Hurricane Julia explodes — Atlantic has two coincident Category 4 hurricanes, very rare

[Is KFC an acceptable substitute, if this goes on a long time?];)
No, too oily, good to make eco-fuel.

Richard Holle says:
September 15, 2010 at 12:31 pm
You could be still right; if so that couple would degrade.

editorial comment:
But Igor and Julia just are not major hurricanes
I think you mean “are not just”, since they are major hurricanes.
[ryan: true enough, fixed up]

Re: Ric Werme on September 15, 2010 at 2:38 pm
There was a firm transition date at one point. Just a few years ago (at least it feels that way) there was a network TV news report about the upcoming transition. I mainly remember the reporter showing a dual-system speed limit sign, mph and kph, saying how these will be going up soon for the transition period, after which there would only be metric signs.
…
Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t.

“”” kadaka (KD Knoebel) says:
September 15, 2010 at 1:19 pm
Excerpts from: George E. Smith on September 15, 2010 at 12:00 pm
The metre (meter) is the IS unit of length and k for kilo (keylow) is the approved prefix for 1000 of; so that means it should be keylowmeter; but we Kiwis speak kinda lazy, so I’m sure that I say kil-uh-meter sans hyphens.
And here I thought the debate was between kilo-meh-ter or kilo-meet-er. “”
Well KD, I’m good for either of yours; it was the k-lomuhtuh that I would like to see squished.

kadaka (KD Knoebel) says:
“…Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t…”
As soon as they run out of ways to attach pork to the other rules they will take care of that pretty quickly.

SSam said on September 15, 2010 at 4:08 pm

kadaka (KD Knoebel) says:
“…Have you noticed any states or municipalities rewriting their traffic laws to use metric? I sure haven’t…”
As soon as they run out of ways to attach pork to the other rules they will take care of that pretty quickly.

More confirmation the United States will never go metric.

The storms this year don’t seem to be following the historic tracks. If the weather prognosticators have the hurricane prediction thing so well in hand, where are the predictions that these storms will form and intensify so far east and turn north so far out to sea?
Gerry
[ryan: they have no skill in predicting the season’s track characteristics in advance, let alone 7-days ahead of time]

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Richard Holle says:
September 15, 2010 at 12:31 pm
So I was wrong about a (complete) lull in hurricane production from Sept 3rd through the 20th, (crow are fattening up in the cage) But what about the possibility of a continued increased surge in strong hurricane production after the 21st? (If what we have now is a slowdown from the max potential?)
I am still awaiting the rest of the season, popcorn and BBQ crow in hand, [Is KFC an acceptable substitute, if this goes on a long time?];)….
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BBQ crow has got to be more tasty than the deep fried seagull they used to serve in the company cafeteria. The seagulls perched on the company roof after resting from raiding the garbage dump nearby. Parking spaces along the line of flight were left for unwary visitors….

Question for the more meteorology inclined.
Looking at the 5-day forecasts for both storms, the projected turn back Westward for Igor is reasonable, but Julia looks like it’s going to break her damn neck turning around. Do the forecasts suppose that Igor is going to push Julia back, and if so, why won’t the same effect push Igor a little more Eastward? I noticed that they still have it going right over Bermuda, even though it seems to have stayed on a more southerly route than originally anticipated (going back 2 days on that, haven’t been tracking Igor as carefully since all the forecasts show it going way out to sea and not even making it to the Continental US).

ryan: just wait for the Arctic blast behind Igor during the next 5-7 days over the Northern half of the US and Canada. Time to harvest your tomatoes…
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Too late – frost already on the way, forecast is for frost for the next week in central Alberta, 6 below Celsius for Saturday night.

Been there, done that, in Canada decades ago. The transition was real fun. Now metric only. But I’m in my 60s, so I still translate most metric back into British.
In the process, I’ve learned a few interesting things about that creaky old system. An ounce of water weighs about an ounce. A British gallon weighs 10 lbs. (160 oz.) A pint (16 oz) weighs about a pound.
I’m sure there are more convenient matchings buried in there!

