Tuesday, August 26, 2014

Hurricane Cristobal: August 25, Update A

An eminent geologist gave me the low-down on what happened in Iceland with Bardarbunga ... "Actually the Icelanders turned the volcano off using big underground magma valves. They decided that they can create more havoc and thus hold the airline industry for a larger  ransom at a later time. Hey, you gotta do what you gotta do to enhance your GDP." (Source shall remain anonymous to protect his Great Geologicalness). 

Regarding the other natural havoc in the Atlantic arena... not much time for dilly dallying tonight, alas, as I have a bit of ranting to get done.

So Cristobal is a Hurricane, hey? Officially his wind speed is 75mph, which makes him barely a cat 1 (cat 1 range: 74-95mph), central pressure is 989mb. He is located at 25.1N, 71.9W, heading NNE at 2mph. He has barely moved from the poor Turks and Caicos, who are well and truly drenched at this point I imagine!

I'm not sure I quite agree with this analysis of him being a hurricane. <Rant Alert!> Ok, truth be told, I really don't agree with this. You can't go around naming storms hurricane willy-nilly just because you measured some high wind speeds! In that case a winter gale or a tornado should be named a hurricane because it has high wind speeds. It's just not on. Cristobal is more of a front meeting a Tropical Storm rather than a full out Hurricane. Sigh. <End Rant Alert!>

Let's look at the evidence...

1. There is a lot of convection, I give them that. You can see this in the infrared satellite video:

But you would expect a lot of convection with any stormy weather over water temperatures in the 29-30 deg C. It looks more like a blob than a well-organized tropical system.

Even the NHC admit: "this system's cloud pattern does not resemble that of a hurricane, with little or no evidence of banding on satellite images." No banding. No eye. Nothing.

Of course, you could say that the long line of very active thunderstorms and rain showers streaming off to the northwest (over Bermuda) is because of wind shear. It does look like wind shear. But is it just wind shear or is something else afoot (aloft)?

2. We can look at the structure of the atmosphere to find out, and we do that by looking at the vorticity fields....

These show a long line of higher vorticity (greater circulation) stretching across the Atlantic in a SW-NE direction at all levels of the troposphere. This is the signal of a front.

Lower level of troposphere (850mb):

Middle troposphere (500mb):

Upper troposphere (200mb):

By comparison, Hurricane Marie off to the left, has the well-organized circular structure of a Hurricane. Looks very different, doesn't she?

So, the circulation is not showing the structure of a Hurricane, and the convection is not showing a Hurricane. And therefore... why would one call this a Hurricane?!? It should still be a Tropical Storm as there is a signal of one still in the lower half of the troposphere, even it if is getting a bit entangled. If I was cynical, I might even say that this is one of those 'we need the numbers' things. But luckily for you, I'm young and carefree and not cynical or skeptical or any of those other words ending in 'ical' at all, so I won't say that. Not At All.

All this silliness aside, what does it mean for you Bermudians? It looks like you're going to get a spot of rain (it looks like you may already have had some?). Although the track has Cristobal passing to your west on Weds, I would still dust off the galoshes and stock up on the tea, wine and ice cream (good advice for most situations I think ;-)). The NHC have generally been rather good on the track at 1 day (even if their intensity estimates are poor), but Cristobal is caught up with that front and is a bit bulky, so although the center may not pass over you, you might still get a bit of a breeze. I would be ready also in case the track does shift a bit more to the east - I'm not ruling that out yet.

More tomorrow. Must run... mudpie ice cream is melting... ;-)

Toodles for now!

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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