1-2-3 To Hurricane Safety

[GordMay]

DETERMINING THE HURRICANE DANGER AREA

1. Plot the initial and forecast hurricane positions on a navigation chart.

2. Find the maximum radius of 34 KT winds at the initial, 24, 48, and 72 hour forecast times of the Tropical cyclone forecast messages (TCM).

3. Apply the 1-2-3 rule to each of the radii at the 24, 48, and 72 hour forecast positions.

4. Draw a circle around the hurricane initial position with radius equal to the maximum radius of 34 KT winds given in the TCM.

5. Draw circles around the 24, 48, and 72 hour forecast positions of the hurricane using the respective radii found in step 3.

6. Connect tangent lines to each circle constructed in steps 3 and 4 along both sides of the hurricane track.

7.The area enclosed by these tangent lines is known as the danger area of the hurricane and must be avoided as a vessel attempts to navigate in the vicinity of the hurricane.

1-2-3 Rule of Thumb
1- 100 mile error radius for 24hr forecast
2- 200 mile error radius for 48hr forecast
3- 300 mile error radius for 72hr forecast

Mariner’s Guide For Hurricane Awareness In The North Atlantic Basin
http://www.nhc.noaa.gov/marinersguide.pdf

[GordMay]

The Saffir-Simpson Hurricane Scale
The scale was formulated in 1969 by Herbert Saffir, a consulting engineer, and Dr. Bob Simpson, director of the National Hurricane Center.

The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf in the landfall region. Note that all winds are using the U.S. 1-minute average - not the International 10-minute average*.

* Since surface winds and gusts can change dramatically over short time intervals, it is necessary to define the length of time over which the winds are to be measured. For a cyclone of some given intensity, longer wind averaging times will yield lower maximum winds. Unfortunately, different meteorological services use different averaging times. Following World Meteorological Organization (WMO) guidelines, most regions use a 10-minute average. However, the Joint Typhoon Warning Center (JTWC), Guam, and WMO Region IV (United States and Caribbean area) use a 1-minute standard average. This use of a different time base results in sustained winds on foreign warnings being about 12 percent lower than those of U.S. warnings.

Storm Category ~ Barometric Pressure (Inches) ~ Winds (MPH) ~ Storm Surge (Feet)
1 ~ 28.94" ~ 74 – 95 mph ~ 4 – 5'
2 ~ 28.50 – 28.91" ~ 96 – 110 mph ~ 6 – 8'
3 ~ 27.91 – 28.47" ~ 111 – 130 mph ~ 9 – 12'
4 ~ 27.17 – 27.88" ~ 131 – 155 mph ~ 13 – 18'
5 ~ 27.17" ~ 155 mph ~ 18'+

Tropical Depression < 39 mph
Tropical Storm 39-73 mph

Category One Hurricane:
Winds 74-95 mph (64-82 kt or 119-153 km/hr). Storm surge generally 4-5 ft above normal. No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs. Also, some coastal road flooding and minor pier damage. Hurricanes Allison of 1995 and Danny of 1997 were Category One hurricanes at peak intensity.

Category Two Hurricane:
Winds 96-110 mph (83-95 kt or 154-177 km/hr). Storm surge generally 6-8 feet above normal. Some roofing material, door, and window damage of buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of the hurricane center. Small craft in unprotected anchorages break moorings. Hurricane Bonnie of 1998 was a Category Two hurricane when it hit the North Carolina coast, while Hurricane Georges of 1998 was a Category Two Hurricane when it hit the Florida Keys and the Mississippi Gulf Coast.

Category Three Hurricane:
Winds 111-130 mph (96-113 kt or 178-209 km/hr). Storm surge generally 9-12 ft above normal. Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large trees blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the center of the hurricane. Flooding near the coast destroys smaller structures with larger structures damaged by battering from floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences with several blocks of the shoreline may be required. Hurricanes Roxanne of 1995 and Fran of 1996 were Category Three hurricanes at landfall on the Yucatan Peninsula of Mexico and in North Carolina, respectively.

