Posted on 09/02/2011 5:15:32 AM PDT by kidd
When is a hurricane not a hurricane? Well, when it doesn’t blow 64 knots (33 m/sec, 74 mph), because then it’s only a tropical storm. Inspired by a post over at the Cliff Mass Weather Blog, I’ve been trying to find a single report of sustained hurricane force winds anywhere along Irene’s path at or near landfall … no joy. I knew exaggeration was the order of the day for some folks in the climate debate, but I hadn’t realized that the illness had infected the Weather Service itself.
Figure 1. The path of Tropical Storm Irene over the mainland of the US. Symbols with a yellow center to the black storm symbol indicate a (claimed) hurricane. SOURCE ibiseye
We were fortunate in that we have very good records of the wind speed when Irene made landfall. It went almost directly over the wind recording station at Cape Lookout, at the bottom of Figure 2.
Figure 2. A closeup of Irene’s landfall. There are four wind recording stations in the area, at Beaufort (below the “70″ marker at lower left), at Cape Lookout (bottom left) and at Cape Hatteras (upper right). The Onslow Buoy is located offshore, southwest of Cape Lookout.
The wind record at Cape Lookout is quite interesting, as the eye of the hurricane passed right over the anemometer there. Figure 3 shows the wind dropping as the eye went over, coincident with the deep plunge of the barometric pressure to 950 hPa.
Figure 3. TS Irene wind (light blue) and barometric pressure (violet) at Cape Lookout before, during, and after landfall. Green line at the top shows the minimum wind speed for a storm to be classified as a hurricane (64 knots).
Figure 3 shows the classic pattern of a hurricane passing directly overhead. The “eye” of the hurricane has almost no wind, and is at the center of the low pressure area. You can also see the “calm before the storm. But what you can’t see is any trace of hurricane force winds.
Not finding hurricane force winds at the eye, I looked at the other nearby stations as well. The weather station at Cape Hatteras is in the “dangerous semicircle”, the right hand side of the storm track (Fig. 2) where the speed of the storm is added to the speed of the winds circulating around the eye. Beaufort, on the other hand, is in the safer half of the storm, where the speed of the storm is subtracted from the circulating speed of the winds. The Onslow Buoy is also in the safer semicircle, on the left of the storm track in Figure 2. Figure 4 shows those records.
Figure 4. Winds at TS Irene landfall for Cape Lookout, Beaufort, Onslow Offshore Buoy, and Cape Hatteras.
As you can see, although Irene definitely qualifies as a solid tropical storm (winds greater than 35 knots), it does not reach or even really approach the 64-knot threshold for hurricanes. Other than at the eye itself, the winds did not exceed 50 knots, much less reach 64 knots.
After crossing over the land near Cape Hatteras, Irene headed back out to sea again. I thought perhaps it might have picked up steam when it went out over the ocean again. It made a second landfall in Atlantic City and went along the coast to New York.
Figure 5. Second landfall for Irene.The nearest stations to Irene’s track are Costeau (near Mystic Island above Atlantic City), NY Harbor Buoy (outside the mouth of the harbor, in the dangerous semicircle), Sandy Hook (hook shaped peninsula just above Long Branch and central hurricane symbol) and Kings Point (near New Rochelle above New York City). Note that the storm is claimed to be a hurricane until it gets well into New York State.
It appears from an examination of the station data shown below in Figure 6 that it did not pick up strength over the water. By the time Irene reached land a second time, it barely qualified as a tropical storm, much less a hurricane.
Figure 6. Wind speed from Tropical Storm Irene as it made the second landfall.
So, despite looking at Irene before, during, and after both landfalls, there is no hint of a hurricane anywhere. By the time it got to New York the eye of the storm had dissipated, what was left were huge bands of rain clouds.
Is there a moral in this story? Well, I can understand people taking extra precautions, better safe than sorry is a good rule. And I certainly imagine that when the Weather Service re-examines the records, the error will be corrected.
But that doesn’t help in making the decisions. As soon as Irene hit land, it should have been downgraded immediately to a tropical storm. That’s what it was, not a hurricane making landfall but a tropical storm. As far as I can tell, we still haven’t had a hurricane make landfall during Obama’s presidency, a historical oddity.
Individuals and city mayors and the people in charge of the emergency response can call for any level of reaction to storm threats. They may decide an exaggerated response is appropriate.
But they need accurate information to do that, not exaggerated claims. They need the actual facts, the best estimates with no exaggeration on either the high or low side.
In this case, it appears that people got so wrapped up in the question of the winds, and the fear of the winds, that they overlooked what actually made Irene unusual. This was not the wind speed, but the size of the storm. Combined with Irene’s generally slow movement over the ground, Irene’s huge dimensions meant that any given area would get rained on for a really, really long time.
And in turn that meant that the cities and towns along the coast, the ones receiving all of the attention from the fear of high winds and attendant storm surges, weren’t the towns in danger. Unlike the coastal cities, the vast expanses inland were not able to have the rainwater just flow back into the ocean. Inland, the water piled up and overflowed the banks.
And so, because of the overestimation of the wind speeds, our attention was diverted from the real threat. Because of the claimed hurricane-force winds, a storm surge up to eight feet was predicted in New York Harbor. But in the event, the storm surge was barely three feet, a non-event … and meanwhile, New England was getting badly flooded.
So the moral to me is, honesty is the best policy for a National Weather Service. Don’t exaggerate the possible effects to be on the “safe side”, don’t minimize the possible effects. Just give us the best information you have, and let us make up our own minds. As Sergeant Friday used to say … “Just the facts, ma’am” …
w.
