Hurricane Size Discrepancies

[Ptarmigan]

I notice between the Best Track and Post Wind Analysis, there are discrepancies, especially with the 1851-1987 data set.

1851-1987 Best Track Data Set
ftp://rammftp.cira.colostate.edu/demari ... oradii.txt

1988-Present Best Track
ftp://rammftp.cira.colostate.edu/demari ... k_atlc.txt

HRD Wind Analysis For Alicia
http://www.aoml.noaa.gov/hrd/Storm_page ... /wind.html

HRD Wind Analysis For Ike
http://www.aoml.noaa.gov/hrd/Storm_page ... /wind.html

For example, Alicia of 1983 has a large area of TS wind in the Best Track. The Post Wind Analysis has Alicia with much smaller winds.

Alicia
Alicia at 8/18/1983 06Z From Best Track
TS Wind
185 168 147 161
Hurricane Wind
67 64 59 62

Alicia at 8/18/1983 06Z From Wind Analysis
TS Wind
81 96 73 60
Hurricane Wind
39 33 0 33

Ike
Ike at 9/13/2008 06Z From Best Track
TS Wind
225 200 125 125
Hurricane Wind
110 90 55 45

Ike at 9/13/2008 0730Z From Wind Analysis
TS Wind
183 185 150 91
Hurricane Wind
94 95 62 33


That is a huge discrepancy right there. I know Alicia was not that large of hurricane. When I average up the Best Track for Alicia, the TS wind is almost as large as Ike. The discrepancy gets smaller with Ike, but it is there.

[wxman57]

I scrutinized the best track database (ftp://rammftp.cira.colostate.edu/demari ... oradii.txt and ftp://rammftp.cira.colostate.edu/demari ... k_atlc.txt) last year looking for small hurricanes. What I searched for was hurricanes with 74+ mph radii of 25nm or less. I just wanted to compare the number of small hurricanes in the "modern age" (1988-present) to those from 1851-1987.

I remember counting 122 hurricanes between 1988 and 2009 that at one time had 74 mph radii of 25nm or less. Then I went through the best track database prior to 1988 way back to 1851. Want to know how many hurricanes I found with 74 mph radii 25nm or less? ONE! A single hurricane on a single track point!

What does this say about our best track database? Well, I think it's pretty clear we have a poor idea of TC size prior to the modern age of recon and satellite. And it's likely we have a very poor idea of hurricane intensity, too, as we could only measure a hurricane's true intensity if it passed right over a land weather station. That's why there were so few Cat 4-5 hurricanes in the early part of the record (prior to the 1950s).

[Ptarmigan]

I am pretty certain there were more Category 4-5 hurricanes that we realize. Some seasons prior to 1950s had no hurricanes at all! Look at the 19th century or 1914 for example and I am very suspicious of that. It is strange prior to 1987 Best Track, that there is no small hurricane. I know the 1932 Freeport Hurricane was a small hurricane, probably with hurricane force winds extending around 15 to 25 nm.

The 1886 Indianola Hurricane in the Best Track is larger than average and in reality it was a really large hurricane, like Carla. Hurricane force wind extended throughout the Texas coast when it hit Indianola. I think the 1886 Indianola Hurricane was actually a Category 3 despite having a central pressure of 925 mb because Katrina had 920 mb and had 105 to 110 knot winds. The Indianola Hurricane was probably the size of Gilbert, Carla, Katrina, and Ike.

I also looked at the Best Track for Wilma and had it had 5 nm Radius of Maximum WInd (RMW) despite having 135 knot winds and central pressure of 892 mb. I am sure it is common with typhoons though because of lower ambient pressure. The ambient pressure for Wilma was about average for that area. Ike on the other hand had a central pressure of 944 mb and 85 knot winds, which is easily explained by its really large size.

Here is what Stu Ostro wrote about Ike.

This hurricane is an odd bird. NHC did up the intensity from Category 1 to 2, but the pressure plummeted Wednesday afternoon and evening, down to 944 millibars, which is totally out of whack with what one would typically see with what is officially barely a Category 2.

Some of that can be explained by the fact that the wind field is so large, as it's not purely the pressure value which is important, it's the pressure gradient between high and low pressure which creates the wind, and in this case that's pretty widely dispersed. So rather than extreme winds in a concentrated area, there are strong winds across a big area.

But the 944 millibars is just 8 millibars higher than that of the 1900 Galveston Hurricane when it made landfall, and it also had a large wind field but was a mid Category 4.

Ike has an anomalous structure, with a very small eye embedded within the large wind field. It'll be interesting to see what happens from this point forward, but in any event don't be fooled by that barely-above-Category-1 status. This just goes to show that the official wind intensity only tells part of the story.

Ike is stirring up the Gulf so much that water levels on the Mississippi coast and Lake Borgne just east of New Orleans in Louisiana are running 2-3' above normal astronomical tides and the winds there are light.

That's not where the core of the hurricane is headed, but it's a tip-off that Ike is going to have a large surge/wave impact, not just wind/rain. As for where the center of Ike is going, the trend has continued to be farther north, but just a little, with most models having nudged from Corpus Christi - Port Lavaca to Port Lavaca - Freeport; regardless, effects will extend up the coast from where the center comes in.

http://www.weather.com/blog/weather/8_17152.html

[Ptarmigan]

The 1932 Freeport Hurricane is listed as being large and it formed rather close to Texas. From what it looks like, it is a small hurricane. Also, it intensified rather quickly from Category 1 to 4.

[Scott747]

The 1886 Indianola Hurricane in the Best Track is larger than average and in reality it was a really large hurricane, like Carla. Hurricane force wind extended throughout the Texas coast when it hit Indianola. I think the 1886 Indianola Hurricane was actually a Category 3 despite having a central pressure of 925 mb because Katrina had 920 mb and had 105 to 110 knot winds. The Indianola Hurricane was probably the size of Gilbert, Carla, Katrina, and Ike.

There has always been debate about how strong both of the Indianola storms were. I've done quite a bit of research over the years and still haven't come to a solid conclusion on the 86 storm. Some of the few photos that are available online and also the ones at the musuem in Port Lavaca (And for anyone that has a interest in historical hurricanes this museum is a MUST visit) does lead me into leaning that the 86 storm was probably a solid four and not a borderline 4/5. However I don't think it was quite the size of Gilbert, Carla, Katrina and Ike. The area where Indianola was at (Matagorda Bay) was a recipe for disaster from a surge standpoint with not only the initial surge but the returning ebb surge, something that few realize in Galveston that's more of a threat than the initial surge.



The August Frank warehouse was still standing after the hurricane and fire in 1886. The U.S. Signal Office was not that lucky. The signal officer Capt. Isaac A. Reed and Dr. H. Rosencranz were trapped in the building as it collapsed and were burned to death by the fire while the hurricane was raging. A burning lamp in the signal office caught the building on fire as it was being pounded by the hurricane and the fire quickly spread to other structures located in the area.
The area became known as the "burnt district." (Reed is buried in the Evergreen Cemetery in Victoria, Texas.) (From the Indianola Scrapbook - 1936)

[Ptarmigan]

The only reason I think the 1886 Indianola Hurricane is large because I read that hurricane force winds could be felt throughout the Texas coast. We will probably never know how large and intense this storm was.

[Ptarmigan]

From this link:
http://docs.lib.noaa.gov/rescue/dwm/dat ... _maps.html

I noticed that the August 1945 Hurricane was quite small, which shows a great discrepancy with the Best Track database. The October 1949 Hurricane was average size on the map. The Freeport Hurricane of 1932 was described as small, it left a 30-40 mile swath of destruction.