Archive for the Records Category

An excellent article over at the Houston Chronicle on the NHC’s recent rush to name storms.  http://www.chron.com/disp/story.mpl/front/5337583.html

… a controversy is brewing over decisions of the National Hurricane Center to designate several borderline systems as tropical storms.

Some meteorologists, including former hurricane center director Neil Frank, say as many as six of this year’s 14 named tropical systems might have failed in earlier decades to earn “named storm” status.
…such information is vital to scientists trying to determine whether global warming has had a measurable impact on hurricane activity.

Looking back at Hurricane Humberto, it is notable that Hurricane Humberto developed from a tropical depression into a category 1 hurricane in less than 18 hours. Quite a feat. Even within hours of our previous post the satellite pictures were looking quite impressive and radar too.

Hurricane Dean had the third lowest landfall central pressure of any Atlantic Hurricane. This is after Hurricane Gilbert in 1988 and the Labor Day hurricane of 1935.

Maximum winds were 165 mpg with gusts reaching 200 mph with a centeral pressure of 906 mb.

The 1935 Labor Day hurricane (892 mb) which hit the Florida Keys.
Hurricane Gilbert (900 mb estimated) hit Cancun, Mexico in 1988.

Only 8 other Category 5 Hurricanes have hit land in recorded history: Hurricane Andrew in 1992 (165 mph winds at landfall) and Hurricane Camille in 1969 were two others.

Hurricane Wilma (2005) remains the strongest Atlantic hurricane with 882 millibars while the strongest Pacific storm was Typhoon Tip (1979) with 870 mb and 190 mph winds.

As June 2007 comes to an end let’s take stock to see where the season stands. So far the Atlantic Basin has had 2 tropical storms – Andrea and Barry with Chantal to be next. Seems like a pretty quiet season so far, doesn’t it?

To see where we stand, let’s recall some other record breaking years, starting with 2005 which as we all know was a record-breaking season. If you had to guess, how many storms had formed by the end of June 2005? Well? 5? 7? By June 30, 2005, there had been a total of 2 storms – Arlene and Bret. It wasn’t until July 5 that we had both Tropical Storm Cindy and Dennis. We had Emily on July 11th and then Franklin on July 22. Gert arrived on July 23. So, we had 2 storms through the end of June in 2005 and 7 storms by the end of July 2005.

The second busiest season was 1933 had one storm form in May and one storm form in June. Just like 2007. July ended with five storms and the season ended with 21 storms. 1934 also had one May storm and one June storm, and three storms by the end of July, again just like 2007. It ended with 11 storms. So a record breaking season, and a below average season both had the same number of storms by the end of June.

Now, looking at 2004, another season that was memorable. By the end of June 2004 we already had 0 storms. Zero? Seriously? Yes. Alex didn’t arrive until July 31st. But by the end of August 2004 though, we had already had Hermine. 2004 was memorable not for the shear number of storms, but for the places they hit.

Some other seasons:
2002: 1 by the end of July, season ended with Lili.
2003: By June 30th, we had had Ana (April 20-24) and Bill (June 29-July 02) and we ended up the season with Peter.
2004: Zero storms by the end of June and 1 on July 31st. Ended with Otto.
2005: 2 storms by the end of June and ended with Zeta.
2006: 1 storm by the end of June, 3 by the end of July, ended with Isaac.

(Interesting note, in 1981, Arlene formed on May 6-May 9 and Bret from June 29-July 1, so the season was similar to 2007 so far and 1981 ended with 12 storms including a subtropical storm in November).

So what does it mean that there have “only” been two storms by the end of June, 2007? Absolutely nothing in our view. Busy seasons like 2005 and 1933 have had a June like this, while more quiet seasons like 1981 and 1934 have had similar Junes.

In fact, there are only 13 known seasons (as of 2007) since 1851 that have had 2 tropical storms form in June. June 2007 has only had one storm form during the month, but one in May.

The Chicken Littles would have you think that the Junes of 2005, 2006, and 2007 should be significantly worse than the Junes of 1933 and 1934 given we’ve had nearly 75 years of carbon emissions. Perhaps the link isn’t quite as strong as some people want to believe? Remember that it only takes one storm – see Andrew, the first storm of the season in 1992 hitting Miami – to have a devastating and memorable season. Preparation is key whether we have one storm or ten storms.

Will 2007 be a busy season? We’ll let you know in November 2007, but it is difficult to predict the rest of the season based on the season up through June.

