Hurricane Hilary now serious threat to US southwest?

Short answer: yes, it’s potentially a real threat and should be taken seriously (so sadly I can’t use my stockpile of political double entendres). Hilary underwent rapid intensification yesterday, only 45 knots (middling tropical storm) at 8pm Wednesday night,75 knots (Cat 1 hurricane) 12 hours later, and is as of 6am ET Friday is now a powerful 125 knot (Strong Category 3).

The sun hasn’t come up over the storm this morning as I write this, but here is a shot just before sunset last night:

click any image to see full size.

Hilary will likely hit peak intensity later today, forecast at 130 knots (minimal Category 4) before starting to decay as it moves over colder water and interacts with land. Here is a link to NHC’s Key Messages regarding Hurricane Hilary, and here is my map of the estimated impacts of the storm using my TAOS/TC model, based on the official forecast:

On this track it looks like there will be impacts to the US southwest, but how bad? While I normally don’t show the track models for reasons I frequently rant about, in this case looking at the models is important to get the full story. Here are the major track forecasts as of 6am this morning:

Here is one problem from an impact forecast standpoint: how strong the storm is will depend on if the eyewall (assuming there is still one at that point) and core of the storm makes landfall in Mexico before reaching San Diego. A wobble to the left (west) will keep it offshore, and that can make the difference between a tropical storm and hurricane for San Diego. The current NHC forecast assumes the storm will go inland a bit, but if it follows a track closer to the European Model or GFS (purple and dark blue lines), winds over San Diego and LA will be higher, as will wind damage. In either event, Hilary will be decaying rapidly by that point in terms of wind, so wind impacts aren’t likely going to be the biggest problem.

The big risk from Hilary is rain. Of course the landscape and human systems in the region are not equipped for tropical rain rates and totals. Even if Hilary is post-tropical in terms of wind and structure, by next Monday the remnants will be pumping a lot of moisture over the southwest. Here is what the GFS model is showing …

Six to ten inches of rain across the LA basin, much less inland towards Las Vegas, will wreck havoc and cause significant damage in the form of flash flooding, mudslides, and so forth. These impacts may well extend across much of southern and central California, Nevada, and western Arizona. So, while there will be the usual excessive media hype, Hilary is a legitimate problem, and looks to cause significant misery in an already miserable state (California – OK, couldn’t help at least one snarky comment).

Quick note on the Atlantic, yes, there are invests, one starting to gain structure but it is in the far eastern Atlantic, so nothing to worry or talk about at this point.

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