Pilot Chart Section showing Wind Roses

Pilot Charts are an excellent source of climate data readily available for the mariner and depict averages in prevailing winds and currents, air and sea temperatures, wave heights, ice limits, visibility, barometric pressure, and weather conditions at different times of the year. The information used to compile these averages was obtained from oceanographic and meteorologic observations over many decades during the late 18th and 19th centuries. The charts are not intended to be used for navigation. 

A valuable tool available on the Pilot Charts are the wind roses that depict the long-term prevailing winds for each 5 degree square of latitude and longitude. The wind roses show the distribution of winds that have prevailed within each square over a long time period. The wind percentages are summarized for the eight points of the compas with the percentage of calms shown in the center of the circle.

Arrows are used to depict the percentage of wind observations that occurred for each direction with the length of the arrow shaft being proportional to the percent frequency. The arrows fly with the wind so the arrow extending out to the south, for example, shows the percent frequency of observations that reported winds blowing from the south. In the example below 37 percent of the observations showed winds from the south. The length of the arrow shaft as measured from the outside of the circle to the tip of the arrow shaft (not the the tip of the feathers) using a provided scale.

Whenever the length is too long to be depicted proportionally, the shaft will be shortened and the percentage will appear as a number on the shaft as in the example below.  The number of feathers on each arrows shows the average force of the wind based on the Beaufort scale so in the example here, the average force of wind from the south was beaufort force 4 (11-16 knots) while the average force from the southeast was force 5 (17-21 knots).

Sample Wind Rose

Pilot Charts can be found on the NGA Portal

Blue lines show the average surface pressue, red lines show the mean extratropical storm tracks, green the mean tropical storm tracks while the red numbers indicated the risk of encountering gale force or higher winds within 5×5 degree squares.

The 500 mb chart can be a useful chart for the weather savvy mariner along with the more familiar surface pressure charts. The 500mb chart is a constant pressure chart which means that everywhere on the chart the air pressure is the same (500mb). This occurs in our atmosphere, on average, at a height of about 5600 meters or about 18,000ft above sea level but varies from place to place due differences in the density of the air column.  

The heights depicted on this chart represent the level at which the air pressure reaches 500mb or about one half the normal surface pressure of about 1013mb).  The lines depicted on the chart are lines of equal height and are given in “tens of meters” above sea level  so that the “540 line” on the chart means that the 500mb level is located at a height of 5,400 meters above sea level.  Heights increase when the air is warmer and less dense and fall when the air is colder and denser so that the distance between these height lines indicates the slope of the 500MB surface.

The 500mb forecast chart is an excellent tool for mariners to estimate where to anticipate the heaviest sea and swell conditions as well as a guide to the expected surface stormtracks and intensities.  On the marine version of the 500mb charts the “564” (5640 meter contour) is highlighted in dark black as it often depicts the southern limit of force 7 westerlies during the winter and force 6 westerlies during the summer.   Also the primary surface low stormtracks will tend to lie about 300 to 600 nautical miles northward of this line.  

A good rule of thumb is that surface lows and fronts will advance at a rate of 1/3 to 1/2 of the 500mb wind speed.  Another rule is that the surface winds in the cold southwestern quadrant of surface lows tend to be about one half the intensity of the 500mb wind speed above.  The closer the height contours on the 500mb chart, the faster the upper level wind flow, the stronger the temperature contrasts and the more active is the surface weather below.  The development and strengthening of surface lows and the associated bad weather most often occurs on the eastern side of 500mb troughs while surface high pressure and good weather is associated with the western side of these troughs.

Without even looking at the surface pressure charts, a mariner can estimate what areas might be best to avoid. Look at the example below of a 500mb 96hr forecast chart and you can see that the strongest 500 mb gradient was forecast to be concentrated off the US East coast and over the waters southward of Nova Scotia and Newfoundland.

NOAA 500MB Forecast Chart for 12Z 11 Dec 2009

NOAA 500 MB Forecast Chart

At the same time, the heaviest sea/swell conditions were forecasted for the same area so in this case westbound traffic to US ports north of Hatteras would have been in for some significant delays.  

NOAA Ocean Wave Height Forecast 12Z 11 Dec 2009

NOAA Wave Forecast Chart for the same time period

An excellent and more detailed look at the use of the 500 mb chart can be found in the December 2008 edition of Mariner’s Weather Log.  

