8004 Monthly New South Wales Review magazine

8004 Monthly New South Wales Review magazine

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AUSTRALIA

DEPARTMENT OF SCIENCE
AND THE ENVIRONMENT

BUREAU OF METEOROLOGY

# MONTHLY WEATHER REVIEW

NEW SOUTH WALES

APRIL 1980


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EXPLANATION OF USE OF DECILE RANGE NUMBERS

Decile range numbers are used in this publication as indicators of rainfall in preference to monthly averages.

Rainfall, unlike many other meteorological elements such as temperature and pressure, is non-continuous in time and space. As a result the statistical description of rainfall occurrence is quite complex.

The best known and most commonly used rainfall statistic is the arithmetic mean (often called the 'average' or 'normal'). Monthly means are computed by adding the rainfalls in a given month over a long period and dividing the total by the number of years of record.

Another statistic is the 'median' or '50 per cent' value, which is the value that is exceeded by half the occurrences and not exceeded by the other half. With many meteorological quantities the mean and median values are equal or very close and the use of 'average' for either value causes no confusion. Although this is often the case with annual rainfall, for shorter periods (3 months or less) the mean can differ significantly from the median.

As an example let us look at January rainfalls for Sydney, Melbourne and Alice Springs, and Halls Creek July rainfall:

MONTHLY RAINFALLS - MILLIMETRES

| Place | Month | Mean | Median |
|---|---|---|---|
| Sydney | January | 95 | 71 |
| Melbourne | January | 48 | 36 |
| Alice Springs | January | 39 | 15 |
| Halls Creek | July | 6 | Nil |

It will be seen that in these cases the mean value is not the same as the median value. At Alice Springs the January mean of 39mm is equalled or exceeded in only about 35 per cent of years, and at Halls Creek the July mean of 6mm is equalled or exceeded in about 20 per cent of years. In fact at Halls Creek July rainfall is nil in almost 70 per cent of years although the mean is 6mm.

For this reason we prefer to describe monthly, and longer periods up to annual, rainfalls by the median or 50 per cent value rather than the mean.

To obtain some idea of the 'spread' or variability of monthly rainfall, the amount which is not exceeded in the driest 10 per cent of years (the first decile) and that exceeded in the wettest 10 per cent of years (the ninth decile) are often quoted.

We can imagine these decile values, which are the values dividing each 10 per cent of occurrences from the driest to the wettest years, as giving some indication of rainfall variability. In the Monthly Rainfall Review we use decile ranges. The first decile range (decile range 1) is the range of the driest 10 per cent of rainfalls, the second decile range is the next driest 10 per cent and so on. We consider the middle 40 per cent (decile ranges 4-7) as being 'average' although in some cases the arithmetic mean may lie outside this range.

We use the following terminology:

| Extent of range | Formal title | Descriptive name |
|---|---|---|
| Lowest 10 per cent of monthly rainfalls | Decile range 1 | Very much below 'average' |
| Next lowest 10 per cent | Decile range 2 | Much below 'average' |
| Next lowest 10 per cent | Decile range 3 | Below 'average' |
| Middle 40 per cent of monthly rainfalls | Decile ranges 4-7 | 'Average' |
| Next higher 10 per cent | Decile range 8 | Above 'average' |
| Next higher 10 per cent | Decile range 9 | Much above 'average' |
| Highest 10 per cent of monthly rainfalls | Decile range 10 | Very much above 'average' |


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METEOROLOGICAL SUMMARY

WEATHER REVIEW

NEW SOUTH WALES

APRIL, 1980

CONTENTS

| | | PAGE |
|---|---|---|
| 1. | Introduction | 1 |
| 2. | Synoptic Circulation | 1 & 2 |
| 3. | Rainfall | 2 |
| 4. | Temperature | 2 & 3 |
| 5. | Phenomena | 3 & 4 |
| 6. | Bushfires and Floods | 4 |
| 7. | Normal Meteorological Conditions for May | 4 & 5 |
| 8. | Table 1 -- Rainfall District Averages for April, 1980 | 6 |
| 9. | Table 2 -- Daily Rainfall at Selected Stations for April, 1980 | 7 & 8 |
| 10. | Table 3 -- Irrigation and Hydroelectric Stores water April, 1980 | 9 |
| 11. | Table 4 -- Temperatures at Selected Stations for April, 1980. | 10 |
| 12. | Table 5 -- Summary of Sydney Observations for April, 1980 | 11 |
| 13. | Table 6 -- Summary of Canberra Observations for April, 1980 | 12 |
| 14. | Table 7 -- Evaporation and Sunshine at Selected Stations for April, 1980 | 13 |
| 15. | Maps for April, 1980 | | |
| | Map 1 -- Rainfall -- Isohyets | | |
| | Map 2 -- Rainfall -- Distribution of Decile Ranges of Rainfall | | |
| | Map 3 -- Maximum Temperatures -- Departures from Normal | | |
| | Map 4 -- Minimum Temperatures -- Departures from Normal | | |
| 16. | Daily Weather Maps -- 1st to 30th April, 1980. | |


