Southwest Monsoon Routing Challenges
Katelyn Bahr, Meteorologist
The Indian Ocean monsoon is one of the most prominent weather features in the world, categorized by heavy rains in the summer months, and dry conditions in the winter. The Southwest Monsoon occurs in the summer, where strong SW’ly winds bring challenging conditions across the Arabian Sea and Bay of Bengal. The monsoon develops due to the temperature difference between land and sea during the summer months.
Figure 1: Image of the monsoon cycle and overall circulation of the winds and precipitation.
These Southwest Monsoon events pose significant challenges to vessels navigating in these areas. During strong monsoon events, gale force winds and high swells can produce a risk to vessels navigating through these waters, with enhanced conditions on the beam of the vessel leading to excess rolling and poor handling. The high winds can also alter the currents, shifting them to a E’ly-NE’ly setting direction.
Figure 2: Routing along the W'rn coast of India (pink) can help to avoid swell of up to 4m and winds up to 30kts related to the Southwest Monsoon. This change can save nearly a day of steaming time compared to a direct route (white) during the most severe events.
There are alternate routing methods to reduce the negative impacts of the Southwest Monsoon. A coastal approach along the W’rn Coast of India will significantly minimize slowdowns associated with the SW’ly winds and seas for vessels heading southbound, as shown above in Figure 1. While these options will add close to 130-150nm to the voyage, they will typically reduce the amount of time steamed by at least 18-24 hours during the more extreme events by avoiding the most enhanced conditions and providing more favorable angles for the vessels.
The below summarizes a common scenario during an extreme Southwest Monsoon event over the Arabian Sea:
*Persian Gulf vicinity (basis Fujairah) to Singapore basis most direct routing (3340nm) versus routing coastal toward along West Coast of India (3475nm)
*Above costs calculated assuming Panamax vessel travelling at a speed of 12.0kts, consumptions of 23.0 MT FO/day (assuming LSFO price of USD $593.50 at Fujairah), and 0.1 MT DO/day (average price USD $840.0/MT), and hire rate approximately USD $18,000/day.
Looking ahead, India has already been experiencing record warm temperatures and this is not expected to change over the next several months. Furthermore, the monsoon has commenced early this year. With this in mind, we are expecting and preparing for a particularly strong monsoon this year in the Bay of Bengal and Arabian Sea.
Knowledge and understanding of the Southwest Monsoon and other complicated weather patterns and phenomena along with our years of experience make WRI the experts for combatting these navigational situations. We can provide guidance and routing information to ensure vessels reach their destinations in a swift and safe manner. Additionally, WRI’s Dolphin, an online fleet management service, provides forecast wind, swells, and current charts at a glance to assist owner’s/charterers and captains and crews while transiting anywhere across the globe.
