The Largest Security-Cleared Career Network for Defense and Intelligence Jobs - JOIN NOW


FM 34-81: Weather Support for Army Operations



Weather significantly impacts on the feasibility of using military force and on ensuing operations. It impacts differently on various types of forces and, in some cases, dictates the types of forces that can be employed effectively. Weather data is part of the intelligence information required by commanders and staffs to plan and conduct combat operations. The answers achieved by analyzing weather data, identifying weather effects, and assessing the impact of weather on systems, tactics, and operations provide vital information for commanders to optimally employ their forces.

The global mission of the United States Armed Forces requires an extensive network of weather observers, analysts, and forecasters. The network consists of the national weather services of each friendly country, our own National Oceanographic and Atmospheric Administration (NOAA), and weather or environmental units within the US Army, Navy, Air Force, and Marine Corps.

Meteorological services of each country provide the basic observation network and related weather facilities in the country. Current and future global weather conditions can be forecast by exchanging data among nations. Peacetime cooperation among nations for weather services provides global and hemispheric analyses in support of military operations anywhere in the world. During wartime, meteorological control and other security restrictions may drastically limit the availability of other national and indigenous weather information.

US military weather services and units are specialized organizations with worldwide capabilities structured to satisfy unique military requirements. They exchange weather data with national weather services and have access to national and international weather data bases. Characteristics of the military weather services are--

  • Mobility.
  • Responsiveness to command.
  • Combat readiness.

Weather support is most effective when weather personnel know the mission, organization, capabilities, plans, and procedures of the Army units they support. The demands placed on weather support organizations are more realistic when Army personnel understand the basic principles of weather forecasting and recognize the capabilities, limitations, and support requirements of the WETM.


Weather support for Army tactical operations is based on the following principles. Each of these principles as they apply to Army operations is described in chapters and appendixes as shown.

  • Weather effects must be considered by all tactical units during all planning and operational phases, including deployment, employment, CS, and CSS (Chapter 3).
  • Commanders must consider favorable and unfavorable weather conditions to determine the best course of action to accomplish the mission (Appendixes B and C).
  • Accuracy of weather forecasts is dependent on the density and timeliness of weather observations. All weather observations, particularly those taken by Army personnel forward of the division TOC, must have high priority and be rapidly transmitted to an Air Force WETM (Appendix A).
  • Timely, reliable primary and alternate communications must be provided (Chapter 5).
  • Because of continually changing atmospheric conditions, weather information is highly perishable. Weather observations and forecasts must be monitored and updated continually.


The Air Force provides the bulk of weather support required by the Army. AR 115-10/AFR 105-3 specifies each service's functions and responsibilities associated with that support.


The USAF Chief of Staff, through the Military Airlift Commander (MAC) Air Weather Service (AWS), provides--

  • Weather personnel with the technical training and skills necessary to support their Army customer.
  • Direct weather support for EAC, corps, divisions, separate brigades, aviation brigades, regiments, and groups according to jointly agreed upon tactical doctrine and operational support concepts.
  • Weather training for Army personnel assigned to take limited surface weather observations in support of Air Force forecasting operations, or in support of Army ATC operations.
  • The general effect of weather on systems, tactics, and operations based on critical threshold values identified by the Army.
  • Weather observations, forecasts, staff support, and timely warnings of expected weather that may adversely affect operations or that could be a hazard to personnel or materiel.
  • Weather support products for use in soil trafficability and hydrographical prediction.
  • Unique and specialized meteorological observations and forecasts of data elements not include in standard surface weather observations or critical values on request.
  • Climatological support for tactical missions, IPB, and tactical decision aids.


The US Army provides--

  • Surface observations forward of division command elements and all upper-air observations. This does not preclude the Air Force from placing personnel in forward areas to collect and relay weather information and to take weather observations.
  • Critical or threshold values for determining the weather effects on systems, tactics, or operations.
  • The assessment of the impact of weather effects on systems, tactics, or operations.
  • Trafficability and hydrographic forecasts.
  • Weather communications circuits from the Defense Communications System (DCS) interface point to tactical locations.


Joint responsibilities of the individual services are determined in contingencies and wartime by--

  • AR 115-10/AFR 105-3.
  • Joint agreements governing US major Army commands (MACOMs) to include USAF WETMs early in their war plans.
  • The type of operation.
  • The service that provides the majority of forces.
  • Directives of the unified or specified commands, subordinate unified commands, or other joint force commanders.

Wartime support required by individual combat arm units is described in the field manuals and doctrinal publications of those units. Peacetime support required by US Army garrisons, other fixed installations, and combat elements for peacetime training is determined in accordance with Army and joint regulations listed in the references. This peacetime training support may exceed the level of wartime support. US Army commanders should be well informed of the differences between peacetime and wartime support.


