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FM 34-81: Weather Support for Army Operations



Weather is critical to Army tactical operations and operational level planning. History is filled with examples of the weather's effects on combat operations on a variety of battlefields. The AirLand battlefield of today may provide additional examples of victories and defeats attributable to skillful integration of weather in military planning and execution of combat operations. Weather, enemy, and terrain are often referred to as the wet trilogy, as shown in Figure 1-1.

Weather information is as much a part of combat intelligence as enemy and terrain data. It is often as significant as enemy intentions and trafficability. It affects enemy actions and the decisions of both forces. Adverse weather conditions--

  • Affect mobility.
  • Decrease the ability to see and attack deep.
  • Degrade electro-optical (E-O) systems.
  • Increase the requirement for thoroughly integrated air and ground operations.
  • Slow the movement of supplies and reinforcements.

Weather is one dynamic factor on the battlefield which commanders cannot control but which has the potential to affect every combatant, piece of equipment, and operation. Weather becomes more significant to success on the Air Land battlefield as advanced E-O weapon systems are fielded because of their vulnerability to adverse weather.

Commanders must be aware of and prepare for general and specific effects of weather on enemy and friendly major weapons systems and operations. This includes evaluating plans to minimize the adverse weather effects on friendly forces and to maximize the effects on the enemy.

Potential adversaries do not place as much emphasis on numerical weather prediction as the United States and its North Atlantic Treaty Organization (NATO) Allies. Warsaw Pact doctrine minimizes the effects of changing weather conditions by seizing and holding the initiative through speed, mass, and disruption. Timely and accurate weather forecasts help our commanders exploit this Warsaw Pact vulnerability. In a low-intensity conflict (LIC), the enemy will most likely have very primitive weather support. Sophisticated support to US forces allows commanders to employ their forces to maximum effectiveness according to the major tenets of the AirLand Battle.

  • Initative. Adverse weather normally favors the attacker. However, changing conditions provide both sides with windows of opportunity and vulnerability. Defenders use these windows to set the terms of battle, defeat the enemy attack, and seize the initiative. Attackers use these windows to enhance the attack and carry the battle to conclusion.
  • Depth. As the battlefield is extended in space and time it becomes more likely that weather conditions will vary, opening windows of opportunity and vulnerability.
  • Agility. If commanders are knowledgeable of weather effects on the enemy and friendly forces, then timely and accurate weather support will enable them to respond to changing conditions more rapidly than the enemy.
  • Synchronization. The combat power of AirLand Battle forces is made up of many components, each with its own unique weather sensitivities. in order to employ these component forces for maximum effect on the battlefield, commanders must know of weather conditions and weather effects on the components.


The AirLand Battle is an extended, integrated battle involving the use of all available air and land forces. It is extended because the battle is fought from the rear boundary out to the range of available weapons as a single, continuous battle. It is integrated in that nuclear and chemical weapons are merged with electronic and conventional weapons in all operations and plans. The use of nuclear and chemical weapons depends on the tactical situation and requires a release from the national command authority.

Inherent in the AirLand Battle is the simultaneous fighting of deep, close-in, and rear operations. The need for deep attack emerges from the nature of our potential enemy's doctrine and numerical superiority. Our objectives are to--

  • Gain a degree of manipulative control over enemy follow-on forces.
  • Destroy enemy combat power before they can join in the close-in operations in the defense.
  • Carry the battle to the enemy's depth through bold but calculated offensive operations.

Whether the enemy is doctrinally echeloned is not critical. What is important is that superiority in numbers permits the enemy to keep a significant portion of its force out of the fight, with freedom to either overwhelm or to bypass the friendly force. The existence of these follow-on echelons gives the enemy an advantage which must be overcome. Friendly forces must seize and retain the initiative in order to fight successfully and win. To gain the initiative, friendly forces must--

  • See deep and begin early to disrupt, delay, and destroy enemy follow-on or reinforcing echelons.
  • Move quickly against enemy assault echelons to prevent them from achieving their objectives.
  • Finish the opening fight against assault echelons rapidly and go on the attack before follow-on echelons can join the battle.
  • Prevent enemy forces from reinforcing the assault forces and achieving their objectives through mass and continuous combat.
  • Find the opportunity to seize the initiative--to attack and destroy the integrity of the enemy operations plan, forcing the enemy to stop the attack or risk defeat.

