Typhoon Chanthu threatens West Pacific Shipping

Typhoon Chanthu IR satellite image NOAA

Typhoon Chanthu has been downgraded from a super typhoon, however it is still packing winds to 120 knots with gusts to 145 knots.  Chanthu is moving NNE (015) at 7 knots. Chanthu is currently located south of Taipei, Taiwan and is producing significant wave heights to 48 feet (about 14.5 meters).

 

Chanthu is forecast to continue northward for the next 48 hours but may track somewhat more to the west due to interaction with the high mountains on Taiwan.  Presently the eye is expected to remain off the east coast of Taiwan.   After 48 hours, the track becomes more uncertain as weakening steering winds may result in Chanthu becoming semi-stationary for a time and could pass near or over Shanghai before turning eastward. 

Typhoon Chanthu forecast track via Joint Typhoon Warning Center

 

Given the shipping delays due to Covid and previous weather events, a slow moving storm along the coast of China could result in additional massive delays adding to what is already huge backlog of vessels loading cargo in China to US West Coast and European ports. 

 

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What is Vessel Performance Analysis and Performance Monitoring?

Vessel Performance Monitoring

Vessel Performance Report Daily positions

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 in near real-time. 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 while underway so that the charterer or vessel operator/owner has a “heads-up” on performance issues prior to the ship’s arrival.

Vessel Performance Analysis

 

 

Detailed Voyage Performance Analysis Report 

At the end of the voyage, a full “Voyage Performance Evaluation Report” can be 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. 

The goal of the Post Voyage Performance Analysis is to reduce costly disputes regarding the vessel’s performance vs. the contracted charter party obligations.  This will include a general overview of performance in terms of time gained or lost, as well as FO/DO over/under consumption as well as performance in verified good weather conditions. 

 Section 1  Charter Party Details:
Summary of the C/P speed and fuel consumption clauses

Section 2 Overall Vessel Performance Summary:
Summary of daily speed and consumption with wind, wave and relative ocean currents encountered plus an overall analysis of performance after accounting for the effects of wind, wave and ocean currents with overall time gained or lost.

Section 3  Good Weather Performance Analysis
Summary of time, speed and distances during periods of verified good weather conditions, including the total time gained or lost during those good weather days. 

Section 4  Fuel Consumption Summary
Summary of daily fuel consumption and the calculated total over/under consumption based on the C/P warranted consumption. 

For more information please contact us 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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What is the weather like cruising the Caribbean Sea and Gulf of Mexico during August?

The weather during August is a very warm in the Caribbean Sea and Gulf of Mexico and this is also the month when tropical cyclones become active. Gale force winds are rare, however,  but can occur in the vicinity of tropical storms and hurricanes. 

August Pilot Chart

Wind

The prevailing winds across the Caribbean during August tend to be from the east,  generally light to moderate (7-16 knots) except in the south-central portion of the Caribbean where moderate to fresh (11-21 knot) winds prevail from the east or northeast and where  rough seas of  8 feet or higher can be expected about 20-30% of the time. 

Over the Gulf of Mexico the wind tends to be light (7-11 knots) and more variable in direction. 

Tropical Cyclones 

Tropical cyclone activity is most frequent over the northeastern Caribbean Sea and waters north of Puerto Rico and Hispaniola as well as the Bahamas and east of Florida  where there is a 30-40% risk of at least one storm occurring during  the month of August.   The risk decreases to around  20% over the Gulf of Mexico and to below 10% over the southwestern Caribbean.

August Tropical Cyclone tracks

Temperature

August is very warm with air temperatures averaging 82F to 85F and sea temperatures range between 83F to 86F.

 

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Elsa less than forecast for Tampa Bay

NOAA NWS Surface Analysis

As Tropical Storm Elsa was moving north off the west coast of Florida on July 6th, the National Hurricane Center in Miami upgraded Elsa to a hurricane at 1:45pm on the 6th based on an Air Force Recon report that the max winds had increased to 60 knots (70mph) and as a result a hurricane warning was issued for a portion of the west coast of Florida, including Tampa Bay.

