Cyclone Megh in Arabian Sea Could Be Unprecedented Back-to-Back Threat for Socotra Island, Yemen

Jon Erdman
Published: November 6,2015

Cyclone Megh, another Arabian Sea tropical cyclone, is heading toward Socotra Island and may track near mainland Yemen roughly one week after Cyclone Chapala made an extremely rare pass through the region, triggering destructive flash flooding.
(CHAPALA RECAPS: A Rare, Destructive Landfall | News Reports, Photos)
According to the India Meteorological Department, the agency sanctioned by the World Meteorological Organization for issuing official tropical cyclone bulletins for the Arabian Sea, the center of Cyclone Megh is just over 400 miles (about 640 kilometers) east of Socotra Island, an island about 150 miles east of the Horn of Africa in the central Arabian Sea.

Latest Location, Infrared Satellite

Cyclone Megh has not yet strengthened appreciably as of early Friday night, U.S. time. Early Friday, its central core convection looked less consolidated than it did Thursday morning, but recent satellite imagery appears to show improved organization of the system.
Megh is still situated in a narrow east-west zone of relatively low wind shear, which otherwise would weaken the cyclone by displacing convection away from the center of circulation.
A satellite analysis from the University of Wisconsin's CIMSS group also shows a pair of decent outflow jets, which are bands of upper-atmospheric winds blowing away from the cyclone, both north and south of Megh. These, in turn, are increasing near-sea-level winds toward the center and the co-located convection.
While Megh formed in roughly the same location as Cyclone Chapala did just over a week ago, there are key differences and similarities in the forecast ahead.

Forecast: Another Threat to Socotra Island, Yemen?

Cyclone Megh is expected to slowly intensify into the weekend, but is not expected to become nearly as intense as Chapala.
One reason for this may be due to the much weaker upper-atmospheric outflow channel north of Megh, compared to what was in place before Chapala rapidly intensified.
Correspondingly, this means near-sea-level air wouldn't be pulled as strongly toward the center of Megh, and convection may not be as vigorous, leading to a slower intensification than with Chapala.
In the wake of Chapala also lies a pool of cooler sea-surface temperatures. This may also further limit the ability of Megh to strengthen over the next couple of days.
At any rate, Megh is expected to move west or west-southwest, tracking near Socotra Island Sunday, as either the equivalent of a strong tropical storm or, perhaps a Category 1 hurricane.
Heavy rain leading to flash flooding, strong winds, coastal flooding and dangerous surf are possible on Socotra with Megh.

Cyclone Megh Forecast Path

This weaker Cyclone Megh, with a less robust central core of convection, could be weakened further after interacting with the higher terrain of Socotra, and will be more susceptible to dry air from the Horn of Africa and the Arabian Peninsula than Chapala was once it neared the Gulf of Aden.
Chapala fended off this dry air for awhile, but eventually weakened from a Category 3 to a Category 1-equivalent cyclone when it neared the coast of Yemen. Megh will likely not be able to fend it off as long as Chapala.
Increased wind shear may also come into play near the Gulf of Aden, as well.
The bottom line is the future of Megh in the Gulf of Aden remains highly uncertain at this time.
Instead of a Category 1 landfall like Chapala, Megh may be weakened to the equivalent of a tropical storm, depression, or fizzle altogether by the time it reaches the south Yemen coast sometime Tuesday or Wednesday.
Before that, Megh's circulation or at least its peripheral convection, could brush far northeast Somalia, the "Horn of Africa", Monday, bringing locally heavy rain and some stronger wind gusts.
Chapala's core of hurricane-force winds passed near, or just west of Yemen's fifth largest city, the coastal, war-ravaged port of Al Mukalla, with a population of about 300,000.
The south coast of Yemen is fronted by hills and mountains. Persistent rainbands from Chapala slamming into those mountains may have produced 3 to 16 inches (75 to 400 mm) of rain, according to satellite rainfall estimates from NASA's Global Precipitation Measurement mission.
Rivers running from these mountains that are normally dry, known locally as wadis, saw rapid rises with rainfall of this magnitude, with destructive mudslides and debris flows.

