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I. Basics of Observing

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You are on assignment on the USS Kearsarge. It's 9:40 a.m. EDT and time to begin your weather observations for the 10:00 a.m. (1400Z) report. This is the first day of the deployment and your first day as a shipboard observer, but you have a couple things in your favor. First, sailing with you is AG2 Ferguson, a seasoned observer who can provide you guidance as you fulfil your role. Second, even before taking your first official observation this morning, you spent some time familiarizing yourself with the weather situation of the day. Sailing in this part of the North Atlantic in October, you know that sea water temperatures tend to be warm. The morning METARs indicate the air temperatures are quite warm today, humidity is high, winds so far have been mostly calm, and visibility has been unrestricted. Thunderstorms are in the forecast though, so you'll want to keep an eye on the evolving weather situation through the day.

photo of the USS Kearsarge under sail with helicoptor operations in progress

In your job as an Aerographer's Mate, Quartermaster, or Military Sealift Command (MSC) civilian contracted observer, you may be tasked with taking and reporting meteorological and oceanographic observations both on land and while you are at sea. These observations are important for a range of shipboard and airborne operations as weather or sea conditions can seriously impact crew and vessel safety.

photo of aerographer taking a wind direction using an anemometer

Surface weather observations play an important role in numerical weather prediction (NWP). They provide data for the initial conditions of weather forecast model runs and are used to evaluate how well a model is predicting future conditions. In these ways, the observations directly contribute to the accuracy of forecasts and weather warnings.

10m Winds Mean (contours) and Spread (shading)
NUOPC 48-hr Forecast valid 00z 30 Oct 2012

The winds, surface pressure and specific humidity values are input in the National Center for Environmental Prediction's data assimilation system. These data have resulted in improved analysis of storm systems over the ocean and more accurate forecasts of their strength.

photo of aerographer launching a weather balloon from aboard a ship

Accurate routine observations are necessary to ensure data going into NWP models correctly represent the current conditions. Without adequate initial conditions, the models cannot provide reasonable forecasts of conditions farther out, be it a 6-hour or 6-day time period.

photo taken aboard the Navy vessel Kearsarge

Your diligence in taking and reporting consistent, high quality observations provides the models with the best possible current view of the atmosphere and ocean. Because oceans are generally data-sparse regions, these observations are particularly important when a vessel is underway or stationed offshore. Observed winds, surface pressure and specific humidity values ingested into weather forecast models have resulted in significant improvements in the analysis of storm systems over the ocean and more accurate forecasts of their strength.


This lesson will summarize the best practices and techniques for making and reporting weather and sea observations. The material presented here is based on the U.S. Navy Manual for Ship's Surface Observations (COMNAVMETOCCOMINST 3144.E) and will aid you in correctly observing and encoding weather data to complete a shipboard weather observations form, CNMOC 3141/3. This lesson covers a large amount of content. You may wish to work through the lesson in multiple sessions.

photo of sea and sky  on a day with cumulus cloud present

After completing this training, you'll be able to:

  • Observe and identify the 27 states of the sky
  • Estimate the height of cloud bases and tops
  • Encode observed weather using 99 present weather symbols displayed on weather charts
  • Determine present weather types and intensities
  • Determine significant wave heights, primary and secondary wave height, period, direction from afloat platforms
  • Determine temperature and dewpoint
  • Determine sea level pressure, station pressure, altimeter pressure
  • Encode observed elements into Synoptic Code
  • Explain how weather observations are used in Numerical Weather Prediction
  • Use special weather observation criteria (ice, snow depth, SPECI criteria) to determine when weather conditions require special observations to be recorded
  • Perform bathythermograph observations

Where to Observe

Shipboard observations are best taken on the windward side of the ship, in a relatively open area away from:

  • ship's stacks
  • air vents
  • steam lines and catapults
  • jet blast propeller and rotor wash
  • operating internal combustion engines
  • dark surfaces that receive prolonged direct sun
Weather staff working

Why is it important to be away from ship's stacks, air vents, steam lines, catapults, jet blast propeller and rotor wash, operating internal combustion engines and dark surfaces that receive prolonged sun? Choose the best answer.

The correct answer is a).

All the equipment above can produce heat and result in higher temperature readings than are actually occurring. While taking the weather observations near the ship’s stacks is appealing on a cold, windy day, it will result in incorrect temperature observation.

Please make a selection.

Tips for determining the best places to take various types of observations will be presented in the following pages.

When to Observe

photo of aerographer's mate at work aboard the USS Kearsarge

Because the weather has so far been calm this morning, your focus has been on routine observations, or METARs.