Most of the well-known forecasters have weighed in with their 2007 forecasts now, so let’s take a look at what is being predicted.

• NHC/NOAA Hurricane forecast summary:
13 to 17 tropical storms
7 to 10 of them becoming hurricanes.
75% chance of above normal hurricane activity according to the NOAA’s NHC.

Other people are predicting:
• William Gray from Colorado State predicts 17 named storms with 9 hurricanes.
• AccuWeather calls for 13-14 tropical storms with 9 becoming hurricanes.
• Tropical Storm Risk (back in March) expected to bring 17 tropical storms, of which nine will strengthen into hurricanes.

Essentially all within the same ball-park.

What does this MEAN? It means that the experts think that we’ll have a busy season – we may or we may not, see below. So what should you do now? You have two choices: prepare now and be ready if a hurricane hits your area or don’t prepare and have no options. Preparation is a pretty simple matter when you have time to prepare, so the smart choice is to be ready.

In our view, these forecasts are an educated guess based on statistical analysis of previous seasons as applied to current seasons’ weather patterns. There is currently no magic box (or even sophisticated computer program) that can provide an accurate forecast for the number of storms. That said, the annual predictions are a worthwhile exercise in order to advance our knowledge. Studying current weather patterns, comparing these patterns with previous years, and then attempting to forecast based on the intersection between the two advances our knowledge incrementally and advancing knowledge is very worthwhile.

When the actual number of storms falls near the long term average, the forecasts are general correct since the forecasters generally end up predicting trends near the average while adjusting for various well known factors. The way forecasting works (usually) is you start with a long term average as your prediction and then you adjust it up or down based on various factors. For example, El Nino or La Nina’s presence or lack thereof will cause forecasters to adjust their predictions up or down. Patterns over the Atlantic, dust or lack of dust from Africa work similarly. Sea surface temperatures impact the forecasts also. It is merely a matter of how much each factor will impact storm formation and whether the impact will be up or down.

Let’s recall previous year predictions compared with the actually events. Please remember, the forecasters do their best with the knowledge they have.

****2006****
2006 ended with 10 named storms (one between Alberto and Beryl that was unnamed during the season and only identified in the post-season analysis).
CSU had predicted 17 storms
AccuWeather: 6 tropical cyclones (3 major) will strike US coast (none did), with a total number “above average”
NHC/NOAA predicted:
* 13-16 named storms (hurricanes and tropical storms)
* 8-10 of which will become hurricanes
* 4-6 of which will be major hurricanes (category 3 or higher)

In summary, the number of storms was well below predictions.

****2005*****
Actual: 28 tropical storms, 15 hurricanes, 7 major
CSU’s May forecast, predicted 13 named storms for 2005, which was obviously well off.
NOAA: 12-15 Storms, 7-9 hurricanes, 3-5 of them major

In short, the number of storms greatly exceeded pre-season predictions.

****2004****
Actual: 15 storms, 9 hurricanes, 6 major
NOAA: 12-15 Storms, 6-8 hurricanes, 2-4 major
CSU: 14 storms, 8 hurricanes, 3 major (May 2004 forecast)

The number of storms in 2004 fell in the average range and consequently pre-season predictions were quite accurate, only fall well below actual numbers in the “major storms” category.

The Final report from the National Hurricane Center on Hurricane Katrina has been issued.

The highlights on Hurricane Katrina are as follows:

1. Hurricane Katrina was a category three (3) storm when it made its closest approach to New Orleans, although it had been a category five (5) storm previously.

2. “The strongest winds corresponding to that [Category 3] intensity were likely present only over water to the east of the eye.” This means that the category 3 winds were well east of New Orleans.

3. “The sustained winds over all of metropolitan New Orleans and Lake Pontchartrain likely remained weaker than Category 3 strength.” New Orleans was experiencing a Category 2 hurricane. A majority of the damage was due to flooding, not winds. Flooding was caused by political failures in terms of 40-50 years of neglect and political games.

4. Surge was signficant and pentrated miles inland along bays and rivers. In some cases up to 12 miles inland. It was worse east of the eye, but still significant to the west of the eye – e.g. in the New Orleans area.

The facts on Katrina and Wilma should illustrate several important points that must be remembered.

a. Storm strength can change quickly. In 24 hours Hurricane Wilma went from a small tropical storm to the most powerful hurricane (measured by low central pressure) ever measured in the Atlantic Basin (to that point). Likewise Hurricane Katrina strengthened rapidly.

b. There is no such thing as “only a Category 1 or 2” hurricane – let alone “only category 3.” When both Hurricane Wilma and Hurricane Katrina made landfall neither was a Category 4 or 5 storm and New Orleans only experienced Category 2 force winds. In both cases the damage was significant. Much damage was due to neglect of flood control systems over 40 years due to political neglect and political game playing.

