Khareef season explained and outlook for 2020
By
Jason Nicholls, AccuWeather senior meteorologist
Published May 8, 2020 2:39 PM EDT
Khareef season is an Arabic term which means 'autumn' and is used to describe the cooler and damp period across the southern Dhofar Governorate of Oman and the southeastern Al Mahrah Governorate of Yemen. Khareef season usually runs from 22 June until 21 September and is basically the western extension of the monsoon circulation that brings rain to India in the summer.
The map shows the area impacted by the khareef season with Salalah, Oman, one the biggest cities in the region and a popular tourist destination during this period of cool and refreshing weather. This cool weather is brought on by the arrival of the Somali jet in June which leads to a moist southeast flow off the Arabian Sea into southwestern Oman and southeastern Yemen. As moist air reaches the coast, it encounters higher elevations just inland and the upsloping squeezes out the moisture resulting in extensive low clouds, light rain and drizzle closer to the coast. During the height of the season, low clouds will linger over these areas all day for several weeks with drizzle and light rain on occasion.
Photos from around Salalah, Oman, during khareef season.
The low clouds in these areas hold daytime temperatures mostly in the upper 20s to around 30 degrees Celsius or upper 70s and 80s degrees Fahrenheit with nighttime lows in the lower to middle 20s C or mostly in the 70s F, while the rest of Oman swelters in hot weather during summer.
Meanwhile, some moisture from the southeast flow off the Arabian Sea that leads to khareef season also helps fuel daily thunderstorms over the mountains of western Yemen and southwestern Saudi Arabia during the summer. As a result, summer rainfall is very important for the southern Arabian Peninsula.
So what can we expect for rainfall across Oman and Yemen this summer? First, looking at my top analogs and all my analogs we can see the years favored suggest a fairly robust Somali jet and a healthy lower-level southeast flow into western Oman and Yemen during the summer.
A few teleconnections we look at for summer rainfall in the southern Arabian Peninsula are the Indian Ocean Dipole or IOD, ENSO and the Equatorial Indian Ocean Oscillation or EQUINOO which is basically the atmospheric response to the IOD. The IOD itself only displays a weak correlation with rainfall over Oman and Yemen, so we look at EQUINOO which has a better correlation.
As we can see above, many models continue to favor a negative IOD forming in late summer into autumn which could mean a negative EQUINOO developing. A -EQUINOO usually means rainfall deficits during khareef season, but the EQUINOO is not always in phase with the IOD. EQUINOO is usually measured using outgoing longwave radiation anomalies or OLR anomalies across the equatorial Indian Ocean, but few climate models show this parameter so we are using precipitation anomalies as a close approximation.
Most modeling as shown above and my analogs favor the EQUINOO being largely neutral most of the khareef season which means it should not be a major factor in 2020.
Next, we look at the equatorial Pacific for the ENSO. La Nina conditions tend to favor good rains during khareef season while El Nino conditions tend to favor rainfall deficits. That being said, most modeling and several teleconnections favor the development of La Nina conditions later in 2020. Timing of the onset of La Nina is unclear, but we are favoring onset in boreal autumn, so this teleconnection can become a factor late in the khareef season.
Overall, there is a lack of strong teleconnections, but most of the teleconnections are neutral to favorable for summer rainfall in the southern Arabian Peninsula. Several climate models reflect a similar idea to the teleconnections.
After looking at several factors, we are favoring rainfall near to above normal or 100-150% of normal across the southern Dhofar Governorate of Oman and the southeastern Al Mahrah Governorate of Yemen. Onset of khareef season is expected late in week three or week four of June, which is around the normal onset of 22 June.
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Weather Blogs / Global weather
Khareef season explained and outlook for 2020
By Jason Nicholls, AccuWeather senior meteorologist
Published May 8, 2020 2:39 PM EDT
Khareef season is an Arabic term which means 'autumn' and is used to describe the cooler and damp period across the southern Dhofar Governorate of Oman and the southeastern Al Mahrah Governorate of Yemen. Khareef season usually runs from 22 June until 21 September and is basically the western extension of the monsoon circulation that brings rain to India in the summer.
Courtesy of Google Maps
The map shows the area impacted by the khareef season with Salalah, Oman, one the biggest cities in the region and a popular tourist destination during this period of cool and refreshing weather. This cool weather is brought on by the arrival of the Somali jet in June which leads to a moist southeast flow off the Arabian Sea into southwestern Oman and southeastern Yemen. As moist air reaches the coast, it encounters higher elevations just inland and the upsloping squeezes out the moisture resulting in extensive low clouds, light rain and drizzle closer to the coast. During the height of the season, low clouds will linger over these areas all day for several weeks with drizzle and light rain on occasion.
Photos from around Salalah, Oman, during khareef season.
The low clouds in these areas hold daytime temperatures mostly in the upper 20s to around 30 degrees Celsius or upper 70s and 80s degrees Fahrenheit with nighttime lows in the lower to middle 20s C or mostly in the 70s F, while the rest of Oman swelters in hot weather during summer.
Meanwhile, some moisture from the southeast flow off the Arabian Sea that leads to khareef season also helps fuel daily thunderstorms over the mountains of western Yemen and southwestern Saudi Arabia during the summer. As a result, summer rainfall is very important for the southern Arabian Peninsula.
So what can we expect for rainfall across Oman and Yemen this summer? First, looking at my top analogs and all my analogs we can see the years favored suggest a fairly robust Somali jet and a healthy lower-level southeast flow into western Oman and Yemen during the summer.
A few teleconnections we look at for summer rainfall in the southern Arabian Peninsula are the Indian Ocean Dipole or IOD, ENSO and the Equatorial Indian Ocean Oscillation or EQUINOO which is basically the atmospheric response to the IOD. The IOD itself only displays a weak correlation with rainfall over Oman and Yemen, so we look at EQUINOO which has a better correlation.
As we can see above, many models continue to favor a negative IOD forming in late summer into autumn which could mean a negative EQUINOO developing. A -EQUINOO usually means rainfall deficits during khareef season, but the EQUINOO is not always in phase with the IOD. EQUINOO is usually measured using outgoing longwave radiation anomalies or OLR anomalies across the equatorial Indian Ocean, but few climate models show this parameter so we are using precipitation anomalies as a close approximation.
Most modeling as shown above and my analogs favor the EQUINOO being largely neutral most of the khareef season which means it should not be a major factor in 2020.
Next, we look at the equatorial Pacific for the ENSO. La Nina conditions tend to favor good rains during khareef season while El Nino conditions tend to favor rainfall deficits. That being said, most modeling and several teleconnections favor the development of La Nina conditions later in 2020. Timing of the onset of La Nina is unclear, but we are favoring onset in boreal autumn, so this teleconnection can become a factor late in the khareef season.
Overall, there is a lack of strong teleconnections, but most of the teleconnections are neutral to favorable for summer rainfall in the southern Arabian Peninsula. Several climate models reflect a similar idea to the teleconnections.
After looking at several factors, we are favoring rainfall near to above normal or 100-150% of normal across the southern Dhofar Governorate of Oman and the southeastern Al Mahrah Governorate of Yemen. Onset of khareef season is expected late in week three or week four of June, which is around the normal onset of 22 June.
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