Forecast for Wednesday, August 21

Issued: Tuesday, August 20 Launch Weather Officer: Jim Sardonia, 45th Weather Squadron Synoptic Discussion: "Weather is expected to be generally favorable for rollout today. There is a slight chance of rainshowers developing along the east coast sea-breeze in the early PM hours however I expect most of the activity to be concentrated west of SLC 41 near I-95. Thunderstorms are expected inland in the Orlando area later in the afternoon. "Overnight, I do not expect any threat to the Launch Vehicle as far as lightning or high winds. "On launch day, there will be a slight chance of isolated rainshowers along the coast in the AM and early PM hours. Isolated thunderstorms are again possible in the Orlando/Sanford area in the afternoon. There is a slight chance these thunderstorms to the west and northwest could produce anvil clouds that drift towards Cape Canaveral during the launch window. "Overall, weather looks very favorable for this time of the year (August afternoon launch countdown). The main concerns at this time are the chance of violating the Cumulus Cloud Rule (due to coastal rainshowers) and the Anvil Cloud rule during the launch window." Clouds: Scattered Cumulus at 3,000 feet with 3/8ths sky coverage and tops at 8,000 feet; and Scattered Cirrus at 25,000 feet with 3/8ths sky coverage and tops at 28,000 feet Visibility: 7 miles Launch Pad Winds: Southeasterly from 120 degrees at 10 gusting to 18 knots Temperature: 84 to 87 degrees F Relative Humidity: 80 percent Weather: Isolated rainshowers Solar Activity: Moderate Probability of Violating Weather Constraints: 30 percent Concerns: Isolated coastal rainshowers, slight chance of anvil clouds overhead

Forecast for Thursday and Friday

Thursday's Probability of Violating Constraints: 30 percent Concerns: Isolated coastal rainshowers, slight chance of anvil clouds overhead Friday's Probability of Violating Constraints: 40 percent Concerns: Isolated coastal rainshowers, slight chance of anvil clouds overhead

Atlas 5 weather rules

Launch vehicle exposure constraints for first Atlas 5

Winds: - Mobile Launch Platform rollout and return: 32 knot limit - Mobile Launch Platform at the pad (prior to tanking): 35 knot limit - Mobile Launch Platform at the pad (cryo tanking/detank): 41 knot limit Lightning: - No cloud to ground lightning strikes within 5 nautical miles of Complex 41 while the launch vehicle and MLP are on the pad. (Depends on intensity of strikes)

Launch commit criteria for first Atlas 5

Winds: - Maximum allowable launch winds is 30 knots - If winds are from 060-110 degrees or 230-340 degrees, then the wind limit is 23 knots Temperature: - Ambient air temperature cannot be cooler than 40 degrees F Solar Radiation: - 50 MeV Proton Flex not greater than 100 pfu

