Update: Saturday Morning
The storm is likely to start affecting land Sunday, and to make landfall late Sunday or some time Monday, probably as a Category I equivalent.
Meanwhile this is the first tropical storm I've ever seen associated on the Internet with sites that seem to want to plant viruses on your computer. Stick with trusted sources, like the Wonder Blog or Yours Truly.
Update Friday AM:
TC Chapala is expected to be the strongest cyclone ever recorded in this part of the Indian Ocean basin. At present the storm is strengthening and is just under Category 5 strength (it will probably remain in the Category 4 range). This is the third time a major tropical cyclone has formed in this area since 1945, and the last two were Gonu in 2007 and Phet in 2010. Chapala may become the first tropical cyclone in recorded history to directly hit Yemen.
The storm is expected to bring significant rain to parts of Yemen and Oman, and a bit of Saudi Arabia. Coastal areas of Yemen may have up to a foot of rain. Some parts of this arid region will experience about eight years worth of rainfall over a 48 hour period, according to the Weather Channel.
The storm surge could be as much as three meters (15 feet). While the storm is expected to weaken before landfall, it is likely to retain major cyclone/hurricane status.
The reason the storm formed and became so strong is likely the record breaking sea surface temperatures in the region. These sea surface temperatures partly the result of El Nino, but also, of overall global warming.
I don't think there are a lot of tropical cyclones (hurricanes) in the Indian Basin, but one is forming up and is expected to be pretty severe when it hits the southern portion of the Arabian Peninsula.
From the Current Storm Information section on Wikipedia:
As of 17:30 IST (12:00 UTC), 29 October 2015, Severe Cyclonic Storm Chapala was located near latitude 14.1°N and longitude 63.3°E, about 1,040 km (650 mi) east-southeast of Salalah, Oman and 1,150 km (710 mi) west-southwest of Mumbai, India. Maximum sustained 3-minute winds are estimated near 100 km/h (60 mph), gusting to 120 km/h (75 mph). Minimum central pressure is about 992 hPa (29.29 inHg). Dvorak intensity is at T3.5. The storm is expected to move west-northwestwards, intensify into a very severe cyclonic storm in the next 12 hours and subsequently develop into an extremely severe cyclonic storm in the next 48 hours. It is then expected to move towards the eastern part of Yemen or the southern part of Oman.
The map above is from Weather Underground.
India effectively splits the northern Indian Ocean into two separate basins: Bengal to the east and Arabia to the west. Neither basin is all that large, and the southwest (wet) monsoon tends to suppress tropical cyclone formation. Nevertheless, the public advisory identifies this storm as 04A, meaning that at least three other storms have reached tropical depression strength in the Arabian part of the northern Indian Ocean this year.
The Bengal side has a history of nasty tropical cyclones, including the deadliest in history (which hit Bangladesh in, IIRC, 1971). Category 3 or higher cyclones are less common on the Arabian side, and few cyclones hit the Arabian peninsula; the ones that make landfall usually do so in Pakistan or northwest India. This one looks especially nasty; I wouldn't want to be anywhere near landfall. Flash flooding is going to be a major problem in that climate and terrain.