Socotra Island, east of the Horn of Africa, is still reeling from Chapala.
Emirates247.com Tuesday reported 117 homes were completely destroyed, and another 612 homes were partially damaged on the island, according to a local authority in damage estimation. An estimated 203 fishing boats were either destroyed or missing, and hundreds of dead animals and trees were still lining the streets as of November 3.

Tropical cyclones in the Indian Ocean basin, which includes the Arabian Sea, are simply known in English as "cyclones" or "cyclonic storms" once they produce winds equivalent to tropical storm force. There are no special terms such as "hurricane" or "typhoon" applied based on reaching higher intensity, but the India Meteorological Department does apply various adjectives such as "severe" or "very severe" to describe different intensity levels.
(MORE: Why Tropical Cyclones Are Named)

Unprecedented Back-to-Back Cyclones

There was no record of a cyclone of Category 4 strength or stronger tracking as far south in the Arabian Sea prior to Chapala.
You may wonder, then, if there is any record of back-to-back cyclones within roughly a week's time affecting this region of the Arabian Sea.
According to NOAA's historical hurricane tracks database, only once before on record have a pair of cyclones tracked within 200 nautical miles of Socotra Island within the same season.
Cyclone Twelve passed over the island on Oct. 24, 1972. Less than one month later, Cyclone Thirteen fizzled southeast of Socotra on Nov. 21.
So, assuming Megh holds together, it's safe to say back-to-back cyclones affecting Socotra Island within a week's time is unprecedented in the historical record.
According to NOAA, prior to Chapala, there had been 16 cyclones of record that tracked within 200 nautical miles of the mouth of the Gulf of Aden.
No more than one had done so in any year, so that would be another record-setter if Megh can hold together as a cyclone into the Gulf of Aden.
(MORE: Hurricanes in Strange Places | Strange Things in the Tropics in 2015

Tracks of tropical cyclones within 200 nautical miles of the mouth of the Gulf of Aden prior to 2015's Cyclone Chapala.
(NOAA Historical Hurricane Tracks)

Coincidentally, just over a year ago, back-to-back hurricanes struck Bermuda six days apart, an unprecedented such occurrence there.
Despite all this, Arabian Sea tropical cyclones are not as unusual as they sound.
Each year, an average of one to two tropical cyclones form in the Arabian Sea, according to a 2011 climatology study by Amato Evan and Suzana Camargo.

Tracks of all recorded global tropical cyclones from 1851-2008. Tracks in the Arabian Sea are highlighted by the yellow box. (NOAA/NCDC)

These cyclones are most likely to form in two periods: May-June and October-November. The mid-late summer period is typically not favorable, thanks to increased wind shear from the wet phase of the Asian monsoon.
(MORE: Where the Season Peaks Twice)
Somalian tropical cyclones aren't even as rare as they may sound, according to Colorado State University tropical expert, Dr. Phil Klotzbach.

In June 2007, Cyclone Gonu was the most intense Arabian Sea storm on record, making landfall in Oman, then in southern Iran.
Gonu claimed 100 lives in Oman, Iran and the United Arab Emirates and was responsible for $4 billion in damage, according to the Evan and Camargo study.
Almost exactly three years later, Cyclone Phet alarmingly intensified to a Category 4 equivalent cyclone, before weakening to a Category 1 storm upon making landfall on the eastern tip of Oman, east of the capital city of Muscat.
In May 1999, Cyclone ARB 01 slammed into Pakistan near Karachi as a strong Category 3 equivalent storm, killing at least 700 in Pakistan. This was the strongest tropical cyclone on record to hit Pakistan.
(MORE: Deadliest Tropical Cyclones in World History)
In the limited historical record, however, strong cyclones in the Arabian Sea are more rare than other basins, due to the proximity of dry air from the Arabian Desert, the aforementioned increased wind shear during the wet phase of the Asian monsoon, and the basin's overall small size.

MORE: Cyclone Chapala Photos, Images