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

Jon Erdman
Published: November 5,2015

Cyclone Megh, another Arabian Sea tropical cyclone, may track near Socotra Island and 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 over 600 miles (960 kilometers) east of Socotra Island in the central Arabian Sea.

Latest Location, Infrared Satellite

Cyclone Megh's organization has improved, with a central cluster of convection and spiral banding in infrared satellite imagery.
Megh is also situated in an 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.
In fact, Megh formed in roughly the same location as Cyclone Chapala did just over a week ago.
Despite that, 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.
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, 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.

Aerial view of Socotra, Yemen, following Tropical Cyclone Chapala on Monday, Nov. 2, 2015.
(Abd Ul-Lafef Saad, Facebook)

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.
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)
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