By Dr Sushil K. Sharma.
Tropical Cyclone Pam is now becoming extra-tropical, losing its original characteristics and forming into a deep depression, still retaining very destructive storm force winds over the Southern Oceans.
It is heading into the higher latitudes and over colder waters; coming under very strong upper level wind shearing, which is contributing to its weakening and the formation of a major depression.
This system is giving extreme weather conditions over the northern parts of the North Island of New Zealand, with very strong southeasterly winds, overcast and heavy rain and phenomenal seas.
Pam left the tropical regions of the South Pacific, only a few days ago, leaving a trail of destruction in its path.
The nation of Vanuatu is still coming to terms with the magnitude of the devastation, death of many citizens from drowning and injuries from fallen trees and structures, loss of their livelihood, loss and destruction of farmlands and crops, businesses, and a total dispossession of personal effects for many people.
As Vanuatu citizens weep and look for their dead in the debris, bury their dead and slowly try to open up communications and infrastructure within its nation and internationally, and seek and receive international emergency aid and help to try to slowly move towards some sort of normalcy of life, we in Fiji have to realize how God, nature and in fact science, has helped us this past week.
Fiji should count itself very lucky indeed to have escaped from a multi-billion dollar destruction of its housing, infra-structure, farming, animal and livestock, including the existing plant and vegetation – which would have become a major burden on all of us to recover from, for many years to come.
Fiji was saved also from enormous potential storm surge and coastal area inundation and damage, in areas saved from a direct land-fall of the super and monster system, of all times.
Many thousands of acres of very productive land were saved from being enveloped with salt water, as the system with an extreme low pressure with low pressures below sub-900 hectopascal, had bloated and raised the sea levels by 30-50 meters. Storm surge damage and loss of coastal communities with this phenomenal size of giant waves travelling inland, with the approaching system, was also averted.
With a super system of intense destructive intensity, almost stationary in the initial few days 1000 km north-northwest of Fiji, slowly gaining more momentum, energy and destructive might, TC Pam was going to be one of the most destructive systems to cut a swath through the middle of the Fiji Islands, enveloping the entire island archipelago with a path through a northwest to a southwest trajectory, cutting a swath across a centre line through the middle of the most populated areas of the nation.
It was to have travelled through the Yasawa and the Mamanuca group, through the middle of populated Lautoka and Nadi and across the middle of Viti Levu, passing right over Suva, and through the smaller islands in the Eastern Division.
Science was in Fiji’s favor to deny the system, the normal passage in the usual fashion, where systems are steered initially in a southerly and then more to the southeasterly quarter, under the influence of upper level atmospheric steering currents, fields and energetics.
In all normal case scenarios – looking at the subject of tropical cyclone, genesis, climatology and forecasting for our southwest Pacific region - Tropical Cyclone Pam, or any other similar system –would have made a direct hit on some part of the Fiji Islands, approaching it from the northwestern quadrant and exiting from the southeastern quadrant, of the group of islands.
The Madden Julian Oscillation (MJO) which is a measure of the 30-60 day perturbations in the global upper atmosphere, atmospheric wave energetics and cyclonic or anticyclonic vorticity measure, leading up to an increased or decreased activity in preferred locations, led to a burst of activity in our tropical Pacific regions in the last few weeks. This also included an abnormally high westerly wind bursts on the surface in the low latitudes, helping the genesis and sustenance of TC Pam.
The MJO was thus not only responsible for one, two or three but four major tropical cyclone systems, forming from these enhanced phase of the MJO.
Simultaneous formation like this has been experienced in the past, but to have a number of major systems so close to each other and in the opposite hemisphere, with a feed-back mechanism into each other is quite rare.
Science or an act of God is what saved Fiji from a multi-billion dollar bill, traumatic pains from needless deaths, and a scenario in which the nation would have gone back a decade, despite its recent attempts to forge ahead.