As the center of Elsa passed west of Tampa at about 2am EDT on the 7th hurricane models were indicating sustained winds of 50 knots (58 mph) or more should have been widespread across the Tampa Bay area, however, actual surface wind reports were less than forecast.

NOAA Model wind analysis TS Elsa

As Elsa passed the Bay to the west, the actual wind reports were, thankfully, quite a bit less.
Reports showed that the peak sustained winds were between 21 knots (24 mph) and 34 knots (39 mph) and peak wind gusts only reached 31 knots (36 mph) to 47 knots (54 mph).

Actual wind reports

A surface wind analysis made just prior showed that the gale force and storm force winds were confined to the coastal waters with lesser wind speeds extending east over land.
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2021 North Atlantic Hurricane forecasts

Hurricane Laura

NOAA GOES-East image Hurricane Laura

Each spring there are numerous government and private organizations that undertake the task of predicting the North Atlantic Hurricane season.  This year, the 2021 North Atlantic hurricane forecasts are calling for another above-normal hurricane season with between 12 and 20 named storms.   

 

2021 TC Names

2021 NOAA NHC Atlantic Tropical Cyclone names

What factors influence the hurricane season?

There are several large-scale atmospheric systems that tend to enhance the Atlantic hurricane season such as low vertical wind shear,  high sea surface temperatures and high mid-level moisture. 

Warmer than normal ocean temperatures are favorable for hurricane formation and intensification. A warmer Tropical North Atlantic also can create lower air pressures and reduced trade winds which enhance tropical development.

Another factor is the El Nino Southern Oscillation (ENSO)

El Nino

El NINO: NOAA National Environmental Satellite, Data, and Information Service (NESDIS)

ENSO is driven by changes in ocean temperature in the tropical Pacific, where warmer than average conditions (El Niño) in the Central and Eastern Pacific tend to increase vertical wind shear over the tropical North Atlantic and thus dampen tropical cyclone development.   During the cooler La Niña phase, vertical wind shear over the tropical North Atlantic is reduced which tends to favor tropical cyclone development. 

Changes in precipitation patterns over the Sahel region of North Africa can also affect vertical wind shear over the Atlantic hurricane producing area. Years with higher Sahel rainfall have been associated with more active hurricane seasons.  Also, episodes of dust from the Sahara tend to reduce Atlantic sea surface temperature and are also associated with very dry air, both factors tend to reduce activity. 

On June 18, 2020, NASA-NOAA’s Suomi NPP satellite captured this visible image of the large light brown plume of Saharan dust over the North Atlantic Ocean. The image showed that the dust from Africa’s west coast extended almost to the Lesser Antilles in the western North Atlantic Ocean.
Credits: NASA Worldview

 

 

 

 

 

 

 

 

 

Below is a summary of the various  2021 Tropical Cyclone Forecasts for the North Atlantic:

2021 North Atlantic Tropical Cyclone Forecasts

 

In addition, Colorado State University also provides a forecast by county for Tropical Cyclone Impact  (defined as one or more storms within 50 miles of location)

Sources

NOAA National Hurricane Center

Colorado State University (CSU) 

Tropical Storm Risk (TSR)

University of Arizona 

Penn State University   

AccuWeather  

North Carolina State University

The Weather Channel  

UK Met Office

 

 

 

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Monster North Pacific Storm Sets Record

Satellite image

NOAA Visual Satellite image of Monster North Pacific Storm

As 2020 transitioned into 2021, a rapidly deepening and intense hurricane-force storm over the western North Pacific has set an all-time record low central pressure of 921 mb breaking the previous record of 924 mb recorded on Nov 8th, 2014 over the Bering and tied in Dec 2015.

High Seas Forecast

The NOAA NWS High Seas Forecast earlier today was predicting winds of 60-95 knots within 300 south of the low center with significant wave heights up to 60 feet(18.3 meters). I cannot remember ever seeing a forecast up to 95 knots wind for an extratropical storm.

