Climatology for the Operational Forecaster

While weather describes the state of the atmosphere at a given time and place, climate represents the average meteorological conditions that prevail in a particular location or region over a long period of time. Weather changes rapidly, within minutes and hours. Climate varies much more slowly, usually over scales of decades and is often summarized in terms of monthly or seasonal averages.

Climatological information can be presented as a statistical summary of weather parameters over time.

Average and record high and low temperatures, prevailing winds and currents, and significant wave heights are all climatological parameters. This information offers important guidance for weather-dependent operations.

Planning for a range of tasks—including facilities siting, ship deployments, or plane and helicopter maneuvers—can be aided tremendously by knowledge of the climatology for the region of interest.

In this module, we'll examine the climatological information useful in planning a ship deployment across a large area of the globe.

After completing the content, you'll be able to:

• Describe climatology and its use and limitations for operations
• Identify the products available to Navy users and methods of representing climatic elements
• Summarize different types of climatological information, including products available through the Advanced Climate Analysis and Forecasting (ACAF) system (accessible to DoD users only)
• Develop a climatological brief containing the necessary elements for naval operations

To summarize climatological information in a useful way, we need to know about the data we are assembling. Can the temperature for any given date be accurately forecast three to nine months in advance? Currently no, and probably not ever.

However, can we determine whether the temperature, precipitation, or sea heights for a period of time, like a month to three months, are expected to deviate from the norm? Skill tests performed on various prediction methods have shown the deviation from the norm may be predictable.

The key may lie with inputs of moisture and energy into the global climate system. Correlations between climate variables and sea surface temperature (SST), pressure, vertical velocity, or wind direction can show relationships, often called teleconnections, for use in long-range forecasting. Known oscillations, including the monsoon cycle, El Niño-Southern Oscillation (ENSO), and the Madden-Julian Oscillation (MJO), also provide climate prediction information.

Complex calculations and modeling allow the development of long-range outlooks, which are available from various sources, including the 14th Weather Squadron, NOAA's Climate Prediction Center, and the International Research Institute (IRI).

Long-range outlooks can be beneficial to add to tour or deployment briefings even though there are still some difficulties and uncertainties associated with the prediction processes.

As skill increases, the long-range information will become increasingly valuable for identifying locations that may need heightened international aid due to drought or flooding, or security due to civil unrest, or for selecting the most efficient trans-ocean routes. Due to the long lead times and uncertainty in long-term prediction products, they are best used for planning purposes rather than direct operational decision-making. The information can be used to assess potential impacts to personnel, materials, and operations.

In your role as an operational forecaster, you will likely be tasked with providing climate information for a specific purpose, such as a briefing for deployment. The Climate Analysis Process, or CAP, provides a framework for determining the needs associated with a climate information request so you can obtain the most useful data as quickly as possible. The CAP consists of five steps.

The first step is to identify the needs of the situation. When given a specific request, such as preparing a deployment climatological brief, begin by identifying the decisions that need to be made, what questions need to be answered, and what climate variables are involved. When briefing for a new area, you need to figure out what you need to know to become familiar with its weather and climate. What information needs to be gathered?

Next, you'll explore the area's physical setting and the basic climatology. This information includes geography, elevation, topography, climate, and weather patterns.

Some basic knowledge of the area and climate will allow you to refine the questions. With an understanding of the area's physical features, you can hone in on the climate variables and statistical parameters involved in the situation. This refinement will prepare you to explore the products and focus on the particular information you need to gather.

In Step 4, it's time to gather the climatological products and data and to interpret them in a way that addresses the needs and questions defined in previous steps.

Lastly, you'll resolve the request by communicating the information back to the customer. If you are asked for a deployment brief, you will want to include the parameters relevant to the operations and information on any changes in these parameters based on season.

Let's consider a scenario in which CAP is applied to a request received for a climatological brief for a ship deployment. We'll listen in as the Chief Aerographer's Mate works through the steps to determine the information needed, become familiar with the area, refine the questions, obtain the products, and, lastly, resolve the request.

