SYNOPTIC AND PROGNOSTIC OVERVIEW
ISSUED :07Z Sunday 19/11/95 VALID TILL: 12Z Monday 20/11/95
Synoptic Situaton at 00Z:
High 1027 hPa near 46S 136E moving E at 20 knots, extends a ridge well south towards 60S 140E. The high is forecast to be near 47S 144E at 00Z Monday, 47S 151E at 12Z Monday and 46S 158E at 12Z Tuesday night, with a ridge extending northeastwards into the Tasman Sea..
Deep low below 980 hPa well southeast of Macquarie moving further away.
A weakening cold front near 125E moving east at about 30 knots, forecast to be oriented north/south near 128E at 00Z tomorrow, then slowing and weakening further. The remnant trough is forecast to be close to western Tasmania on Wednesday morning.
Prognoses:
0-24:
All progs seem to be pushing the high eastwards to the south of Tasmania in the wake of the intensely cold southwesterly airstream now moving through the Macquarie region. This seems quite reasonable given the current pattern, maintaining an easterly component over northern Tasmania tomorrow and a slowly moderating southwesterly through the Macquarie/Disco area.
24-72:
The GASP prog is moving the next front onto the west coast by Tuesday night, which is quicker than both the US and EC progs. Given the current upper pattern, I am inclined to agree with the EC and US progs and keep the front off Tasmania until Wednesday, and even then be a weak change. This should maintain a northeast stream over much of the ACE area for the period, tending more northwesterly south of about 48S.
FORECASTS:
Cape Grim:
Weather:
The chance of a shower or two this evening otherwise fine.
Wind:
Southwest winds 10/15 knots turning southeast to easterly this evening and freshening to 15 to 20 knots tomorrow afternoon.
Outlook Tuesday: Cloudy at first with the chance of a little drizzle, otherwise fine. Easterly winds 15/20 knots possibly reaching 25 knots at times in the afternoon.
Macquarie Island:
Weather:
Snow showers slowly easing tomorrow.
Winds:
Southwesterly 20/30 knots easing to 15 to 25 knots during the day.
Outlook Tuesday:
Showers easing and turning to drizzle. Southwest winds easig and turning west to northwesterly 20/25 knots.
R/V Discoverer
Weather:
Showers, possibly of snow or sleet tonight, easing slowly as you move northwards. Winds:
Southwesterly 20/30 knots easing to 15/25knots tomorrow morning and 15/20 knots tomorrow afternoon.3 to 4 metre seas decreasing to 2 metres during the day. West to southwest swell 3 to 5 metres decreasing to 2 to 3 metres tomorrow and around 2 metres tomorrow evening. Outlook Tuesday: Variable winds to 10 knots turning northeasterly. Seas and swell to 1.5 metres.
R/V Southern Surveyor
Weather:
Fine. Winds:
Southeast winds 15/25 knots easing to 10/20 knots this evening and tending southeast to northeasterly at 5 to 15 knots overnight and tomorrow morning. Seas to 2 metres decreasing to 1 metres overnight. Southwest swell 3 metres decreasing to 2 metres tomorrow.
Outlook Tuesday:
Fine weather continuing. Chiefly northeast winds 5 to 15 knots increasing to 10/20 knots during the morning. Seas to 1.5 metres. Southwest swell 1.5 to 2 metres.
REVIEW OF PREVIOUS DAY:
The prognoses did well for today and the forecasts seem reasonably accurate. Very cold conditions, snow and gale force southwesterlies developed over the Macquarie/Discoverer area as predicted and the southwesterlies have moderated over Cape Grim today. I am unable to guage how accurate the forecast for the Southern Surveyor was with very little data being received, however, satellite pics and surrounding obs suggest that the predicted moderation has taken place there as well. Yesterdays flight forecast seems to have been accurate, except winds on the surface in the area forecast near 52S may have been a little lighter than predicted.