Mariner’s Weather Log Vol. 52 No. 3 December 2008  by Joe Sienkiewicz*, NOAA National Weather Service, Ocean Prediction Center
Lee Chesneau**, Lee Chesneau’s Marine Weather

• Optimum Ship Routing

• Vessel Performance Monitoring

Optimum Ship Routing (Weather Routing)

Optimum ship routing is the art and science of developing the “best route” for a ship based on the existing weather forecasts, ship characteristics, ocean currents and special cargo requirements. For most transits this will mean the minimum transit time that avoids significant risk to the vessel, crew and cargo. Other routing considerations might include passenger comfort, fuel savings or schedule keeping. The goal is not to avoid all adverse weather but to find the best balance to minimize time of transit and fuel consumption without placing the vessel at risk to weather damage or crew injury.

A preliminary routing message is transmitted to the master of a vessel prior to departure with a detailed forecast of expected storm tracks, an initial route proposal with reasoning behind the recommendation and also the expected weather conditions to be encountered along that route or any alternate routes. This allows the master to better plan his route and offers an opportunity to communicate with the routing service any special concerns that he or she might have due to special cargo requirements or ship condition. Once the vessel departs, the vessel’s progress is monitored closely with weather and route updates sent as needed.

Routing services save ship operators money by reducing the average time of transit and therefore also saving on fuel.  By avoiding the worst weather conditions, weather routing minimizes the risk for damage to cargo or ship as well as the risk of injury to crew or passengers. Over time, routed ships benefit from reduce insurance premiums as well based on an improved track record.

Modern ship routing ideas began during the early stages of WWII when the US Navy established the “Naval Meteorology and Oceanography Center” at the Naval Air Station in Norfolk in 1958. “Optimum Track Ship Routing” (OTSR) was started to provide tailored safety and cost saving routing services to all ships utilized by the military for long duration open ocean voyages.

Commercial marine weather routing had it start in the 1950’s when Howard Kaster, a meteorologist for United Airlines, started a company called “Pacific Weather Analysis Corporation” which later evolved into Ocean Routes under Ray Maier and Bill Dupin.  Other pioneers of commercial ship routing in the 1960’s included Bill Kaciak the founder of “Weather Routing Inc.”, Louis Allen who started “Allen Weather Corp” and “Bendix Marine Science Services” under Robert A Raguso.   

Vessel Performance Analysis (Performance Monitoring)

Vessel performance monitoring services allow a ship operator, owner or charterer to get a daily performance analysis regarding a vessel’s speed and fuel consumption based on the charter-party specifications and the actual weather and currents encountered.  Although no weather or routing advice is offered, alerts can be generated to the vessel owner, operator or charterer whenever a performance issue is discovered enroute so that the charterer or vessel operator/owner has a “heads-up” on performance issues prior to the ship’s arrival.  

At the end of the voyage, a full “Voyage Performance Evaluation Report” is generated to offer a more detailed look at the actual performance or non-performance of the vessel.  This report will look at several factors, including the charter party terms, the actual speed and consumption, whether the vessel was in ballast or in a laden condition and the actual wind, sea, swell and ocean currents encountered.  In addition, the performance during “good weather conditions” as specified in a charter party agreement is often reviewed separately.  This type of report can allow a charter to withhold hire or gives the owner/operator a better opportunity to negotiate a settlement or head-off an unwarranted speed claim. 

For more information please visit the Ocean Weather Services website.

1. Wind generated
2. Tides
3. Seiches
4. Tsunamis
5. Pressure induced

1. Wind-Generated

Wind-generated waves are the most common waves found on the ocean and are the result from stress on the water surface caused by the wind. The smallest of these are capillary waves which can be quickly brought back to equilibrium solely by the cohesion of the individual water molecules. Most wind-generated waves, however, are referred to as gravity waves since it is gravity that acts to restore them to equilibrium. Wind driven waves are the waves that have the greatest impact on ships.

2. Tides

Tides are the rise and fall of sea level caused by the gravitational attractions of the moon and sun and by the centrifugal force of the spinning earth.

When the solar and lunar gravitational forces are in line they combine to create the highest of the high tides and lowest of the low tides which are referred to as “spring tides.” When the forces are perpendicular to each other, the forces are pulling the water in different directions so the difference between high and low tides are minimized and is referred to as a “neap tide”.