NOTE: All wind data is from the NOAA National Buoy Data Center http://www.ndbc.noaa.gov/.
In other words, barometric pressure was that normally associated with a Cat 3 hurricane.
For some reason, Irene's surface winds did not mesh with the barometric pressure, nor did the flight-level winds found by the Hurricane Hunters make their way down to the ground at the intensity level normally encountered.
I don't think the NHC was being dishonest about Irene - I think they just hadn't seen a storm like this one before. But that's weather for you.
As usual, there are really excellent comments to the article at the link at “Watts Up With That?”
That’s true, but as the article mentions, when it made landfall with winds well under hurricane force, the storm should have been downgraded
This is simply not correct. It was forecast for a couple of days that Irene could be a 24-hour rainfall event. Fortunately, the west side of the storm dried out and the rainfall was a couple of inches less than forecast for areas such as PA and NJ.
Vermont and upstate NY weren't so lucky.
But, once again, that's weather.
This piece isn't up to the usual standards of the source website.
AND NOT ONE WORD OF THANKS TO GEORGE BUSH FOR FIXING FEMA
(you dont think it was in this good of a shape from anything Obambi did since he took over, do you?)
The NHC did a very good job forecasting the track. And they are the first to admit that intensity forecasts are much more inaccurate. But they have to forecast with the entire set of data they are seeing.
And also realize that the evacuations had been set in motion the day before the North Carolina landfall.
By the time it got to New York the strongest winds were well off to the east, wreaking havoc on the power grid in CT.
As the article mentions, local officials are free to act, or overreact, as they please. But they need the correct facts.
And the article notes, as did the Weather Channel, that what was remarkable about this storm was its sheer size.
But the fact remains, Irene was NOT a hurricane when it made landfall. Nor was anyone in the United States affected by hurricane force winds.
It was a very serious rain event. With some gusts of high winds. But it was not a hurricane when it made landfall.
We had the Weather Channel on in the background here all say. We always knew Irene would be nothing but a tropical storm by the time it got to New York.
Also, the WC explained that winds aloft are going to be 20% higher than surface winds. In a city of high rise buildings that could be significant.
The current “trash the forecasters” bandwagon has me concerned. The forecasters will never be able to give us a flawless forecast. That doesn’t mean they should be criticized or ignored.
Forecasters first and foremost rely on observation history of weather.
Everything they had observed in the past said this storm was stronger than what they were seeing at the surface.
So quite frankly, observed history was not helping them correctly forecast what was happening with Irene. They errored on the side of caution and kept the forecast for Irene at the intensity their models were telling them it could reach, given the barometeric pressure - if anything, they split the difference downwards between what the barometeric pressure was telling them (Cat 3) and what surface observations were telling them.
And Irene was rated at a strong tropical storm when it hit NYC. And the strongest wind gusts in CT were 66 mph, consistent with that rating.
And once again, if anything, the rainfall forecast for Irene was either on-target or a bit less than projected, so that complaint is, quite frankly, bunkum.
The author and yourself have the luxury of hindsight to second-guess the NHC.
In turn, I'm sure the NHC will be studying all of the data they have fore Irene and incorporating that into future forecasts. But it quite frankly is silly to say they should have discarded all of their past experience with hurricanes. They would have caught hell if they had downgraded Irene 24 hours earlier and then suddenly the storm surprised them again and started acting more 'normal' by jumping up to strong Cat 2 strength. And just reference Ike to see what a large Cat 2 can do.
Yeah, the pastcasters always get it right.
The article doesn’t trash the forecasters.
It notes that measured ground wind speeds were not widely reported when the storm made landfall. That’s not an error in forecasting, that’s an error in reporting current conditions.
I live near Hartford, so I saw the meat of the storm first hand. There were some serious gusts of wind that could easily topple a tree. But for most of the time, even when the remnant of the eye passed closest, sustained winds were well below 20 mph.
A hurricane has SUSTAINED winds greater than 74 mph. I was in Gloria in 1985, so I know what a sustained wind of more than 74 mph is.
Irene was a tropical storm, not a hurricane, when it made landfall.
This is actually a GOOD thing. From what I’ve heard, insurance companies have been trying to invoke the hurricane damage clause on many people’s policies, and the deductible is 5X or more compared to the typical deductible where damage is not due to a hurricane.
I’m sorry, I didn’t see a question posed.
From the article:
“because of the overestimation of the wind speeds, our attention was diverted from the real threat. Because of the claimed hurricane-force winds, a storm surge up to eight feet was predicted in New York Harbor. But in the event, the storm surge was barely three feet, a non-event … and meanwhile, New England was getting badly flooded”
Second, you keep avoiding the question - what of the gap between the pressure (which was no lie and was supported by surface observations along the entire path) and the surface winds?
The NHC clearly did not fully understand what was happening with Irene - should they discard all of their previous experience and not hedge the risk that the storm could start having surface winds consistent with Cat 3 barometric pressure?
Please answer that one.
And once again that paragraph is pure bunkum, unless you or the author can point to a forecast that downplayed the flood risk to Vermont at the expense of the surge forecast.
But that is dishonest.
First, the media has changed what is meant by a “recession” (formerly two quarters of negative growth) to suit their political needs.
Now, the media has changed what is meant by a “hurricane” (formerly sustained winds in excess of 74 mph) to sell news and to bilk money out of insurance companies.
The argument usually given for the hype (better to be safe than sorry) flies in the face of “the boy who cried wolf”.
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