From the harsh winter at Valley Forge during the Revolutionary War to the raging sandstorm in Operation Iraqi Freedom, weather has played an important role in war. Historically, atmospheric conditions invariably would favor one side over the other, but weather’s capricious nature quickly could reverse the advantage, sometimes during the course of a single battle. Often the combatants with a better understanding of the weather would emerge victorious. Today, advances in technology have allowed the military to provide commanders on the battlefield sophisticated weather forecasts, which they use to their advantage as they deploy ground troops or target precision-guided munitions.

Several advanced weather centers operated by the military use supercomputers to assimilate data from many sources, integrate it into a reliable forecast, and feed it back to battlefield commanders. Information from satellites, similar past conditions, and real-time observations all are entered into the computer to produce a model of what the weather probably will look like in the near future. More computing power translates into a higher resolution, that is, a more detailed forecast for a smaller area than was possible in the past.

Capt. Chris Gunderson, commanding officer of the Navy’s Fleet Numerical Meteorology and Oceanography Center in Monterey, Calif., notes advances in supercomputing are making today’s forecasts much more accurate. “The resolution of the model available to support Desert Storm was on 
the order of 120 miles. The resolution in Iraqi Freedom was less than 4 miles,” he explains. “So if you have a more detailed equation and a higher-powered computer to run it, you can significantly improve the accuracy of your forecast.”

Supercomputers and satellites have revolutionized the science of forecasting, but the human element still is critical in combat situations. Here in the United States, the National Weather Service maintains a vast network of ground stations that give it immediate feedback on forecast accuracy, but at the beginning of most foreign conflicts, such “ground truth” is in short supply.

“In those areas we must rely more heavily on weather satellite imagery and on the limited surface weather observations from combat weather team personnel who are actually there,” says Lt. Col. Thomas Frooninckx, commander of the Air Force’s 28th Operational Weather Squadron in Sumter, S.C. The 28th is charged with weather analysis and forecasting for the U.S. Central Command’s area of responsibility in the Middle East. 

Military forecasters met an immediate challenge in the first week of Operation Iraqi Freedom, when “the mother of all dust storms” descended on the country. “It was the largest sandstorm in geographical area and the most severe in terms of wind speed and low visibility in over a decade,” says Frooninckx. “Fortunately, military forecasters predicted this major storm five days before it occurred. That was particularly impressive, because the storm didn’t exist in advance and then move into the region, but developed in the war zone.”

“The concept of weather support in the military is ‘reachback,’” says Cmdr. William Schulz, director of the Naval Oceanographic Office’s Warfighting Support Center at Stennis Space Center in Mississippi. Schulz explains that war fighters in the field now can use communications links to retrieve real-time weather data from a variety of stateside resources, giving them a huge battlefield advantage. 

Valley Forge 

The Revolutionary War took place long before accurate weather forecasting became a science or even a possibility. When Gen. George Washington decided to stay at Valley Forge, he had no idea how brutally cold and snowy the winter of 1777–78 would be.

After two defeats in the quest for American independence in the fall of 1777, including the capture of Philadelphia by the British, Washington and his troops were forced to fall back to a position 20 miles from the city. Some in Congress urged him to attack the Redcoats and retake Philadelphia, but Washington knew that his ragtag troops, already suffering from food shortages and a lack of supplies, were unprepared and would be slaughtered.

In December he began the march to Valley Forge, situated on a defensible plateau above the Schuylkill River, to camp for the winter. The encampment area previously had been stocked with supplies, but on arrival Washington learned the stores had been discovered and seized by the British. His men set to work building shelters but were hampered by the cold, icy conditions. Eight days after the troops arrived, Valley Forge experienced its single deepest snow of the season, followed by sub-freezing weather that reached a low of six degrees. 

The frigid weather was bad enough, but continual cycles of freezing and thawing turned the roads into slush, cutting off Washington’s supply lines. On Feb. 8, the camp received its heaviest snowfall yet, followed three days later by a heavy rain. As the men began to fall ill and die, morale in the besieged encampment plummeted. Meanwhile, British Maj. Gen. William Howe remained comfortably lodged with his 15,000 troops in Philadelphia. Had Howe decided to attack, he easily would have defeated the beleaguered Continental Army.

