Tropical Climate Update

First typhoon for northwest Pacific region in 2017

The northwest Pacific Ocean, the most active ocean basin for tropical cyclones, has had a sluggish start to the season, with its first typhoon, Noru, forming on Monday 23 July. Prior to Noru, only four tropical cyclones had developed in the region, (compared to the average to the end of July of nearly eight) with no systems having reached typhoon intensity (10-minute mean wind speed of more than 118 km/h). Since 1950, only 1998 had a later first typhoon of the year. In the last few days, tropical cyclone activity increased markedly as tropical storms Kulap and Sonca also formed in the region. Sonca is forecast to affect Hong Kong and central Vietnam in the next day or two. Noru and Kulap are both expected to remain over ocean waters for the next few days and not make landfall as significant systems. For the latest information on tropical cyclones in the northwest Pacific go to the Japan Meteorological Agency’s Tropical Cyclone Information page.

In addition to the recent tropical cyclone activity in the northwestern Pacific, there has also been a major increase in tropical cyclone activity in the northeastern Pacific Ocean, off the west coast of Mexico. Since the start of July, five tropical storms, including two major hurricanes, have formed. The strongest storm was hurricane Fernanda which had peak 1-minute mean winds in excess of 230 km/h on 15 July. There are currently six active tropical cyclones across the whole Pacific region.

Flooding continues across India

The active Indian Southwest Monsoon continues, generating heavy rainfall over many parts of the Indian subcontinent. Flooding was reported in the northwest and northeast of India where monsoonal lows have had a significant impact; parts of the state of Odisha in the northeast had daily rainfall totals to 260 mm. The west coast of India, which receives the full brunt of the southwesterly monsoonal winds, also experienced some very heavy falls in the last week with daily totals between 100 and 200 mm at many sites in Ratnagiri, a district south of Mumbai. As of 20 July, the Indian monsoon covered the entire country, 51 days after its onset on May 30.

Madden–Julian Oscillation over the Maritime Continent

Overall, the current Madden–Julian Oscillation (MJO) signal, located over the Maritime Continent, is relatively weak. In recent days however, one of the components of the MJO signal, which relates to upper-atmosphere dynamics, has indicated an upper-air pattern very favourable for enhanced convection. Typically, the July to August period is the time of peak tropical cyclone activity over the northwest Pacific Ocean and so the favourable upper-air pattern may have facilitated the recent increase in tropical cyclone activity.

Most international climate models indicate the weak MJO signal currently over the Maritime Continent will remain subdued and track further east, while other models predict the signal will be too weak to discern from other weather systems. Either scenario means the MJO is unlikely to significantly enhance tropical weather this coming week.

See the Bureau's current MJO monitoring for more information.