Hi. I'm Chief Aerographer's Mate Powers at the Fleet Weather Center in San Diego, and I've just received a request to develop a climatology brief for a ship deployment from the U.S. West Coast to the Northern Indian Ocean, with time on station in Bahrain.

They're departing July 1 and will be on station in the Northern Indian Ocean and Bahrain until December before returning across the Pacific. I'll need to provide them climate data for the Eastern Pacific, Western Pacific, Northern Indian Ocean, and Bahrain for the times of their deployment and summarize the information in a brief.

Defining the needs of a situation is critical to achieving the desired results. When a climate request is received, the first task is to identify the questions to be answered and decisions to be made and to understand the parameters involved. Understanding these requirements should precede any search for actual climate information.

I'll begin by considering the following questions:

• What is being requested? What information do I as a forecaster need to provide? Is the situation clear enough? Do I need more clarification?
• What climatological questions must be answered to handle the situation? What weather and climate parameters are needed and where can I get the data? What information will I get from the data?
• Who is requesting the information, how do they want to get the results, by when do they need the information, and whom do I contact for additional information or clarification?

These questions will help detail what is being requested and the climate variables that are most likely to relate to the situation.

To provide relevant METOC information, I'll need to present a climatological brief that is based on significant thresholds for the mission. The Joint METOC Handbook contains these thresholds for all of the Navy's platforms, including the Carrier Operations I'm most concerned with for this request. The climatology information I select to communicate potential environmental impacts to leadership will be based on these relevant values and on the mission.

Next, I need to get familiar with the physical setting for the deployment and the major climate features for the time of year. The Naval Research Laboratory's Forecast Handbooks are a great source for this type of information. These handbooks identify the physical geography, major climate features, and significant weather patterns for areas of interest. For instance, the Southeast Asia Handbook contains detailed information for various areas of the region and offers a useful overview of the geography and climate drivers expected for that area. The Handbooks are available for several regions, including the Mediterranean, the Arctic, Central America, South Africa, and the Arabian Gulf. This information provides a good grounding as I determine what will be important to include in the climatological brief.

The Naval Research Laboratory also publishes Port Studies, with port and severe weather haven information for a number of locations worldwide.

These Port Studies and the Forecaster Handbooks are available from the NRL publications webpage.

I'll use these sources to review the basic synoptic set-up for the region and timeframe.

This approach to climate information works similarly to the forecast funnel—working from the large scale downward, and from obvious features to those that are more subtle. To be able to summarize the main features, I'll start with the larger-scale global view and then move to smaller scales.

With a clearer picture of area's physical setting and climate, I can now hone in on the information that I'll need to gather from the climate products. I'll narrow and focus the questions from Step 1, considering the following:

• What statistical parameters should offer the most useful information about the climate variables of interest? Maximums and minimums? Extremes? Averages?
• What time periods are relevant? Do I need hourly, daily, seasonal, or yearly information, or a long-term average?
• What are the expected magnitudes and timing of any seasonal changes?

The refined questions will include timeframes, location, specific climate variables of interest, and the application for which the climate information will be used.

Being as specific as possible will help in obtaining the right information and products. For example, while annual average winds, temperatures, or other parameters might be easy to provide, they will likely not be that useful, particularly in areas that undergo significant seasonal variations. Monthly climatologies will be much more relevant.

As a reference for the types of data to include, I consider how the information compares to the details provided in an aviation brief on a 175-1. In that case, the forecaster conveys weather information affecting take-off, route, and destination, providing a good outline for mission support. When scaling up to larger-scale climate information, I'll contemplate the various data products and whether they meet operational needs for en route, on station, and return operations. I'll put the information in the context of ship/airframe limits, as well as personnel needs. And I'll include information about specific weather events that might be encountered, including hurricanes/typhoons or monsoons.

CAP Step 4: Explore Products and Data

Based on the understanding of what to expect in general, I can now locate data for the relevant parameters, including winds, currents, ceiling and visibilities, and other operational information. I'll choose the specific parameters that will be most useful for operations planning, including both ship movement and aircraft maneuvers.

In this case, my primary sources of information will be Department of Defense sites, but there are also civilian sources, including NOAA websites, that provide useful data.