All four cyclones, three on the southern side of the Equator and one to the north of the Equator –TC Olwyn, TC Nathan, TC Pam to the south and TC Bavi to the north, were linked together forming a cohesive linked unit, with feed-back mechanism of their own, sustaining each other and controlling each other’s movement.
Two tropical cyclones in the same basin in the same season is not unusual, especially in the peak of the season, which is March for our region. In the Atlantic four simultaneous tropical cyclones has happened only twice in history –in 1998 and in 1893. Incredibly the USA National Hurricane Centre reports that there were five tropical cyclones simultaneously in the Atlantic between September 11-12, 1971.
In the 1982-83 intense El-Nino season, the South Pacific recorded 19 tropical cyclones, the average being only 9 for the season. Further the National Weather Forecasting Centre at Nadi at one stage was tracking four tropical cyclones simultaneously, in its area of responsibility-each one affecting some part of the South Pacific nation. This season was also extended to May, when one tropical cyclone formed at latitude 110 degrees East, to the far east of the Pacific Ocean –where waters are very cold indeed –and this was unheard of historically.
Coming back to Fiji and a look at science or an act of God, which saved Fiji from the potential devastations of TC Pam, we note that TC Pam was interlinked to its twin on the opposite side of the Equator, called TC Bavi spinning well eat of Guam.
Both these systems were about 2570 km apart and in two separate northern and southern Hemispheres, but a streamline upper air synoptic analysis shows clearly the direct linkage, and feedback mechanism to the life cycle, intensity and even movement of these two systems.
TC Bavin was feeding and sustaining TC Pam and vice-versa, and in fact this was the reason for the initial stationary nature and eventual development without any outside forces on this system to a category 5 system. TC Pam thus whilst still around latitude 10 degrees North, some 1000 km northwest of Fiji, had attained a fully developed eye visible in satellite pictures, with an excellent axial symmetry – a characteristic which it kept for the following week.
This is uncommon. Not many systems have this type of unfretted excellent visible eye walls for this length of time, as shown by satellite pictures. In fact TC Pam kept its visible eye wall for all to see even when it had passed out of latitude 25 degrees South – from Fiji’s area of responsibility.
TC Nathan just off the Queensland coast, provided further dynamics which strayed TC Pam on a south-south west course as far as Port Villa, after which it became more southerly and then finally after latitude 25 degrees South the system was finally caught in the upper level steering currents, heading southeastwards.
Synoptic analysis of all data and the upper atmospheric and low level data clearly establish that TC Pam, if formed on its own in a solitary manner –without any outside influence of TC Bavi and TC Nathan -in the area and manner it did –northwest of Fiji -would have been a direct threat and hit Fiji from the northwestern sector with a very high probability of over 90%.
Analysis and research also shows that the sole reason for Fiji being saved was the mere existence of TC Bavi and TC Nathan, which were counterbalancing and even stopping the system from moving away towards the southeast and onto Fiji directly.
Further this was also the reason that the Vanuatu Islands had a direct and a persistent southerly TC Pam course and impact, which posed to be the most destructive for Vanuatu, as the majority of the islands are spread in a north to south orientation and spread, all of whom coming into a direct prolonged and parallel path of impact.
TC Bavi and TC Nathan also were responsible for the very slow moving TC Pam in its passage past from the genesis point to its initial south-southwest and then a more southerly track west of Fiji, which meant that the destruction, loss of lives, and carnage went on for much longer. This is not the case from traditional fast moving systems.
It is without doubt that the atmospheric dynamics of TC Bavi and TC Nathan on TC Pam, saved Fiji from going back a decade in time. With its enormous fury and power of devastation and destruction kept under leash by these two systems, and moving TC Pam more southwesterly initially, we all benefitted.
This is what we can truly call an “Act of God”, without any doubt in my mind.
(Dr Sushil K Sharma BA MA MEng PhD is a WMO Class 1 Professional Meteorologist and an Associate Professor of Meteorology and the former Head of the Meteorology Department, Fiji National University).