NOAA OPC North Pacific Surface Analysis 18Z 31 Dec 2020

Hurricane-force Storms

These winter storms are extratopical cyclones, storm systems that get energy from horizontal temperature gradients and are often associated with frontal zones. Tropical cyclones, in contrast, are generated by the energy released as clouds and rain form in warm, moist, tropical air masses.
Extratropical cyclones occur throughout the year and can vary widely in size from under 100 nautical miles to over 2500 nautical miles. On average, extra-tropical cyclones last about 5 days, however, hurricane-force wind events associated with these systems typically occur during the rapidly deepening phase of the cyclone and that hurricane force conditions were short lived, on average lasting less than 24 hours in duration.
During the cold weather season Arctic air masses will move out over both the North Pacific and North Atlantic Oceans and interact with low latitude tropical air to produce large temperature gradients and strong frontal boundaries. Low pressure centers will then intensify using the temperature contrast as one of the main ingredients for development. When surface winds reach 64 knots the system is classified as “hurricane force”.

Warm ocean currents like the Gulf Stream in the Atlantic and the Kuroshio current in the North Pacific enhance the temperature contrast and thus add significant energy to these developing storm systems.

NOAA OPC Significant Wave Height 00Z 01 Jan 2021

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Case Study: Marine Weather Reconstruction, Arabian Sea

Beaufort Force 9

I was asked to review a marine weather analysis report of conditions in the northern Arabian Sea, east of Socotra Island during July of 2008 that was presented by a weather consulting company on behalf of cargo interests.

The report stated that the weather conditions at a specific location from 4th July 2008 through 8th July 2008 were from the Southwest and gradually strengthened from Beaufort Force 6 to Force 7 with the significant wave heights increasing from around 4 meters to between 5.0 and 5.5 meters.  The peak wave period increased from 9-9.5 seconds to 10-10.5 seconds and those conditions were very typical of the SW monsoon. The report concludes that Beaufort Force 9 conditions with 8 meter waves did not occur as was reported by the master of the vessel.

Reviewed in that report were:

  • 3 hourly wind data from the archive from the NCEP (USA) operational global forecast    model
  • 3 hour wave data from NOAA Wave Watch III Model
  • 3 hour interval NCEP Hi Resolution (fine mesh) Reanalysis models
  • 6 hourly re-analysis project model by the European Centre for Medium Range Forecasts (ECMWF)
  • Derived surface wind data from QuikSCAT and WindSat satellites estimating winds over a 12.5 or 25 km squares and rounded to the nearest 5 knots.

Initial Research
The most accurate source of surface marine weather data are instrumented weather buoys. From my research there were no such buoys near the coordinates at the time of the incident, so to establish the prevailing wind and sea conditions, other sources, such as ship weather reports, must be considered along with any pertinent computer model data.

Ship Observations
Ship observations are usually taken by experienced seaman with wind speed and direction either measured directly with allowances made for ship motion or by estimating those conditions by viewing the sea state.  Wave observations taken from onboard ships are, for the most part, estimated. Ship observations are, however, actual observations and as such are an essential source of information to be considered along with other data sources. Since, in this particular case there were no buoys reporting wind or sea conditions then the only available actual observations were the ship based observations.

Computer Models
The model data outputs used in the report are highly dependent on the accuracy of the initial conditions and the grid spacing used when running the model. The initial conditions will include all available weather observations and available satellite derived data. The initial data inputs were not available in this report so I cannot tell how many, if any, ship observations were used in formulating the initial conditions.

The conclusions in the report regarding the prevailing wind and wave conditions were based on calculations made by various atmospheric and wave model algorithms.  As stated in the report “These are not direct measurements. They are extracted from charts based on the analysis fields generated by the numerical model”.  Since the model grid points can vary from 12.5 km up to 50 km they can sometimes miss smaller atmospheric features so any actual marine weather observations must also be considered along with  model data when making such an analysis.

Research
In order to review the actual observations, I downloaded the ship weather observation for the time period 4 July to 8 July, 2008. These observations were obtained from the NOAA National Climatic Data Center (NCDC) website and included all the ship weather observations available for the area from 10N to 20N latitude between 50E and 60E longitude for the time period in question.  Below are the position reports of all gale force or higher observations:

Conclusions
The listing of actual ship observations obtained from NOAA NCDC included a total of 4 observations of Beaufort force 8 wind conditions and 6 observations of ships reporting Beaufort force 9 wind conditions in the general vicinity of the vessel during this time period 4 July to 7 July 2008 with significant wave heights reported of between 4 and 6 meters.

