Western Australia's northwest is bracing for Severe Tropical Cyclone Narelle — a system BOM Senior Meteorologist Angus Hines has described as "a really powerful, really major weather system" — as it approaches the North West Cape and is forecast to reach Category 4 intensity today, 26 March. The warning zone currently spans from Bidyadanga south to Exmouth, taking in Port Hedland, Karratha, and Onslow, and a dangerous storm tide is forecast along the coast between Onslow and Denham as the system closes in.

This is the same Narelle that has already made landfall twice. It struck Cape York as a Category 4 system on 20 March before crossing the Gulf of Carpentaria and making a second landfall north of Numbulwar in the Northern Territory on 21 March. That passage forced the pre-emptive evacuation of approximately 500 Numbulwar residents and the emergency transfer of 30 Katherine Hospital patients — including nine pregnant women — as the Katherine River climbed to major flood levels. The Adelaide River at Adelaide River township peaked near 12.6 m, according to NT emergency services, inundating nearby properties and triggering community evacuations. Narelle then weakened over land, re-entered the Indian Ocean, and has been rapidly rebuilding ever since. Today it returns as a fully reorganised severe cyclone aimed squarely at the WA coast.

A system that keeps going — and the reason it matters for WA

Narelle's cross-continental endurance sets it apart from most systems in the historical record. Only Cyclone Ingrid in 2005 made comparable multi-state Category 3+ landfalls across Queensland, the Northern Territory, and Western Australia within a single season. The difference here is that Narelle is making its WA approach over sea surface temperatures well above the 26°C threshold needed to sustain cyclone intensity, according to BOM data, providing an unusually large energy reservoir for re-intensification. The result is a system arriving at the WA coast in far better shape than many trans-continental storms typically manage.

The synoptic driver behind this re-intensification is a combination of the active Australian monsoon trough — still positioned across northern Australia in late March — and anomalously warm Indian Ocean sea surface temperatures. BOM's tropical climate monitoring shows the monsoon trough has remained active and well south of its climatological average this season, channelling moisture and low-level convergence into the Indian Ocean basin west of WA. Low vertical wind shear along Narelle's projected track, forecast to persist through today before mid-latitude westerlies begin interacting with the system late Thursday, has given Narelle a largely unobstructed path to major intensity. That westerly interaction — the same baroclinic process that curves mature cyclones southward — is precisely what now threatens the Gascoyne and potentially the Mid West coast.

"That is a really powerful, really major weather system." — BOM Senior Meteorologist Angus Hines

What the warning zone means on the ground

The tropical cyclone warning from Bidyadanga to Exmouth covers the heart of WA's offshore fishing and marine industry. Very destructive gusts to 260 km/h are forecast west of Onslow as Narelle passes near the North West Cape today, according to The Watchers, with destructive gusts exceeding 125 km/h reaching Karratha's coast and Carnarvon by late Thursday. Pilbara Ports Authority has already cleared the ports of Ashburton, Cape Preston West, Dampier, and Varanus Island — facilities that service the Pilbara's LNG and iron ore export operations — and issued a formal directive that all recreational vessel owners must safely secure their boats for cyclonic conditions.

Storm tide is the hazard that most coastal mariners underestimate relative to wind. A dangerous storm tide — the combination of storm surge and normal tide height — is forecast between Onslow and Denham as Narelle's circulation drives water onshore. Low-lying coastal areas, boat ramps, and marina infrastructure in this zone face inundation risk well above what any wind-driven swell alone would produce. The timing of storm tide peak relative to the astronomical high tide matters enormously here: a surge arriving at or near high tide produces far worse inundation than the same surge at low tide. In the current forecast window, coastal users from Onslow south through Carnarvon and toward Denham should treat any area within a few hundred metres of the waterline as potentially inundated through Friday.

For boaters and water users: what this means right now

If your vessel is still on a mooring, trailer, or in the water anywhere in the Pilbara or Gascoyne, it needs to be dealt with immediately. The Pilbara Ports directive to secure all recreational vessels is not advisory — it's the kind of formal instruction that precedes port closures and infrastructure lockdown. For vessels that cannot be hauled out, the minimum action is to double all lines, add breast lines, remove canvas and running rigging, secure halyards, and identify whether the marina can sustain storm surge above the dock level. If you are north of Carnarvon and your vessel is not yet secured or hauled, you are behind the timeline.

