Mission Plan:
Primary Mission : None Alternate Mission: N/A Future Mission(s): Possible Lagrangian starting Thurs or Fri.Aircraft Operations
Take-off Time: N/A Pre-flight Weather Briefing Time: N/A Updates: N/A Airborne Mission Scientist: N/A Mission Scientist: N/AShip Operations
Discoverer: Discoverer located at 41 02'S 143 19'E this evening. ISS soundings continue every 6 hours. The ship will move toward Cape Grim sometime on Wednesday. The helicopter operation was successful early this morning. See catalog reference below for detailed instrument status. Discoverer Lead Scientist: Tim Bates Southern Surveyor: Southern Surveyor position at 0600 UTC 28/11 at station P5 53S 145.5E. They will then begin to move northbound along approx. 145E. Soundings are being taken every 12 hours. See catalog reference below for detailed instrument status. 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
BMRC Hysplit trajectories are here
GASP trajectory analysis is here
Synoptic Situaton at 00z Tuesday 28/11/95:
Cold front near 38S 141E/46S 146E/45S 145E/wrapping around a 968 hPa low near 51S 138E. Front moving E at 30 knots to be near 40S 158E/48S 160E/55S 155E at 00Z and through Macquarie shortly after. Associated low to continue moving southwards.
962 hPa low near 52S 120E moving NE. Low forecast to be near 55S 132E at 00z tomorrow and moving SSE, and 56S 136E at 12z tomorrow night.
Broad and strong west to northwest stream over the ACE area west of the cold front.
Prognoses:
0-24 hours: There appears to be little variation in the progs for the first 24 hours, all showing a continuation of the broad northwest to southwest airstream through the ACE area around a major low south of 50S between 130E and 140E. A weak front may pass through the area around the Discoverer tomorrow, however this is a weak feature.
24-72 hours: The US aviation model and the EC prog have picked up a small cyclonic perturbation near 45S 120E on Wednesday night, moving rapidly around the main low near 57S 140E. However, with the fronts moving so rapidly through the area, variations of this nature are likely and decisions regarding precise locations of these systems should be made closer to the time.
Towards the end of the week, the deep lows near 140E are likely to weaken and the westerly stream moderate somewhat, allowing the fronts to move through the area at a slightly more leisurely pace.
FORECASTS:
Cape Grim: Weather:Showers developing overnight, easing during the morning but a few further showers persisting during the day. Wind: Chiefly northwest winds 15/25 knots.
Macquarie Island: Weather:Low cloud tending to fog at times with some light rain or drizzle. Wind: Northeast to northerly increasing to 20/30 knots then turning northwesterly at similar strength around the middle of the day.
R/V Discoverer Weather:Showers developing tonight and continuing tomorrow. Wind: Chiefly northwest winds 20/25 knots reaching 30 knots at times tomorrow. A northwest to westerly change of similar strength around noon.. This is a very ill defined front and may not actually be all that noticeable. The next significant front looks likely to cross you on Thursday. 2 to 3 metres seas rising to 4 metres at times. Westerly swell 3 to 4 metres.
R/V Southern Surveyor Weather: (Assuming the front has passed already...) A shower or two this evening, increasing slightly tomorrow. Wind: North to northwest winds 25/30 knots, reaching 35 knots at times. 3 to 4 metre seas. Northwest swell around 4 metres. The next significant front looks likely to cross you on Thursday.
REVIEW OF PREVIOUS DAY'S FORECAST: The front that crossed Tasmania today has moved slightly faster than was expected, so rain at Cape Grim and the Discoverer eased earlier than forecast. The airmass following the front was also more subsided than expected, resulting in slightly less shower activity post frontally. Winds on the Southern Surveyor were lighter this morning than indicated, however, this afternoon could have seen the winds strenghen substantially.
Reporter: Barry Huebert
There will be no flight tomorrow. We are awaiting the delivery of sulfur calibration gas cylinders for Drexel. Although one of these has been back and forth to the US repeatedly and the other was sent when the C-130 left Hawaii, neither has arrived yet. After today's flght we are grounded until at least one cylinder arrives. The Hawaii cylinder only has enough gas for 1 or 2 flights, so the one from the East Coast is a must for continued operations.
We discussed the issue of how to use our remaining flight hours. In addition to the 42 hours dedicated to the transect back to Jeffco, we have 100.8 hours remaining in Hobart and 15 days (assuming one cal cylinder arrives tomorrow) in which to fly them. That sounds like a lot of hours, but 63.1 of them remain dedicated to the 7 Lagrangian flights we have yet to fly. That leaves 37.7 hours for non-Lagrangian flights out of Hobart, or roughly four flights.
One of those (9 hrs) has been dedicated to a stratocumulus mission, and about another 9 have been committed to studying the outflow from cumulus clouds and column closure. (Since a number of missions, including yesterday's, have included column closure opportunities, we may not need to keep that 4.6 hours for a dedicated flight.) I personally feel strongly that we need to have a relatively clear-air flight near Disco to repeat the DMS flux method intercomparison, which might also meet the need for more time to look at clear-air photochemistry. Pete McMurry and Fred Eisele have argued that we need to devote more flight hours to studying the source of particles aloft, yet we don't know quite how to design such flights. We are gaining more experience with studying these layers as we profile on ferry flights, however, and today's flight will tell us a lot more about the source of high particle concentrations in the free troposphere.
All this means that we are at the point where hard decisions will need to be made about how we allocate the few remianing non-Lagrangian flights. Some objectives, like the need for photochemical flights in clear air (<20% loss of UV) across sunrise and the late afternoon periods, may be met very nicely by a properly-timed Lagrangian experiment. (Mother Nature will have a large say in when the right conditons whiz past us, however.) Even the DMS flux intercomparison could conceivably be done during the first flight of a Lagrangian, if the boundary layer was well-enough behaved to use all three methods.
We're halfway through our deployment in Hobart, and are at the point where the competition between objectives is becoming clear. DMS concentrations should begin to climb in the next two weeks, which suggests that we might want to save a couple of our photochemical flights for the last week here. After a week of domination by a huge low near Antarctica, the meteorology is beginning to look more zonal (summer-like), which means that Lagrangian opportunities should be more frequent. We welcome all opinions as to which objectives should recieve more or less of our dwindling flight-hour resource. (Only 100 left!)
We are beginning to watch several modest disturbances which are to fly by Hobart later in the week at 35-40 knots. Each should have some clear air behind it, and may represent an opportunity for at least a two-flight Lagrangian, if not three. (There is no question that at these speeds we would not have adequate station time on the extreme flights to try for four flights.) Disco could apparently be in the vicinity of 46S by Friday, so we will be closely watching for possible starting points in that time frame. Since a balloon transmitter was recovered from Disco by helicopter this morning, we have every reason to believe that the reciever problem will have been resolved by that time.
