03 December 2004

2004 Tropical Atlantic Activity Summary

The 2004 hurricane season is over, so it is time for my annual Season Summary. I sent out about 60 updates to this mailing list (which I’m proud to say has grown from about 4 subscribers in 1996 to 270 subscribers in 2004, not to mention the updates being posted on several websites) over the past 4 months; now it's time for the final one. This report is structured in the following manner: 1) the Saffir-Simpson Scale, 2) Lifetimes and Intensities, 3) Statistics and Storm Summaries, and 4) Landfall.
Thanks to the National Hurricane Center and Unisys Weather for the data, and a special thanks to Jonathan Vigh and Phil Klotzbach at CSU for valuable discussion and assistance throughout the season. The data presented here are the most current available to me, but could be altered in the post-season timeframe as more information becomes available.

1. Saffir-Simpson Scale of Tropical Cyclone Intensity

Depression        < 35          N/A
Tropical Storm   35-63          N/A
1                64-82        > 980
2                83-95        965-979
3               96-113        945-964
4              114-135        920-944
5                > 135        < 919

2. Lifetimes and Intensities

NAME      ACTIVE            VMAX (kts) MSLP (mb)

ALEX      31 JUL – 06 AUG     105       957 (N,H,M)
BONNIE    03 AUG – 12 AUG      55      1001 (N)
CHARLEY   09 AUG – 15 AUG     130       941 (N,H,M)
DANIELLE  13 AUG – 21 AUG      95       964 (N,H)
EARL      13 AUG – 16 AUG      45      1009 (N)
FRANCES   25 AUG – 07 SEP     125       935 (N,H,M)
GASTON    27 AUG – 01 SEP      65       985 (N,H)
HERMINE   29 AUG – 31 AUG      50      1002 (N)
IVAN      02 SEP – 24 SEP     145       910 (N,H,M)
TD 10     07 SEP – 09 SEP      30      1009
JEANNE    13 SEP – 27 SEP     105       950 (N,H,M)
KARL      16 SEP – 24 SEP     120       938 (N,H,M)
LISA      19 SEP – 03 OCT      65       987 (N)
MATTHEW   08 OCT – 10 OCT      40       997 (N)
NICOLE    10 OCT – 11 OCT      45       988 (N)
OTTO      30 NOV – 02 DEC      45       993 (N)

In the previous chart, the N, H, and M denote what statistic they contributed to; Named storm (TS+), Hurricane (CAT1+), Major hurricane (CAT3+). VMAX is the maximum sustained wind speed and MSLP is the minimum sea-level pressure, both at peak intensity.
3. Statistics and Storm Summaries


Named Storm Days refers to the number of days during which a storm with 35kt+ winds was present. If there are two named storms active during a given day, 2 NSD are accrued, etc. The Hurricane Days value is similar but for storms with 65kt+ winds, and Major Hurricanes Days is for storms with winds 100kt+.

NTC is the Net Tropical Cyclone activity, which is a benchmark that combines the number of storms and the longevity of them (all 12 of the parameters in the table above). The climatological values used here are for the 1950-2000 timeframe. You can learn more about NTC and compare this season to recent past seasons at

A fairly unique aspect of the past season was the late start and early end to the activity. Nearly all of the active portion of the season fit in 10 consecutive weeks, but those 10 weeks were extremely active. Alex formed on 31 July which is the latest formation date since 2000. The outlier was Otto which formed on the last day of the official hurricane season, 30 November. Otto also dissipated on 2 December, after the official end of the season. Three of the past four years have had activity beyond the end of the season.

Following Mitch in October 1998 and Isabel in 2003, Hurricane Ivan joined the ranks of recent Category 5 hurricanes in the Atlantic. Hurricane Ivan was not only a CAT5 storm, but maintained that intensity for a total of 60 hours. Even more noteworthy is that it set the all-time Atlantic record for time spent as a major hurricane at 240 hours (old record was set in 1926 at 222 hours).

Two of the six intense hurricanes (Frances and Ivan) were also notable because they maintained that intensity for so long. Frances contributed 7.25 Intense Hurricane Days, and Ivan contributed 10.00. Combined, Frances and Ivan were the longest-lived intense hurricanes to ever stir up the Atlantic basin with a total of 414 hours and comprised 49% of the season’s NTC.

The NTC reached an amazing 233.1% of the climatological mean, i.e., this season was 2.3 times more active than the "normal" season. If this sounds like a lot, it IS. 2004 had the highest NTC in recorded history, surpassing the amazing years of 1950, 1926, 1995, and 1933.