Natural and triggered lightning launch commit criteria

1. Lightning: - Do not launch for 30 minutes after any type of lightning occurs in a thunderstorm if the flight path will carry the vehicle within 10 nautical miles of that thunderstorm - Do not launch for 30 minutes after any type of lightning occurs within 10 nautical miles of the flight path unless: 1. The cloud that produced the lightning is not within 10 nautical miles of the flight path; and 2. There is at least one working field mill within 5 nautical miles of each such lightning flash; and 3. The absolute values of all electric field measurements at the surface within 5 nautical miles of the flight path and at the mill(s) specified in (2) above have been less than 1000 V/m for 15 minutes. 2. Cumulus Clouds: - Do not launch if the flight path will carry the vehicle within 10 nautical miles of any cumulus cloud with its cloud top higher than the -20 deg C level - Do not launch if the flight path will carry the vehicle within 5 nautical miles of any cumulus cloud with its cloud top higher than the -10 deg C level - Do not launch if the flight path will carry the vehicle through any cumulus cloud with its cloud top higher than the -5 deg C level - Do not launch if the flight path will carry the vehicle through any cumulus cloud with its cloud top between the +5 deg C and -5 deg C levels unless: 1. The cloud is not producing precipitation; and 2. The horizontal distance from the center of the cloud top to at least one working field mill is less than 2 NM; and 3. All electric field measurements at the surface within 5 nautical miles of the flight path and at the mill(s) specified in (2) above have been between -100 V/m and +500 V/m for 15 minutes. If mill 33 or 25 is exhibiting a negative offset that (1) is characteristic of powerlines and (2) preceded the occurrence of any clouds that might produce electric fields at the surface, the field at these sites must have been between - 500 V/m and + 500 V/m for 15 minutes. 3. Anvil Clouds: Attached Anvils: - Do not launch if the flight path will carry the vehicle through nontransparent parts of attached anvil clouds - Do not launch if the flight path will carry the vehicle within 5 nautical miles of nontransparent parts of attached anvil clouds for the first 3 hours after the time of the last lightning discharge that occurs in the parent cloud or anvil cloud. - Do not launch if the flight path will carry the vehicle within 10 nautical miles of nontransparent parts of attached anvil clouds for the first 30 minutes after the time of the last lightning discharge that occurs in the parent cloud or anvil cloud Detached Anvils: - Do not launch if the flight path will carry the vehicle through nontransparent parts of a detached anvil cloud for the first 3 hours after the time that the anvil cloud is observed to have detached from the parent cloud - Do not launch if the flight path will carry the vehicle through nontransparent parts of a detached anvil cloud for the first 43 hours after the time of the last lightning discharge that occurs in the detached anvil cloud - Do not launch if the flight path will carry the vehicle within 5 nautical miles of nontransparent parts of a detached anvil cloud for the first 3 hours after the time of the last lightning discharge that occurs in the parent cloud or anvil cloud before detachment or in the detached anvil cloud after detachment unless: (a) There is at least one working field mill within 5 nautical miles of the detached anvil cloud; and (b) The absolute values of all electric field measurements at the surface within 5 nautical miles of the flight path and at the mill(s) specified in (a) above have been less than 1000 V/m for 15 minutes; and (c) The maximum radar return from any part of the detached anvil cloud within 5 nautical miles of the flight path has been less than 10 dBZ for 15 minutes. - Do not launch if the flight path will carry the vehicle within 10 nautical miles of nontransparent parts of a detached anvil cloud for the first 30 minutes after the time of the last lightning discharge that occurs in the parent cloud or anvil cloud before detachment or in the detached anvil cloud after detachment. 4. Debris Clouds: - Do not launch if the flight path will carry the vehicle through any nontransparent parts of a debris cloud during the 3-hour period defined below - Do not launch if the flight path will carry the vehicle within 5 nautical miles of any nontransparent parts of a debris cloud during the 3-hour period defined below unless: 1. There is at least one working field mill within 5 nautical miles of the debris cloud; and 2. The absolute values of all electric field measurements at the surface within 5 nautical miles of the flight path and at the mill(s) specified in (1) above have been less than 1000 V/m for 15 minutes; and 3. The maximum radar return from any part of the debris cloud within 5 nautical miles of the flight path has been less than 10 dBZ for 15 minutes. The 3-hour period in above begins at the time when the debris cloud is observed to have detached from the parent cloud or when the debris cloud is observed to have formed from the decay of the parent cloud top to below the altitude of the -10 deg C level. The 3-hour period begins anew at the time of any lightning discharge that occurs in the debris cloud. 5. Disturbed Weather: - Do not launch if the flight path will carry the vehicle through any nontransparent clouds that are associated with a weather disturbance having clouds that extend to altitudes at or above the 0 deg C level and contain moderate or greater precipitation or a radar bright band or other evidence of melting precipitation within 5 nautical miles of the flight path. 6. Thick Cloud Layers: - Do not launch if the flight path will carry the vehicle through nontransparent parts of a cloud layer that is 1. Greater than 4,500 ft thick and any part of the cloud layer along the flight path is located between the 0 deg C and the -20 deg C levels; or 2. Connected to a cloud layer that, within 5 nautical miles of the flight path, is greater than 4,500 ft thick and has any part located between the 0 deg C and the -20 deg C levels; unless the cloud layer is a cirriform cloud that has never been associated with convective clouds, is located entirely at temperatures of -15 deg C or colder, and shows no evidence of containing liquid water (e.g. aircraft icing). 7. Smoke Plumes: - Do not launch if the flight path will carry the vehicle through any cumulus cloud that has developed from a smoke plume while the cloud is attached to the smoke plume, or for the first 60 minutes after the cumulus cloud is observed to have detached from the smoke plume 8. Surface Electric Fields: - Do not launch for 15 minutes after the absolute value of any electric field measurement at the surface within 5 nautical miles of the flight path has been greater than 1500 V/m - Do not launch for 15 minutes after the absolute value of any electric field measurement at the surface within 5 nautical miles of the flight path has been greater than 1000 V/m unless: 1. All clouds within 10 nautical miles of the flight path are transparent; or 2. All nontransparent clouds within 10 nautical miles of the flight path have cloud tops below the +5 deg C level and have not been part of convective clouds with cloud tops above the -10 deg C level within the last 3 hours. 9. Electric Fields Aloft: - Criteria 3, 4, 5, 6, 7, and 8(b) need not be applied if, during the 15 minutes prior to launch time, the instantaneous electric field aloft, throughout the volume of air expected to be along the flight path, does not exceed Ec, where Ec is shown as a function of altitude 10. Triboelectrification: - Do not launch if a vehicle has not been treated for surface electrification and the flight path will go through any clouds above the -10 deg C level up to the altitude at which the vehicle's velocity exceeds 3000 ft/sec