Dangerous North Atlantic Storm Impacting Shipping Lanes

NOAA OPC Surface Analysis 1200UTC 19 Feb 2018

A developing hurricane force storm low over the west-central North Atlantic continues to move eastward at 35 knots producing winds of 55-75 knots with significant wave heights up to 12 meters (40 feet) within 180 NM south and 120 NM west of the center. Over the next 24 hours max winds will be between 50-75 knots with significant wave heights to  15 meters (50 feet)  within 240 NM in the western semi-circle.

This is a dangerous storm as it is tracking eastward at a fairly low latitude and is affecting shipping from North Europe and Mediterranean ports and US  East Coast and Gulf ports.

NOAA OPC Significant Wave Forecast 0000UTC 20 Feb 2018

NOAA OPC Surface Forecast 0000UTC 20 Feb 2018

Learn  more about hurricane-force winter storms here

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What does a Small Craft Advisory mean?

The National Weather Service has developed a multi-tier concept for forecasting hazardous weather which includes outlooks, watches, warnings and advisories.

Make sure you recognize the visual day flag and nighttime light signals that warn you of rough weather.

An outlook is issued to indicate that a hazardous weather or hydrologic event may occur over the next several days.

A watch is issued whenever that risk has increased significantly but the occurrence, location or timing are still uncertain. Marine Watches for “GALE” “STORM”, and “HURRICANE FORCE” wind conditions, not related to tropical cyclones, can be highlighted in extended range forecasts beyond 24-hours for coastal inland waters, and offshore waters (does not include high seas forecasts).

A warning is issued when the hazardous condition or event is either occurring, imminent or likely (for the marine forecasts, within 24-hours).

A weather advisory is issued when a hazardous weather condition or event is occurring, imminent or likely but for less serious conditions than those that would warrant a warning.

A small craft advisory (SCA) is issued by the National Weather Service whenever conditions in the coastal waters or Great Lakes meet specific thresholds that are defined locally and can include wind, waves and sometimes ice. This is issued within 24-hours of expected small craft advisory conditions.

It is important to note that there is NO precise definition of “small craft” and the interpretation is left to the vessel operator. This might include considerations of the operator’s experience level, vessel type, overall size and sea worthiness.

Small Craft Advisories are normally issued for sustained winds or frequent gusts between 20 and 33 knots except that the minimum wind criteria may be as high as 25 knots and as ow as 18 knots, depending on local criteria. Minimum wave heights for a Small Craft Advisory also vary regionally from as little as 5 feet to as much as 10 feet, also depending on local criteria considerations.

Small Craft Advisories can also be issued for winds and waves below the local minimum criteria if hazardous sea conditions exist due to wave period, wave steepness, swell direction or ice. In addition, in or near bars (e.g. Grays and Columba River), advisories might also be issued due to the interaction of swell and currents in shallow water interacting with ebb tides.

Fred Pickhardt, chief meteorologist,
Ocean Weather Services

Lee S. Chesneau
Lee Chesneau’s Marine Weather

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Update: Dangerous North Atlantic Hurricane Force Storm Expected

NOAA OPC Surface Forecast Chart for 1800 UTC 18 Feb. 2018

Atlantic Storm Update

A rapidly deepening storm low is forecast off the USEC Sunday morning then tracks ENE to East with winds reaching 55-70 knots and seas to 10 meters (33 feet) by 1800 UTC 18th and winds off 60-75 knots and seas to 16 meters (52 feet) possible by 0000 UTC 20th over the Central North Atlantic.

Shipping Threat

The forecast for a relatively southerly storm track will cause issues for ship traffic between North Europe and Mediterranean ports to US East and Gulf Coast ports.  This system should be considered a dangerous storm.

NOAA OPC Significant Wave Forcecast 20th 0000UTC

For more information about storms like this, please read “The Other Hurricane Season”

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Hurricane Force Storm Forecast for Central North Atlantic

NOAA OPC Surface Forecast chart

A weak low will move off the USEC near Cape Hatteras Saturday evening then move eastward and deepen rapidly and develop storm to hurricane force winds of 55-70 knots and seas to 9 meters (30 ft) south and southwest of the center by 1800UTC 18 February.  As the storm moves east seas will continue to build up to 14 meters (46 ft) by 1200 UTC 20th.

Shipping Danger

This fast moving system will be a danger to shipping lanes from North Europe to US south of Hatteras and from the Gibraltar to US East and Gulf Coast Ports as highest winds and waves will prevail between 35N and 43N latitudes in the central North Atlantic.

NOAA OPC Surface Forecast

NOAA OPC Significant Wave Height Forecast

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Tropical Cyclone Cebile near peak intensity

JTWC forecast track

Tropical Cyclone Cebile located about 583 NM S-SE of Diego Garcia in the southern Indian Ocean is packing winds to 115 knots with max significant wave heights to 34 feet (10.4 meters). Hurricane force winds extend outward 50 NM to the southeast and 35 NM to the north. Cebile is moving slowly towards the west-northwest at 4 knots.


Cebile is forecast to gradually weaken over the next few days at it turns more towards the south then southeast.

Multi-spectral Satellite image TC Cebile

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Dangerous Hurricane-force storm forecast off Japan

NOAA OPC Forecast for 1200 UTC 23 January 2017

A rapidly developing hurricane-force storm low is forecast over the western North Pacific off the coast of Japan January 22nd-23rd with storm to hurricane force winds and significant wave heights to 17 meters (about 56 Feet). This will be a dangerous storm affecting ships arriving and departing Japan.