In March reinforcements began to arrive at Valley Forge. France entered the war as an American ally in April, and soon afterward Howe abandoned Philadelphia. Washington’s reinvigorated troops, toughened by their trial by ice, were now ready to take the battle to the enemy.

Pearl Harbor

By the time the United States entered World War II in December 1941, the War Department relied heavily on the U.S. Weather Bureau in predicting battlefield conditions. In the Pacific, forecasting ocean conditions became just as important as predicting those in the atmosphere. 

Had high-powered military observation satellites existed then, they no doubt would have picked up the telltale wake of a carrier task force leaving Japan Nov. 26. With four aircraft carriers and several other support vessels, Adm. Isoroku Yamamoto’s fleet had no way of hiding during the 12-day, 4,000-mile journey to Oahu, Hawaii. But the weather was on Yamamoto’s side, with winter storms accompanying the battle group most of the way and allowing it to make the trip undetected. The weather cleared by the time Yamamoto dropped anchor 220 miles from Pearl Harbor Dec. 7, 1941, and the day of infamy began.

D-Day

During the war, the science of weather forecasting advanced rapidly, and by the time the Allies began planning the invasion of Nazi-occupied France, forecasters played a crucial role. The attack had been in the planning stages for more than two years, but Operation Overlord still was dependent on the cooperation of Mother Nature. 

A rising full moon was needed as airborne operations would begin at night, and because naval gunners would need to see their targets, visibility would have to exceed 3 miles. Winds could not exceed 18 mph offshore or 12 mph onshore, and the landing craft would need a low tide at dawn to disembark their troops and allow them to see German beach obstacles. Lastly, aircraft would need a ceiling no lower than 3,000 feet with no more than 60 percent of the sky covered by clouds. 

Faced with such daunting limitations, forecasters realized there likely would be only three days in the entire month that would be suitable: June 5, 6, and 7. Gen. Dwight Eisenhower took the earliest option, deciding June 5 would be the best day for the invasion. Late on the evening of June 2, Eisenhower met with British Prime Minister Winston Churchill, his top generals, and his weather forecasters to review the updated forecasts. They weren’t good. An approaching storm promised to bring low clouds, high seas, heavy rain, and strong winds ripping across the English Channel, a recipe for certain disaster. But Eisenhower decided to wait and see if the forecast would change.

At 0415 hours June 4, less than 24 hours before the scheduled attack, Eisenhower met with his advisors again and was given what is possibly the most important weather forecast in history. His chief meteorological advisor, James Stagg, told the commander the rain should end on the afternoon of June 5, and that June 6 promised a temporary break that should make the invasion possible. If it was delayed, said Stagg, tides wouldn’t be suitable again for two weeks, in which time the secret operation might be discovered by the Germans. Eisenhower reportedly stood up from the table and threw the Allied war machine into gear with the simple words, “ok, we’ll go.” 

German forecasters were well aware of the approaching storm, but had not seen the break in the weather coming. Al Moyers, chief of the Air Force Weather History Office, explains that “the German weather service, a longer-established and probably better weather service than the Allies had, predicted the weather would not be appropriate due to their limited availability of observations in the Atlantic.” The Germans knew an invasion was imminent somewhere along the French coast but assumed the weather was too rough to allow a crossing. As a result, sea and air patrols of the English Channel had been canceled and Field Marshal Edwin Rommel had returned to Germany for his wife’s birthday—June 6. Back in Berlin, Adolf Hitler had taken a sleeping pill with orders not to be awakened. The first inkling the Germans had of the approaching fleet of more than 5,000 ships—part of the largest invading force in history—was when the throbbing of engines reached them around 0200 hours. 

D-Day was the turning point of the war in Europe. The Allies sustained heavy losses, but a superior understanding of the weather helped them hasten the end of the Third Reich.

