my friend.
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00Z GFS has started now at 24H
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Have goodnight all....I'm off to bed!
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Quoting wunderkidcayman:
when in the world is 00Z GFS starting

It has already started.

Member Since: July 6, 2010 Posts: 113 Comments: 31462
Quoting wunderkidcayman:

thanks I was about to go nuts




oh plzs



i think some of you act like little 3 years



some of you guys need too grow up



there likey not any thing fun on the gfs right now any ways
Member Since: Posts: Comments:
Quoting wunderkidcayman:
when in the world is 00Z GFS starting




when its ready
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Quoting JRRP:

10 min

thanks I was about to go nuts
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Quoting moonlightcowboy:


Always is, nigel. My simple guess is that warm waters pile up there as flow narrows towards the mouth of the Yucatan and the Loop Current.

Yeah, that seems a likely reason.
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955. JRRP
Quoting wunderkidcayman:
when in the world is 00Z GFS starting

10 min
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Quoting trHUrrIXC5MMX:
Hurricane potential risk... how does it look for you?


even if you live inland, you must keep yourself vigilant during this season...


Changes:

Moderate Risk: now including more of the Bay of Campeche area
High Risk: now including all Texas coast, Corpus Christi-Padre Is-Brownsville. CARIBBEAN ISLANDS under high risk, except for the Windward Is.
**Very high risk: Have expanded such risk much northwards up North Carolina now also for New Orleans and Galveston and coastal MS ...

Moved north the medium alert a bit in Nicaragua and Belize


click image for larger picture...

Im not joking you guys about this btw!

I'm glad you have included TX in this. Nearly Everyone else seems to think TX has a low risk but I disagree.
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when in the world is 00Z GFS starting
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Quoting nigel20:
It seems as if the TCHP is usually high around Jamaica. Is there a reason for this?


Always is, nigel. My simple guess is that warm waters pile up there as flow narrows towards the mouth of the Yucatan and the Loop Current.
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Quoting Astrometeor:


Ouch Ped. I showed my mother the forecast for the area, my sis is due for a visit soon as Caltech has Alumni weekend.

How often does a heat wave like this happen? From what my sis told us when she was there, the temps were nice most of the time.


This is 30-40 East of Pasadena. That area is cooler and gets more marine influence. It can get Hot there but it cools off better. It is still 87.3 right now.
This isn't a normal thing here. Normal is 80/55. It can get Hot here anytime. It just shouldn't be this Hot.
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Quoting CybrTeddy:


A Category 4/5 hurricane tends to do that. I wonder what the before and after was for the TCHP in the Caribbean after Ivan roared by.

Yeah, I would love to see such a map.
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Quoting nigel20:
Look at what Hurricane Dean did to the TCHP after passing to the south of Jamaica





A Category 4/5 hurricane tends to do that. I wonder what the before and after was for the TCHP in the Caribbean after Ivan roared by.
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NWS Nashville Radar will be offline from Monday 5/13 through Friday 5/17

They say if anything fires up on Thursday and Friday that they can get the radar up-and-running quickly. I hope no t-storms fire on Thursday, that's my free day at school and I wanna play all day.
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Quoting TropicalAnalystwx13:
Just thought this would be a good thing to keep in mind for the season, as I was going through AMS publications.

"The results generally confirm those from previous studies: the average lightning density (strikes per unit area and time) decreases with radius from the storm center; tropical storms tend to have more lightning than hurricanes; intensifying storms tend to have greater lightning density than weakening cyclones; and the lightning density for individual cyclones is very episodic. Results also show that Atlantic tropical cyclones tend to have greater lightning density than east Pacific storms. The largest lightning density values are associated with sheared cyclones that do not intensify very much. The results also show that when the lightning density is compared with intensity change in the subsequent 24 h, Atlantic cyclones that rapidly weaken have a larger inner-core (0–100 km) lightning density than those that rapidly intensify. Thus, large inner-core lightning outbreaks are sometimes a signal that an intensification period is coming to an end. Conversely, the lightning density in the rainband regions (200–300 km) is higher for those cyclones that rapidly intensified in the following 24 h in both the Atlantic and east Pacific."


