Communicating the Weather:
The "Garske Chart"
by Major David L. Martens, USAF
It is well understood that accurate weather information is essential to the Army's success on the battlefield. Armed with a good weather forecast, the battlefield commander can exploit the changing nature of the atmosphere to his advantage. Expert use of the weather can be a force multiplier that can turn defeat into victory and victory into rout.
However, it must be communicated in a simple, straightforward manner. Even the best weather forecast will be of little use if it cannot be effectively communicated to the commander and his staff. The weather teams supporting the 101st Airborne Division (Air Assault) employ an effective communications tool that can quickly put the maximum amount of weather intelligence into the hands of the division's key decisionmakers. This useful communications tool is known throughout the division as the "Garske Chart."
Describing the ChartNamed after its developer, Master Sergeant Don Garske (U.S. Air Force), the Garske Chart displays 24 hours-worth of weather data and analysis required by the division staff. The chart shows a time evolution of weather elements deemed critical to planning the full range of division operations. On a single Garske Chart, a weather forecaster can display the day's solar and lunar data, as well as cloud cover, visibility, wind, and temperature forecasts. The Chart also provides space for remarks related to the weather effects on electro-optical weapons and night vision device usage.
By using this Chart, the battle staff can determine - in a single glance - what time the weather forecaster expects the fog to break, how low the cloud ceilings will be, and how high the temperature will be during the afternoon. During a briefing, the staff weather officer uses the Garske Chart as a jumping-off point to open a dialogue with the battle staff concerning the weather's effect on division missions. The chart is useful in determining the best time of day to launch an air assault or to schedule a reconnaissance flight to best minimize the negative effects of the weather on friendly operations.
To date, the Garske Chart has proven to be the most effective way to communicate critically needed weather information to the division staff. It fuses weather intelligence into the planning cycle to maximize the division's effectiveness in a frequently hostile and uncooperative environment. Using the Garske Chart, the division battle staff is determined to make "Mother Nature" an asset and an ally in its quest for battlefield dominance.
Figure 1. The Garske Chart
Interpreting the Chart
The Garske Weather Chart (see Figure 1) is normally prepared in color. When this article is loaded on the Internet, it will have the full-color chart. The chart includes the following data:
- As of Date. This is the date the Weather Chart was created.
- AO Forecast and Date (or "D+ Day"). The weather data is valid in the area of operations for this day.
- ITO. This is the Integrated Tasking Order for the day that starts at 0600L (local time).
- Time. The two timelines depict information in 2-hour intervals for both Zulu (Z) and local (L) times for a 24-hour period. The hashmarks under the times on each line correspond to the times listed at the top of the Chart.
- Solar Data. A black box depicts darkness, a gray one for twilight, and a yellow box for sunlight. BMNT (beginning morning nautical twilight), sunrise, sunset, and EENT (end evening nautical twilight) are listed, in that order, in local time.
- Lunar Data. The hours of moonlight are depicted by a blue box, with moonrise and moonset listed on each side of the box. The percentage of illumination is listed inside the blue box.
- NVG. The night vision goggle window displays the best time for NVG use. This row depicts the NVG window as a green box and shows the exact start and stop times on each side of the box. The criteria for the window are a moon elevation of at least 30 degrees and moon illumination of at least 26 percent.
- Electro-Optics. A purple box shows the forward-looking infrared (FLIR) window. A red line depicts the thermal crossover between the target and the background. The blank areas on each side of the red line correspond to times unfavorable for FLIR use (times when the temperatures of the target and background are within 2 degrees of each other). The FLIR window depicts the best time to use electro-optical systems. Thermal crossover refers to the worst time to use electro-optical systems (times when the targets cannot be distinguished from the background because their temperatures are equal).
- Sky Condition. This line shows the cloud coverage in terms of how many clouds are present in the sky. The altitudes of the cloud bases are given in hundreds of feet. There are five categories of cloud cover shown in the chart:
SKC (sky clear) refers to a cloudless sky.
FEW refers to cloud coverage of 1/8-2/8 of the sky.
SCT (scattered) refers to clouds present in 3/8-4/8 of the sky.
BKN (broken) refers to cloud coverage in 5/8-7/8 of the sky.
OVC (overcast) refers to solid clouds (over 8/8). A cloud level (in hundreds of feet) of 005 indicates that the base of the cloud is at 500 feet, 030 is 3,000 feet, and 200 means that the base of the clouds is at 20,000 feet above sea level.
- Winds. Winds are listed with the direction from which they are blowing and their exact speed in knots. Wind direction is based on a 360-degree circle. Figure 1 shows winds from a direction of 220 degrees (SW) at 10 knots.
- Visibility. The exact visibility is listed in miles. If there are any restrictions to visibility; the restrictor is stated after the visibility; e.g., 3 MILES FOG, 2 MILES SNOW, or 1 MILE BLDU (blowing dust).
- Temp.This line shows the temperature in 2-hour increments, either in degrees Celsius (C) or degrees Fahrenheit (F).
- Snow Depth. This is the average snow depth in valleys and on mountains (MTNS) for which operations are planned.
- Hazards. This line lists all the weather hazards that will affect operations. Turbulence is depicted as TURBC with intensities depicted as LGT (light), MDT (moderate), or SVR (severe). The altitude where the turbulence is present is given in hundreds of feet after the word TURBC. (On Figure 1, it is from the surface (SFC) to 10,000 feet.) Icing (ICG) has the same levels of intensity as were listed for turbulence, and the altitudes at which icing may occur are given in hundreds of feet. Thunderstorms are shown as TSTMS; it is assumed that lightning will be present for the duration of the thunderstorms. The freezing level (FRZ LVL) altitude is given in hundreds of feet. The time during which the hazards will take place are depicted by solid lines on each side of the hazard description. If there are no lines, the hazard will take place for the entire 24-hour period. Weather advisories and warnings may also be listed here, but they are usually disseminated by other means.
- Sea State. This gives the state of the sea as 1 (green), 2 (amber), or 3 (red). These sea states are based on U.S. Navy descriptions; the states incorporate such factors as wave height and wind speed. This information is used primarily for Joint-Logistics-Over-the-Shore (JLOTS) and amphibious operations.
- Color Legend. The color legend in Figure 1 shows what the various colors mean.
The "Screaming Eagle" Weather Chart was developed as a tool for use in the mission planning process. It depicts all of the weather data significant to Army operations for a 24-hour period. Most importantly, it allows the commander to determine, at a glance, how the weather will influence future operations.
Major David Martens is the Director of Weather Operations at Fort Campbell, Kentucky, and also serves as the Staff Weather Officer in the 101st Airborne Division (Air Assault). He has served as a Weather Officer in the 388th Tactical Fighter Wing at Hill Air Force Base (AFB), Utah, and the Operations Officer, Seventh Air Force Weather Support Unitat, Osan Air Base, Korea. MAJ Martens worked in the Readiness Support Section of the Environmental Technical Applications Center, Scott AFB, Illinois, where he co-authored a study of the climatology of South America. He returned to Korea in 1994 to serve as officer in charge of the Theater Forecast Unit, Yongsan Army Installation, Seoul, Korea. He has a bachelor of science degree in Meteorology from the State University of New York at Oswego and has a master of science degree in Climatology from Utah State University. Readers may contact him via E-mail at [email protected] and telephonically at (502) 798-2519 or DSN 635-2519.