An illustrated guide to tides can be viewed HERE.

3. Seiches

Image Credit: Keith C. Heidorn, PhD The Weather Doctor’s Weather Almanac Sloshing The Lakes: The Seiche

A seiche is the sloshing of water back and forth in lakes and other large bodies of waters. Seiches can be caused by a disturbance such as an earthquake or landslide, changes in air pressure, or changes in the wind. The most common cause of seiches are persistent strong winds blowing along the long axis of large water body causing a rise in the water level at the down-wind side and a lowering of the water level at the up-wind end.

When the wind abates, the water is released as a seiche wave. Flooding and erosion can occur at one end of the lake, while at the other end the decreased water depth can cause hazards to ship navigation.

4. Tsunami

Recent events in Japan have focused our attention on tsunamis. Tsunamis are long-period waves generated by undersea earthquakes, volcanic eruptions and landslides. In the open deep oceans a tsunami wave will have extremely long wavelengths with small amplitudes and might go unnoticed by ships. Tsunami waves travel at very high speeds, often at hundreds of miles per hour through deep water but as the tsunami waves reach shallow water near the coast, they begin to slow down while gradually growing steeper, due to the decreasing water depth and can grow to tens of meters or more as they reach the shoreline. The effects can be further amplified where a bay, harbor, or lagoon funnels the waves as they move inland and well document during Japan’s recent event. Another potential cause of a tsunami is an asteroid impact in the deep ocean which could produce a tsunami wave of over 100 meters (more than 330 feet)!

5. Pressure Induced

The 5th but less significant type of wave develops as air pressure perturbations move over the water surface. The sea surface height rises or falls slightly as the atmospheric pressure changes. Low air pressure within a strong storm can elevate the ocean’s surface up to 0.5m (1.6ft), creating an atmospherically forced pressure wave beneath the storm.

Wave Definitions

Wave definitions: Image credit NOAA

 Wave definitions: Image credit NOAA

A wave crest is the highest point in the wave and a wave trough is the lowest point in the wave.
Wave height (H) is the vertical distance between the wave crest and the wave trough.

Wavelength (L) is the distance from one crest to the next crest or from one trough to the next trough.

Wave period (T) is the time it takes successive wave crests or successive wave troughs to pass a fixed point. In the real world, the wave period is actually a spectrum of periods scattered about a mean wave period.

Wave steepness (S) is defined as wave height divided by wavelength (S = H/L). Therefore, the same wave height will result in high steepness if the wavelength becomes smaller. A small height divided by a large length will produce a low steepness. When the wave steepness exceeds about 1/7 the wave will begin to break or “white cap.”

Wave speed (C) is the speed an individual wave moves through water. If the wave period (T) and wave length (L) are known, then the wave speed (C) can be determined by C=L/T

Other Wave Facts:

Deep Water or Shallow Water
A wave is considered to be a deep water wave as long as water depth exceeds 1/2 the wavelength. A wave is considered to be a shallow water wave as long as water depth is less than 1/20 the wavelength. The area between deep and shallow water is transition zone.

Wave Energy
Wave energy increases by a factor of 4 as the wave height doubles so a 10ft wave is four times more powerful than a 5 ft wave.

The significant wave height (Hs) is the mean height of the highest one third of the waves passing a point. This is of interest as this wave height correlates best with the wave height a trained observer reports after examining a group of wave heights from a ship or platform. The averaged periods of the waves used to compute significant wave height is known as the significant wave period.

Statistical distribution of wave heights

 Statistical distrubution of wave heights

Useful wave height relationships:

Hm (Mean wave height) = 0.64 times Hs
Hs or H1/3 = Significant wave height
H1/10 (Highest 10% wave height) = 1.27Hs
H1/100 (Highest 1% wave height) = 1.67Hs
Hmax (Max probable wave height for a large sample) = about 2.0Hs

Ocean Swell is defined as any wave that has moved out of its wind generation source region. Swells characteristically exhibit smoother, more regular and uniform crests and a longer period than wind waves.

Combined Seas describes the combination or interaction of wind waves and swells in which the separate components are not distinguished. Combined Seas (CS) is the square root of the square of swell plus the square of wind waves: The National Weather Service considers the combined seas as being the same as significant wave height.