I was hoping to wait a few weeks to do a thorough study on inter-seasonal comparison of HU (Hurricane) and TS (Tropical Storm) winds and pressures, but the hoopla given this current episode where NOAA is reporting on the rarity of having a coincident pair of storms simultaneously reporting Cat-4 winds (Category 4: Winds ranging between 114-135 kts or 131-155 mph) prompts me to post some relevant information now.
The criteria for reporting the maximum sustained wind (as opposed to wind gusts) differs from one global region to another. The US uses a one minute average to determine the maximum sustained wind. In TS or HU observations, the max sustained wind is determined by taking a 10 minute average multiplied by 0.88. The “surface” wind is assumed to be a height of 10 m above the surface. Even in dropsonde measurements where winds are measured down to splash, the lowest 10 m is ignored. The reason for this is that closer to the water/ground it is assumed that frictional effects will sharply reduce actual wind speeds.
In the past, before satellites and sophisticated remote sensing techniques from aircraft were available, most of the actual wind observations came from instrumented land sites or ships of opportunity [in some cases when ships got caught in the inner circulation, ships of inopportunity]. Many of these ship reports were from wind instrumentation mounted on the deck or masts. Other means such as the Beaufort Scale used eyeball observations of the state of the sea.
In the modern era, on site ship reports have declined enormously, mainly because unlike the earlier generations, current warnings combined with modern communication have kept most craft from being caught anywhere near the central circulation.
Today, most of these observations of wind and pressure are provided by or deduced from satellite platforms, some using active data and many using passive data. All require some level of processing and analysis. Another source of what is usually considered more reliable data come from reconnaissance aircraft. These aircraft carry a variety of platforms including manmade (eyeball) observations, doppler radar, standard aircraft wind and temperature probes, SFMR (Stepped Frequency Microwave Radiometry) for estimating surface winds and dropsondes (compact instrumented packages released from the aircraft and equipped with GPS to report their precise location and parachutes to slow their descent to the surface) which observe temperatures, pressures and humidity.
As of this writing none of the observations of high winds, temperatures and central pressures for either HU Igor or HU Julia have come from aircraft or surface-based observations. An AF Recon flight is scheduled to be in Igor tomorrow (Thursday).
So, up until now essentially all of the reports of maximum winds and lowest surface pressure have been derived from satellite data and none have been supported by ground truth. One would hope that these estimates are reasonably conservative, but in this age of apparently acceptable hyperbole this may be wishful thinking.
Now here is the most important factor: In regard to winds, whatever they are measuring it is not sustained maximum winds. A valid sustained maximum wind is one that is measured from a fixed location over a particular time interval (or that can be referenced to a fixed location say from a platform moving at a known velocity independent of the ambient wind). Even with dropsondes, one can tell exactly how fast the instrument package is moving, but not what the particular wind speed would be if it were anchored to a fixed location.
Until at least 1996, the record observed “surface” wind speed was in excess of 220 mph with a peak wind (gust?) of 231 mph (372 km/hr) at 1:21PM on April 12, 1934 measured by a heated 3-cup Robinson type anemometer with a human observer on site at Mt Washington NH. Robinson anemometers actually record the distance the cups travel in their rotation about a fixed axis, and on some models the distance is displayed in miles and fractions thereof much like an automobile odometer. Thus, what they are reading is the miles of air moving past the instrument which when divided by 24 gives a true daily average wind speed. Similarly when recorded each hour the data gives a true average wind in mph. Thus one can obtain a true average wind speed for any desired time interval by simple division.
The problem with the remote wind measurements in Tropical storms is that in the absence of a fixed observation point where the wind is actually occurring, it’s nearly impossible to tell whether one is measuring winds or wind gusts. Doppler microwave devices are often gated to observe maximum velocities. These are usually instantaneous wind speeds. If a gust front were approaching a Doppler equipped radar it could provide a fairly precise speed of the gust, but the duration at any point along the path of the gust might only be a few seconds, much too short a time to determine a sustained wind. All of this strongly suggests that the determination of maximum sustained winds in a TS or HU are very likely to be maximum gusts and their relation to the true max wind would depend on the density of the gust pattern and the cross-section across which the instrument is observing.
The determination of whether a record max wind is a gust or a sustained wind might be considered a difference without a distinction except that there are very real differences in the impact of such winds upon fixed objects in the path of the wind. The force of the wind per unit area on a stationary surface normal to the wind is proportional to 4 times the speed of the wind. The power of the wind (the force per unit time) is proportional to 8 times the wind speed. Wind gusts, by definition, have much lower power densities than sustained winds. That’s why it’s importance to know what the real sustained maximum winds are and not just the gusts.
The nearest things to a stationary observation platform are anchored buoys. These can, and do report sustained winds and gusts quite accurately. The only problem is that one can’t easily plan on having these buoys in the path of a storm.
BTW, there are some very interesting wind and SLP observations that were taken near (but not exactly in) the center of HU Earl when it passed to the S and E of New England about a week ago.
One final point: Most historical wind data for TSs and HUs up until the past few decades were obtained from fixed or relatively stationary platforms where the integrated wind over time periods from 1 minute to 10 minutes could reliably be determined. Except for well instrumented and maintained buoys, most of today’s remotely observed winds cannot be accurately compared to the earlier historic records and thus by incorporating such data uncritically, the climate record is being corrupted.