Weather Flags

The WMO (World Meteorological Organization) shows a number of flags an pennants in Annex II. National Systems of Visual Storm Warning Signals (Day Signals).

Chapter 8, part of Vol. D `Information for Shipping', one of WMO's operational documents. The introduction to this Chapter states:

As stipulated in the International Convention for the Safety of Life at Sea (…), Countries concerned should display at coastal points appropriate visual storm warning signals when applicable.

WMO Technical Regulations specifies that any Member establishing a new visual storm warning signal system should adopt the international system.

This part contains information on the systems of visual storm warning systems adopted by the various maritime countries. Where no such signals are used, a statement to this effect is given.

Annex I shows the International System of Visual Storm Warning Signals: black flags describing wind force (bottom of page) which may be however of another colour, if suitable.

There is also a breakdown of signals by country.

This very interesting table mentions countries with or without (official) warning system.

To give a few examples: Egypt uses two yellow crossed anchors on a white field (50a) meaning "Too much sea, pilot can not go out". (51a) being a blue flag pierced yellow is a signal "indicating the locality of storms" in Thailand ("South China Sea bordered by southern Viet Nam coast", etc.). Tunisia does not use signals whereas Sri Lanka uses a single one, but it is not a flag.
Jan Mertens, 27 October 2007

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[Editorial Note: The images on this page are shown at a standard height. Some may be viewed in the FOTW standard size by clicking on the image. Items listed as "contributed by" may be smaller than FOTW standard size]

Antigua and Barbuda use signals 40a and 41a which are red pierced black and red pierced black (double), respectively.

Signal 40a
image by António Martins-Tuválkin

40a is defined as "Tropical disturbance reported; likely to affect the island"

Signal 41a

	image by António Martins-Tuválkin

whereas 41a means Hurricane warning. Danger expected.
Jan Mertens, 1 November 2007

According to the WMO, Barbados uses signals 45a and 41a:

45a, a green flag, is defined as "The island is out of danger. The green flag of the day signal has a white diagonal stripe" which really means that the 45a picture does not apply to Barbados, as it is incomplete.

Signal 41a

	image by António Martins-Tuválkin

41a is the well-known set of two black flags pierced red, meaning "Hurricane conditions are expected within 24 hours."
Jan Mertens, 3 November 2007

Belize uses following flags:

Tropical Depression/Storm

image by António Martins-Tuválkin, 9 August 2007

43a (plain red):

(i) "A tropical depression moves into or develops anywhere in the quadrant south of 211°N latitude and west of 80°W longitude, OR

(ii) A tropical storm or hurricane moves into or develops anywhere in the quadrant south of 21°N latitude and between longitudes 80°W and 83°W".

Storm has passed

image by António Martins-Tuválkin, 9 August 2007

45a (green): "The tropical depression, tropical storm or hurricane has passed or not longer poses a threat to Belize and coastal waters."

Tropical Storm Warnings

	image by António Martins-Tuválkin, 9 August 2007

41a (double set of red pierced black): "A tropical storm or hurricane moves into or develops anywhere in the quadrant south of 20° N latitude and west of 85°W longitude."

image by António Martins-Tuválkin, 9 August 2007

40a (red pierced black): "A tropical [storm] or hurricane moves into or develops anywhere in the quadrant south of 20°N latitude and between longitudes 83°W and 85°W."

However the above needs to be qualified: Specifically the black rectangle is replaced by a black dot.
Jan Mertens, 4 November 2007

Chile uses a separate system (only the flags will be mentioned).

Variable Weather

image contributed by Jan Mertens, 5 November 2007

48a (blue pennant with small white dot enclosed by black circle): “Variable [weather]”.

Loading/Unloading of Cargo suspended

image contributed by Jan Mertens, 5 November 2007

47a (red, rectangular, with yellow cross throughout): “The traffic, loading and unloading of cargo are totally suspended; lighters and tugs should make fast.” Attached as < cl_vsws47a.gif> .

Small craft traffic suspended

image contributed by Jan Mertens, 5 November 2007

46a (blue, rectangular, with white saltire): “The traffic of small craft is suspended in the bay on account of bad weather.”