The full spectrum of wave heights and wave periods in the open sea can be extremely complex with a mix of individual waves interfering with each other so that you can get wave peaks one on top of another adding to a combined higher wave height as well as wave peaks being canceled by wave troughs and reducing the combined height. The significant wave height is defined as the average height of the highest one-third waves in a wave spectrum and this happens to correlate very well with the wave height a skilled mariner perceives in a wave spectrum.

Since the significant wave height represents the average of the 1/3 highest waves then some waves will be higher than the reported significant wave height.  Based on past statistical studies, a significant wave height of 6 meters means that on average, about 10 waves out of 100 within this wave spectrum will reach a height about 7-8 meters and 1 out of 100 waves will reach a height of about 10 meters.

Based on the above, it is my opinion that the vessel likely did encounter winds up to Beaufort force 9 and likely encountered some waves in the range of 7 to 10 meters. There is also the possibility that wind speeds would have exceeded this level in stronger gusts. In general, over open ocean waters, gusts can exceed the average wind speeds by 20-25 percent.

Shipboard Anemometers
We note that ship anemometers tend to be mounted higher than the standard 10 meter wind observation height of land-based weather stations and could lead to some over reporting of the wind speed, however, the difference in heights of various ship anemometers only creates a relatively small effect.  Another consideration with the use of anemometers is that some inexperienced observers might record the apparent wind speed and direction without subtracting out the ship motion so that ships moving into the wind will report higher winds while those moving with the wind will report lower speeds. This is a function of experience and training. The superstructure of ships, like buildings, can also interfere with the wind flow so the placement of the anemometer is important.  Anemometers located above the bridge of tankers/bulk carriers for example have been shown to have the wind accelerated by up to 10 % or decelerated by as much as 100%. It is more likely than not that this results in under recording,  not over recording wind speed.

Climatology
July is well-known for heavy weather in this area of the Arabian Sea. Various sources offer the risk for gale force (BF-8) or higher winds from 16 % to about 30% depending on how small or large an area is considered.  The Atlas of Pilot Charts shows for July that the this area experiences winds from the southwest 83% of the time with the most frequent wind observation at BF -7.  The Atlas of Pilot Charts also shows that there is a 50-60% occurrence of wave heights of 12 feet (3.65 meters) or more in that area during July.

The US Navy forecast handbook states that “Surface winds reach a maximum in July with the highest speeds (up to 50-60 knots) reported northeast of Socotra Island where winds greater than 33 knots occur more than 30 % of the time.”

 

Fred Pickhardt
Ocean Weather Services

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Ship and Yacht Weather Routing Services

Basic Ship and Yacht Weather Routing Services

Ship Weather Routing

Ship and Yacht Weather Routing

Ocean weather routing (Optimum ship routing) provides for a “best route” for ocean transits 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 of 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 or plus any alternate routes to be considered. In addition a forecast of the expected weather conditions to be encountered along that route (wind, sea and swell). 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, on average, about every 2-3 days.

Learn more about the benefits of ship routing here: http://www.oceanweatherservices.com/benefits_of_optimum_shi

Contact us for pricing http://www.oceanweatherservices.com/contact_us

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Florida West Coast Hurricanes 

1921 Hurricane Track

September and October are the two months when the Florida West Coast is most at risk of encountering landfalling hurricanes.  As the cold season approaches, the prevailing westerlies begin to increase and migrate southward across the US and start to encroach out over the Gulf of Mexico.

When tropical cyclones move across the Caribbean Sea or form over the Western Caribbean and then move northwestward through the Yucatan Channel during the early Autumn, they will often  feel the effects of the westerlies and as a result, will turn north then northeastward towards the West Coast of Florida.  A few notable examples where Hurricanes Donna (Sept 1960)Wilma (Oct 2005) and Irma (Sept 2017).