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WEATHER REVIEW

NEW SOUTH WALES

APRIL, 1980

INTRODUCTION

Rainfall varied from very much above average in the far west (where district averages were the highest for April since the record rains of 1974) to much to very much below average over the eastern half of the state.

Averages for the Hunter, Central Tablelands (South), Metropolitan (west) and South Coast Districts were the lowest ever for April (district records have been kept since 1913) whilst in Central Tablelands (North) it was the least April rainfall since 1923, in the Northwestern Slopes and Northern Tablelands (West) the least since 1942 and in the Northern Rivers and Illawarra Districts the least since 1957.

The abundant rains recorded towards the end of the month in the southwest of the state were sufficient to break the five months drought in that area.

Generally above average temperatures.

SYNOPTIC CIRCULATION

In the first five days of the month weak high pressure cells with intervening shallow southern troughs moved over the state and, except for a few light coastal showers, settled weather prevailed.

For the next two and a half weeks an intense slow moving high, centred at latitudes 35 to 40 degrees, dominated the charts as it drifted east from the central Bight (6th) to be located southeast of New Zealand by 22nd. Winds were south to easterly in first five days and north to northeasterly 10th to 22nd. There were a few coastal showers most days and local storms in northeastern and central eastern areas on 6th, caused by a "cold pool" in upper atmosphere, otherwise mainly dry weather persisted 6th to 15th. During 16th to 22nd convergence of upper level moisture followed by a large cloud mass from the west brought widespread rain and storms with variable rainfalls in most regions west of the ranges and widely scattered light showers in coastal areas.


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N.S.W.

During 23rd/24th a southern trough associated with low pressure well south of the continent crossed the state resulting in a spell of south to westerly winds and almost general rain with moderate to heavy falls in southern and central inland districts.

For the rest of the month the main feature for the region was the leading ridge of an almost stationary high centred in the Bight. An upper level trough and associated cloud mass moved eastward 25th/26th and generated light to locally moderate showers along the coast then during 26th/27th a small low in the Tasman Sea and the passage of a cold front along the coast strengthened winds in coastal areas. Apart from the coastal rainfalls 26th/27th and one or two very light seaboard showers on the other days, settled weather with south to easterly winds persisted in this week.

RAINFALL

Highest rainfall totals at Telegraphic Reporting Stations were 129 millimetres at Pooncarie (Lower Darling District), 96 millimetres at Cape Byron (Northern Rivers) and 95 millimetres at Menindee (Lower Darling).

Over the rest of the Western District, in the Riverina and over much of the Southwestern Slopes and southern Central Western Plains, in coastal districts north of Newcastle and around Robertson - Berry in the Illawarra District totals were mostly in the 25 to 50 millimetres range. Elsewhere rainfall was generally less than 10 millimetres with scattered areas along the highlands and in the Hunter and South Coast Districts where totals were less than 0.6 millimetres.

Details of rainfall are shown in Tables 1 and 2 and on Maps 1 and 2.

TEMPERATURES

Below average day temperatures were recorded in southwestern districts during first week and in most inland areas during last week of month. Otherwise they were mostly above average, generally by 5 to 10 degrees in northeastern districts in first week and in southern and central inland areas during days 10th to 18th, very high maxima, more than 10 degrees above average were recorded in Metropolitan District on 3rd.

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N.S.W.

Minima were variable throughout with recordings generally above average mid-month and below average early and late in month.

As shown in Table 4 and on Maps 3 and 4 average maximum temperatures were close to average along most of the coast and in a strip of country lying south from Bourke through central western plains into Riverina and above average elsewhere with greatest departures from average 3 degrees above in the Northern and Southern Tablelands Districts, and, average minima were well above in the far west and central western regions and within one degree of average elsewhere.

Reported extremes were 37°C. at Tibooburra on 5th and minus 7°C. at Perisher Valley on 28th.

