Some of the factors considered in assessing the severity of Coastal storms:
WIND VELOCITY
Wind velocity is simply the speed of the wind, meteorologically it is described
in Knots or occasionally as miles-per-hour.
WIND FETCH
Wind fetch is the unobstructed distance the wind has traveled before it,
or something it is acting on (such as the waves in the ocean), encounter
a significant obstruction (i.e. in the case of waves, a shoal).
WIND DIRECTION
The direction from which the wind blows greatly effects the extent of damage
to a particular location (sheltered or unsheltered), or, in the case of
a ship at sea, it will even indicate the magnitude of the storm threat.
TIDAL STATE
This is a vertical measure of the relative water level. Normally it is expressed
as decimal feet above mean (average) sea level or decimal feet above mean
low water (average of the normal low waters).
AIR DENSITY
This is both a temperature and a humidity component. Relatively cool air
and/or air with high moisture is said to be dense in meteorological storm
sense (even though we say when it is hot and humid that the air is heavy).
CURRENTS
The ebb and flow of the currents are the horizontal components of the "tidal
effect" (the vertical component).
BAROMETRIC PRESSURE
A storm will generally follow the low pressure trough, additionally pressures
within a storm are depressed.
MICROBURSTS
These are highly localized wind velocities that greatly exceed the velocities
of general surrounding area; they are extremely destructive.
STORM FORCE
This term is used to describe the total effect of the storm at a given point.
It is expressed in various ways such as "tons-per-square-foot"
and "kips" (an engineering term denoting 100 pound units acting
in a given direction). There is not really a good working definition for
the term in the 'as encountered' situations; simply because the possible
ratios of the components are infinite. What is meant is the "total
effect" in an arbitrary and somewhat subjective sense of `as perceived'
with some of the components measured.
STORM SURGE
The attained, and measurable, height of storm water due to the effects of
wind, tide, and currents. Unlike "Storm Force" this is a definitive
term.
LOSSES
Included are the loss of life, loss of property, losses which preclude or
delay the normal continuance of economic pursuits, and losses of a behavioral,
cultural, or communicative nature. Note that losses are not always proportionate
to the physical intensities of a storm.
The determination of the ten worst storms included consideration of the
above factors as well as
weighted evaluations at specific sites.
| 1 | 1635 | '35 | ??? | 14&15Aug | ??? | +20.0 ft. | 01 |
| 2 | 1815 | '15 | ??? | 23 Sep | ??? | +17.0 ft. | 02 |
| 3 | 1898 | '98 | ??? | 26&27 Nov. | ??? | ??? | (03) |
| 4 | 1938 | '38 | 161 | 21 Sep. | 200+ | +7.8 ft. | (04) |
| 5 | 1944 | '44 | 138 | 15 Sep. | 150 | <5.0 ft. | (05) |
| 6 | 1954 | EDNA | 121 | 11 Sep. | ??? | +5.4 ft. | (06) |
| 7 | 1955 | DIANE | 121 | 19 Aug. | ??? | <5.0 ft. | (07) |
| 8 | 1960 | DONNA | 161 | 12 Sep. | ??? | <5.0 ft. | (08) |
| 9 | 1984 | DIANA | 132 | 15 Sep. | ??? | <5.0 ft. | (09) |
| 10 | 1991 | BOB | 115 | 19 Aug. | ??? | <5.0 ft. | (10) |
VEL. & VELOCITY = Velocity in knots
LAT. = Latitude box
(01) "The worst storm on record" -
Tidal height recorded near Plymouth.
(02) Tidal height recorded at Providence, RI (plaque marker). The storm
cut the present opening to Lagoon Pond
(03) Also known as the Portland Gale - cause of building Vineyard Haven
Harbor Breakwater. 141 lives and 456 vessels lost; six lives and many vessels
lost or damaged in Vineyard Haven.
(04) Over 500 lives lost, property damage over 800 million (1938 dollars).
A person stood on a car roof on Beach Road, opposite R. M. Packer Co. office,
with the water reaching nearly to his knees. Fire truck ladders were used
to remove passengers from steamer. Storm surge nearly fifteen feet at Menemsha.
(05) The seas began to build many days before the storm and reached over
40 feet in Vineyard Sound and great heights in Buzzards Bay. The Lightship
"Vineyard Sound" was lost with all hands - her seven and a half
ton lead filled mushroom anchors were pulled out.
(06) This storm was characterized by high water - 5.4 feet (vs. 7.8 in 1938)
together with unusually high microburst velocities, most of the damage was
from wind forces..
(07) Extended period of high winds and high water.
(08) Very high winds of extended duration.
(09) The damage from this storm resulted from both the frontal and a trailing
phases, many were caught out after the first phase passed - the storm eye
had stalled.
(10) Although this storm didn't carry extremely high wind velocities, the
wind direction (the worst of it out of the East and ESE) destroyed much
waterfront property and many coastal craft. Overall, the damage was estimated
at 1.5 Billion Dollars (current values).
The storm rankings are subject to interpretation and challenge. They are
however, the result of a long study and consider such things as extremes
of wind and water, loss of live, property damage and the combining of these
considerations. My research was aided by a computer databank covering nearly
150 storms and going back almost that far in years. Also, reference was
made to National Weather Service records, Coast Guard data, newspaper information,
eye witness reports, and several phone conversations with Edward Rowe Snow
(just a year before his death) , who had collected much information about
storms for his several books. The earlier reference made to a latitude box
denotes the area, in latitude, where the computer narrowly tracked the storms;
that is to say that velocities (whether track, side, or quadratically) that
were outside of the box did not figure in the determinations.
Regarding data, of which there seems to be a plethora these days, it should
be kept in mind that the Weather Service hurricane over-flights are very
frequent in the Caribbean and in and just north of the Straits of Florida;
but the more northerly the locus the less frequent are these flights and
the data gathering intervals much longer. Therefore, dynamic readings are
of decreasing value for near term tracking and storm alerts must allow for
a wider warning area and a larger time margin.
1. 31 August 1931 - The Steamer "Naushon" was driven ashore in a gale, near the present Beach Road site of DeSorcy Contracting. She took with her the schooner "Alice S. Wentworth" and six smaller vessels.
2. 6 - 8 February 1978 - Blizzard, three days of heavy snow, winds and high seas.
3. July 1979 - Squall, SW of Nomans Land, 105 knots, lasting no more than 15 minutes. I was out there at the time with several other vessels including the Woods Hole Oceanographic vessel "Atlantic" who was able to record the wind velocity. A rather frightening experience - full power and standing still.
4. 28 July 1953 - Thunder storm with very large hail stones. The hail fell in isolated places (West Chop, Vineyard Haven and the Country Club in Oak Bluffs). My mother lost 23 windows panes, many cars were badly dented, and the soft tops of convertibles were shredded. For three years following the storm I kept a three and five eighths inch diameter hail stone in my freezer. Only recently (November 1998) have I learned of larger ones falling in the mid-west tornado belt.
5. Water Spouts - Two types:"Atmosphere-to-Surface" - This is actually a tornado over water and it warrants respect. Fortunately it is not common. One did occur off Oak Bluffs in 1896.
"Surface-to-Atmosphere" - The characteristics of this type resemble the "Dust-Devils" that occur on land. They are generally small, rise up quickly, last a few minutes and disappear. It is not unusual to see several at a time over a hot calm sea.