Tampa Bay Major Hurricane Landfalls 

The first major hurricane to make landfall in the Tampa Bay region was the “Great Gale of 48”, which was a major hurricane that hit in late Sept of 1848.  The September 1848 storm was an intense hurricane with estimated maximum winds of between 101-135 mph at landfall near Clearwater during the early afternoon of September  25th  with an estimated minimum pressure of about 945mb.  

Thomas B Garland driven ashore – Credit:
Florida State Archives collection

The second major hurricane to make landfall near Tampa was also the most significant hurricane to affect the area, making landfall on October 25th of 1921.  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 (952 mb) was recorded at 2:15 PM. This reading suggests that a max wind at landfall was about 110 knots (125 mph) 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.

Climatology

During the latter half of the hurricane season, the prevailing westerlies begin to increase and migrate southward across the US and start to encroach over the Gulf of Mexico.  Tropical cyclones that move into the southeastern Gulf of Mexico often will feel the effects of the westerlies causing the storms to recurve north then northeastward and thus threaten the west coast of Florida.

During September the primary tracks will cause these storms to make landfall mostly between the Mississippi Delta to the Florida Panhandle or Florida’s Nature Coast.  During October, the storms will tend to recurve sooner targeting the West-Central and Southwestern Florida Coasts. 

Prevailing Hurricane Tracks during September Source NHC

Prevailing Hurricane Tracks during October. Source NHC

 

 

 

 

 

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Gulf of Tehuantepec Gales

The Gulf of Tehuantepec

I first heard about the Gulf of Tehuantepec gales from my father who sailed with the United Fruit Company’s Great White Fleet during the late 1940’s and 1950’s. The Gulf of Tehuantepec (Spanish: Golfo de Tehuantepec) is a large body of water on the Pacific coast of the Isthmus of Tehuantepec in southeastern Mexico.  The gulf extends approximately 300 miles from Puerto Angel, in southern Oaxaca state, southeastward to Barra del Suchiate, in southeastern Chiapas state, and measures approximately 100 miles across its mouth.

The onset of winter brings frequent cold outbreaks across the central and eastern US that can often result in sudden gale to storm force winds over the Gulf of Tehuantepec. The northerly winds funnel through gaps in the Sierra Madre Mountains and spill out over the Gulf of Tehuantepec and out over the eastern North Pacific.

Geography

The Sierra Madre mountains extend southeastward through Mexico and Central America and separates the Gulf of Mexico, the Bay of Campeche´ and Caribbean Sea from the Pacific Ocean. Several mountain gaps allow air to flow across Mexico and the most prominent gap is the Chievela Pass which allows strong cold air surges to pass into the Gulf of Tehuantepec on average about 15 times each winter season with about 2 of these strong enough to reach storm force conditions.

Meteorology

The winds are produced when there is a strong pressure gradient between the Gulf of Mexico to the north and the eastern North Pacific to the south. Northerly winds can increase to storm or even hurricane force during the more extreme events. The first event of each cool season normally occurs in mid-October with the last event occurring in late March or early April.

Gulf of Tehuantepec Surface Analysis

At the outset of gale events, surface pressures reach a maximum value of about 1028mb at Brownsville and 1024 mb at Coatzacoalcos. During storm events the pressure at Brownsville are about 4 mb higher and at Coatzacoalcos about 3 mb more. During Tehuantepec events, the track of the high pressure center is often more critical than the maximum pressure at the center. The path that the anticyclone takes drives the northerly fetch down the coast of Mexico and setting up the strong pressure gradient across the Isthmus of Tehuantepec.

As a practical matter, whenever the Brownsville pressure exceeds 1020 mb there is a good chance that a Gulf of Tehuantepec event may occur so mariners expecting to pass across the Gulf of Tehuantepec should monitor the surface forecast charts for the Western Gulf of Mexico as an indicator.

During gale events, the center of the high could track as far north as the Tennessee and Ohio River valleys while storm events require the high center to track into Mexico or the western Gulf of Mexico. Storm events are also frequently correlated to strong 500 mb upper level troughs.

Hurricane Force Storm event over the Gulf of Tehuantepec

 

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