Forecast for Wednesday, September 18

Issued: Wednesday, September 18 Launch Weather Officer: Jim Sardonia, 45th Weather Squadron Synoptic Discussion: "Favorable weather is expected for tonight's launch attempt. High pressure to the north will bring light easterly winds during the launch window. The only slight concerns are the chance of enhanced Cumulus clouds developing within 10 nautical miles of SLC 36 (Cumulus Cloud Rule) and a slight chance of Anvil clouds drifting towards Cape Canaveral if any thunderstorms develop in the interior portions of Florida during the afternoon. "Tropical Storm Isidore has formed near Jamaica and is approaching the western coast of Cuba. Models are now diverging on the exact path, however the Hurricane Center expects the storm to slowly make it's way into the eastern Gulf of Mexico. Weather is expected to deteriorate locally late Thursday and Friday if Isidore stays on this course, bringing thick cloud cover and widespread rainshowers into central Florida." Clouds: Scattered Cumulus at 2,000 feet with 3/8ths sky coverage and tops at 8,000 feet; and Scattered Cirrus at 25,000 feet with 2/8ths sky coverage and tops at 28,000 feet Visibility: 7 miles or better Launch Pad Winds: Easterly from 100 degrees at 6 gusting to 12 knots Temperature: 81 to 83 degrees F Relative Humidity: 75 percent Weather: None Solar Activity: Low-Moderate Probability of Violating Weather Constraints: 20 percent Concerns: Enhanced Cumulus clouds, Slight chance of Anvil Clouds within 10 nautical miles

Forecast for Thursday and Friday

Thursday's Probability of Violating Constraints: 40 percent Concerns: Scattered Rainshowers, Thick Layered Clouds Friday's Probability of Violating Constraints: 70 percent Concerns: Thick Layered Clouds, Scattered Rainshowers associated with Tropical System

Atlas 2AS weather rules

Launch vehicle constraints for Atlas 2AS

Winds: - Mobile Service Tower rollback and return: 30 knot limit - Maximum allowable launch winds: 29 knots - If winds are from 330-060 degrees, then the launch wind limit is 26 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