Here is a brief summary of the individual storms:

Alex formed off the northeast FL coast and headed north along the coast toward the Outer Banks of NC where it reached its peak intensity and caused some damage, although the center of the eye technically never passed over land. It was the strongest hurricane in the Atlantic north of 38°.

Bonnie began as a tropical wave that organized into a Depression, but fell apart for a few days, finally regenerating north of the Yucatan peninsula. The weak Tropical Storm hit the Florida peninsula on August 12 and caused minimal damage.

Charley formed from a tropical wave near Trinidad, then continued through the Caribbean. It passed around Jamiaca and directly over Cuba. It then rapidly intensified only a few hours before making landfall on the Florida peninsula in Charlotte Harbor to a compact Category 4 hurricane. The central pressure fell 24mb in the 6 hours prior to landfall, one of the most rapid falls ever. It crossed directly over Orlando and Daytona Beach, exited over the Atlantic, then hit the NC/SC border, and exited into the Atlantic again, only to hit Long Island, NY before dissipating near Nova Scotia. Charley was the first major hurricane to strike Florida since 1995 and the strongest to strike Florida since 1992. This was also the second costliest hurricane in US history, only behind Andrew 1992.

Danielle formed from a tropical wave very far east… at 23°W. This was the further east that a tropical storm has existed since Alberto in 2000. It recurved very early (by 41°W) and dissipated over open water.

Earl also developed from a tropical wave. It formed rather far south (9°N) and was also moving very quickly to the west. This rapid motion inhibited forming a closed Low and it degenerated to an open wave in the central Caribbean.

Frances was the fifth storm with tropical wave origins, and formed at 36°W. It quickly intensified to a hurricane and major hurricane and tracked over the northern Bahama islands. It made two US landfalls: as a CAT2 near Stuart, FL and as a TS near St. Marks, FL.

Gaston had origins similar to Alex; a Low off the northeast Florida coast. It meandered slowly for a few days, then hit SC as a minimal hurricane, dissipated inland and then reintensified off the Delmarva peninsula before heading out into the open ocean.

Hermine was the third system with non-tropical origins, forming in the mid-latitudes west of Bermuda. It tracked due north and made landfall in MA, but with minimal damage.

Ivan was a classic and infamous hurricane with tropical wave origins. It formed at 29°W and tracked along the southern periphery of the basin, gradually gaining strength as time progressed. It passed directly over Grenada, destroying 80-90% of the structures on the island. It then passed very near Jamaica, the Cayman Islands, and western Cuba. It made US landfall at Palm Shores, AL. The death toll between Grenada, Jamaica, Caymans, Cuba, and the US is over 100. Ivan was the longest-lived major hurricane in Atlantic history (10 days), and had the lowest central pressure (910mb) since Mitch 1998 (905mb).

Jeanne was another remarkable hurricane with tropical wave origins. It formed near Guadeloupe and tracked over Puerto Rico and then stalled over Hispaniola, causing immense flooding problems, completely burying entire communities under mudslides and making it the deadliest storm of the season by far. It eventually moved away from the island and headed north, doing a clockwise loop and heading toward the US. Like Frances, it passed over the northern Bahama islands and made US landfall near Stuart, FL.

Karl was the 8th storm with tropical origins, although it followed an irregular track. It formed at 33°W and recurved by 49°W, taking a course almost due north through the basin. Under nearly ideal conditions, it strengthened to a CAT4 storm and eventually became extratropical in the far north central Atlantic.

Lisa formed from the wave immediately behind Karl, and was never far behind. The track was nearly identical too. However, being the smaller and later to form, Lisa was always suppressed by Karl’s strong outflow.

Matthew was the 4th system to form in the mid latitudes. It formed from a Low in the Bay of Campeche and became a Depression in the central Gulf of Mexico. Under strong vertical wind shear, it never got well organized before making landfall in central LA and dissipating inland.

Nicole was never truly tropical, but was a sub-tropical storm. It formed near Bermuda and headed northeast for a short time before becoming completely extratropical.

Lastly, Otto formed in the north central part of the basin very late in the season. It began as an extratropical Low that gradually acquired tropical characteristics.

Of the 15 named storms, 9 had tropical wave origins, and 6 had extratropical or subtropical origins.