A wall of water approaches the Stolt Surf in Oct. 1977 Photo Credit: Karsten Petersen, www.global-mariner.com

A wall of water approaches the Stolt Surf in Oct. 1977 Photo: Karsten Petersen, www.global-mariner.com

Rogue waves

Rogue waves (sometimes called freak waves) are simply unusually large waves appearing in a set of smaller waves. A rogue wave will have a height of at least twice the size of surrounding waves, often come from a direction different than the prevailing waves, and they are unpredictable. Most reports of extreme storm waves say they look like “walls of water,” and are seen as steep-sided with unusually deep troughs. The USS Ramapo reported one such wave with a height of 112 feet in the Pacific in 1933.  Another report of a freak wave occurred when one struck the Queen Mary amidships, south of Newfoundland, at the end of World War II, rolling her to within a degree or two of capsizing.

References

The Weather Doctor, Keith C. Heidorn: ”Weather Almanac for June 2004: SLOSHING THE LAKES: THE SEICHE”

NOAA NWS JetStream – Online School for Weather: Wind, Swell and Rouge Waves

NOAA NWS JetStream – Online School for Weather: Tides

NOAA Ocean Service Education:  Tides and Water Levels

Sailor - Global Mariner Photos by Karsten Petersen

Wikipedia, the free encyclopedia: Rogue Wave

Flying Enterprise Image Credit Leigh Bishop www.deepimage.co.uk

Captain Carlsen was a Danish-born seaman that began his sea career at the age of 14 and became master of his first ship at the age of 22 with the Danish-American company American Export-Isbrandtsen Lines which was a New York based US-flag shipping company from 1919 to 1977, offering both cargo and passenger ship services. In 1977 it declared bankruptcy and was acquired by Farrell Lines.

In December 1951 Captain Carlsen was Master of the Flying Enterprise, a 6711 GT cargo ship of the “C1-B” type, a small cargo ship built for the U.S. Maritime Commission before and during WWII.  Most of the C1-B class had steam turbine engines and were built in six different yards, however, the majority of them, including The Flying Enterprise were built at the Consolidated Steel Corporation in Wilmington, California. The Flying Enterprise was built in 1944 as the SS Cape Kumukaki for use during World War II.  The ship was sold in 1947 and then operated as a tramp steamer under the name Flying Enterprise.  

NOAA Daily Weather Map Dec. 23, 1951

On December 21, 1951, The Flying Enterprisedeparted Hamburg, Germany bound for New York with a cargo that included 1,300 tons of pig iron, 900 tons of coffee and 10 passengers. From the departure out of Hamburg through the English channel the vessel encountered heavy fog.  Late on the 23^rd of December, as the Flying Enterprise was steaming southward in fog towards the English Channel, a weak surface low of 1016mb was noted over Michigan. 

UK Met Office Surface Analysis 06Z Sunday 23 Dec 1951

After transiting through the English Channel on Christmas Eve, the Flying Enterprise first encountered heavy weather due to a strong low pressure area that was moving well northward of Ireland and Scotland.

The heavy weather contiuned through Christmas Day and the day after Christmas as the vessel passed out of the Channel and into the North Atlantic.  As gale force winds increased to storm force 10 by the night of Dec. 26, Capt. Carlsen decided to heave the vessel to as winds contined to increase and approach force 12 (hurricane).  At the same time the weak disturbance far to the west moved out over the western North Atlantic and began to deepen reaching 1006mb by 12Z Christmas Day as it passed southward of Cape Race, Newfoundland.  Twenty-four hours later, at 12Z on December 26^th, the western low was rapidly deepening into a 974mb storm low and was racing east-northeastward near 50N 24W.

NOAA Reanalysis for 12Z 26 December 1951

Rapid deepening continued through the 26^th and by 06Z on Dec. 27^th the now violent storm low had reached 944mb near 55N 12W,  just as it passed to the north of the Flying Enterprise position.   (Between Dec 25/12z to Dec 27/06z the storm had deepened 62mb in just 42 hours!).

As the storm center passed north of the Flying Enterprisethat morning, the vessel encounterd what was described as “a very high sea” at position 50-41N 15-26W (about 400 miles west of Lands End). Several load bangs where heard (like the firing of a gun) throughout the ship and an examination determined that the vessel had sufferd two main fracures.  The first began at the after port corner of #3 hatch and ran across the deck and back to the accommodation ladder opening at the side and ran down the side to the longitudinal riveting at the base of the sheer strake. 

