Typhoon Khanun does a “Z”, East Pacific/Hawaii watch

Sorry about the gap in posts, that crisis that can’t be discussed rationally in the Western world had some major developments. During the interval, Khanun totally blew up the forecasts and decided to spend the last week loitering near Okinawa, doing a “Z” over the Ryukyu Islands. Oh, wait, not supposed to use that letter 😛 … anyway, here’s what the track and forecast from JTWC looks like this morning (Sunday 6 August):

Khanun weakened a lot in the stall and turn and on satellite this morning is a broad comma shaped system …

Click any image to embiggen

but is expected to regain some strength and climb back into hurricane force before swiping the southern main island of Kyushu on its way to the Korean Peninsula. As a reminder, here is what the Joint Typhoon Warning Center (US based) and Japan Meteorological Agency (WMO RSMC) forecast tracks looked like a week ago (July 30st at 06Z) as compared to the forecasts this morning:

In meteorology this is call a busted forecast. In this case, the original expectation was that Khanun would slip under a frontal system and maintain a straight line towards China. However, the system that ended up steering the storm was stronger, and extended further south than expected, so Khanun stalled and began a northeastward track. The steering should weaken in the next 24 hours, allowing Khanun to resume a northwesterly track. So were there signs the track was going to weird out? Yes, some of the forecast models did show a possible stall and turn. Here is the full “spaghetti map” from last Sunday:

Now, the coarse minded might go “AHA! This is why you should cook your own spaghetti!” Well, this is the exception that proves the rule – yes, some of the models were showing the stall and turn – but the synoptic situation was such that there were indications the models were over-emphasizing that potential and the rapid intensification expected by Khanun (that did in fact materialize) would be dominant. In the vast majority of cases the human forecasters will get it right; this time they missed it. By Monday the official tracks were showing the possible turns as it became clearer. Which raises the second point: forecasts beyond 72 hours become increasingly uncertain in most cases, especially for weaker storms (remember Khanun was just a tropical storm last Sunday). We tend to get spoiled when things agree, and forget how hard is is when they don’t …

Elsewhere, the Atlantic is quiet, but there are two storms in the East Pacific:

Dora is tracking south of Hawai’i, mostly of interest to fish and surfers as it will generate some big waves on the south coasts of the Islands. Eugene is skirting the coast of Mexico, might reach hurricane force briefly tomorrow, but should stay off shore. From NHC …

Eugene will likely produce areas of heavy rains and gusty winds across southern portions of the Baja California Sur today as it passes to the south of the peninsula. Interests there should monitor the progress of this system.

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