The first tropical storm for California in over 80 years is moving in and brings significant rain and flooding risks to desert parts of the south-western United States and western Mexico.

1 to 3 year’s worth of rain may fall in just the next 1 to 3 days in some locations, in an area that is usually a desert with dry riverbeds and dry lakes. The risk for catastrophic flooding and serious damage to infrastructure from this historic hurricane is very high between Los Angeles and Las Vegas, impacting 3 US states.

We take a look at the track of Hilary, the areas most exposed, and why this hurricane is so historic and unusual – even with the wind portion weakening.

We also compare why Los Angeles and Sydney are similar in that they tend to avoid tropical storms…and explain why countries like NZ and Canada – which are further from the tropics – usually are more exposed than New South Wales and California for tropical storms.

🌀Tropical Storms (Hurricanes, Typhoons, Cyclones) form in the tropics & usually track westwards.⬅️

As they slide further away from the equator, & if they survive long enough, they are then usually pulled towards the poles.⬆️⬇️

Knowing this helps make sense of future storms! pic.twitter.com/S1Sno86Tb8

— WeatherWatch.co.nz (@WeatherWatchNZ) August 19, 2023