The Fleet Numerical Meteorology and Oceanography Center (FNMOC), (accessible through the Navy Enterprise Portal – Oceanography, or NEP-Oc), can provide data for several different parameters through the Advanced Climate Analysis and Forecasting (ACAF) system. This tool is only available to DoD registered users.

The ACAF site is set up with a menu to help access the available information.

ACAF provides wind, air temperature, relative humidity, geopotential height, and tropical cyclone data across the globe, as well as wave height, direction, and period information. It also provides evaporative duct heights and upper air ducting statistics for select ocean basins.

If I can't find what I need through the interface, I can request a tailored climatology product via an online form on the NEP-Oc. For instance, I might want standard deviations or high spatial resolution data for a particular area.

Recently added ACAF products include evaporative duct height climatologies for the Western North Pacific Ocean, the Northern Indian Ocean, and Mediterranean Sea. The Naval Postgraduate School is working on expanding the dataset to the Eastern Pacific, Western Atlantic, and Caribbean basins. This information should be operational by late 2014.

Currents and wave data will help the leadership know what to expect en route. These data are available from the Naval Oceanographic Office and also from NOAA. The NAVO website (accessible via the NEP–Oc) provides access to a range of meteorology and oceanography data, including ocean wave prediction charts and climatological values for ocean temperature, salinity, and velocity structures.

I'll get information about winds from the U.S. Air Force 14th Weather Squadron. The data will be useful for understanding the prevailing surface flow, as well as upper-level winds. The 14th Weather Squadron also provides ceilings and visibility data, dust climatologies, and information for other climate parameters. Products are accessible through the Air Force Weather website, portions of which require DoD registration for access. Once I've accessed the site, a KML Product Locator will let me select the climate parameter and geographic area of interest.

Various products are available through the Air Force 14th Weather Squadron. Many of the examples that follow are for San Diego, California, where our deployment will begin. The 14th Weather Squadron interface allows a forecaster to locate similar products for various locations worldwide.

Ceilings, visibility, and other data for various global locations come from the 14th Weather Squadron via ACMES, or Advanced Climate Modeling and Environmental Simulations. ACMES provides high-resolution modeled climatologies for various meteorological and climatological parameters.

The Operational Climatic Data Summary uses a sliding 10-year mean to define a location's climate. Extremes are calculated over the entire period of record for a station, and a quality assessment of the data is also provided for determining confidence. Users are able to define their own record period for a station and can also select specific months and years based on the ENSO index.

The Wind Stratified Conditional Climatology leverages current conditions to provide a 24-hour statistical ceilings/visibility forecast based on the historical period of record. The products show the likelihood that conditions will change based on the entire database for a specified location.

For the brief, my primary sources of information will be Department of Defense sites, but there are also civilian sources, including NOAA websites, that will be useful. Various locations for climate information are listed in the Resources section of the module. Parameters available through NOAA or other civilian sources include air temperature, sea surface temperature, precipitation, winds, humidity, currents, tides, wave heights, and, for some locations, fog and visibility.

Once I've reviewed the products and interpreted the data, I'll communicate the findings to the customer. Here's where the information gathered in Step 1 comes in handy. It tells me what was requested and lets me know the information that is critical to provide.

Building a useful deployment climatology brief is key for leadership and mission planning success. Providing a set of relevant products and information will address basic climatology needs, but a brief should be tailored to the mission leadership and their specific operational thresholds. It is easy to show, for example, that the average temperatures or expected wave heights in a deployment region will be within a certain range. However, a good operational meteorologist will be able to discuss the probability that the given temperatures or wave heights will affect maritime operations.

Annual average meteorological variables can typically be summarized very quickly. But remember that extremely general information about annual average temperatures, extremes, and/or wind directions might not be beneficial to operations. In some cases, this general information can even lead to a misunderstanding of the expected conditions for a given time period.

A successful climate brief is one that, first, meets the customers' needs, and second, is easy to understand. A brief can be arranged either by topic (winds, currents, etc.) or chronologically. As I put together the information, I need to be prepared to shift timeframes and to review monthly climatologies as needed.

I know that mission leadership is unlikely to be interested in lengthy discussions of climate science. Instead, I'll use my background knowledge to alert them to things that might affect operations and to respond to specific questions as asked.