The highest significant wave height ever recorded was a massive 19 meters (62.3 feet!) measured by a buoy in the North Atlantic.

Wave Relationships

Hs or H1/3 = Significant wave height (average of the highest 1/3 waves)
H1/10 (Highest 10% wave height) = 1.27 x Hs
H1/100 (Highest 1% wave height) = 1.67 x Hs

Read more about ocean waves here 

Read more about Hurricane-force extra-tropical storms here

NOAA Significant Wave Forecast 1200 UTC Jan 23rd.

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Hurricane-Force Storm off US East Coast

NOAA NWS 1200 UTC Surface Analysis 04 Jan 2018

A rapidly deepening and dangerous hurricane-force storm off the US East Coast is moving northeastward at 30 knots.  Winds of 60-80 knots (70-90 mph) and seas to 49 feet (about 15 meters) are expected  during the next 12 hours within 180 nm south of the center.

The central pressure in this storm has fallen about 54 mb over the past 24 hours, so it easily qualifies as a meteorological “bomb” (an official term for an extratropical cyclone with a pressure drop of at least 24  mb in a 24 hr time period).

This storm will adversely affect shipping along  the US East Coast into Friday.  In addition to the high winds and waves, heavy snow is occurring from New York City Northeastward to Maine.



Well Forecast

NOAA OPC 96 hour forecast issued New Years Eve for Jan 4th

As far back as New Year’s eve NOAA was predicting a rapidly deepening hurricane-force storm off the US East Coast for the 4th so this one was no surprise!

The Other Hurricane Season

This type of storm is not as rare a most think. Few people (outside of Mariners) realize that there is another season of hurricane winds that occur each year over both the Atlantic and the Pacific that runs from September to May.   The current storm off the East Cost is a good example.


Read more about this type of storm here.

Check out NOAA Satellite loop here.

NOAA Visible Satellite Image 1345 UTC 4 Jan 2018

NOAA OPC Surface Forecast 0000 UTC 5 Jan 2018

NOAA OPC Wave Forecast 0000 UTC 5 Jan 2018

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Omega Block developing over eastern North Atlantic

Omega  block on  500 mb forecast chart

NOAA OPC 48 hour 500 mb forecast chart

The current North Atlantic upper-air pattern is developing  an Omega block over the northeastern North Atlantic. This pattern gets its name because this upper air pattern looks like the Greek letter omega (Ω). Omega blocks tend to have two cut-off lows with one blocking high sandwiched between them. They also tend to be large in size, producing a persistent surface pattern.

Often the cut-off upper lows tend to dig southeastward into the lower-left portion of the omega which can, in turn, force the omega pattern to extend farther northward.  This disrupts the normal southwest to northeast storm  tracks which can allow options for minimum distance great-circle weather routes during winter from North Europe ports to US East Coast Ports.

Learn more about using the 500mb chart for weather routing.

NOAA OPC 48 hour surface forecast showing blocking high pressure

NOAA OPC 48 hour surface forecast.


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Hurricane Force storms affecting North Pacific shipping


NOAA OPC North Pacific surface analysis

NOAA OPC North Pacific surface analysis

Two Hurricane Force storms affecting North Pacific shipping


An intense 950 mb storm low over the north-central North Pacific is moving east with winds of 50-65 knots and seas to 46 feet (14 meters) within 480 NM south and southwest of the center.

A second developing complex low system to the west is moving eastward and is forecast to deepen to 953  mb with a secondary low center to the south over the next 18-24 hours. Winds forecast 50-65 knots with seas to 37 feet (about 11 meters) south and southwest of the lows.

The stormy combination will likely adversely affect ships transiting the North Pacific north of 40N for the next couple of days.

NOAA OPC North Pacific Forecast Chart

NOAA OPC North Pacific Forecast Chart

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What’s the weather like cruising the Caribbean during December?

Pilot Chart of the North Atlantic (Caribbean section) for December

Pilot Chart of the North Atlantic (Caribbean section) for December

Over the Caribbean during December winds tend to be mostly from the east or northeast averaging forces 4-5 (11-21 knots).  Over the Gulf of Mexico winds tend to be more variable but still averaging mostly forces 4-5 (11-21 knots).  The risk for gale force or higher winds is low, generally 1 % or less, except for the westernmost Gulf of Mexico where the gale risk is 2-3%.


Strong to near gale conditions, often do occur so the risk of encountering rough 8 foot or higher seas is about 10% over the Gulf of Mexico and ranges from 10 to 30 percent over the central and western Caribbean with the highest risk concentrated north of the Columbian coast.   The eastern Caribbean tends to have less risk for rough seas, occurring less than 10% of the time and winds averaging force 4 (11-16 knots).


Air temperatures during December average 27C-28C (80-83 F) across the Caribbean, 16C-22C (61-72 F) over the northern and western Gulf of Mexico and 22-25C (72-77 F) across the Bay of Campeche and southern Gulf of Mexico.  Sea surface temperatures range from 26-28C (79-82 F) in the Caribbean, 18-24C (64-75 F) over the northern and western Gulf of Mexico and 24-27C (75-81 F) in the Bay of Campeche and southeastern Gulf of Mexico.

Pilot Chart for the North Atlantic (Caribbean Section) depicting air and sea temperatures

Pilot Chart for the North Atlantic (Caribbean Section) depicting average air pressure and temperatures










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