There are several other sources of weather information besides national and international sources. These sources--Air Force, Army, and Navy--acquire weather data from locations throughout the AI. This information ranges from intermittent measurements of a few weather elements to detailed observations of many environmental elements taken on a regular schedule by trained weather observers. The detailed observations contribute most significantly to the data base from which tactical weather products are derived. The primary sources of tactical surface weather observations and upper-air data are the--

  • AWS WETMs.
  • Army artillery meteorological (ARTYMET) sections.
  • Forward Area Limited Observing Program (FALOP).


The AWS obtains, evaluates, and disseminates weather information for the Army. The AWS operates on a global scale. Its mission is to provide weather support for Army, Air Force, and certain joint operations. Support includes--

  • Weather observations.
  • Forecasts.
  • Climatological data.
  • Light and tide data.
  • Atmospheric and astronomical information affecting radar, wireless communications, and E-O weapon systems.

This global support requires the input of both surface and upper-air data from AWS, National Weather Service (NWS), Federal Aviation Administration (FAA), Navy, and allied meteorological services, as well as data furnished by Army sources.

A reliable forecast depends on an accurate description of the atmosphere over a large geographical area. In parts of the world where surface observation sites are sparse or nonexistent, data are partially obtained by aerial reconnaissance flights and weather satellites. Aircraft weather observations are available from several sources. Data derived and extracted from these sources are relayed to the forecast unit (FU) for distribution to both Army and Air Force WETMs. Other weather observations are available from--

  • Civilian and military aircraft that provide information along their routes.
  • Military aircraft performing tactical missions.

The Defense Meteorological Satellite Program (DMSP) is a joint service program whose mission is to provide--

  • Timely, high-quality stored data for support of special strategic missions and EAC operations.
  • Real-time direct readout data for support of tactical air and ground operations to EAC or other locations. This satellite imagery then can be interpreted, and forecasts based on it will be relayed to corps and division.
  • Research and development in advancing meteorological satellite technology.

DMSP satellites are in near polar orbit and can provide coverage of a theater of operations. Visible, infrared, and high resolution data can be obtained. The AWS has transportable receivers that can receive imagery as a satellite passes over or near the area. These receivers can be airlifted by C-130, C-141, or C-5 aircraft, or transported over improved roads.

DMSP imagery can be obtained from these receivers and relayed to EAC, corps, and division WETMs where the appropriate receivers are installed. Satellite imagery may be the single available source to fill in data-sparse areas.

The Naval Oceanographic Command (NOC) provides the AWS the necessary charts and tidal data for Army tactical operations. Ships at sea also provide data.

WETMs support the tactical Army by providing SWO support and forecasting and observing services. Weather observations are taken and disseminated to weather units throughout the theater. They are interpreted by a forecaster and incorporated into tailored weather products for the Army. These observations are included in the worldwide data base for national use. The SWO provides tailored support to the Army for effective integration into all facets of tactical operations. A detailed description of the AWS support system is in Chapter 3.


Within an Army command, ARTYMET sections acquire upper-air data and surface weather observations. They disseminate current meteorological data to their assigned field artillery unit and for the USAF WETM.

The mission of ARTYMET sections is to support the needs of the Army by providing--

  • Ballistic meteorological messages.
  • Meteorological data for fallout prediction.
  • Computer meteorological messages.
  • Upper-air weather observations to the AWS WETM.
  • Limited surface weather observations to the AWS WETM.
  • Target acquisition meteorological messages.

The data obtained by an ARTYMET section can be vital in developing tactical weather forecasts. Similarly, data collected by the AWS can help the ARTYMET section perform its other missions. Therefore, corps and division WETMs, fire support elements (FSEs), and ARTYMET sections must develop a harmonious working relationship. To ensure the expeditious exchange of data, standing operating procedures (SOPs) should specify the support requirements, including frequency of contact, scheduling, and mode of communication. A complete description of the ARTYMET section is in Chapter 4.


The FALOP is a G2 directed program designed to obtain timely weather observations in the forward areas of the battlefield. A complete description of FALOP is in Chapter 4 and Appendix A.


Other Army organizations obtain limited weather data in support of their missions and weapons systems. These organizations include maneuver, chemical, aviation, and engineer units.

Availability of these sources varies. Therefore, the SWOs must identify them within their supported Army units, have the requirement to transmit the observations published in tactical SOPs, and ensure that reliable communications links are established in appropriate signal annexes to operation plans (OPLANs) or operation orders (OPORDs). The G2 provides command emphasis in stressing the importance of these observations to major subordinate commands (MSCs).

Collectively, the above organizations can provide a variety of surface and low-level observations on an unscheduled basis, such as--

  • Onsite observations of--

--Surface temperature.

--Dewpoint temperature.

--Wind direction and speed.

--Surface pressure.

--Visibility and obstructions to visibility.

--Special phenomena.

--Cloud cover and height.

--Type and amount of precipitation.

