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7 04, 2018

Severe Tropical Cyclone to impact Fiji

Models are coming into agreement that Fiji is likely to receive severe impacts from a severe tropical cyclone over the next few days! Above image via Windy.

 

 

Over the past 24hrs, a tropical low located to the East of Vanuatu has become more consolidated and is now expected to strengthen into a tropical cyclone overnight tonight (Saturday into Sunday) and become named as Tropical Cyclone Kala. Due to this likely occurrence, JTWC have already issued a tropical cyclone formation alert along with the Fiji Metservice doing the same, whilst keeping the same as a high risk over the next 3 days for development. The monsoon flow over the region has already produced falls of 50mm+ across the North of Viti Levu during Saturday.

 

 

During Sunday, Monday and Tuesday… after meandering around the waters East of Vanuatu for a day, Tropical Cyclone Kala is expected to track quickly towards the East to South East and approach Fiji. The majority of models are in agreement that as the system bypasses Fiji to the South, its likely to be upgraded to a Severe Tropical Cyclone (Category 3) with winds in excess of 165km/h. Thankfully, as stated above, the system at this stage isn’t expected to DIRECTLY hit Fiji… but severe impacts are still expected. There are some islands however, South of the main Islands of Fiji could could sustain a direct hit if the track remains as is.

 

Extended forecast track map issued by Fiji Metservice

Extended forecast track map issued by Fiji Metservice

 

Conditions should rapidly deteriorate from Monday night and across Tuesday as the system bypasses to the South. Kala is expected to take an almost identical path to the recent Cyclone Josie, and the fast movement of the system should see conditions improve on Wednesday. So realistically its about a 24-36hr period of poor conditions. Strong winds are likely to lash the Islands of Fiji with damaging to possibly locally destructive winds (depending on how close Kala gets) likely over the Southern beaches of Viti Levu and offshore Islands to the South. Heavy rain with widespread falls of 100-200mm is likely across all of the Islands with isolated much higher falls possible. The rainfall should be the main threat, with flooding likely, especially across areas that have only recently been impacted by catastrophic flooding caused by Josie.

During Wednesday and Thursday, the system is expected to impact Tonga also with strong winds and heavy rain that could cause some areas of flooding, but like Josie… Kala is expected to turn South before reaching Tonga, so no direct impact is expected.

 

Forecast accumulated rainfall via ACCESS / weather.us

Forecast accumulated rainfall via ACCESS / weather.us

 

6 04, 2018

New Tropical System to impact Fiji

Fiji is currently on watch for severe impacts from a new systems (Invest 91P) after only a week ago being impacted by catastrophic and deadly flooding across Viti Levu! Above image via Windy

 

Invest 91P (an area of low pressure under an investigation alert) is currently situated roughly halfway between Fiji and Vanuatu in the South West Pacific. The system is slowly developing at the moment but is currently forecast by all global models to track towards the East (towards Fiji) where impacts are likely to begin being felt across the latter part of the weekend. There is a rather large variation in intensity for the system so its hard at this stage to gauge how strong it could be…. however, heavy rainfall leading to further flooding and damaging winds are expected as a bare minimum across Fiji.

HWRF (highest forecast intensity of all global models) for Invest 91P as it moves South of Fiji

HWRF (highest forecast intensity of all global models) for Invest 91P as it moves South of Fiji

 

At this stage, widespread falls of 150-300mm are expected across all of the Fijian Islands over the next 5 days with isolated higher falls possible. These kinds of falls, especially so soon after catastrophic flooding have the potential to produce rapid flash flooding and rapid river rises as the systems are yet to recover fully. 

Current forecast rainfall forecast until Wednesday night via ACCESS (AUS) / weather.us

Current forecast rainfall forecast until Wednesday night via ACCESS (AUS) / weather.us

 

The system is likely to become a tropical cyclone and move just South of Fiji (so not quite a direct hit) – with the Fiji Metservice already placing it under a high threat, but as stated above there is a large variation in intensity. It looks most likely to become either a Category 1 or 2 system near Fiji on Monday and Tuesday, but other heavyweight models are indicating it could be much stronger. Both the tracking and intensity of the system will be something closely monitored over the weekend with further updates possible across the weekend.