For instance, leadership might not care that a monsoon circulation results from temperatures contrasts due to differential heating of land and ocean. But they will want to know to specifics like when to anticipate onshore flow as the land becomes warmer. For an extended deployment, information about the start and end of monsoon season will be useful. Likewise, I might not go into detail about the Madden-Julian Oscillation (MJO), but if it's relevant, I'll provide information about expected rainfall based on what I know about the MJO status during the time of deployment.

Now that I've gathered all the products, I'll build a brief to communicate potential environmental impacts to mission planners based on climatology. A PowerPoint presentation provides a useful way for organizing the information. I'll start with the significant thresholds for the operations and let mission planners know if conditions could be favorable, marginal, or unfavorable during the journey to the Northern Indian Ocean, on station in Bahrain, and for the return voyage in six months.

We begin with information about weather and sea conditions expected en route. The climate in the eastern Pacific and central Pacific is dominated by the North Pacific High, a semi-permanent subtropical high pressure system. In the Navy, we refer to this as the Eastern Pacific High, or EASTPAC High. This system is farthest north and west (typically just north of Hawaii) during July and August.

The dominance of the semi-permanent high is displayed in the monthly mean 10-meter surface winds for the Pacific in July. Eastern Pacific winds are northerly along the southeast U.S. coast, becoming northeasterly over the deep ocean. Strong easterly winds dominate beginning at around 160°W. In the WestPAC, winds are typically easterly and speeds are light. Marginal wind thresholds for carrier operations are > 20 kts and unfavorable conditions are winds > 30 kts. Overall, it appears that winds are likely to be favorable for the westward transit.

Now we shift from the winds to the corresponding ocean conditions. For the route westward across the Pacific in July, the weakest currents are found in a zone from approximately 15°N to 30°N latitude. The strongest westward currents are typically positioned at 10°N latitude in the direction of transit. Meanwhile, the strongest east currents are generally located between the equator and 5°N latitude. The currents in this area would be against the direction of ship movement.

The mean currents data for the Indian Ocean show east currents of about ½ knot to 1 kt against the direction of transit. In the Northern Indian Ocean, one of the dominant currents is the Somali current, a boundary current along the coast of East Africa. This current moves northeastward along the Somalia and Oman coastlines, pushed by the southwest winds of the summer monsoon.

As the monsoon flow ceases in September and October, the Somali current weakens.

The sea state can be described based on mean significant wave height information produced using the ACAF tool. Here is a look at the typical wind-driven seas for the month of July when the ship moves through the western Pacific and Indian Ocean. The significant wave height is generally less than 6 feet for the west Pacific, but seas increase to a mean significant wave height of 6 to 9 feet in the Indian Ocean. The highest significant waves are in the North Arabian Sea with a maximum of 12 to 15 feet. The higher seas in the Arabian Sea are a result of the Southwest Monsoon, which is evident from the 1000 mb wind pattern. These winds are on average greater than 30 kts, which is the threshold for unfavorable conditions based on the wind criteria for carrier operations.

The ACAF tool enables us to view the probability of seas greater than 12 feet for the Indian Ocean. Most of the Indian Ocean has a less than 10% chance of seas more than 12 feet. A maximum exists in the Arabian Sea where there is a 90-100% chance of 12-foot seas during the month of July. Combining this information with the mission thresholds shown earlier, conditions are likely to be unfavorable for carrier operations in the Arabian Sea in July. Conditions in the rest of the Indian Ocean are generally favorable during the month of July.

The threat of tropical cyclones is a concern during the transit toward the Persian Gulf from Hawaii. Here are tropical cyclone tracks during the month of July from 1970 to 2009, produced using ACAF. Historically, the largest threat is primarily in the West Pacific.

In the Indian Ocean, tropical cyclones are less frequent and have only occurred in the Bay of Bengal and the Southern Hemisphere.

As expected, the tropical cyclones of the West Pacific form in areas where mean sea surface temperatures values exceed 80°F in July. Cooler water temperatures exist along the coast of Somalia and in the Arabian Sea due to upwelling caused by the strong winds associated with the Southwest Monsoon.