In general, there are three types of observations you will take:

  • Routine Observations (METARs)
  • Special Observations (SPECIs)
  • Local Observations (LOCAL)

Routine observations are taken and reported hourly. Required elements are observed within the 15 minutes preceding the hour. When in port, a ship should continue regular observing and reporting unless there is a nearby U.S. manned weather reporting activity meeting the requirements. Your METARs will need to be reported between 5 minutes and 1 minute before the hour, so for a 1400Z observation, you will submit your data between 1355Z and 1359Z.

AG2 Ferguson gives you guidance for taking your METAR.

AG2 Ferguson: "When taking a weather observation you need to start 15 minutes prior to observation time, as it will take about 10 minutes to take your observation. Where to take your observation depends on your platform – on a large ship like this, you want to take it next to the bridge. On a small ship, such as a frigate, you'd take it on a bridge wing. When taking an observation, you want to start at the surface and work your way up. So you'd start with the seas, then move to visibility, then low clouds, mid clouds and high clouds. OK, let's get started."

waterspouts over the ocean

If conditions warrant, you will also need to take special observations (SPECIs) to report significant changes in weather elements affecting aircraft or ship operations. SPECIs are also taken to record the weather conditions at the time of any significant event, including an aircraft mishap, collision at sea, or man overboard. SPECI observation criteria include:

  • changes in ceiling that cross 3000-feet, 1500-feet, 1000-feet, and 500-feet thresholds, or the lowest standard instrument approach minimum as published
  • development of clouds or obstructions aloft at altitudes below 1000 feet
  • changes in visibility across 3-mile, 2-mile, and 1-mile thresholds, or the lowest standard instrument approach minimum as published
  • a tornado, funnel cloud, or water spout observed or disappearing from sight
  • the first occurrence of thunder is heard, or if thunder cannot be heard directly because of flight deck noise, at the first sight of lightning
  • an aircraft mishap
  • wind direction changes of 45 degrees or more in less than 15 minutes when the sustained wind speed is 10 kts or more
  • beginning or ending of hail ¾ inch or greater, beginning, ending, or change in intensity of freezing precipitation or ice pellets
  • squalls
  • a volcanic eruption
  • any other meteorological situation that is critical to the safety of aircraft operations

Today, you know that there is a chance of thunderstorms, which can bring visibility issues, lowered ceilings, squalls and shifting winds, lightning, and other hazards, particularly for any aviation operations in progress on the ship. If thunderstorm or other significant weather conditions begin to materialize, you will want to make sure to do the SPECIs and document the weather changes.

photo of Aerographers Mate 2nd Class on a six-month carrier deployment in the Western Pacific

In addition to METARs and SPECIs, your reporting will include synoptic observations, which are recorded at the standard synoptic hours of 0000Z, 0600Z, 1200Z, and 1800Z. Additional synoptic reports are filed at 0300Z, 0900Z, 1500Z, and 2100Z per applicable fleet operation hours or at the discretion of the unit when unusual or significant weather phenomena are encountered.

photo of plane launch from carrier

Local observations are taken at the discretion of the individual METOC teams as operations and conditions warrant. These can include half-hourly observations during flight operations, strait transits, or other weather-sensitive activities.

Observation Timing Exercise

Twenty minutes after you submitted your the latest observations, a fellow shipmate stops by to tell you that low stratus and fog have been developing at the ship's location and ceilings are lowering quickly. In your observations, you noted that the visibility was 3 miles. What would you do next? Choose the best answer.

The correct answer is b).

Because the visibility was 3 miles about 25 minutes ago, the new report that the clouds are gathering around the ship could indicate that the visibility has dropped even further. It is a good idea to head outside and determine whether the visibility has dropped below the 2 or 1 mile thresholds. If so, you will issue a very timely SPECI.

Please make a selection.

By familiarizing yourself with the weather expected for the day and taking regular observations, you will start building situational awareness. This awareness will enable you to anticipate when a SPECI needs to be taken.

Making the Observations

photo showing view of sea conditions from a lower-level observation area aboard the Kearsarge

How you go about taking your hourly observations can vary a bit depending on the vessel, but in general, AGs have found it efficient to work from the bottom of the ship upward.

Starting on the lower deck, observe the seas. You'll want to be on the windward side of the ship and be able to look out to a distance of at least 50 yards to where the seas are unaffected by the ship. It can be useful to look at reported sea states for the previous hour to see if conditions appear to be the same or if they are changing.

Seaman Nicholas Pennington stands watch from the pilot house aboard the Arleigh Burke-class guided missile destroyer USS Preble (DDG 88).

Next, move upward to a high point where you are able to get the best 360-degree views. This will give you a good vantage point for the sky cover and visibility.

Temperatures and winds should be measured in a shady area out of direct sunlight and away from artificial heat sources that can set up temperature variations and microscale circulations or eddies. Also look for an open area where the wind is not blocked, channeled, or otherwise affected by the ship's structure.

Observation Sequencing Exercise