Am I amazing because I noticed this before this was published? :)
Member Since: July 18, 2010 Posts: 50 Comments: 1793
Quoting PedleyCA:
Told you it would be ugly today. Riverside, CA hit 103F which tied a record set in 1927.



Hope it cools down. Humidity is very low, so it isn't all drippy.


Ouch Ped. I showed my mother the forecast for the area, my sis is due for a visit soon as Caltech has Alumni weekend.

How often does a heat wave like this happen? From what my sis told us when she was there, the temps were nice most of the time.
Member Since: Posts: Comments:
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Just thought this would be a good thing to keep in mind for the season, as I was going through AMS publications.

"The results generally confirm those from previous studies: the average lightning density (strikes per unit area and time) decreases with radius from the storm center; tropical storms tend to have more lightning than hurricanes; intensifying storms tend to have greater lightning density than weakening cyclones; and the lightning density for individual cyclones is very episodic. Results also show that Atlantic tropical cyclones tend to have greater lightning density than east Pacific storms. The largest lightning density values are associated with sheared cyclones that do not intensify very much. The results also show that when the lightning density is compared with intensity change in the subsequent 24 h, Atlantic cyclones that rapidly weaken have a larger inner-core (0–100 km) lightning density than those that rapidly intensify. Thus, large inner-core lightning outbreaks are sometimes a signal that an intensification period is coming to an end. Conversely, the lightning density in the rainband regions (200–300 km) is higher for those cyclones that rapidly intensified in the following 24 h in both the Atlantic and east Pacific."
Member Since: July 6, 2010 Posts: 113 Comments: 31462
942. beell
No further mention of a wave or wave-like feature just off the African coast in the 8:05PM EDT TWD. A brief mention in the 2:05PM EDT Discussion.


Member Since: September 11, 2007 Posts: 141 Comments: 16213
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940. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Advisory #19
CYCLONIC STORM MAHASEN (BOB01-2013)
2:30 AM IST May 13 2013
==========================================

At 21:00 PM UTC, The cyclonic storm Mahasen over southeast Bay of Bengal remained practically stationary and lays near 11.N 86.5E, about 700 km northwest of Car Nicobar, 630 km northeast of Trincomalee, Sri Lanka, 720 km southeast of Chennai, India, and 1380 km south southwest of Chittagong, Bangladesh.

System is forecast to move initially northward during the next 18 hours and recurve thereafter northeastward towards Bangladesh-Myanmar coast.

According to satellite imagery, satellite estimate Dvorak intensity is T2.5. Associated intense to very intense convection over southern Bay of Bengal, adjoining Indian Ocean between 7.0N to 14.0 and 81.0E to 88.0E, adjoining Sri Lanka, and Palk Strait. The lowest cloud top temperature due to convection is -70C.

3 minutes sustained wind near the center is 40 knots with gusts of 50 knots. The central pressure of the system is 996 hPa. The state of the sea is high around the center of the system.
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Quoting nigel20:
It seems as if the TCHP is usually high around Jamaica. Is there a reason for this?


Maybe Hispanola has to do with it as the high mountains block the trade winds but it may be another reason.
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Told you it would be ugly today. Riverside, CA hit 103F which tied a record set in 1927.



Hope it cools down. Humidity is very low, so it isn't all drippy.
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It seems as if the TCHP is usually high around Jamaica. Is there a reason for this?
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Quoting HurricaneDean07:
Dang! Nino Regions have really cooled...
March 11th


May 9th


New Anomalies come out tomorrow, I assume they will be a little warmer per this chart.