--Snow depth.

  • Observation from ground observers, aircraft, and ground radars of--

--Cloud cover.

--Visibility and obstructions to visibility.

--Type and amount of precipitation.

--Special phenomena over both friendly and enemy-held territories.

These observations must be provided quickly to AWS WETMs if they are to be of value.


Weather information provided by each of the sources in the preceding paragraphs must be integrated with operational data to determine its impact on tactical operations. Intelligence staffs of EAC, corps, divisions, ACRs, separate brigades, aviation brigades, and SOFs convert correlated data into information that is useful to the commander.

Weather information is the staff responsibility of the intelligence officer at each echelon. At EAC, corps, divisions, ACRs, separate brigades, aviation brigades, and SOF the intelligence officer is supported by a USAF WETM commanded by the SWO. Additionally, the terrain team supporting corps and divisions assists the intelligence officer at those echelons in assessing the environment's effect on the terrain.

The intelligence section, the USAF WETM, and the terrain analysis detachment provide integrated environmental support at EAC, corps, and divisions. This close relationship ensures that the best possible weather and environmental effects information is available to planners and decision makers when needed.


At the tactical level, requirements for forecasts are of shorter range. Shorter lead times enable more accurate forecasts and, subsequently, better determination of weather effects information. Weather effects apply to specific weapons systems, vehicles, tactics, personnel, and equipment; they also impact on resupply and reinforcement because they affect rates of movement.

Weather effects information is becoming more important as smart, sophisticated weapon systems and faster more maneuverable vehicles are entering our inventory. Adverse weather conditions can--

  • Reduce speed.
  • Eliminate avenues of approach.
  • Thwart a well thought-out concept of operations.
  • Limit some smart munitions.
  • Cause thermal devices to become blind to the target.

Because of this, a system of tactical decision aids can be used to determine effects. Tactical decision aids can be as simple as a look-up table giving simple results; or a complex software package on a tactical computer terminal which produces graphics of weapons limited by weather conditions. Results of the tactical decision aids can be--

  • Acquisition and lock-on ranges for thermal sights or smart munitions.
  • Cross-country movement rates of specific vehicles.
  • Air or ground avenues of approach.
  • Effects on ammunition requirements.
  • Needs of individual soldiers to remain effective in combat.

Threshold weather effect values are established by testing equipment or by actual experience. When weather passes below that value, a flag is triggered to identify an impact on a specific mission. Thus, through the use of tactical decision aids, users are warned of the specific impacts of weather on operations.

At lower echelons weather effects determinations may be based on observations instead of forecasts; they provide information of what the weather is actually doing to the troops and equipment engaged on the battlefield.


The G2 at EAC, corps, and division and the S2 at brigade, ACR, separate brigade, aviation brigade, SOF, ranger regiment, and battalion operations have primary staff responsibility for weather analysis at their respective echelons. Each ensures that critical weather data required for current and projected operations are reviewed on a timely basis and integrated into the planning cycle. The intelligence officer--

  • Knows where to obtain weather data and the types of weather products available.
  • Coordinates support and consolidates the commander's requirements for weather support.
  • Coordinates with the SWO to ensure that weather information affecting intelligence is interpreted correctly.
  • Interprets the effects of weather on tactical operations.
  • Coordinates with the SWO and artillery commander to arrange for the timely exchange of meteorological information.
  • Informs subordinate Army units of FALOP requirements. The SWO coordinates the FALOP requirements with the G2 or S2. The G2 or S2 informs subordinate units at brigade and battalion levels what information is required, the priority of requirements, and how the information is forwarded. Tasking as shown below is included in the intelligence annex provided by the G2 or S2.
  • Transmits weather forecasts and warnings down the chain of command to lower echelons.
  • Ensures Army weather observations are transmitted up the chain of command to the G2 or S2.
  • Integrates weather analysis into advanced planning.
  • Ensures all AWS elements are provided with communications, logistic, and administrative support from Army resources in accordance with AR 115-10/AFR 105-3.
  • Coordinates weather observation training requirements of Army personnel with the G3 or S3, ensuring that Army personnel are trained to take FALOP observations.


The SWO is an Air Force officer supporting Army echelons by providing direct weather service support to the Army unit to which assigned. The SWO is a member of the commander's special staff, under the staff supervision of the G2. The SWO and the WETM are under the operational control of the Army commander. The SWO's primary duty is to advise the tactical commander and staff on all matters pertaining to weather and climate. A complete description of SWO duties is in Chapter 3.


Terrain analysis detachments support corps and division terrain intelligence requirements. Terrain analysis detachments--

  • Interpret the effects of weather in terms of trafficability and mobility.
  • Produce terrain studies and terrain-related intelligence data.
  • Collect and compile graphic and textual data required by supported units.

When necessary, terrain analysis detachments update maps by using all available information including weather and environmental data.


Join the mailing list