UK Met Office Surface Analysis for 06Z Thursday 27 Dec 1951

On the starboard side the crack ran from the forward corner of the deck house straight across to the accomation opening and from there down to the riveting as on the opposite site. The cracks  were estimated to be between 1/8 and 3/8 inches in width.  A smaller crack ran from the after starboard corner of the #3 hatch toward the side of the ship and was estimated to be 18 inches long.  At the time, Capt. Carlsen reported force 12 winds and 40ft seas.  A measurement of the pressure gradient near the vessel suggests winds were at least 60kts which would be consistent with a violent storm BF 11 (56-63 kt wind and 30-45 ft waves) and could have easily reached force 12 at times.   

Given the ship’s position it is apparent that the captain had set out on a minimum distance great circle route from Bishop Rock towards Nantucket.  Had Carlsen chosen a more southerly wintertime track, perhaps the vessel would not have encountered conditions that severe.   

In an effort to reduce the strain on the now damaged vessel, Capt. Carlsen turned the ship southwestward so that the wind and sea were broad on the bow and later more southerly bringing the wind almost abeam.  During this time period, Carlsen had the crew fill the cracks with cement then run cable from the bitts at #3 hold to bitts aft in order to bind the deck together. 

UK Met Office Surface Analysis for 06Z Friday 28 Dec 1951

As the Flying Enterprise proceeded south keeping the seas on the starboard beam, Capt. Carlsen concluded that he must put in at either an English or French port or head to the Azores for repairs. During the night of the 27^th into the morning of the 28^th as yet another storm passed to the north, the vessel experienced rolling of up to 20 degrees. At about 1130 on the morning of the 28^ththe vessel was hit broadside by another high wave which rolled the vessel between 50-70 degrees to port shifting the cargo and causing the vessel to return to a permanent list of about 25 degrees.  The list increased gradually and eventually the engine lost lubrication oil due to the list which resulted in the loss of both boilers forcing Capt. Carlsen to have his radio operator send out an SOS.

Flying Enterprise Listing Heavily - Image Credit Leigh Bishop www.deepimage.co.uk

The SOS was answered by several ships and the passengers and crew were rescued in heavy seas by lifeboats from the US Navy troop ship USS General A W Greely and the steamer Southland on Dec. 29^th.  Because of the heavy list, the lifeboats on board the Flying Enterprise could not be launched and both passengers and crew were forced to jump into the cold North Atlantic before being recovered by the lifeboats. One middle-age passenger drowned during this operation, otherwise, all of the remaining passengers and crew were successfully rescued. 

Captain Carlsen chose to remain with his ship in order to wait for the arrival of a salvage tug.  The salvage tug Turmoil finally arrived on January 3^rd some 5 days after the passengers and crew were rescued but it quickly became evident that it would be impossible for Capt. Carlsen, alone aboard a heavily listing vessel (now listing at 60 degrees), to secure a tow line himself.

After several unsuccessful attempts to secure the tow line, the 27-year-old chief mate on the Tug Turmoil, Kenneth Dancy, leaped from the deck of the tug onto the railing of the Flying Enterprise on one of the very close approaches made by Capt. Dan Parker of the Turmoil during one of the failed attempts to secure the tow line.  With Dancy’s help, however, a tow line was secured and the long tow back towards Falmouth England began.

As the tug and tow approached the English coast on January 8^th the weather started to deteriorate and on January 9^th, just 45 miles from Falmouth, heavy seas parted the towline.  The Flying Enterprise drifted eastward while several attempts were made to re-secure another towline but all attempts were unsuccessful.   At 1536 on the afternoon of January 10, 1952 as the Flying Enterprise, now listing at 90 degrees and taking water down the stack both Dancy and Carlsen jumped into the sea from off the stack and were taken aboard the Turmoil where they watched the Flying Enterprise sink under the waves, stern first at 1609.

Flying Enterprise just prior to sinking - Image Credit Leigh Bishop www.deepimage.co.uk

By now this ongoing sea drama was being reported around the world and Capt. Carlsen had become world-famous for staying on his crippled freighter. Captain Carlsen received a hero’s welcome when he came ashore at Falmouth and later was awarded the Lloyd’s Silver Medal for meritorious service in recognition for his attempts to save his ship.