There is a note (a) saying that “these signals correspond to the current synoptic chart”, a further note (b) is not flag related.
Jan Mertens, 5 November 2007

Egypt uses an elaborate warning system: comprising only one flag:

image by Eugene Ipavec, 8 November 2007

50a (white, two yellow anchors, crossed, the stocks turned towards the hoist): “Too much sea, pilot can not go out”. Attached as < eg_vsws50a.gif> .
Jan Mertens, 7 November 2007

Fiji uses one signal, which is a flag:

image contributed by Jan Mertens, 8 November 2007

35a: yellow pennant meaning “Storm/hurricane alert. A tropical cyclone of storm or hurricane intensity exists and may affect the locality within 24 or 36 hours.”
Jan Mertens, 8 November 2007

Grenada uses a signal flag set closely resembling US use:

Winds: above 63 knots

	image by António Martins-Tuválkin

41a (double set of red pierced black): "Winds above 63 kt".

Winds: 34-63 knots

image by António Martins-Tuválkin

40a (red pierced black): "Winds 34-63 kt".

Winds: 28-33 knots

image by António Martins-Tuválkin

56a (red pennant): "Winds 28-33 kt"
Jan Mertens, 9 November 2007

There is an interesting set of signal flags that are (were) used as weather signals by the US Department of Agriculture. Perhaps these went out of use with the widespread use of radio in the early years of this century (or maybe they are still used?  This is what "The World Almanac" (1893) had to say (my comments in square brackets):

"The weather bureau furnishes, when practicable, for the benefit of the general public and those interests dependent to a greater or less extent upon weather conditions, the 'forecasts' which are prepared at that office daily at 10am and 10pm, for the following day. These weather forecasts are telegraphed to observers at stations of the weather bureau, railway officials, and many others, and are so worded as to be readily communicated to the public by means of flags or steam whistles. The flags adopted for this purpose are five in number, and of the form and dimensions indicated below:

A special Storm flag, red with black square in the centre, is prescribed for use in North and South Dakota, Minnesota (except at lake stations), Iowa, Nebraska, and Wyoming, to indicate high winds, accompanied by snow, with temperature below freezing.

When displayed on poles, the signals should be arranged to read downward; when displayed from horizontal supports, a small streamer [colour unspecified] should be attached to indicate the point from which the signals are to be read."
James Dignan, 06 December 1997

These flags are depicted in "Signal flags used at Weather Bureau Display Stations" In: The Aims and Methods of Meteorological Work by Cleveland Abbe. In: Maryland Weather Service, Johns Hopkins Press, Baltimore, 1899. Vol I. Page 296.

Red pennant above square red flag pierced black: captioned "N.E. WINDS".

Square red flag pierced black above red pennant: captioned "S.E. WINDS".

White pennant above square red flag pierced black: captioned "N.W. WINDS".

Square red flag pierced black above white pennant: captioned "S.W. WINDS".

WIND SIGNAL. Pennants with the Storm Signal indicate the direction of the wind; red, easterly. from northeast to south; white, westerly, from southwest to north. The Pennant above the flag indicates that the wind is expected to blow from the northerly quadrants; below, from the southerly quadrants.

Jan Mertens, 7 November 2005

From navytimes.com:

Coasties revive foul-weather warning flags
By Patricia Kime - Staff writer
Posted : Wednesday May 30, 2007 18:19:14 EDT

Double red-and-black storm-warning flags once heralded an impending hurricane, urging mariners to take cover and seaside residents to flee.

The flags disappeared from common use in 1989, when the National Weather Service discontinued the program.

This summer, the Coast Guard officially is bringing them back.

Starting June 1, select Coast Guard stations will hoist storm flags in foul weather: red triangle for small craft warning; double red triangle for gale warning; single red-and-black square for storm warning; and the feared double flags for hurricane warning.

“[This is] a Coast Guard initiative to reinforce the Coast Guard’s role as lifesavers, reaffirm to local communities the Coast Guard’s role as experts concerning local boating matters and visually communicate ... the lesson of Hurricane Katrina to take personal responsibility for individual safety,” said Rear Adm. David Pekoske in an announcement May 30.

Some marinas and stations voluntarily have carried on the tradition of hoisting such flags, but participation was spotty.

The Coast Guard hopes that residents in storm-prone areas will see the flags and listen to National Oceanographic and Atmospherics Administration radio broadcasts for further details, officials say.

According to NOAA, more than half the country’s population lives along the coasts. In 2003, roughly 153 million people lived in 673 coastal counties.

David C. Fowler, 31 May 2007