Mission Plan:
Primary Mission : Cumulus outflow Alternate Mission: None Future Mission(s): Possible stratocumulus flight on TuesAircraft Operations
Take-off Time: Mission #27: 0700 LDT, 11 Dec (2000 UTC, 10 Dec) Pre-flight Weather Briefing Time: Mission #27: 0500 LDT, 11 Dec (1800 UTC, 10 Dec) Updates: Mission #27: 2030 LDT, 10 Dec (0930 UTC, 10 Dec) Airborne Mission Scientist: Mission #27: Clarke Mission Scientist: Mission #27: HuebertShip Operations
Discoverer: Discoverer followed Lagrangian track to approximately 49S, 148E when heavy seas hampered effective data collection (at 1935 UTC, 9 Dec). Discoverer is now proceding northward toward a position approximately 44-45S where it will take up a final sampling position prior to its return to port in Hobart on Wed morning. See catalog reference below for detailed instrument status. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor has completed its cruise and is in port in Hobart. Southern Surveyor Lead Scientist: Bronte Tilbrook
48 hour MSL P Prognosis is here
72 hour MSL P Prognosis is here
Latest Visible Sat Picture is here
Surface Wind 24-h forecast is here
GASP trajectory analysis is here
Synoptic Situaton at 00Z Sunday 10/12/95:
Cold front just east of the ACE area and Macquarie Island moving away at 30 knots.
A deep low of 966 hPa near 58S 148E moving SSE at 30 knots. A trough extends north from the low to near Tasmania and a strong NW to SW stream persists around the low over the ACE area. The coldest air appears to be in this trough region with some enhanced cumuliform convection and cumulonimbus evident, however the cu field extending to the west indicates further cold air is present.
A 1032 hPa high lies to the far south west of Western Australia and this is forecast to move eastwards only very slowly. The high is extending a ridge into the Great Australian Bight region and the southeast part of the continent, and little movement of this ridge is expected for the next 48 hours or so.
Prognoses:
0-24 hours: The progs indicate the development of another cold front in the cold air approaching Tasmania, crossing the state and the Discoverer tomorrow morning and coinciding with the passage of the thermal trough. By 12z tomorrow night, the front is likely to be between 155E and 160E. Another front is likely to move into the western parts of the ACE area late tomorrow, to be near a line 40S 130E/50S 138E/60S 138E at 12z tomorrow night. A ridge is forecast to form between it and the front that crosses Tasmania tomorrow morning, resulting in the pressure gradient decreasing slightly over Tas/Disco tomorrow afternoon and evening.
24-72 hours: The next front is forecast to cross Tasmania/Disco early Tuesday morning with a deep low below 960 hPa near 60S 140E maintaining a strong, cold northwest to southwest stream across the ACE area on Tuesday and early Wednesday. Winds are likely to ease north of 45S on Wednesday afternoon and Thursday as the ridge to the west finally starts to move eastwards and acts to decrease the pressure gradient to the west of Tasmania.
FORECASTS FOR TONIGHT AND MONDAY 11/11/95:
Cape Grim: Weather: Showers with the risk of some hail at times, particularly tomorrow morning. Showers easing a little tomorrow afternoon. Wind: Westerly winds 30/35 knots tending southwesterly 30/40 knots tomorrow morning before gradually easing to 20/25 knots tomorrow afternoon and evening.
Macquarie Island: Weather: Becoming progressively cooler with occasional showers. Wind: Northwest winds increasing to 20/30 knots tonight but possibly moderating slightly tomorrow afternoon and evening.
R/V Discoverer Weather: Showers with the risk of some hail at times, particularly tonight and tomorrow morning. Showers easing a little tomorrow afternoon. Wind: West to southwest winds 25/35 knots easing to 20/25 knots tomorrow afternoon and evening then tending west to northwesterly and restrengthening to 25/30knots tomorrow night. Some stronger squalls possible in showers. 3 to 4 metre seas. West to southwest swell around 4 metres.
REVIEW OF PREVIOUS DAY's FORECASTS:
The EC and GASP proved to be very accurate with their prediction of a low forming south of Tasmania near 55S 145E at 12z Saturday night and as a result, forecasts and outlooks for the weekend appear to have gone very much according to plan. Cape Grim, Discoverer and Macquarie Island have all experienced the predicted gale force winds during the period, as well as significant precipitation during the change of airmass from warm, continental air to colder air of far southern maritime origins.
Reporter: Barry Huebert
Tony Clarke, Fred Eisele, and Pete McMurry are planning a flight to study the outflow from cumulus clouds. They will make a go/no go decision tonight at an 8 PM meeting, concerning a 9 hour mission beginning at 7 AM tomorrow.
The last Lagrangian sequence appears to have been very successsful. We stayed with the balloons for three flights and watched the development of that air for almost two days, including the pre-lagrangian flight. Although the balloons maintained their relative positions, there is a curious aspect of their behavior: at night, they all flew at altitudes very close to the surface, where their trajectories became as southerly as the surface winds on the last flight. During the daytime, however, they rose again to 500-600 m, where the winds had more of a westerly component. This is a clear demonstration of the impact of wind shear on trajectories, even though we don't know what caused this behavior of the balloons.
Since these were fairly complex flights, the flight reports are not yet completed. They should be ready the 11th, since I am not planning to fly.
We have 20.3 flight hours remaining in Hobart. About half of this is time that was saved from test and transit flights, so by tomorrow we will have flown virtually all the hours we originally budgeted for Hobart. A large majority of the C-130 PI's would like to use the remaining 11 hours on the transect home. Their reasoning is that 1) sulfur photochemistry is slow in this area, and possibly goes through DMSO and DMSO2, for which we do not have measurement systems in this program and 2) the multilayered boundary layers here make budget calculations difficult. In view of this, these PI's feel that they should take advantage of the excellent package we have on the C-130 to resolve some questions about sulfur chemistry and particle formation in the Christmas Island area and in the Kilauea plume. During our previous Kilauea flights we lacked NH3 measurements, which Eisele and McMurry believe may hold the key to looking for the controls on new particle formation.
Tim Bates expressed the need for another flux intercomparison near the ship, and asked that 4 hours be allocated for this mission on Tuesday. Even though there may not be much sulfur photochemistry occurring, the flux of DMS can be measured in the mixed layer by our circles, and adding a point at a moderate windspeed would vastly improve our evaluation of the thin-film method for estimating fluxes.
Tim also expressed the opinion that Cape Grim has been slighted in our use of aircraft hours. Flying upwind of Cape Grim, profiling in their vicinity, and intercomparing with their measurement systems comprised a significant fraction of our "survey" flight hours, yet we have flown only one track past Cape Grim in the entire program. John Gras called to make the same point. He reported that Dave Covert also feels strongly that Cape Grim has never gotten any vertical profiles flown, which would add value to their data. In our S&I Plan, we placed considerable emphasis on the ways in which the various platforms could do experiments together, but we have not found opportunities to do so with Cape Grim.
After tomorrow's flight, Don Thornton will present a proposal at a 4:30 PM meeting for the rearrangement of the transect schedule. We will make a decision then on the use of the remaining hours.