Category Four Hurricane:
Winds 131-155 mph (114-135 kt or 210-249 km/hr). Storm surge generally 13-18 ft above normal. More extensive curtainwall failures with some complete roof structure failures on small residences. Shrubs, trees, and all signs are blown down. Complete destruction of mobile homes. Extensive damage to doors and windows. Low-lying escape routes may be cut by rising water 3-5 hours before arrival of the center of the hurricane. Major damage to lower floors of structures near the shore. Terrain lower than 10 ft above sea level may be flooded requiring massive evacuation of residential areas as far inland as 6 miles (10 km). Hurricane Luis of 1995 was a Category Four hurricane while moving over the Leeward Islands. Hurricanes Felix and Opal of 1995 also reached Category Four status at peak intensity.

”Andrew” became a hurricane on August 22 and strengthened to a strong category 4 hurricane the next day. As it moved westward, it weakened to 941 millibars as it passed over Great Bahama Bank on the 24th, but rapidly re-intensified as it moved over the Gulfstream on its approach to Florida. Andrew was the third most intense U.S. land-falling (August 24, 1992) hurricane this century, and the strongest since Hurricane Camille in 1969. With a central pressure of 922 mb, and sustained wind speeds of 125 knots (about 145 mph) with gusts near 150 knots (175 mph), Andrew was a Category Four hurricane. Andrew came ashore near high tide and brought with it a 16.9 foot storm tide (the sum of the storm surge and astronomical tide) into Biscayne Bay, a record maximum for the southeast Florida peninsula. After striking Florida, Andrew moved northwest across the Gulf of Mexico to make a second U.S. landfall in a sparsely populated area of south-central Louisiana as a Category 3 storm on August 26.

Category Five Hurricane:
Winds greater than 155 mph (135 kt or 249 km/hr). Storm surge generally greater than 18 ft above normal. Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. All shrubs, trees, and signs blown down. Complete destruction of mobile homes. Severe and extensive window and door damage. Low-lying escape routes are cut by rising water 3-5 hours before arrival of the center of the hurricane. Major damage to lower floors of all structures located less than 15 ft above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5-10 miles (8-16 km) of the shoreline may be required. Hurricane Mitch of 1998 was a Category Five hurricane at peak intensity over the western Caribbean. Hurricane Gilbert of 1988 was a Category Five hurricane at peak intensity and is one of the strongest Atlantic tropical cyclones of record.

[GordMay]

"HURRICANE MODELS INFORMATION"
This page contains information of interest to those who want to know what computer models are being used for forecasting and a layman's explanation of what those models do and the basis for their design and operation. This page lists and describes the "movement", "intensity", and "surge" models.
http://www.hurricanealley.net/hurmdls.htm

and

"Summary of the NHC/TPC Tropical Cyclone Track and Intensity Guidance Models"
http://www.nhc.noaa.gov/aboutmodels.shtml

A tropical cyclone forecast involves the prediction of several interrelated quantities, but the fundamental element of the forecast is the future motion of the storm. Track prediction serves as the basis for forecasting other storm features, such as winds, rainfall, and storm surge, and, of course, the areas threatened. Normally, motion forecasts out to 72 h are issued every 6 h.
Three different types of computer models are used by NHC: statistical, dynamical, or combination (statistical and dynamical together).
Statistical models use current information about the hurricane and compare it to historical data about the behavior of similar storms. The historical record for storms over the north Atlantic begins in 1871, but the record for the east Pacific only goes back to 1945.
Dynamical models work differently. To make a forecast, they combine computer simulations of the atmosphere with inputs of current wind, temperature, pressure, and humidity conditions. Dynamical models ignore historical storms. Combination models use the strengths of both models.

Today's three-day forecast is as accurate as a two-day forecast during the late 1980s.
Average errors in the hurricane tracks are now:
24-hours: 80 miles (40%-50% Probability of exact accuracy)
48-hours: 110 miles (20%-25% Probability)
72 hours: 230 miles (10%-15% Probability)

[GordMay]

Hurricane Survival ~ by Brad Glidden
” The time for taking all measures for a ship's safety is while still able to do so. Nothing is more dangerous for a seaman to be grudging in taking precautions lest they turn out to have been unnecessary. Safety at sea for a thousand years has depended on exactly the opposite philosophy ...”
- Fleet Admiral Chester Nimitz