Carlsen received a ticker-tape parade in New York City on January 17^th and a few months later took command of the Flying Enterprise II, passing up several lucrative offers from Hollywood for his story.  Carlsen, and his ordeal aboard the Flying Enterprise, is the subject of  an excellent the book “Simple Courage: a True Story of Peril on the Sea” by Frank Delaney.

The US Coast Guard inquiry found that the damage, abandonment and loss of the vessel were caused by circumstances beyond the control of the master and crew.  The fracture sustained while hove to in head seas was not a direct cause of the vessel’s loss but merely an indirect contribution to the loss.

The Coast Guard did remark about the stowage of the pig iron cargo in #2 hold and noted that it was not leveled out as was the pig iron in #4 hold but was stacked in a pyrimid shape.   The report stated that this did constitute a certain hazard as to shifting, however, this type of stowage  was a common practice at the time and had been sanctioned by the shipper, underwriter, owner and the master.   It was also believed that the empty condition of the double bottoms aft and the deep tanks in #4 hold had an appreciable effect on the great degree of list which the vessel took. 

References and Links

Wikipedia article on the Flying Enterprise

Wikipedia article on Henrik Kurt Carlsen    

Wikipedia article on American Export Lines 

Wikipedia article on Type C1 Ships  

Frank Delaney, Simple Courage – A True Story of Peril on the Sea  

Beaufort Wind Scale: NOAA 

Explore the Flying Enterprise wreck at www.deepimage.co.uk

US Coast Guard Marine Board of Investigation: Flying Enterprise    

UK Met Office

News Reels

British PATHE Newsreels 1952 – Flying Enterprise

Universal Newsreel from criticalpast.com “The SS Flying Enterprise ship sinks in the Atlantic Ocean”

Edmund Fitzgerald - Image Credit NOAA

At 1915UTC on the 9th, the Edmund Fitzgerald departed from Superior, WI bound for Detroit. A short time later, the Arthur M. Anderson left Two Harbors, MN and was also headed eastbound. Both masters decided to take a northerly route to keep in the lee of the forecasted northerly gale winds.

Edmund Fitzgerald Most Probable Track - American Meteorological Society

At first, the Arthur M. Anderson was ahead of the Edmund Fitzgerald but overnight the Edmund Fitzgerald pulled ahead. At 0700UTC on the 10^th the National Weather Service issued a Storm Warning for Lake Superior as the now deepening low was moving northeastward reaching a position near Marquette, Michigan by 1200 UTC (982mb).  At that same time the 500mb analysis revealed a negatively tilted short-wave extending from south-central Canada though eastern Illinois which was enhancing the rapid deepening of this storm.

500mb Analysis 1200 UTC 10 Nov 1975 – Image: American Meteorological Society

At 2030UTC on November 10^th, the master of the Edmund Fitzgerald (Capt. McSorley) reported that a fence rail was down and that a couple of vents were lost and that the vessel was developing a list so he decided to reduce speed in order to allow the Arthur M Anderson to close the distance between them. Just 40 minutes later, Capt. McSorley reported that both of his radars were out of order and asked the master of the Arthur M Anderson if they could assist with navigation.

NOAA Daily Weather Map 12Z November 10. 1975

During the period between 1800 UTC November 10^th and 0000 UTC November 11^th the low moved northeast to near James Bay deepening to 978mb causing westerly to northwesterly winds to increase over Lake Superior. At 2139UTC the Coast Guard reported that the radio beacon at Whitefish Point was not functioning. Between 2200 and 2230 UTC Capt. McSorley reported that the vessel was now listing badly and that they were taking heavy seas over the deck. At 0010 UTC on the 11^th, Capt. McSorley reported “We are holding our own” but this was the last message sent by the doomed vessel. 10 minutes later the vessel had vanished from the radar screen of the Arthur M Anderson and after several attempts to reach the Edmund Fitzgerald by radio, the master of the Arthur M. Anderson informed the U.S. Coast Guard that the Edmund Fitzgerald may have suffered a casualty.

Storm Reanalysis

A reanalysis of this event was done in 2005 by NOAA, National Weather Service utilizing the Regional Atmospheric Modeling System (RAMS). The model run started at 0000 UTC 9 November 1975 and ran through 0600 UTC 11 November 1975.

