Record
heat, bushfires in NSW/Qld border countryNEWSBITS: Strong inversion given NSW weird overnight temperatures
Yesterday's heat spread east into NE NSW and central Queensland today providing a raft of new October high temperature records (see below), and the hottest October day in at least 30 to 40 years. The temperature at Longreach Qld reached 40.1° and a number of centres in northwestern Queensland recorded 39. Northeast of Crows Nest, 40km north of Toowoomba, a fire that was started last Sunday has burnt through 1000ha of farm country and is still out of control
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| The lowest 10,000 feet of this morning's 6am radiosonde balloon ascent trace from Sydney Airport. BoM |
NEWSBITS: An unusually strong temperature inversion led to a reversal of the usual temperature pattern across eastern NSW this morning, with places like Bowral and the upper Blue Mountains recording overnight temperatures close to 20° while sheltered coastal valleys were well below 10°.
The Skew-T diagram for Sydney Airport at right explains why. The straight brown lines skewed from left to right show temperature, with the scale from 0 to 30 across the bottom. The four horizontal lines above the baseline show the points at which pressure was measured at 1000, 900, 800 and 700hPa. The right-hand blue line shows the temperature recorded as yesterday's 3pm balloon ascended, starting at 26° at the surface, kicking down then up slightly before dropping evenly away to 3° at 700hPa, or about 10,000 feet. The left-hand blue line shows the dew point, with the air very dry immediately above the surface where a light seabreeze was bringing in moisture.
The red lines are for this morning's 6am ascent. From a surface temperature of 16.5, the thermometer rose to 26° a few hundred feet up, and only equalled the surface temperature when it reached 830hPa, or about 5,000 feet. Surface winds were negligible, but increased rapidly to 35 to 45km/h northwesterlies at about 500 feet. Yesterday's seabreeze moisture clings to the surface, protected by the inversion.
In the Hunter Valley, Cessnock, which spent the night under the inversion, recorded a 6am temperature of 6.8, while Murrurundi in the Upper Hunter was 19. With a big inversion not far above ground level and a windflow close to the critical level needed to disturb substantially cooler, moister air below, there were quite a few observations of the inversion being blown out and suddenly replaced by much warmer air. Forbes airport reported a temperature of 26.3 at 1.36am with a northerly averaging 59km/h and gusting to 77, while Parkes reported 25.4° at 3.04am with a NNW of 61 gusting 81.