Battle of the Bulge

The weather also played a major part in the Ardennes Offensive — better known as the Battle of the Bulge—which began in December 1944. At 0530 hours Dec. 16, eight German Panzer Divisions and 13 infantry divisions smashed through the American front in the Ardennes forest in a bid to cut Allied supply lines and recapture the city of Antwerp, Belgium. By this time the Allies enjoyed full air superiority over Belgium, but an overcast sky and foggy conditions had grounded the Allied air forces, a situation the Germans were quick to exploit. 

In all, Hitler sent a quarter-million troops across an 85-mile stretch of the Allied front during the battle, from southern Belgium into Luxembourg. Both the Allies and Germans rushed to take Bastogne, a location stategically important for mounting a counteroffensive. The American 101st Airborne division got there first and occupied the city, but the Germans immediately surrounded and laid siege to Bastogne, forcing the defenders to rely on air drops for supplies. But the weather made that impossible. For most of the month, cloudy, rainy weather kept supply aircraft grounded, until Dec. 22 when a cold front blasted through Belgium. The front swept the clouds away, and for the next five days, not only were the troops at Bastogne resupplied, but also Allied warplanes began to rain fire on German tanks and troops.

In late January 1945, the Allies had regained all the ground lost, Bastogne had been liberated, and the Battle of the Bulge was over. The weather had favored first one side and then the other in what was the United States’ largest land battle of World War II. 

The atomic bomb

Just as the weather played a role at the beginning of the war, so it helped determine its end. On Aug. 8, 1945, the atomic bomb that would prompt a Japanese surrender was loaded into a b-29 named Bockscar on the island of Tinian. The first A-bomb had been dropped from the Enola Gay on Hiroshima just two days earlier, but the enemy remained defiant. Bockscar’s mission was to unleash a second, more powerful bomb on Kokura.

Shortly after takeoff Aug. 9, Bockscar became separated from its two b-29 escorts by a line of thunderstorms that stretched from the Marianas Islands to Japan. Flying on alone, Bockscar arrived at the rendezvous point over Yakoshima to find only one escort there and waited for nearly an hour for the other plane—a camera ship—to show up before flying on toward Kokura. In that short time, the clouds had closed in over the target city, and on arrival the aiming point was obscured completely. Bockscar’s commander Maj. Charles W. Sweeney made three unsuccessful runs over Kokura and then turned his b-29 toward the secondary target of Nagasaki.

Arriving over the city, the Bockscar crew was dismayed to find that it too was covered in clouds, the ground visible only through a few widely scattered breaks. They had been instructed to bring the atomic bomb back if they were unable to drop it, but no one on board relished the thought of trying to land with a fully-armed A-bomb aboard. Against orders, Sweeney decided to drop the bomb by radar and began his run, but just 20 seconds before releasing the bomb, the bombardier yelled, “I’ve got a hole! I can see it! I can see the target!”

The bomb was dropped, and five days later, the Japanese announced their acceptance of the Allied terms of unconditional surrender. The long war finally was over. 

The future 

In the 21st century, clouds and stormy weather no longer automatically bring combat operations to a halt or force a change in targets. Technologies such as the gps now allow cruise missiles and other smart weapons to home in on their targets using preloaded coordinates. But the weather still is a factor that must be reckoned with, especially with precision-guided munitions that must be highly accurate to be effective.

Fortunately, the ability to obtain weather forecasts only will get better. In the next few years, remote weather sensors will proliferate on unmanned vehicles, predicts Cmdr. Archer Wright, the Naval Meteorology and Oceanography Command’s deputy for resources at Stennis. This will create a network of observing platforms that will give commanders an instant overview of weather in the battle zone. “I think in some areas you’ll have direct delivery of weather information straight from the computers to black boxes in aircraft and other vehicles. That will be especially important for target-bound aircraft,” says Wright. 

Such technology will give U.S. forces a tremendous edge over the enemy and enable them to use developing weather conditions to their advantage. “As we get superior satellites into space, we’ll gain huge advantages in observing meteorological conditions in denied areas, where we don’t have people on the ground. And our modeling ability will continue to improve as our computers get more powerful,” says Wright. “I feel like I’ve been riding the wave of a revolution for the past 10 years as our communications and computer abilities have increased. It’s exciting to think of what the next 10 years will bring.”