PHENOMENA

Thunderstorms. Scattered thunderstorm activity was reported in parts of coast and tablelands 6th, 16th, 17th, 19th and 30th, in Riverina and Southwestern Slopes Districts 16th and 17th, in Upper Western District 16th and in Central Western Plains District on 17th.

Hail was reported in Metropolitan, Illawarra and Southern Tablelands Districts during afternoon and evening hours of 30th -- in the Warragamba to Bargo area heavy hail associated with heavy rain caused property and stock losses and minor flooding.

Fog. Early morning fogs were reported at a few places in coastal and/or highland areas most days.

Frost level temperatures were reported in parts of the southern highlands all days except 4th, 16th to 20th, 22nd and 23rd, in parts of central highlands during days 7th to 10th and 25th to 30th and at one or two centres in the coastal plains 8th, 29th and 30th.

Dust areas were reported in the northwest on 11th, parts of southwest and central west 16th and 23rd and at places on southern and central tablelands on 23rd.

Snow )
) No occurrences were reported.
Tornadic squalls )

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N.S.W.

**Gales and Strong Winds.** Gale force winds occurred over New South Wales ocean waters during 9th and 20th to 22nd and there were periods of strong winds in coastal waters 14th to 16th, 23rd and 26th/27th.

BUSHFIRES AND FLOODS

**Bushfires.** With persistent dry northerly winds mid-month an extreme fire danger rating occurred in the Upper Western, Lower Western and Riverina Districts, as a result the State Minister for Services issued a total ban on the lighting of fires for these districts from 9 p.m. 15th to 9 p.m. 16th.

**Flooding.** Nil occurrences.

NORMAL CONDITIONS IN N.S.W.FOR MAY

With high pressure systems tending to pursue paths over more northern parts of the State, normally the influence of southern depression systems and their predominantly westerly air flow extends gradually northwards over N.S.W. during May. In general, both these controls lead to somewhat lower rainfalls, due to the dryness of the air masses involved. However, frontal systems associated with southern depressions and/or topographical effects, result in slightly higher rainfalls in southern inland districts and on southern parts of the Western Slopes and Tablelands.

While average coastal rainfalls in May vary from 75 millimetres in the south to 175 millimetres in the north, a rapid tapering off to 50 millimetres occurs on the eastern slopes and escarpments of the main Divide. Falls average from 50 to 125 millimetres on the South West Slopes and western sides of the Southern Alps, but fall off rapidly from 50 millimetres to 25 millimetres elsewhere from the top of the ranges to the Central Plains. In the far west average rainfall is usually below 25 mm and in many cases less than 12 millimetres.

Cyclonic storms are uncommon in May, even in coastal districts. However these occasionally give heavy rains between the coast and Ranges, and on very rare occasions, in inland districts. Monthly totals from 200 millimetres to 300 millimetres on coastal sections are usual on

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N.S.W.

such occasions, and at times are as high as 375 millimetres, but falls in excess of 500 millimetres per month are rare.

While flooding of all coastal rivers has occurred in May, apart from the Murray and Murrumbidgee systems inland rivers are very seldom affected directly. However water from heavy rains earlier in the year usually takes many months in its course to the sea down the Darling River system, so that flooding can occur from this cause.

During May, although inland and coastal districts experience average day temperatures varying between $19^{\circ}$C. in the south and $21^{\circ}$C. in the north, the Tablelands report readings below $15^{\circ}$C. and as low as $7^{\circ}$C. in the south.

On the tablelands night temperatures are usually below $1^{\circ}$ in the south and seldom above $5^{\circ}$C. in the remainder. In consequence in these regions frosts are common and fairly extensive particularly in the more elevated regions. Over the rest of the State minima usually vary from about $7^{\circ}$C. in the west to $10^{\circ}$ to $15^{\circ}$C. on the coast.

Serious bushfires occur during May only when dry conditions have been experienced in preceding months.


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N.S.W.