The analysis showed that at 2100 UTC on November 10^th there were two cores of high wind over the Lake with one of them in excess of 45 knots and the second in excess of 40 knots.  The highest winds occurred over the southeastern part of Lake Superior where the Edmond Fitzgerald was heading.  Wave heights increased to near 6 meters and by 0000 UTC November 11^th and winds were exceeding 45 knots over most of southeastern Lake Superior.

Edmund Fitzgerald Wave Heights 01Z Nov 11 1975

The Edmund Fitzgerald sank at the eastern edge of the area of high wind where the long fetch (distance that the wind blows over water) produced significant wave heights (average of the highest 1/3 of waves) to over 7 meters (23 ft) by 0000 UTC and to over 7.5 meters (25 ft) at 0100 UTC with a maximum significant wave of 7.8 meters (26ft). Given a significant wave of 7.5 meters (25ft) about 1 in 100 waves could reach over 11 meters (36ft) and one out of 1000 waves could have been as high as 14 meters (46ft). Since the vessel was heading east-southeastward, the waves were quartering to following which resulted in heavy rolling.

At the time of the sinking he Arthur M Anderson reported NW winds of 50 knots which matched the model output of 47 knots. The model showed that the maximum sustained winds occurred between 0000 and 0100 UTC at 60- 65 knots with gusts upwards of 75 knots. Just a couple hours later (0300 UTC) conditions had eased to under 45 knots.

The National Transportation Safety Board determines that “the probable cause of this accident was the sudden massive flooding of the cargo hold due to the collapse of one or more hatch covers. Before the hatch covers collapsed, flooding into the ballast tanks and tunnel through topside damage and flooding into the cargo hold through non-weathertight hatch covers caused a reduction of freeboard and a list. The hydrostatic and hydrodynamic forces imposed on the hatch covers by heavy boarding seas at this reduced freeboard and with the list caused the hatch covers to collapse.

Contributing to the accident was the lack of transverse weathertight bulkheads in the cargo hold and the reduction of freeboard authorized by the 1969, 1971, and 1973 amendments to the Great Lakes Load Line Regulations.”

Sources:
Reexamination of the 9–10 November 1975 “Edmund Fitzgerald” Storm Using Today’s Technology BY THOMAS R. HULTQUIST, MICHAEL R. DUTTER, AND DAVID J. SCHWAB; American Meteorological Society  2006 

US Coast Guard National Transportation Safety Board Bureau of Accident Investigation (1978) 

S.S. Edmund Fitzgerald Online  

Great Lakes Shipwreck Museum

NOAA News

You Tube Tribute

Fred Pickhardt

One of the most significant hurricanes to hit Tampa occurred 90 years ago this month. The first  recorded major hurricane to hit Tampa occurred 73 years earlier in September of 1848.

Thomas B Garland Tampa Hurricane 1921

The Chief Hydrographer at the Panama Canal may have reported the first indication of a developing disturbance over the Caribbean Sea between October 13th and 18^th when the barometer fell steadily and winds prevailed out of the north with frequent heavy rains, particularly on the Pacific side of the Canal Zone. Suddenly, on Oct. 18th, the winds reversed and blew steadily from the south ending the rain. The wind also picked up after the 18th, averaging nearly 20 mph between the 20th and the 22nd with a peak 5-minute wind speed of 35 mph. 

On October 21st the first indications of disturbance was reported by other Caribbean stations and a few weather-reporting ships over the Caribbean sea which caused the US Weather Bureau to issue its first advisory at 10 am that day:

 ”A disturbance appears to be forming over the western Caribbean Sea southwest of      Jamaica; movement uncertain, but probably northward”

The developing disturbance moved north-northwest from the Southwestern Caribbean Sea passing near Swan Island on the 22nd where the barometer dropped to 29.20 inches (989mb) between 10 am and Noon. The wind, which had been blowing out of the north across the island, shifted to the south-southwest and reached a peak velocity of 80 mph (70 knots). A hurricane had indeed been born!

By October 23rd the hurricane moved through the Yucatan Channel where the schooner Virginia reported a minimum pressure of 27.80 (941mb) as it entered the eye of what was now a category 4 hurricane. The next day the SS El Estero at latitude 25-36N longitude 84-24W encountered the eye of the hurricane at about 10 pm as the barometer reached a minimum of 27.84 inches (943mb). At noon that same day, a Hurricane Warning was issued for the West Coast of Florida from Key West to Apalachicola.

