Tropical Cyclone Chapala
28 October 2015 17:24 UTC–03 November 12:00 UTC
Tropical Cyclone Chapala was one of the strongest cyclones to ever hit Yemen.
14 November 2020
28 October 2015
By Hans-Peter Roesli (Switzerland), Mark Higgins and Ian Mills (EUMETSAT), Gabriele Formentini (SMHI)
Tropical Cyclone Chapala was formed from a depression in the Eastern Arabian Sea on 28 October. The formation and progression of the storm can be seen in the Meteosat-7 infrared loop, 27 Oct 07:00 UTC– 1 Nov 07:00 UTC.
It is unusual for cyclones in this basin to pass along the Gulf of Eden and make landfall in Yemen, which this cyclone did.
The visible image from Meteosat-7 (Figure 1) shows the storm as it began to weaken. The winds are from the ASCAT instrument on Metop-B.
From 29 October onward Tropical Cyclone Chapala moved westward (Figure 2), in some contrast to the track forecasts that had it moving north-westward toward the coast where Yemen and Oman meet. At the same time, it evolved into a Category 3 storm and accelerated its forward speed.
Following their experience from the Tropical Cyclone Ashobaa in the summer and due to the incorrect track forecasts, Oman braced for an emergency situation along its southern coastline. Fortunately, the stormy weather only grazed the area with short downpours and high wind at places.
During the Category 3 stage the cyclone underwent some wall replacement cycles, as can be seen on the Meteosat-10 Enhanced Tropical Airmass animation, 29 October 00:00 UTC–3 November 12:00 UTC and showed a big eye (Figure 3).
On 3 November, hurtling passed Socotra, it made landfall on the Yemeni coast well inside the Gulf of Aden.
The powerful storm dumped huge amounts of rain on an arid region. At least 228 mm of rain was originally estimated to have fallen, in areas which usually get an average of 101 mm of rain per year.
Later NASA's Global Precipitation Measurement mission showed rainfall amounts up to 380 mm over south central Yemen and along the coast, with the highest total over Yemen being 398 mm (~16 inches). Gusts of 167 km/h (103 mph) were reported in Yemen.
Shortly after crossing the coast, when the source of moisture was removed, the typhoon quickly decayed.
On the Meteosat-10 Airmass RGB imagery tuning is used which takes into account the colder cloud tops with respect to mid-latitude.
In his comprehensive scientific report on Tropical Cyclone Chapala, Gabriele Formentini, from SMHI, took a closer look at the wind and wave data from the time period.
Overview of the report
The overall forecast reliability for the tropical cyclone Chapala was good from the beginning, however, the rapid intensification process the storm went through between 29–30 October was not well forecast, either by the global models or the official weather forecast.
The use of the satellite imagery and data is of inestimable value in the understanding of the processes involved in the evolution of such systems and could help explain what happened during those 12–24 hours that Chapala went from a strong tropical cyclone to a Category 4 hurricane.
The unusual track of the storm had a significant impact in our daily Weather Routing job at SMHI. The western Arabian Sea and Gulf of Aden is well known as one of the most dangerous stretches of water for shipping, due to the Somalian piracy activity. All the merchant vessels have to sail through the Gulf of Aden Internationally Recommended Transit Corridor (IRTC) in groups in order to exploit the additional protection and assurance of being in a group. Chapala had a track that crossed the IRTC and the impact on the vessels route was important.
Tropical Cyclone Chapala was formed from a depression in the Eastern Arabian Sea on 28 October. The ASCAT wind product from 28 October, 17:24 UTC (Figure 4), revealed winds speeds of up to 50 knots (about 90 km/h) and also allowed a clear view of the detailed surface circulation (note also the wind vector wind ambiguity of 180° in the black box).
From 29 October the tropical cyclone started its movement west, with an average speed of 7–8 knots (13–15 km/h). On 30 October when it reached Category 4 status a very clear eye could be seen on MODIS imagery, 30 Oct 09:10 UTC.
The ASCAT wind product from 31 October at 05:59 (Figure 5) shows that the tropical cyclone continued to move towards the west with wind speeds above 50 knots (93 km/h).
The VIIRS image from 1 November 21:46 UTC (Figure 6) shows Chapala between Socotra Island, the south of Yemen and the northern region of Somalia. The satellite image, together with the near-simultaneous ECMWF wave model analysis of 2 November at 00:00 UTC (Figure 7), revealed significant wave height values of up to 12 m, which were confirmed by Jason-2 altimeter measurements (overpass between 21:00 and 00:00 UTC).
On 3 November Chapala went over land causing severe damage in Yemen, Socotra and in northern parts of Somalia. In the worst affected areas, such as the southern region of Yemen, rainfall records were broken.
Landsat-8 satellite images (Figure 8) enable us to evaluate the effects of the Tropical Cyclone Chapala inland, where a large flooded area is clearly seen. Due to the flooding, thousands were evacuated from the most vulnerable parts of coastal regions. At Al Mukalla (Yemen), the sea level rose up to 9 m and rainfall records were broken causing eight deaths.
Cyclone Chapala Makes Landfall in Yemen (PHOTOS) (The Weather Channel)
Cyclone Chapala dumps years' worth of rain in Yemen, causing extensive damage (Mashable)
Tropical Cyclone Chapala seen from the International Space Station (Twitter/Capt Scott Kelly)
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