TABLE 1. RAINFALL - DISTRICT AVERAGES

| NO. | DISTRICT | MONTH APRIL 1980 MM | NORMAL APRIL MM | DEPARTURE FROM NORMAL % |
|---|---|---|---|---|
| 46 | Western (Far North West) | 54 | 14 | +285 |
| 47 | Western (Lower Darling) | 85 | 16 | +431 |
| 48 | Western Upper Darling | 17 | 22 | - 23 |
| 49 | Western (S.W. Plains) | 46 | 23 | +100 |
| 50 | C.W. Plains (Southern) | 30 | 35 | - 15 |
| 51 | C.W. Plains (Northern) | 11 | 33 | - 67 |
| 52 | N.W. Plains (West) | 6 | 32 | - 82 |
| 53 | N.W. Plains (East) | 4 | 33 | - 88 |
| 54 | N.W. Slopes (North) | 2 | 37 | - 95 |
| 55 | N.W. Slopes (South) | 2 | 40 | - 95 |
| 56 | N. Tablelands (Western) | 3 | 40 | - 93 |
| 57 | N. Tablelands (Eastern) | 23 | 70 | - 68 |
| 58 | North Coast (Upper) | 39 | 136 | - 72 |
| 59 | North Coast (Lower) | 35 | 149 | - 77 |
| 60 | Manning | 51 | 142 | - 65 |
| 61 | Hunter | 4 | 83 | - 96 |
| 62 | C. Tablelands (North) | 1 | 45 | - 98 |
| 63 | C. Tablelands (South) | 8 | 72 | - 89 |
| 64 | C.W. Slopes (North) | 7 | 45 | - 85 |
| 65 | C.W. Slopes (South) | 16 | 44 | - 64 |
| 66 | Metropolitan (East) | 15 | 114 | - 87 |
| 67 | Metropolitan (West) | 2 | 74 | - 98 |
| 68 | Illawarra | 15 | 104 | - 86 |
| 69 | South Coast | 6 | 87 | - 94 |
| 70 | S. Tablelands (Goulburn-Monaro) | 6 | 51 | - 89 |
| 71 | S. Tablelands (Snowy Mountains) | 10 | 64 | - 85 |
| 72 | S.W. Slopes (South) | 39 | 60 | - 35 |
| 73 | S.W. Slopes (North) | 21 | 47 | - 56 |
| 74 | Riverina (East) | 40 | 36 | + 11 |
| 75 | Riverina (West) | 39 | 28 | + 39 |

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N.S.W.

TABLE 2. DAILY RAINFALL - SELECTED STATIONS - FOR APRIL, 1980
(FROM TELEGRAPHIC REPORTS)
(AMOUNTS OVER 1.0 MILLIMETRES ROUNDED TO NEAREST MM)

| DATE | TIBOOBURRA | BROKEN HILL | BOURKE | BALRANALD | CONDOBOLIN | NYNGAN | WALGETT | MOREE | BARRABA | TAMWORTH | ARMIDALE | TABULAM (MUIRNE) | LISMORE | COFFS HARBOUR | TAREE |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | | | | | | | | | | | | | | | |
| 2 | | | | | | | | | | | | | | 1 | |
| 3 | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | |
| 5 | | | | | | | | | | | | | | | |
| 6 | | | | | | | | | | | | | | | |
| 7 | | | | | | | | | | | | | | | 11 |
| 8 | | | | | | | | | | | | | | | |
| 9 | | | | | | | | | | | | | | | |
| 10 | | | | | | | | | | | | | | | |
| 11 | | | | | | | | | | | | | | 0.8 | 3 |
| 12 | | | | | | | | | | | | | | | |
| 13 | | | | | | | | | | | | | 0.2 | | |
| 14 | | | | | | | | | | | | | 0.2 | 4 | |
| 15 | | | | | | | | | | | 2 | 7 | 9 | 4 | |
| 16 | | | | 2 | | | | | | | | 0.4 | | 17 | |
| 17 | | | | | 10 | | | | | | | 0.2 | 0.6 | 4 | |
| 18 | | 0.8 | | | | | | | | | | | | 6 | |
| 19 | 2 | 15 | | 8 | 1 | | | | | | 0.2 | 0.2 | 3 | 5 | |
| 20 | 12 | 3 | 2 | 7 | 7 | 3 | 4 | | | | | 5 | 11 | 2 | |
| 21 | 9 | | 3 | | | 3 | | | 0.4 | | 0.4 | | 2 | | 4 |
| 22 | | 2 | | 1 | | | | | | | | | | | 1 |
| 23 | 37 | 42 | | 24 | | | | | | | | | | | |
| 24 | 3 | 5 | 10 | 16 | 13 | 8 | 6 | 4 | 2 | 2 | | | | | 0.6 |
| 25 | | | | | | | | | | | | 6 | | | |
| 26 | | | | | | | | | | | | | | | 12 |
| 27 | | | | | | | | | | | | | | | |
| 28 | | | | | | | | | | | | 0.8 | | 2 | 2 |
| 29 | | | | | | | | | | | | | | | |
| 30 | | | | | | | | | | | | | | | |
| 31 | | | | | | | | | | | | | | | |


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N.S.W.

