Forecaster Blog: Tropical Cyclone 2013/ 2014 Seasonal Outlook

19 Nov 2013 1 Share

What To Expect This Tropical Cyclone Season
By Chief Swell Forecaster Ben Macartney, Tuesday 19 November 2013

Summary

- Around 8 tropical cyclones are forecast to form over the Coral Sea, between November 2013 and April 2014.

- Factoring in the broader south-west Pacific, a total of 15 tropical cyclones are forecast to form.

- The development of a tropical cyclone is not a guarantee of surf.

Officially November 1st marks the start of the 2013/14 cyclone season, but the bulk of tropical storms usually appear later in the season. Image: Randy Sparrow.

Officially November 1st marks the start of the 2013/14 cyclone season, but the bulk of tropical storms usually appear later in the season. Image: Randy Sparrow.

Overview

With summer just around the corner it’s time to take a look at the impending cyclone season for Australasia and the associated implications for surfing conditions. This process by and large involves assessing the probability of a given number of tropical cyclones affecting our swell window. The starting point is analysing El Nino-Southern Oscillation (ENSO);  being the oscillation between El Nino and La Nina. To be more specific, this refers to the state of sea surface temperatures and subsequent tradewind strength across the tropical South Pacific. Since October 2012 tropical Pacific Ocean temperatures have been in a neutral state (meaning no bias towards either El Nino or La Nina) and these neutral conditions have has persisted through 2013. The Australian Bureau of Meteorology (BOM) use a statistical relationship between cyclone numbers and previous neutral ENSO years to derive an average number of tropical cyclone events forecast to affect the region this season. Further, they asses the probability of above average TC activity and divide our swell window into two regions. As the above image shows an average of eight TCs are forecast to develop over the Coral Sea as far east as the 165E parallel with a 53% chance of more with a total of 15 projected to form over the broader South Pacific.  New Zealand’s National Institute of Water and Atmospheric Research is in general agreement with this assessment, forecasting eight to twelve TCs to develop between 135E (mid Gulf of Carpentaria and 120W (French Polynesia), with one or more of these TCs being a severe system (Category 3 or higher).

So what does this mean for surf? Well, if there’s one thing we know, the development of a tropical cyclone does not guarantee swell. As we’ve seen over the last few seasons, many tropical cyclones are fickle swell producers; often forming too far north to impact our swell window. Even TCs that develop inside our swell window, south of Fiji, have a tendency to track swiftly away to the south-east without sending any notable swell our way. So what is it about TCs that makes them so fickle? For a start, they are usually very compact storms exhibiting a short radius and a well defined, clockwise wind circulation of gale to storm force strengths (34 knots plus). Often these super strong clockwise rotating wind fields exist over a confined area spanning a few hundred nautical miles or less. It’s the absence of any length of fetch and constant, unpredictable movement that constrains their wave generating potential. More often than not, it’s the presence of an intense high pressure system over New Zealand and a slow moving tropical depression of ex-tropical cyclone that tend to be the major E/NE swell producers for the Eastern Seaboard. Although these synoptic patterns usually exhibit lower wind speeds of gale force or weaker, they are more likely to exhibit all the prerequisites for large, good quality swell: Good length of fetch sustained over a duration of several days at constant wind speeds. A good case in point being ex-tropical cyclone Oswald that tracked slowly south over inland south-east Queensland and far northern NSW for several days in late January, generating a heavy ENE swell in conjunction with a stable high pressure system over NZ.

Global Warming
The other question on many minds is what’s the impact of Global Warming. A 2012 collaborative report from the BOM and the CSIRO suggest the warming trend will result in fewer tropical cyclones in the Australian region on average, but an increase the proportion of intense tropical cyclones. The recent devastation caused by Typhoon Hiayan across the Phillipines is in line with this trend.

Super Typhoon Haiyan formed over the western Pacific and made landfall near the Philippine city of Tacloban. The storm first reached tropical cyclone strength on 4 November and continued to strengthen, over the subsequent days, generating maximum wind strengths of 125 knots with a central pressure of 895 hPa on 7 November. Typhoon Haiyan was the strongest storm of the northern hemisphere 2013 season and ranks among the strongest storms on record for the northwest Pacific.

