Was that a Hurricane? In Oklahoma?

During the last Atlantic hurricane season, our "E" storm was Erin. It occurred in mid-August.

But only now, in April, has the corresponding National Hurricane Center tropical cyclone report (PDF) finally been released. The extraordinarily long time gap underscores just how mysterious a meteorological phenomenon Erin actually was, and how long it must have taken meteorologists to figure out what they could say about it.

Consider: Over water, Erin was never anything but a weak and disorganized tropical storm, one that struck the Texas coast on August 16 with maximum sustained winds of 30 knots (tropical depression class).

But then something beyond crazy happened.

Over land, the remnants of the storm system looped up towards Oklahoma and reorganized, so much so that August 19 satellite images show Erin, its center very close to Oklahoma City, resembling an overland hurricane with an "eye" that it had never managed to develop over water. Meanwhile, the winds picked up far more than they ever had over the Gulf – reaching 50 knots sustained, 70 knot gusts – even as pressure fell as far as 995 millibars (far lower than when Erin had been an easily categorizable tropical storm).

So what on earth was Erin after it re-intensified over land?

Debate about this among hurricane specialists appears to be the reason the official report on Erin took so long to come out. The answer is that the experts don't know what to call it – none of the familiar categories work. As the report explains:

While the system's structure, particularly its convective organization as seen on radar, resembled and had some characteristics of a tropical storm for a few hours on 19 August, the prevailing view from the Hurricane Specialists at the National Hurricane Center (NHC) is that the system was not a tropical cyclone over Oklahoma… Since the system was clearly non-frontal, designating it as an extratropical cyclone is also not the most appropriate solution. In addition, the prevailing view among the NHC’s Hurricane Specialists is that the system’s duration over Oklahoma on 19 August was also too short to classify it as a subtropical cyclone. Given all of the considerations described above, the system is simply designated as a “low” by NHC on 19 August.

Or to quote the great Jeff Masters, perhaps Erin was a "Thingamabobbercane"!

But whatever Erin was, it was deadly. In its second, uncategorizable phase, the storm killed seven people, casualties of intense rainfall and flooding.

I don't know precisely what caused Erin to reintensify over Oklahoma or become a "Southern Plains Cyclone." I'm sure scientists are studying that pretty vigorously.

But I do know that this storm really makes it hard to resist a particular butchering of Hamlet: "There are more things on heaven and earth, Horatio, than are dreamt of in your meteorology."

Weather or Not
Meteorologists are puzzled by the hurricane-like characteristics that
Tropical Storm Erin featured over land in Oklahoma in August 2007