Fiji Metservice High Risk issued for Monday (April 9th)

Fiji Metservice High Risk issued for Monday (April 9th)

 

4 04, 2018

9PM Tropical Cyclone Iris (Category 1) Update 4/4/18

Cyclone Iris (Category 1) is now on her last legs as a tropical cyclone has she begins to turn back towards the North West off the Central QLD Coast. Above image via NOAA

 

Over the past 6 hours or so, Iris has maintained a general South East movement, however its starting to veer more towards the East South East now. That along with a decrease in forward momentum has meant Iris is beginning the turn. This turn will mean Iris will remain positioned over the Central Coast and South East of the Whitsundays for the next 12-18 hours by the looks of things. During this time, Iris will likely drop below cyclone strength due to a remarkable increase in vertical wind shear along with an increase in dry air intruding which will complete the process of tearing apart. This weakening so far, along with her positioning has resulted in just isolated to scattered showers over the Central Coast where less than 10mm has been recorded across all areas except Cannonvale since 9am this morning, while wind gusts have dropped below 60km/h across the Whitsundays. Creal Reef on the Great Barrier Reef has maintained 90km/h+ winds through the day with the system on top of the area.

Water Vapour and Radar supplied by Weatherzone showing Iris becoming very weak with minimal rainfall over land.

Water Vapour and Radar supplied by Weatherzone showing Iris becoming very weak with minimal rainfall over land.

 

 

River conditions via BOM showing no flood threats across the Central QLD area

River conditions via BOM showing no flood threats across the Central QLD area

 

Iris will transition / weaken into a tropical low where she will become so weak that the deep onshore South East flow which is dominating the QLD Coast at the moment will become the dominant steering factor. This will push her towards the North West where she “may” cross the Coast as a weak tropical low… the “may” is in there because there is a chance that she will wash out before she reaches the Coast. Conditions should begin to improve over the Central Coast and Whitsundays from late Thursday onwards while there is no major threat expected anywhere else along the QLD Coast.

 

Current road conditions via QLD Traffic showing some minor flood issues around Mackay, but otherwise good road conditions.

Current road conditions via QLD Traffic showing some minor flood issues around Mackay, but otherwise good road conditions.

 

 

4 04, 2018

4PM Tropical Cyclone Iris (Category 2) Update 4/4/18

Iris is not well and truly starting to undergo a weakening phase as the system becomes situated off the Central Coast and Whitsunday region. Above image via NOAA

 

Throughout the course of Wednesday, Tropical Cyclone Iris has continued to track towards the South East. She is now situated around 240km East of Hamilton Island or 250km North East of Mackay and maintaining that South East track. The system is also starting to lose intensity, and rather quickly. While there is good convection still evident over the Southern periphery of the system, the Northern periphery has become as good as useless in terms of the system’s longevity as increased vertical wind shear starts to take control. 

 

Over the rest of Wednesday, the system should maintain a South East track as she rides along the leading edge of the subtropical ridge situated over QLD. However, she is expected to weaken back down to a Category 1 system this afternoon / this evening and then eventually a tropical low overnight with the vertical wind shear becoming increasingly stronger. This will inevitably cause the system to no longer be steered by the subtropical ridge but instead become steered by the deep and dominating South East onshore flow. This will cause the system to stall for a while during that weakening phase, then transition into an Ex-Tropical Cyclone and push back North West. 

Right now, models are split on whether or not she will make landfall as an Ex Tropical Cyclone over areas North of Bowen. It won’t realistically matter too much, as minimal rainfall is expected and winds will only be moderate to strong at best… but models are split between a weak tropical low or nothing crossing the Coast.