The mean relative humidity during July from 1979 through 2009 in the Indian Ocean is depicted from the NCAR NCEP Reanalysis-2. The highest values occur on the west coast of India and the Strait of Malacca with mean values greater than 90%. High temperatures combined with large relative humidities result in high heat index values, which are a concern for personnel safety.

Once the ship arrives in the Persian Gulf, other factors based on the area's climatology and geography become important, particularly because the ship will operate in the area for several months. Monthly climatology for local countries and ports can be used to understand expected conditions. This quick overview includes monthly high and low temperatures, average monthly precipitation, and wind and wave data.

Many of these parameters are available via the Operational Climatic Data Summary or OCDS. This chart depicts the monthly variability of the weather parameters and provides information on the probable environmental conditions when operating in a location for many months.

Various text products detailing currents, tides, visibility, and seasonal hazards for port locations are available through the Naval Research Laboratory's port studies. In this case, I'll include information for Mina Salman near Manama in northern Bahrain.

While operating in the Arabian Gulf, dust storms from the Arabian Peninsula or Iraq become relevant due to the arid landscape upwind. These storms can impact several mission areas, particularly flight operations.

The frequency of occurrence of reduced visibilities due to dust storms can be produced from Air Force Weather Agency data. The graph indicates that events causing visibilities of four nautical miles or less occur most frequently during the months the carrier will be operating in the area. When applying the carrier threshold information, this plot indicates the mean number of days with marginal and unfavorable visibility conditions.

The Navy Research Laboratory can also produce information about surface dust. The information can be used to create generalized graphics showing areas particularly prone to dust storm events.

The 14th Weather Squadron ACMES data provide a climatology of monthly low ceilings/visibilities for various regions. Here, we look at the percentage of time during July with ceilings less than 1500 feet or visibility less than three miles. The data suggest that most of the Persian Gulf experiences these conditions 0-5% of the time in July. Maximums occur in the southeast Persian Gulf where frequencies increase to 10-20%. The analysis identifies the frequency that areas are at best marginal for carrier operations due to visibility and ceiling thresholds for carrier operations.

In addition to the climate parameters summarized previously, FNMOC can provide information about evaporative duct heights.

Here is a plot of the long-term mean evaporative duct height (EDH), in feet, for the month of August at 12Z. Comparing with the 0Z values can provide information about the expected diurnal variations of these heights.

Here's a view of the currents for the return trip through the Indian Ocean for December. West currents, against the direction of the ship's movement, exist from the equator to 5°N latitude. An east current, following the ship's intended movement, is likely from the equator to 5°S latitude.

By December, mean 10-meter surface wind speeds in the Pacific are favorable for carrier operations based on the thresholds. In terms of direction, the winds will primarily be easterly, which will be against the ship's direction of movement.

Once in the Pacific, little to no current exists on the route toward Hawaii if the ship stays north of 15°N latitude.

When presenting a brief to mission leadership, you should also document all data sources. Here's the list of data locations for the Northern Indian Ocean deployment brief.

Data Sources:

• AFWA/14th WS - Air Force Weather Agency/14th Weather Squadron
• FNMOC - Fleet Numerical Meteorology and Oceanography Center
• NAVO - Naval Oceanographic Office
• NRL – Naval Research Laboratory
• NOAA - National Oceanic and Atmospheric Administration
• UCAR/NCAR - University Corporation for Atmospheric Research/National Center for Atmospheric Research

As you completed the module, you learned about the Climate Analysis Process and how each step ensures that the most useful information is provided to your customer. Remember that the overall schema for a climatological brief will include the products, methods, information, and data sources. Following the Climate Analysis Process will help you produce a brief that is modified and tailored to your leadership and customers. A good operational brief will also include discussions of multifaceted aspects of seasonal climate shifts and hazards.

In addition to providing information about the conditions expected on deployment, climatological data can be useful for a range of other applications. These include siting a deployment area or a base facility, determining what seasons or times of day will best accommodate air operations, or estimating the fuel resources necessary for a deployment. Climatological data are also used in situations in which real-time weather information is not available or is very low quality.