Welcome to our tenth wet season wrap up for Northern Australia where we take a look at Northern Australian towns/cities and go through their previous wet season. In October, we continue our features by speculating at what the early modelling might be showing for the upcoming wet season for these locations so become a subscriber, show your support and get access to this exclusive information. Today we remain in North-West WA and specifically the city of Karratha (pop approx 17 000).
Iron Ore and salt mining are the major economic drivers of this city and the Port allows the easy exporting of those resources. The city has a very similar climate to Port Hedland (last night's wrap) but is a little more on the arid side of 'Semi Arid' climate classification. The city relies on Tropical Cyclones and rogue thunderstorms for its Summer rainfall and then NW cloud bands and cold fronts for its Autumn/Winter rainfall. Just like Hedland, Karratha lies too far south for the monsoon and too far north for the Winter rains and therefore only gets a small taste of both. Summers are hot hot hot, but not quite as hot as Hedland. The Wet Season here runs from December to June and we see about 280mm fall in an average wet season, but the rainfall here is highly variable so there are very few 'average' years.
The 2018/19 Wet Season was well below average for Karratha, even though a cyclone sat on their doorstep for 4 days in March.
WET SEASON 2018/19 RAINFALL Outside of Veronica's influence there was very little rainfall over Karratha the entire wet season. Incredibly the first significant storm of the wet season actually didn't happen until days before Cyclone Veronica. A gusty storm on Sunday the 17th March at 8PM broke the drought that saw just 2mm for the entire season to that day. That gusty storm provided the city with 18mm of rain. As Tropical Cyclone Veronica began bearing down on the area to Karratha's east, it was creating some severe thunderstorms on its south-west flank. One of these hit the city on the 22nd March Winds were recorded to 87km/hr during that storm just before lunch along with a quick 15mm of rain. Tropical Cyclone Veronica then made its presence felt directly on March 23rd and especially on the 24th. It continued to impact the region until lunch time on the 26th March. However with Karratha being located on the south-western flank of the cyclone for much of its slow moving tour of the NW coast it meant that southerly winds were keeping a significant portion of the cyclone's rain offshore. And unlike Port Hedland's 350 odd mm directly from Cyclone Veronica, Karratha received just 10% of that with 35mm. It was a cruel blow to a city that endured such a dry Wet Season to come agonizingly close to so much rain but miss out on it.
Following Veronica no further significant rainfall occurred over the city, making it a very dry Wet Season.
TROPICAL CYCLONE IMPACTS
Tropical Cyclone Veronica impacted the city directly from the 23rd until the 26th March 2019. The cyclone dumped 35mm of rain on Karratha and created a maximum wind gust recorded of 124.0km/hr at 9:00AM on March 24th. That wind gust was 5km/hr higher than the peak winds reported at Port Hedland. The difference though is that the winds over Karratha were southerlies coming off the land and therefore the winds were not accompanied by a storm surge. Building standards in the city are high and these types of winds cause little structural damage. The presence of the Tropical Cyclone for an extended 3 day period meant that port at Dampier was closed costing hundreds of millions of dollars in delayed exports to our economy. The estimated total loss of revenue at the time between the two major ports of Dampier and Hedland was approximately 1.7 billion Australian dollars making this our costliest national natural disaster of 2018/19
While K City missed the worst/best that Vonnie had to offer, up the road at Roebourne it was a different story. Wind gusts were recorded officially to 154km/hr at 11:52AM 24th March from the south. Once again this wind was coming off land and therefore did not create a storm surge. However with Roebourne located on the edge of the cyclone's eyewall it was subject to much more rainfall than K City with the cyclone dumping over 150mm of rain before the rain gauge malfunctioned on the 26th. That rain gauge was fixed late in June.
The start of Summer followed on similar to most of Spring with cooler than normal conditions which a few residents noted to us privately. In fact on December 1 the temperature only got to 29.3 degrees a new record low daily maximum temperature for December. The culprit was a cool westerly surface winds that did not allow the more usual south-easterlies to assert their dominance. That cool period lasted the whole first week of December. But just as residents got comfortable, the thermal weather Gods sprung to action. Despite the record braking cold snap of early December, the rest of the month saw warmer than normal temps bringing the overall max right near normal. In fact from then on, the maximums were above average with a lack of cloud across almost all the wet season. The hot weather was most noticeable in May where not a single cloud band or cold front impacted the city resulting in a period of much warmer than normal weather with a daily record max for May being broken on the 6th May with a blistering 38.3 degrees.
Tomorrow evening we're off to Nhulunbuy, the section of the Top End where storms go to die.
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