In short, there is no such thing as a minor hurricane. Evacuation is always your safest option – get out of the path of the storm. Following hurricane preparation guidelines – for water, food, yard etc. Too often we hear people blaming others for their own failure to prepare. Your own safety is your own responsibility first. Simple steps will help you to ensure that you do remain safe, but they do require planning.

Likewise, when the City, State, and Federal governments are assuring you that levees (or buildings or any structure) can survive a category 3 (or higher) storm do not always believe them. The National Hurricane Center will provide extremely accurate facts and information. However, politicians will use that information for their own political gain – look at the Hurricane Katrina hearings and the finger pointing in Hurricane Katrina’s aftermath. Politicians who are quick to assign blame to anyone they can in order to cover themselves are people to whom you should not look to for advice. They’ll take credit when they can, and deflect blame for everything else. No one who behaves that way is a leader, they are a disgrace.

Christian H F Riley

You can read the entire Hurricane Katrina report on the web. Hurricane Katrina Report

You can read the entire Hurricane Wilma report on the web.

A great satellite image of Katrina

Hurricanes are categorized by several methods, the most well known being the Saffir-Simpson Hurricane Scale. The Saffir-Simpson scale, developed in 1969, is based on the wind speed of the hurricane. The various categories are listed below in their traditional form:

Category 1: 74 to 95 mph
Category 2: 96-110 mph
Category 3: 111-130 mph
Category 4: 131-155 mph
Category 5: greater than or equal to 156 mph

The amount of damage between each category does not increase linearly. Each increase in category greatly increases the damage potential. The original scale included no Category 6 hurricane. Robert Simpson has stated that there was no reason to include an additional category because the damage would be severe no matter the wind speed over 155 mph. Improvements in building engineering over the past roughly 35-40 years may have changed that dynamic and might necessitate the addition of a category 6 hurricane.

In our view, if the Saffir-Simpson scale were adjusted to include another category, it would likely be as follows:

Category 1 hurricane: 74 to 95 mph
Category 2 hurricane: 96-110 mph
Category 3 hurricane: 111-130 mph
Category 4 hurricane: 131-155 mph
Category 5 hurricane: 156-175 mph
Category 6 hurricane: greater than or equal to 176 mph

The current Saffir-Simpson scale has the following wind speed bands for its categories:

Category 1: 21 mph band
Category 2: 14 mph band
Category 3: 19 mph band
Category 4: 24 mph band
Category 5: unlimited band since there is no upper limit besides atmospheric limitations

A Category 5 band would likely be a 19 or 24 mph band and therefore a category 6 hurricane would have winds greater than or equal to 176 mph (or 181 mph). The 176 mph figure seems to make the most sense based on wind speeds and engineering.

On a related note, the question has come about, what about a storm that has winds of 95.5 mph or 110.5 mph or 131.5 mph or 155.5 mph etc? It would seem that the scale does not provide for those wind speeds. A continuous mathematical restatement of the Saffir-Simpson Scale should be made with the addition of an additional category.

The Saffir-Simpson scale should be restated as:

Category 1 Hurricane: 74 to 95 mph
Category 2 Hurricane: > 95 to 110 mph
Category 3 Hurricane: > 110 to 130 mph
Category 4 Hurricane: > 130 to 155 mph
Category 5 Hurricane: greater than 155 mph

Or, alternatively:

Category 1 Hurricane: 74 to less than 96 mph
Category 2 Hurricane: 96 mph to less than 111 mph
Category 3 Hurricane: 111 mph to less than 131 mph
Category 4 Hurricane: 131 mph to less than 156 mph
Category 5 Hurricane: 156 mph or greater

Or with an additional category:

Category 5 Hurricane: >155 to less than 175 mph
Category 6 Hurricane: 175 mph or greater

or

Category 5 Hurricane: 156 mph to less than 176 mph
Category 6 Hurricane: 176 mph or greater

Precision is important in the sciences and hurricane forecasting is nothing if not a science. Likewise taxonomies assist in the classification and therefore the study of any phenomenon. Our view is that the Saffir-Simpson scale has a few minor areas that need correction.

For more information on the Saffir-Simpson scale, see this page.