TABLE 2. DAILY RAINFALL - SELECTED STATIONS - FOR APRIL. 1980
(FROM TELEGRAPHIC REPORTS).
(AMOUNTS OVER 1.0 MILLIMETRES ROUNDED TO NEAREST MM)

| DATE | NEWCASTLE (MARYVILLE) | MUDGEE | BATHURST | COONABARABRAN | DUBBO | SYDNEY | LIVERPOOL | WOLLONGONG | BEGA | CANBERRA CITY | PERISHER VALLEY | WAGGA | COOTAMUNDRA | NARRANDERA | HAY |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | | | | | | | | | | | | | | | |
| 2 | | | | | | | | | | | | | | | |
| 3 | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | |
| 5 | | | | | | | | | | | | | | | |
| 6 | | | | | | | | | | | | | | | |
| 7 | 2 | | | | | 1 | | 13 | | | | | | | |
| 8 | | | | | | | | | | | | | | | |
| 9 | | | | | | | | | | | | | | | |
| 10 | | | | | | | | | | | | | | | |
| 11 | | | | | | | | | | | | | | | |
| 12 | | | | | | | | | | | | | | | |
| 13 | | | | | | | | | | | | | | | |
| 14 | | | | | | | | | | | | | | | |
| 15 | | | | | | | | | | | | | | | |
| 16 | | | | | | 0.4 | | 2 | | | | | | | 3 |
| 17 | | | | | | | | | 2 | 0.2 | 3 | 4 | 4 | 9 | 1 |
| 18 | | | | | | | | | | 5 | 4 | | | | |
| 19 | | | | | | | | | | | 0.4 | | | 4 | 3 |
| 20 | | | | | 0.4 | | 0.2 | | | | 2 | 2 | 2 | 17 | 1 |
| 21 | 6 | | | | 0.4 | 5 | | | | | | 1 | | | 1 |
| 22 | 3 | | | | | 0.2 | | | | | | | | | |
| 23 | 0.4 | | | | | | | | | | | | | | 8 |
| 24 | | 4 | 3 | 1 | 3 | 0.4 | 2 | 0.2 | | 0.8 | 4 | 27 | 19 | 30 | 23 |
| 25 | | | | | | | | 0.2 | | | | | | | |
| 26 | 6 | | | | | 4 | 1 | 2 | | | | | | | |
| 27 | 0.2 | | | | | 0.2 | | | 0.6 | | | | | | |
| 28 | | | | | | | | | | | | | | | |
| 29 | | | | | | | | | | | | | | | |
| 30 | | | | | | | | | | | | | | | |
| 31 | | | | | | | | | | | | | | | |

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N.S.W.

TABLE 3. IRRIGATION AND HYDROELECTRIC STORED WATER

These figures were supplied by the Authorities controlling the various dams and show the volume of water held in active storage at the end of the month expressed as a percentage of design capacity of these dams.

| DAM | STREAM | % AT END OF APRIL, 1980 |
|---|---|---|
| BLOWERING | TUMUT | 23 |
| BURRENDONG | MACQUARIE | (a) 54 |
| | | (b) -- |
| BURRINJUCK | MURRUMBIDGEE | 32 |
| CARCOAR | BELUBULA | 50 |
| GLENBAWN | HUNTER | (a) 48 |
| | | (b) -- |
| HUME | MURRAY | 19 |
| KEEPIT | NAMOI | 38 |
| LOSTOCK | PATERSON | 64 |
| MENINDEE | DARLING | 64 |
| PINDARI | SEVERN | 45 |
| SNOWY MOUNTAINS SYSTEM | | 41 |
| WYANGALA | LACHLAN | 30 |

(a) Percentage of design capacity for conservation purposes
(b) Percentage of design capacity for flood mitigation purposes.

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N.S.W.