Vulnerabilities are inherently created as the enemy organizes forces into echelons that are needed for success. These same vulnerabilities give us the opportunity to put enemy second-echelon forces at great risk. Intelligence preparation of the battlefield (IPB) and target value analysis (TVA) help us identify high-value targets (HVTs). These targets include bridges and choke points that cause enemy follow-on echelons to bunch up and present lucrative targets. Effective deep attack provides the friendly force commander the opportunity to seize the initiative and dictate battle terms.

Limited strike and acquisition means are applied in a well-organized and coordinated scheme to support this plan. The commander decides when to use deep attack and which targets to destroy to create opportunities for offensive action. The decision is based on a single scheme of maneuver and a fire plan for deep operations. The opportunities for decisive action must be created in areas where sufficient logistic support, fire support, and maneuver forces are available.

Careful coordination of present and future action throughout the depth of the battlefield requires the plan come from one commander's concept. Separation of close and deep operations invites the risk that opportunities will not be generated or, if generated, that forces will be unprepared to identify and exploit them.

Unity of command is essential to the extended battlefield. The commander is fighting one battle, composed of several parts, that are interrelated. The depth of this battlefield extends beyond the forward line of own troops (FLOT) and is a function of the commander's planning horizon. Each level of command has a dual responsibility. Each commander must attack the enemy's assault echelons and delay and disrupt follow-on echelons to seize the initiative and destroy their operational plan. Commanders must also see and determine the intentions of enemy forces that can affect future operations.


Commanders consider the battlefield in terms of the time and space necessary to defeat the enemy force or to complete the assigned mission. Time is the first consideration and must be related to a battlefield area so commanders can direct their reconnaissance, surveillance, and target acquisition resources to identify targets and threats. To convert time into space, commanders must consider the unit's mission and capabilities and the maneuverability, terrain, and capabilities of the enemy. Commanders view the battlefield as having two distinct areas which can be expressed in terms of time. These are the area of operations (AO) and the area of interest (AI). Weather products, like any other intelligence information, must be keyed to those two areas.

The AO is a geographical area assigned to commanders for which they have responsibility and in which they have authority to conduct military operations. Commanders are assigned an AO based on the mission, enemy, terrain, troops, and time available (METT-T). The AO is of sufficient size to allow maneuver for successful completion of the mission, as shown in Figure 1-2.

The AI is an area of concern to the commander. It encompasses adjacent areas and areas occupied by enemy forces that could jeopardize the mission. The time span, as shown in Figure 1-3, is increased to allow planning for future operations.

Whether attacking or defending, each echelon of command must create the time and space needed for subordinate echelons to defeat enemy forces in contact before it becomes necessary to engage those not yet in contact. This is done by attacking deeper enemy echelons to delay, disrupt, and destroy them before they can affect the operations of friendly subordinates. For example, the division may interdict deeper enemy regiments while its brigades fight assaulting enemy regiments or defending enemy battalions; corps may interdict deeper enemy divisions while the division fights assaulting enemy divisions or defending enemy regiments.

Subordinate commanders may request that superior commanders take specific measures against deeper enemy forces, normally in the subordinate's AI. When this is the case, subordinate commanders should also specify what they want done to the enemy formation; for example, delayed for a specific time, canalized along a specific avenue of approach, or defeated in a specific area.


Each echelon of command has a range of responsibilities while fighting a rear, close-in, and deep operation at its own level. Weather support requirements are different at each level and must be tailored to meet the scale and time for the AO and AI.


An Army headquarters normally exists between the theater and the corps echelon. This may occur when--

  • Several corps are employed.
  • There is a dispersion of forces.
  • Political or geographical conditions dictate wide variations in the nature of operations.

