Searching for a Cyclone
The ORCV Race Management Team for the 2018 Melbourne to Osaka Double-Handed Yacht Race includes 6 Duty Race Directors and 2 Fleet Weather Officers – Robin Hewitt & Andrew Roberts. Robin and Andrew are on a Daily Roster and maintain a constant watch on weather conditions for the fleet. They prepare detailed analysis of weather outlook at least twice daily (more often if situation dictates) to Duty Race Directors for review. If forecast conditions exceed pre-defined wind speed and sea state thresholds, Duty Race Directors liaise with Fleet Weather Offices then escalation of Weather Event Warnings to the fleet via SMS (sat phone), Email (sat phone) or HF marine radio during the twice daily mandatory position report communications with the fleet (or more often as required). The fleet also source thier own weather forecast information via various methods.
Fleet Weather Officers and Duty Race Directors have been very busy during this race with 3 of 4 starts delayed and several weather events, including Tropical Cyclone Iris which resulted is racing being suspended. The Fleet Weather Officers commenced tracking a deepening Tropical Low which was initially upgraded/classified as Category 1 Tropical Cyclone Iris by the Fiji Meteorological Service, then subsequently downgraded, then upgraded again by Australian Bureau of Meteorology to a Category 3 Cyclone, a few weeks later.
To follow is a report from Robin Hewitt and some of the extensive research on Tropical Cyclone activity, which was conducted long before this year's race and some detailed analysis on Tropical Cyclone Iris that led to the suspension of racing.
Searching for a Cyclone, by Fleet Weather Officer Robin Hewitt
There have been instances of tropical revolving storms occurring in the history of the Melbourne to Osaka Race, in each case as typhoons in the Northern Hemisphere. First race of 1987 saw some yachts anchoring in shelter for up to four days, while the 1991 race had super typhoon Walt formed near Guam, necessitating some course selection. In the 2003 race some yachts were obliged to shelter in Ulul lagoon (Onoun Island, Southwest corner of the Namonuito Atoll, Federated States of Micronesia) as a typhoon neared.
In the race management team for the 2018 event, Robin Hewitt and Andrew Roberts have shared the task of providing warnings of extreme events. What are the possibilities? Tropical Revolving storms in the area of interest are known as Cyclones in the southern hemisphere and Typhoons in the northern hemisphere. In addition, the spring season in Japan is subject to the storms sweeping in from icy Siberian land masses. The polar jets can intensify these Lows to bring severe weather to competitors as they near Japan. Similarly, cold fronts and deep Lows can escape from Antarctica but in March are unusual, more likely is a cyclone over northern WA crossing land and re-appearing near Perth before joining a front thence heading towards or below Tasmania.
So how to prepare to manage a race through the tropics? Methodology is standard-collect data-analyse-prepare hypothesis. First of all, the race is timed for the least climatic possibility of tropical revolving storms. The period of April and either side has the lowest incidence historically. So firstly a table of occurrences was prepared for the times of interest. Then they are compared to the theoretical model for possible variations. Formation does not occur between 5ᴼN & 5ᴼS and mostly do not form between 10ᴼN & 10ᴼS.
Read the full story, with weather maps, charts and historical cyclone data, at the ORCV website.