The above images show tropical cyclone probabilities for the 2013/14 season. Source: BOM.

The above images show tropical cyclone probabilities for the 2013/14 season. Source: BOM.

Tropical Cyclone Freda developed in a favourable part of our swell window late last year, but failed to generate any substantial swell for the region. Note the absence of high pressure supporting the storm to the south. Source: Met Fiji.

Tropical Cyclone Freda developed in a favourable part of our swell window late last year, but failed to generate any substantial swell for the region. Note the absence of high pressure supporting the storm to the south. Source: Met Fiji.

At first glance, this MSLP chart from 27 January 2013 doesn't look like much. Ex-TC Oswald, depicted over south-east Queensland, remained in place for an extended period, combining with the high over NZ to set up an extended run of large ENE swell ranging from 4 to 10ft through late January.

At first glance, this MSLP chart from 27 January 2013 doesn't look like much. Ex-TC Oswald, depicted over south-east Queensland, remained in place for an extended period, combining with the high over NZ to set up an extended run of large ENE swell ranging from 4 to 10ft through late January.

Tags: surf forecast , tropical cyclone outlook (create Alert from these tags)

blog comments powered by Disqus
More From Forecaster Blog
Forecaster Blog: The 2020 La Nina, East Coast Tropical Cyclone Seasonal Outlook

Forecaster Blog: The 2020 La Nina, East Coast Tropical Cyclone Seasonal Outlook

Will the 2020/21 cyclone season live up to expectations?

4 30 Oct 2020
Forecaster Blog: Climate Models Tipping Towards a Stronger La Niña

Forecaster Blog: Climate Models Tipping Towards a Stronger La Niña

The 2020 La Niña continues to gather momentum: What will the surf be like this November and December?

2 15 Oct 2020
Forecaster Blog: La Niña conditions are here, what does it mean for Surf?

Forecaster Blog: La Niña conditions are here, what does it mean for Surf?

La Nina conditions continue to develop. Will the surf pump?

8 24 Sep 2020
Recent
Nick Carroll: The Aftermath

Nick Carroll: The Aftermath

5 25 Nov 2020
From Air Shows To Death-Defying Code Red Tahiti and Everything in Between – Nathan Fletcher Tells His Story on Jamie Mitchell's Podcast

From Air Shows To Death-Defying Code Red Tahiti and Everything in Between – Nathan Fletcher Tells His Story on Jamie Mitchell's Podcast

1 23 Nov 2020
Nick Carroll: If You’re Waiting for a Custom Surfboard Order, Get Ready To Keep on Waiting

Nick Carroll: If You’re Waiting for a Custom Surfboard Order, Get Ready To Keep on Waiting

9 21 Nov 2020
Kelly's Take on the Machado High-Five, Pumping Mundaka, & Dane Reynolds in Crappy Waves

Kelly's Take on the Machado High-Five, Pumping Mundaka, & Dane Reynolds in Crappy Waves

20 Nov 2020
Latest News

Nick Carroll: The Aftermath

As the surfing world processes the death of John Shimooka, care and concern turns to those left in the backwash

Kelly's Take on the Machado High-Five, Pumping Mundaka, & Dane Reynolds in Crappy Waves

This Week In Surfing: Ten Things from Surfing & the Internet on the Week That Was November 20 2020

Popular This Week

The Beautiful Peruvian Pointbreak Surfing of Jaleesa and Josie, Binge This Kai Lenny Series, and a New Resort-Style Wave Pool Near Sydney

This Week In Surfing: Ten Things from Surfing & the Internet on the Week That Was November 27 2020

Nick Carroll: The Aftermath

As the surfing world processes the death of John Shimooka, care and concern turns to those left in the backwash

Padang Comes to Life as Late Season Swell hits Bali

Golden hour at perfect Padang Padang - it's been a good week to be in Bali... Photo: Childs

Video: The Fizzlot kids – SW Grom Bash

A stoked out portrait of Australian Junior Surfing in the year 2018.

Go to Top