WZ 4pm Iris

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4 04, 2018

7am Tropical Cyclone Iris (Category 2) Update 4/4/18

As expected, Iris is starting to struggle under the increased vertical wind shear and now a very unfavourable environment… but the threats aren’t over yet. Above image via NOAA

 

 

Tropical Cyclone Iris is remaining a marginal category 2 system as expected and tracking towards the South East. She is located roughly 280km North of Mackay or 190km North East of Bowen. Over the past 6-12 hours, the evidence has become very clear that Iris is starting to struggle under the increased vertical wind shear now active over the region. Despite the system being in a very favourable surface environment with 28-30ºc waters, the system is an even more so unfavourable atmospheric environment which is choking Iris from any sort of intensification potential. Given the vertical wind shear is expected to become even stronger over the next few days, this will also be the reason why in about 18 hours time, Iris will become an Ex-Tropical Cyclone.

 

Weatherzone Radar for TC Iris as of 7am AEST 4/4/18

Weatherzone Radar for TC Iris as of 7am AEST 4/4/18

 

 

Don’t let that stop you from thinking its all done and dusted though… Iris itself may be about to weaken quickly, but her impacts are still being felt along the Coast. A tropical cyclone warning remains in place from Yeppoon to Bowen for the potential for damaging winds over the next 24 hours. These winds are already being felt across the Whitsundays with Hamilton Island recording gusts of up to 106km/h. Creal Reef offshore has recorded 109km/h and Middle Percy Island 93km/h. 70-80km/h has been noted elsewhere over the Central Coast. There is a likely potential that conditions will continue to deteriorate over the rest of Wednesday as the system moves that little bit closer to the Whitsunday region. Rain areas are still impacting the Coast though with falls of 50-100mm being recorded around Mackay and the Bowen to Airlie Beach region since 9am yesterday. Conditions should start to improve (but staying a little miserable) during Thursday.

 

Rainfall totals since 9am Tuesday morning via BOM

Rainfall totals since 9am Tuesday morning via BOM

 

3 04, 2018

8pm Tropical Cyclone Iris (Category 2) Update

Tropical Cyclone Iris is looking fractionally better over the past few hours and could enter a period of slow intensification overnight tonight (Tuesday into Wednesday) as moisture content increases. Above image via Weatherzone showing water vapour.

 

During Tuesday afternoon, Tropical Cyclone Iris was looking a little worse for wear as a weak Category 2 system located East of to North East of Townsville. Over the past 6 hours or so, Cyclone Iris has further increased her forward momentum and is now moving at 14km/h towards the South to South East (this is up from 4km/h earlier on). The system throughout the day had reasonable convection over the Southern periphery, with lightning being detected in powerful convective cloud tops… these cloud tops remain active over solely the Southern periphery of the system but the change now is that Iris has much better moisture content.

Rainbow Satellite via NOAA showing TC Iris

Rainbow Satellite via NOAA showing TC Iris

 

The large blue and purple area on the cover image is representative of high water vapour levels in the atmosphere. This is a positive thing for the system as it can help the system further intensify. The only troubling factor for Iris is that she is encountering increased vertical wind shear caused by a subtropical ridge… this ridge will continue to push East across Queensland and cause Iris to enter a more unfavourable environment towards the end of the week. While the system has good moisture content, there is a chance she could slowly intensify into a high-end Category 2 system, but after that she will begin to weaken.

 

Despite rain areas hanging around the Central Coast from Sarina to Ayr for much of the day, rainfall totals have been modest at best. Falls of 25-50mm have occurred around Bowen and Airlie Beach + surrounding areas with very light falls elsewhere. Overnight tonight and into tomorrow, conditions are expected to deteriorate over the Whitsunday’s with damaging to possibly destructive winds impacting the Islands. Rainfall totals however should remain fairly modest. 

 

Rainfall totals since 9am Tuesday morning via BOM

Rainfall totals since 9am Tuesday morning via BOM

 

3 04, 2018

3pm Tropical Cyclone Iris (Category 2) Update

Tropical Cyclone Iris is starting to gain some forward momentum as she begins to track South East, parallel with the Central QLD Coast. Above image via NOAA

 

As of 3pm, Tuesday April 3rd. Tropical Cyclone Iris was positioned approximately 250km North East of Townsville over the Coral Sea. The system after being mostly slow moving towards the South for the past 12-24 hours has now completed the shift towards the South East and is starting to pick up some speed, moving now at (a still slow) 6km/h. Models and live data are both indicating that Iris should maintain this track for the next 24hrs or so, running parallel to the Central QLD Coast and Whitsundays.