Part One: Prepare for Pop Ups
http://www.caribbeancompass.com/hurrisurvival.htm

Part Two: Get Ready, Get Set
http://www.caribbeancompass.com/hurrisecure.htm

Part Three: Preparing for the Worst
http://www.caribbeancompass.com/theworst.htm

and

Cruising Below the Belt ~ by Roger Marshall
” Cruising during hurricane season can be like adultery: fascinating, exciting, fun, and challenging, but woe to him who is caught! This is a first-hand review of the joys and the pitfalls of cruising below the so-called "hurricane belt" in the hurricane season. The southern boundary of the hurricane belt, we'll say, is 12̊40'N.
Come summer in the Caribbean, many cruisers store their boats in so-called safe havens and head for home either in the US or Europe. These cruisers are missing some of the best cruising the Caribbean has to offer. The summer months are for the most part blessed with idyllic conditions: benign weather, calm seas and moderate winds.
I must hasten to add, however, that summer is the hurricane season, and an idyllic cruise can change into a living hell if the necessary precautions are not taken in time ...
Goto: http://www.caribbeancompass.com/belowbelt.htm

[GordMay]

2005 Hurricane Season - It Ain’t Over 'Til It’s Over ~ http://www.ato.faa.gov

September 29/05: It’s a quiet day in the Western Atlantic and Caribbean. No hurricanes, no named tropical storms, not even an active cyclone. After the havoc caused by Katrina and Rita in rapid succession, nature is giving us a needed break. The 2005 hurricane season has been an active one: eighteen named storms, nine of which became hurricanes. That substantially outpaces the seasonal average of ten storms and six hurricanes. Worse yet, it’s not over.

The official hurricane season for the Atlantic Basin (which includes the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico) is from June 1 to November 30. Over the past one hundred years the earliest date a hurricane has struck the United States was June 9 in 1966, and the latest was November 30 in 1925. They have been observed as early as March 7 and as late as December 31. The peak of the season, however, is from mid-August to late October.

The season got off to a fast start when Tropical Storms Arlene and Bret formed during the month of June. There have been only twelve previous years since 1851 in which two or more storms formed in that month. In July, the Atlantic Basin saw unprecedented cyclone activity with the development of five named storms, breaking the previous record of four. The two major hurricanes that developed that month tied a record set in 1916. The combined total of seven storms for the two-month period established a record level of activity to begin the season.

The month of August was merely above average with the development of five tropical storms and two hurricanes. Unfortunately, one of those was Katrina. It is expected that Katrina will be recorded as the worst natural disaster in the history of the United States. It became a Category 5 storm on August 28. At that time it was located 250 miles south-southeast of the mouth of the Mississippi River and had peak winds of 175 mph. The hurricane came ashore near Plaquemines, Louisiana, early on August 29 as a Category 4 storm with winds of 140 mph. The full extent of its destruction is yet to be estimated.

The final tally for September will include at least five additional hurricanes, most of which remained in the Atlantic. Rita, the exception, was the seventeenth named storm of the season and the ninth hurricane. It reached Category 5 status on September 21, setting a record based on achieving a minimum central pressure of 897 millibars. With Katrina fresh in memory, widespread evacuations took place in coastal sections of southeast Texas and southwest Louisiana. Only three Category 5 hurricanes have made recorded landfall in the United States, one of those being Hurricane Andrew which brought widespread destruction to southeast Florida and southeast Louisiana in 1992. As luck would have it, Rita came ashore near Sabine Pass, Texas, as a Category 3 storm. As bad as it was for those living in the affected area and in recovering New Orleans, it could have been far worse.


What will October bring? If it were simply an average year, we would still have cause for concern through late October. Texas and Louisiana, states that suffer an equally high level of threat from major hurricanes in August and September, might start to relax a little. Florida, on the other hand, is most likely to see a major hurricane in October.

In spite of the improving outlook for the month of October, in most areas other than Florida, the risk this year remains elevated beyond the norm. William Gray and Philip Klotzbach of the Colorado State University Department of Atmospheric Science note that the current hurricane season is the most active since 1933. That year there were 21 tropical storms, five of which became major hurricanes. With two months left in this season, Gray and Klotzbach predict three more named tropical storms in October alone, two of which are expected to become hurricanes and one of which may be a major hurricane.

The 2005 Atlantic hurricane season is already one for the record books. Most powerful storms don’t form until mid-August, with September 10 usually considered the peak. This year five hurricanes formed in July. Two of them, Dennis and Emily, became the most powerful hurricanes on record for that month. Gray and Klotzbach expect that by the time the 2005 hurricane season is over, we will have witnessed tropical cyclone activity at near-record levels.

Throughout most of October the likelihood of hurricanes remains high, but, given the extraordinary year to date, we need to remember that the season doesn’t officially end until November 30.
http://www.ato.faa.gov