Offshore and nearshore fishing operations should have been suspended yesterday. Gale-force winds are already extending south from Narelle's outer circulation across the Pilbara coast. The sea state in these conditions — steep, wind-against-swell cross-seas in shallow water over the Pilbara's broad continental shelf — is not survivable for most recreational and commercial vessels. The offshore Pilbara fishing grounds from Exmouth Gulf north to the Rowley Shoals are completely inaccessible and will remain so through the weekend. Charter operators out of Exmouth, Onslow, and Karratha should be treating the remainder of this week as a write-off and focusing on client communication and vessel security.

Further south, the Gascoyne and Shark Bay regions face growing uncertainty as Narelle's track develops. If the system tracks closely along the coast before turning south — as current models suggest — the Carnarvon boat harbour and the Monkey Mia and Denham foreshore will be exposed to storm tide risk on Friday night into Saturday. The Gascoyne River at Carnarvon, which drains a large catchment that will receive heavy rainfall from Narelle's outer rainbands today, will also respond with a rise in river levels through Thursday and Friday. Boats moored in or near the Gascoyne River mouth face compound risk from storm surge and elevated river flow simultaneously.

The NT aftermath as a reference point

The NT passage gives WA communities a concrete frame of reference for what Narelle delivers even in a weakened state. At the NT landfall, Narelle was a Category 2 system with 10-minute sustained winds of 148 km/h, according to BOM. That was enough to force mass evacuations, knock out power to thousands of residents, cause the Adelaide River to exceed major flood levels at 12.6 m, and require the emergency transfer of hospital patients including pregnant women. WA's northwest will receive a Narelle at Category 4 — not Category 2 — over a coastline with extensive shallow-water marine infrastructure, including some of the most productive recreational fishing grounds in Australia. The energy difference between these two intensity levels is not marginal: wind destructive power scales with the cube of speed, meaning Category 4 gusts carry roughly three times the destructive energy of Category 2 winds.

No confirmed casualties have been reported from Narelle's NT passage, according to emergency services — a significant outcome given the storm's track through remote, low-lying communities. Pre-emptive evacuation decisions appear to have been the difference. The same logic applies to any coastal residents or water users in WA's northwest who have not yet relocated from low-lying areas or removed vessels from exposed moorings.

FAQ

Which areas are under tropical cyclone warning right now? The warning zone as of 26 March runs from Bidyadanga south to Exmouth, taking in Port Hedland, Karratha, Pannawonica, Onslow, Coral Bay, and Exmouth itself. Watch the active warnings on the Seabreeze warnings page for real-time updates as the zone changes.

When does the storm tide risk peak? Storm tide risk is forecast to peak along the coast between Onslow and Denham as Narelle makes its closest coastal approach. The exact timing depends on track, but the highest-risk period for Onslow and Exmouth is during daylight hours today, with risk extending south toward Carnarvon and Denham through Friday.

Is it safe to be on the water in Shark Bay or Carnarvon? No. The Gascoyne and Shark Bay regions are within the forecast impact zone for dangerous storm tide and destructive winds through Friday. All recreational boating should be suspended and vessels secured or removed from the water.

What about Perth and the Southwest? A southward track toward Perth remains within the cone of uncertainty at 72-plus hours, but is not the most likely outcome. The more probable scenario sees Narelle make landfall in the Gascoyne or Mid West and weaken as it moves inland. Even under this scenario, Perth and the Southwest will see elevated swells and strong southwesterly winds over the weekend — conditions that will impact surf beaches and make coastal boating uncomfortable. Monitor Seabreeze marine forecasts for the Southwest as the track resolves.

How does this compare to Seroja (2021)? Tropical Cyclone Seroja made landfall south of Kalbarri as a Category 3 system on 11 April 2021, causing extensive destruction across the Midwest and Gascoyne including Kalbarri, Northampton, and Geraldton. Narelle's current forecast intensity at the coast exceeds Seroja at landfall. The two systems share a late-season timing and a southward recurving track — the comparison is the most useful historical benchmark available for understanding the potential scale of impact.