The EAC commander directs the operational level of warfare. Overcoming the enemy's initial numerical advantage must begin at the highest level. EAC is responsible for skillful employment of long-range assets, including--

  • Air power.
  • The movement of reinforcing forces into the battle area.
  • Much of the CSS activities required to support the operations of deployed corps.

Enemy forces and their nuclear delivery systems must be located and destroyed before they can affect close-in operations. EAC commanders must see the enemy forces that will affect friendly operations up to 96 hours and beyond. To see the battlefield enables commanders to make timely decisions to effectively employ friendly forces and long-range weapon systems.

Several operational work centers may exist to support EAC responsibilities. The EAC structure depends on the theater and level of conflict. Geographically separated command and control (C2) centers may exist at EAC main, rear, alternate, and echelon above corps intelligence centers (EACICs). The EACIC is the hub of theater intelligence and normally is part of the EAC Ml brigade. Several components in the EACIC include--

  • An all-source analysis center (ASAC).
  • Ten intelligence support elements.
  • A center support element to direct collection efforts, analyze information, and integrate data into operational planning.

EAC commanders need to know--

  • Current and forecast weather condition effects and impacts in their AO and AI and logistical points of embarkation and debarkation.
  • A general overview of weather effects on subordinate commands and the weather impacts on tactical air support and tactical and strategic airlift.
  • Seasonal conditions and climatology which affects their campaigns across the theater.
  • The plan for the next season and how the combination of terrain and weather will limit or enhance their capabilities.
  • Historical climatological studies for the theater of operations to ensure operations plans include general weather effects on weapon systems, maneuver, logistics, personnel, and the use of aviation and close air support (CAS) assets.


The corps is the highest tactical echelon. The corps directs, coordinates, and allocates resources for operations in its AO up to 72 hours in the future. Corps generally conducts offensive operations by--

  • Massing fires or forces against enemy flanks, gaps, or rear.
  • Seeking to avoid enemy strength.
  • Going against enemy weak areas.
  • Using economy of force in areas from which forces have been drawn.

While divisions normally attack first-and second-echelon defenses, corps plan and conduct operations against deeper defensive echelons, reserves, and reinforcing forces. Corps interdict second-echelon enemy divisions of first-echelon armies to delay and disrupt those forces before they can join the battle. Corps direct the AirLand Battle and provide security for the rear area.

Weather information requirements differ for EAC and subordinate commanders in the time period and the level of detail. Weather effects interpretation efforts key on the engagement of forces during the next 72 hours. However, corps commanders need to know current observed weather conditions and forecasts for their AI out to 96 hours in order to--

  • Judge the weather effects on the enemy plans and movement.
  • Assess the affects on their systems and tactics.
  • Adjust their planning.

Commanders need forecasts of conditions limiting ground and air movement from aerial and sea points of debarkation to support logistical efforts. The same type forecasts provided to divisions but expanded in time and space are needed to support corps combat operations such as artillery and aviation assets.


Divisions are the basic units of maneuver at the tactical level. They possess great flexibility and tailor their brigades for specific missions. Infantry, armored, mechanized infantry, airborne, and air assault divisions are presently in the force. Designed to be largely self-sustaining, portions of their CS and CSS battalions and separate companies may be attached to or placed in support of brigades for the performance of a particular mission. At the direction of the corps, divisions perform major tactical operations and conduct sustained battles and engagements.

Significant planning activities take place at the division level to direct subordinate brigades against first-echelon regiments; this is done while interdicting enemy second-echelon regiments and follow-on divisions with long-range artillery, maneuver, and organic aviation assets. Normally, there are three separate battle planning centers at each division:

  • The current close-in operation is supervised at the forward tactical command post (CP) under the supervision of the assistant division commander for maneuver.
  • Rear operations are supervised at the division rear CP under the supervision of the assistant division commander for support.
  • Deep operations and planning for sustained division operations are conducted at the division main CP.

The division planning staff needs tailored weather forecasts and current observations for synchronizing the combat power components into a comprehensive plan for battle. Detailed, accurate weather information and the effects of the environment on weapon systems, tactics, and logistics are required to conduct and direct operations and to plan for future operations.