4. Landfall

There were eight landfalling storms this year... all of which made landfall on the U.S. There were two major hurricane landfalls in Florida… the last U.S. major landfall before this year was Bret in 1999, and the last time TWO major hurricanes made Florida landfall in the same year was 1950. The last time there were 8 landfalling named storms was 1916. Of the 10 costliest hurricanes to hit the US, 2004 is responsible for 4 of them, and all 4 rank in the top 6 (Andrew ’92 and Hugo ’89 are in there too).

The first column is the storm name, second column is the date of landfall, third column is the approximate time of landfall (UTC or Zulu), fourth column is maximum sustained winds (kts) at landfall, and the fifth column is the nearest location to landfall (preliminary storm-related deaths and damages are shown in parentheses). A row in italics means there was not a direct hit, but close enough to cause damage.


ALEX         8/3  1700   85  near Cape Hatteras, NC, USA (1 death, $5 million)
BONNIE       8/4  1000   30  St. Lucia, Windward Islands
            8/12  1500   45  Apalachicola, FL, USA (3 deaths)
CHARLEY     8/12  0300   65  near Jamaica (1 death)
8/13  0400   90  Guira de Melena, La Habana, Cuba (4 deaths)
            8/13  2000   70  Punta Gorda, FL, USA (30 deaths, $14 billion)
            8/14  1400   70  Cape Romain, SC, USA
            8/14  1600   65  Myrtle Beach, SC, USA
            8/15  0900   35  Fire Island, NY, USA (1 death)
FRANCES      9/3  0900  105  Eleuthera, Bahamas (extensive)
             9/4  0600   90  Grand Bahama, Bahamas (extensive)
             9/5  0500   90  Stuart, FL, USA (33 deaths, $9 billion)
             9/6  1800   55  St. Marks, FL, USA
GASTON      8/29  1300   65  Awendaw, SC, USA ($130 million)
HERMINE     8/31  0600   35  New Bedford, MA, USA
IVAN         9/7  2000  105  Grenada, Windward Islands (40 deaths, extensive)
            9/11  0300  135  near Jamaica (19 deaths, extensive)
            9/12  1200  135  near Grand Cayman (extensive) ~10 deaths
            9/13  2100  140  near Cabo San Antonio, Pinar Del Rio, Cuba(extensive)
            9/16  0700  115  Gulf Shores, AL, USA (52 deaths, $12 billion)
            9/24  0000   40  Lake Charles, LA, USA
JEANNE      9/14  0400   30  Guadeloupe, Leeward Islands
            9/15  1600   60  Puerto Rico, USA (2 deaths, $200 million)
            9/16  1100   70  Dominican Republic & Haiti (3000+ deaths, extensive)
            9/18  1200   40  Great Inagua, Bahamas (extensive)
            9/25  1200  100  Great Abaco, Bahamas (9 deaths, extensive)
            9/26  0400  105  Stuart, FL, USA (9 deaths, $7 billion)
            9/27  0300   45  St. Marks, FL, USA
MATTHEW    10/10  1100   35  Houma, LA, USA

Hurricane Season 2005 begins June 1; the first names in the lineup are Arlene, Bret, and Cindy. New names for the season are Franklin and Lee, which replace Floyd and Lenny whose names were retired in 1999. As an aside, there will likely be several new names in the 2010 list because of the death and devastation caused by so many of this year’s storms (namely Charley, Frances, Ivan, and Jeanne).

Please visit my tropical Atlantic headquarters.

01 December 2004

Otto weakening...

Convection near the center of the circulation is much weaker today, and
less symmetric.  TS Otto reached a peak intensity around 09Z today at
45kts and 993mb, but has since weakened to 35kts and 999mb.  It has been
drifting to the east to southeast at about 5kts. 

Three of the last four years have gone into "overtime", or post-season
activity.  The storms in recent history that have been active past
November 30 are Olga '01, Odette '03, Peter '03, and Otto '04. 
Something magical about the "O" storms in December??

As I mentioned about two weeks ago, Gaston was officially upgraded to a
hurricane prior to landfall, and that increase in the number of
hurricanes was enough to nudge 2004 into first place in terms of NTC
(Net Tropical Cyclone activity).  Before Otto, NTC was 230.8%, and as of
the 21Z advisory today, the NTC is 232.9%... breaking the old record of
229.6% set back in 1950 by an even larger margin.  Keep in mind that
100% is a climatologically average season.

Once Otto dissipates, I will send out my season summary, done in the
same fashion since 1996!

Please visit my tropical Atlantic headquarters.