The 1921 Tampa Hurricane Image Credit NOAA

During the night of the 24th and the morning of the 25th the hurricane turned toward the north-northeast then later northeast finally making landfall near Tarpon Springs, Florida where a minimum barometer reading of 28.12 inches (952mb) was recorded at about 2:15 PM that same afternoon. This reading suggests that a max wind at landfall of about 110 knots (125mph) which would make this storm a Cat 3 hurricane.  After landfall, the storm tracked east-northeast across Florida exiting near Daytona Beach early on the 26th as a Cat.1 hurricane. 

The US Weather Bureau office in Tampa reported a storm surge of 10.5 feet above mean low water at about 2 PM EST on the 25th and a rainfall total of over 8.5 inches, along with a minimum barometer reading of 28.81 inches (976 mb). The radius of hurricane force winds was fortunately small and the peak wind reported at Tampa was 59 knots (68mph) with a peak gust of 75 mph recorded atop a tall building in downtown Tampa. The adjusted surface peak wind was later estimated to have  been 49 knots (56 mph). 

NOAA NWS Storm Surge Simulation of 1921 Hurricane

Ship Favorite aground October 1921 - Image Credit Hillsborough County Public Library - Burgert Brothers Collection

Most of the damage done by this storm in Tampa and St. Petersburg was due to the storm surge. The 10.5 foot storm surge in Tampa Bay was the highest since the Great Gale of 1848. The tide swept over the seawall along Bayshore Drive in Tampa flooding some of the most expensive houses in the city. There was considerable flooding in downtown Tampa where 3 people were reported as drowned.

At St. Petersburg the tide was reported at 8 feet 5 inches above normal and all four city piers were badly damaged or destroyed. At Egmont Key and at Sanibel island to the south, the tide was reported to have nearly covered both islands with water. Flooding was also severe at Palmetto Beach, Edgewater Park and Desoto Park where some houses had the water rise up to the second story windows. At Palmetto Beach 50 houses were reported destroyed by the tide and by drifting cedar logs that were chained together and had been enroute to the Tampa box company to be made into cigar boxes. Many vessels were wrecked or washed ashore including the “Geneveve”, the “Hypnotist”, the “Pokonoket” and the steamer “Favorite”.

An American vessel SS Truxillo weathered the storm 24 miles west of Edgmont key and reported the following weather in her logbook:

Date/Time       Barometer         Wind in Beaufort Force
24th Midnight  29.62               East Hurricane Force (73+ mph)
25th 04:00       29.27               East Force 11 (64-72mph)
25th 06:30       29.00               East Hurricane Force (73+ mph)
25th 08:00       28.90               East Hurricane Force (73+ mph)
25th 10:20       28.28                Calm, Terrific cross sea
25th 10:50       28.28                West Hurricane Force (73+ mph)
25th 11:00       28.32                West Hurricane Force (73+ mph)
25th Noon        28.40               West Hurricane Force (73+ mph)
25th 16:00       29.02               West Force 11 (64-72mph)
25th 20:00       29.36               North Force 10 (55-63mph)
25th Midnight  29.48               North Force 9 (47-54mph)

Overall damage was estimated to be at about $3 million (1921 dollars). The total number of hurricane related deaths is unknown but at least 8 deaths were directly related to the storm. 

 Then and Now The 1921 Hurricane 

 References/Resources:
Barnes, J., 1998: Florida’s Hurricane History. The University of North Carolina Press, Chapel Hill

Bowie, E. H., 1921: The hurricane of October 25, 1921, at Tampa, Fl. Mon. Weather Review v., 49, 567-570.

Ballingurd, David It Could Happen Here St. Petersburg Times

Other Sources:

NOAA NWS Tampa Bay: 1929 Tarpon Springs Hurricane

THE REANALYSIS OF ATLANTIC BASIN TROPICAL CYCLONES FROM THE 1920s: A REEXAMINATION OF THREE CATASTROPHIC HURRICANES THAT IMPACTED FLORIDA  By Steven E. Feuer, Christopher W. Landsea, Lenworth Woolcock, and Joyce Berkeley
NOAA/AOML/Hurricane Research Division, Miami, Florida

1921 Hurricane: The Forgotten Nightmare  NOAA NWS Tampa Office

The Burgert Brothers Photography Collection – 1921 Hurricane
At the Tampa-Hillsborough County Public Library