I think thats because the slow trade winds in that region like CFS is forecasting, they are claiming the comeback of the trade wind again for Nino 1 2 region, however..
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Look at what Hurricane Dean did to the TCHP after passing to the south of Jamaica



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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1032 PM AST SUN MAY 12 2013

.UPDATE...CLOUDINESS AND SHOWER ACTIVITY ACROSS PUERTO RICO DIMINISHED
OR MOVED OFFSHORE DURING THE LATE EVENING HOURS...LEAVING PARTLY CLOUDY
SKIES WITH ONLY A FEW SHOWERS JUST BRUSHING PARTS OF THE NORTHEAST COASTAL
AREAS OF THE ISLAND. SOME SHOWERS WERE ALSO NOTED ACROSS THE COASTAL
WATERS...AND BRUSHING PARTS OF THE VIRGIN ISLANDS FROM TIME TO TIME.
EXPECT THE INVERTED SURFACE TROUGH WITH AXIS NOW OVER THE MONA
PASSAGE...TO CONTINUE TO SLOWLY WEAKEN OVER THE NEXT DAY OR SO AS
STRONG HIGH PRESSURE RIDGE WILL NUDGE SLIGHTLY SOUTHWEST ACROSS
THE NORTHEAST CARIBBEAN. THIS WILL EVENTUALLY SLIGHTLY INCREASE
THE EASTERLY TRADES BY THE MIDWEEK. IN THE MEANTIME...EXPECT THE
PREVAILING TRADE WINDS TO BE SUFFICIENTLY MOIST TO MAINTAIN PWAT
VALUES BETWEEN 1.40 AND 1.75 INCHES THROUGH THE THE BEGINNING OF
THE WEEK THEN GRADUALLY INCREASING THEREAFTER. LOCAL TERRAIN INFLUENCES
AND DIURNAL EFFECTS ALONG WITH THE AVAILABLE LOW LEVEL MOISTURE WILL
BE SUFFICIENT FOR ISOLATED TO SCATTERED AFTERNOON CONVECTION ACROSS
PARTS OF THE ISLANDS EACH DAY. IN ADDITION...BASE OF MID TO UPPER
TROUGH SHOULD CONTINUE TO SHIFT EASTWARD TOWARDS THE LESSER ANTILLES
OVER THE NEXT FEW DAYS. THIS SHOULD BE JUST ENOUGH TO HELP ENHANCE
THE PASSING NOCTURNAL TRADE WIND SHOWERS BETWEEN THE NORTHERN LEEWARDS
AND EAST COASTAL SECTION OF PUERTO RICO. FOR NOW...EXPECT ONLY FEW
TO ISOLATED PASSING EARLY MORNING SHOWERS TO AFFECT REGIONAL WATERS
OVER THE NEXT FEW DAYS. NO CHANGES MADE TO THE INHERITED FORECAST
PACKAGE FOR NOW.
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X-class flare just released by the sun. Not directed at the Earth however.

Member Since: July 6, 2010 Posts: 113 Comments: 31462
Quoting Tropicsweatherpr:
Much warmer TCHP on 2013 than 2012 in Caribbean. Hi nigel.

2012



2013


Hey Tropics!

Yeah, especially to east and south of Jamaica.
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XXE/AOI/XX
MARK
9.56N/92.63W
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Much warmer TCHP on 2013 than 2012 in Caribbean. Hi nigel.

2012



2013

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Quoting HurricaneDean07:
Dang! Nino Regions have really cooled...
March 11th


May 9th


New Anomalies come out tomorrow, I assume they will be a little warmer per this chart.

I saw that as well...goodnight all!
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Has anyone ever notice the CFS ensembles spread..holy terror..






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Quoting HurricaneDean07:
Dang! Nino Regions have really cooled...
March 11th


May 9th


New Anomalies come out tomorrow, I assume they will be a little warmer per this chart.

Seems like Ive spotted a pattern, The Nino regions spike, then reverse back down just as the MDR spikes up and then goes back down...
Probably due to changes in Trade winds... ;)
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Quoting MadinBoy:
23N65W....Some windshear but ..... interesting !





Some shear. Just... some. ;)
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Dang! Nino Regions have really cooled...
March 11th


May 9th


New Anomalies come out tomorrow, I assume they will be a little warmer per this chart.
Member Since: October 3, 2010 Posts: 40 Comments: 4129
23N65W....Some windshear but ..... interesting !



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Pole-land
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This week in science

Member Since: July 18, 2010 Posts: 50 Comments: 1793

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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.