 

Some things to note are water vapour and infrared satellite imagery is picking up some increased convection over the Southern side of Iris, between the system and Bowen / Whitsundays. This convection likely contains the strongest gusts within the system that are likely exceeding destructive thresholds of 125km/h. The other thing would be that there is a severe lack of convection over the Northern periphery of the system which has suppressed the intensification process. This would be partially due to dry air intruding most likely, or possibly a slight increase in vertical wind shear. Never the less, this has lead to Iris maintaining a 130km/h peak gust range, rather than the 150km/h winds she was packing much earlier this morning.

Weatherzone Radar for TC Iris as of 3pm AEST 3/4/18

Weatherzone Radar for TC Iris as of 3pm AEST 3/4/18

 

Despite Iris being somewhat closer to the Coast, rainfall totals have significantly dropped. Falls of 50-100mm were widespread around the Central Coast with isolated falls of up to 200mm over the Eungella Ranges to 9am this morning… however since 9am, maximum rainfall totals of less than 20mm have been recorded. Conditions should start to deteriorate with damaging to destructive winds gusts over the Central Coast & Whitsundays tonight and tomorrow morning.

BOM Track Map for TC Iris issued at 2pm 3/4/18

BOM Track Map for TC Iris issued at 2pm 3/4/18

 

3 04, 2018

Tropical Cyclone Iris 11am 3/4/18

11AM UPDATE 3/4/18 – Tropical Cyclone Iris is remaining a Category 2 system and has weakened slightly over the past 3 hours, but in general she is expected to continuing to slowly intensifying off the NQLD Coast. Iris appears to be adopting a more South Easterly track now as expected, although she is remaining slow moving. High levels of convection over the Southern side of the system are indicating there is still room for intensification and she may become a Category 3 system overnight tonight. Light rain areas are impacting the Coast between Mackay and Ayr with light falls since 9am being recorded so far.

IDQ65001-1

Track Map issued by BOM at 11am 3/4/18

Live data is showing a large area of dry air suffocating large parts of QLD. This dry air is expected to eventually impact Iris and lead to a reduction in rainfall across the Central QLD Coast. However for the next 48-72hrs there is the potential for Iris to remain in a favourable, but deteriorating environment and briefly reach Category 3 strength off the Whitsunday Coast. Conditions are forecast to deteriorate across the Central QLD Coast over the next 12-18hrs with damaging to destructive winds likely over the Whitsundays and strong to damaging winds over areas between Ayr and Sarina including Mackay and Proserpine.

Iris 11am Dry Air

Image via Weatherzone showing the dry air over QLD with Iris off the Coast. 

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3 04, 2018

Iris has 2 scenarios to play out her death

Iris has been a constant pain over the last week or so as she circumnavigates around the Coral Sea from New Caledonia to Queensland.. however her tale has 1 more twist before it comes to an end, and it can go 1 of 2 ways. Above image via NOAA

So we are going to propose both scenarios, please be sure to read both carefully and don’t jump to conclusions. Neither are overly dramatic, but hopefully they can answer some questions and queries.

 

 

Scenario 1: Some models are hinting at what has been expected the entire time. Iris is currently a Category 1 tropical cyclone. Over the next 24 to 72hrs, she is expected to track South East parallel with the Central QLD Coast due to a ridging pattern over Inland QLD which is pushing East. Her broad wind field is expected to allow for some damaging gusts across mainland areas between about Bowen and Sarina, as well as the Northern Capricornia Coast which is exposed to the South East wind channel (i.e Yeppoon). There is also the potential for some locally destructive winds of 125km/h+ over the Whitsundays. As the system drifts away from the Coast later in the week, it should interact with increased vertical wind shear and begin to die a somewhat slow death and become a distant memory. Despite the system being close to the Coast during Wednesday and Thursday, minimal rainfall is expected due to some dry air aloft (kind of like what happened with Linda over South East QLD).