Division artillery requires observations and forecasts for the tactical fire (TACFIRE) direction computer system. Chemical teams need data for chemical and nuclear support planning. All divisions need illumination forecasts for night vision devices.

Many divisions require more tailored weather information. Heavy divisions require more tailored weather information. Heavy divisions are especially concerned with weather affecting trafficability, thermal sights, laser range finders, and aviation. Air assault divisions are mostly concerned with weather affecting aircraft operations. Light infantry divisions are more concerned with visibility and illumination as well as weather conditions affecting the individual soldier and mobility on foot. Some divisions have areas of specialization such as cold weather, desert, and mountain operations which require tailored support.


Maneuver brigades are the major combat units of all types of divisions. They control two or more battalions. Capabilities for self-support and independent action vary with the type of brigade. It is in the brigade AO where friendly forces must gain the initiative and destroy enemy forces. Brigades direct, coordinate, and support operations against enemy first-echelon regiments and interdict second-echelon battalions of first-echelon regiments.

Brigades are concerned primarily with current weather conditions and weather which would affect operations during the next 12 hours. Current and near-term conditions are more important to today's battle; the outcome will play a major role in future planning. Division WETMs ensure brigade commanders are updated on current weather observations and provided timely weather forecasts.


Separate brigades and armored cavalry regiments (ACRs) can be used to reinforce corps or divisions and can be shifted to tailor forces for combat. They are employed as units when attached to corps or divisions. Separate brigades provide corps commanders with the assets to execute several missions, especially deep operations. ACRs engage in the battle early in the covering force area (CFA) and are very mobile. ACRs have organic air cavalry assets.

ACRs and separate brigades require dedicated weather support similar to divisions because they operate as corps assets. Their AO and AI vary with their missions but normally coincide with that of a division or brigade, depending on how they are employed.


SOF are normally employed at the direction of EAC. They may deploy before announced hostilities and often operate in a stand-alone mode. Large distances may exist between the group headquarters and subordinate battalions at forward operating bases (FOBs). Battalions may deploy teams over continent-sized operational areas for special missions deep in enemy territory.

Independent, direct weather support is needed for long-range planning, mission execution, and resupply operations. Support must be tailored to--

  • The unique weapon systems.
  • Particular mission objectives.
  • Aviation requirements.
  • Infiltration, exfiltration, and resupply operations. Time and space considerations are often similar to the EAC AO and AI with particular attention to specific geographical points and routes.


Aviation brigades are organic to each corps and division. Operations are similar for corps and division aviation brigades, except the division's AO planning timeframe is shorter. Deep, close, and rear operational missions include--

  • Direct attack.
  • Air insertion or extraction.
  • Resupply.
  • Reconnaissance.

Aviation brigades receive mission taskings from their respective corps or division to employ support or attack aircraft. However, they independently plan and execute their missions. Single and multiple aircraft missions will also be flown in conjunction with ground and joint operations. Each brigade will have a tactical operations center (TOC) which will be geographically separated from the corps or division TOC.

Aviation brigades are especially susceptible to weather factors. Direct, dedicated weather support is required to ensure the optimum employment of these highly technical, weather-sensitive systems. Weather support for aviation brigades should coincide with the corps or division AO and AI versus that of a brigade.


Air traffic control (ATC) facilities control supporting rotary wing resupply efforts moving from the corps rear to the forward areas. The main corps WETM provides forecasts and observations to the corps airfield, which then relays them to mobile ATC facilities. Careful coordination between ATC and the staff weather officer (SWO) is required to ensure latest forecasts are provided. Weather forecasts made at lower echelons (for example, divisions, ACRs, and separate brigades) are transmitted to the corps WETM. The corps WETM passes them to the corps airfield and into the A2C2 system. The SWO coordinates to ensure the communications for this linkage are included in communications annexes and all aviation support annexes to the war plans.


Battalions fight what they can see and shoot. The AO normally covers out to about 5 kilometers (km) from the FLOT to meet objectives over the next 3 hours. Battalion commanders need weather information--near real time--for their AO and for planning operations for their AI.

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