 

ECMWF showing Iris remaining a weak system off the Central QLD Coast, not coming ashore. Strong South to South East winds would occur along the Coast and produce some scattered showers. Image via Windy

ECMWF showing Iris remaining a weak system off the Central QLD Coast, not coming ashore. Strong South to South East winds would occur along the Coast and produce some scattered showers. Image via Windy

ECMWF Forecast 5 day rainfall via Windy. Heavy falls offshore with 100-200mm possible over Coastal parts of Central QLD.

ECMWF Forecast 5 day rainfall via Windy. Heavy falls offshore with 100-200mm possible over Coastal parts of Central QLD.

 

Scenario 2: Some models (including heavyweight models) are now on the prospects of Iris making landfall over the Central QLD Coast, but there is a twist to that. The above mentioned ridge in this scenario is expected to track East as expected… however its expected to cause Iris to stall as it blocks her South East, South and Westerly movements. Once the ridge overruns Iris, she will become sheared off and become nothing but a low level circulation off the Whitsundays. Once this occurs, she will no longer be steered by the ridging pattern, but by the South East flow which is dominating the QLD Coast.. this will allow her to make landfall as a weak tropical low over the Central Coast & Whitsundays… the catch, apart from some strong to damaging winds over the Whitsundays and exposed Coastal areas between Yeppoon and Bowen, it will seem like a normal day. Dry air aloft from about 12,000ft and above will suppress any potential rainfall across the region, so that will lead to mostly fine and blowy conditions. 

 

GFS Scenario for Iris (both images supplied by BSCH) for Thursday afternoon. Left image is Winds just above the surface. Right image is a skew-t plot which shows the atmospheric setup.

GFS Scenario for Iris (both images supplied by BSCH) for Thursday afternoon.
Left image is Winds just above the surface. Right image is a skew-t plot which shows the atmospheric setup.

GFS Forecast 5 day rainfall via Windy. Heavy falls offshore with 100-200mm possible over Coastal parts of Central QLD.

GFS Forecast 5 day rainfall via Windy. Heavy falls offshore with 100-200mm possible over Coastal parts of Central QLD.

 

As you can see, the overall prospects either way aren’t too dramatic. They can make tracking the system a little bit harder (especially when you have accurate heavyweight models butting heads with each other), but the overall consensus is generally minimal rainfall, strong to damaging winds likely with possible brief destructive gusts and a marginally increased swell. She poses no threat to the North QLD Coast or the South East Coast (for those who think she will impact the Commonwealth Games). 

 

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2 04, 2018

[UPDATED] Heavy Rain likely over the CQLD & NQLD Coast

Models are chopping and changing non stop with rainfall predictions, but they are remaining confident on some heavy rain over the Central Coast and Whitsundays, as well as possibly over the Tropical North QLD Coast over the next 3 to 4 days. Above image via BOM.

 

 

Forecasting rainfall with tropical systems is one of the hardest things to do as the rainfall totals themselves can fluctuate greatly, and even a change in position of the system by less than 50km can significantly alter the totals. Iris is proving this theory, with a dramatic shift in rainfall totals over the past 12 to 24hrs (and its good for those who are holidaying in the area).

Global models have all come into agreement on Iris remaining a little more offshore than previously predicted. This also also meant her impacts (heavy rain, strong to damaging winds and large swell) are expected to remain confined to the Coast. It also looks like her impacts will last for a shorter amount of time and this has meant global models are now in agreement on falls between 100 and 200mm across the Central Coast and Whitsundays between Sarina and Bowen including Mackay, Proserpine and Airlie Beach and lighter falls of 50-100mm possible across areas between Bowen and Cairns with the odd higher total not ruled out. 

 

Rainfall accumulation totals until Midnight Thursday via EC Model (weather.us).

Rainfall accumulation totals until Midnight Thursday via EC Model (weather.us).

 

 

A flood watch does remain in place, with a severe weather warning for heavy rain and damaging winds. This reduction in rainfall shouldnt be taken as a complacency alert.. there is still the potential for significant 24hr falls between late Monday and early Tuesday which could lead to flash flooding as well as river and creek rises across the Whitsunday Coast. 

 

Severe Weather Warning issued by BOM at 5am Monday, April 2nd.

Severe Weather Warning issued by BOM at 5am Monday, April 2nd.

 

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