TABLE 4. TEMPERATURES AT SELECTED STATIONS
(from daily telegraphic reports)

APRIL, 1980.

| STATION | MAXIMUM (°C) EXTREME | MAXIMUM (°C) MEAN | MAXIMUM (°C) DEPART | MINIMUM (°C) EXTREME | MINIMUM (°C) MEAN | MINIMUM (°C) DEPART | MEAN (°C) MEAN | MEAN (°C) DEPART |
|---|---|---|---|---|---|---|---|---|
| ARMIDALE | 27 | 23.4 | + 2.9 | 3 | 7.1 | - 0.4 | 15.3 | + 1.3 |
| BALRANALD | 34 | 25.2 | + 1.5 | 5 | 11.8 | + 2.4 | 18.5 | + 1.9 |
| BATHURST | 27 | 23.8 | + 2.2 | - 1 | 5.5 | - 0.8 | 14.7 | + 0.7 |
| BOMBALA | 27 | 20.5 | + 2.3 | - 1 | 4.9 | - 0.3 | 12.7 | + 1.0 |
| BOURKE | 34 | 28.0 | + 0.5 | 7 | 13.7 | + 0.9 | 20.9 | + 0.7 |
| BROKEN HILL | 33 | 25.8 | + 2.0 | 5 | 13.4 | + 2.0 | 19.6 | + 2.0 |
| CANBERRA CITY | 28 | 22.7 | + 3.1 | - 2 | 6.6 | + 0.2 | 14.7 | + 1.7 |
| CONDOBOLIN | 30 | 25.1 | + 0.2 | 5 | 12.4 | + 1.8 | 18.8 | + 1.0 |
| DENILIQUIN | 32 | 23.8 | + 1.4 | 2 | 10.3 | + 0.3 | 17.1 | + 0.9 |
| DUBBO | 32 | 26.1 | + 1.2 | 6 | 12.2 | + 1.8 | 19.1 | + 1.4 |
| HAY | 31 | 24.4 | + 0.3 | 4 | 12.0 | + 2.4 | 18.2 | + 1.3 |
| INVERELL | 30 | 26.7 | + 2.2 | 3 | 7.0 | - 0.6 | 16.8 | + 0.7 |
| JERRYS PLAINS | 35 | 27.1 | + 1.7 | 4 | 10.2 | - 0.4 | 18.6 | + 0.5 |
| LISMORE | 35 | 26.0 | + 0.3 | 10 | 15.0 | + 0.9 | 20.5 | + 0.6 |
| MORUYA HEADS | 26 | 21.5 | - 0.2 | 6 | 12.1 | - 0.1 | 16.8 | - 0.2 |
| NEWCASTLE (MARYVILLE) | 33 | 24.2 | + 0.1 | 9 | 15.3 | + 0.7 | 19.7 | + 0.3 |
| SYDNEY | 33 | 23.8 | + 1.7 | 10 | 15.1 | + 0.6 | 19.5 | + 1.2 |
| TAMWORTH | 32 | 26.8 | + 2.0 | 7 | 11.3 | + 1.0 | 19.0 | + 1.4 |
| WAGGA | 30 | 24.0 | + 0.8 | 2 | 8.8 | - 0.4 | 16.4 | + 0.2 |
| WALGETT | 35 | 28.7 | + 2.1 | 8 | 13.5 | + 0.8 | 21.1 | + 1.4 |
| WILCANNIA | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- | ---------- |
| YAMBA | 33 | 24.5 | + 0.2 | 13 | 16.6 | + 0.2 | 20.5 | + 0.1 |

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TABLE NO. 5

N.S.W.

SUMMARY OF SYDNEY OBSERVATIONS FOR APRIL, 1980.

| ITEM | | MONTH OF APRIL, '80 | NORMAL OR EXTREME |
|---|---|---|---|
| PRESSURE (reduced to M.S.L.) | | | |
| Mean (9 a.m. and 3 p.m.) | (mb) | 1020.5 | 1018.3 |
| TEMPERATURE | | | |
| Mean 9 a.m. | (°C) | 18.8 | 17.7 |
| Mean 3 p.m. | (°C) | 22.6 | 20.7 |
| Mean daily maximum | (°C) | 23.8 | 22.1 |
| Mean daily minimum | (°C) | 15.1 | 14.5 |
| Mean for month | (°C) | 19.5 | 18.3 |
| Highest during month | (°C) | 33.5* | 33.0 |
| Lowest during month | (°C) | 9.8 | 7.0 |
| Days 40°C or higher | (No.) | 0 | 0 |
| Days 30°C or higher | (No.) | 1 | 0 |
| Days 2°C or lower | (No.) | 0 | 0 |
| Days 0°C or lower | (No.) | 0 | 0 |
| RELATIVE HUMIDITY | | | |
| Mean at 9 a.m. | (%) | 69 | 74 |
| Mean at 3 p.m. | (%) | 56 | 65 |
| WIND | | | |
| Mean speed | (km/hr) | 10.8 | 11.0 |
| Strongest gust | (km/hr) | W/83 | WSW/126 |
| Days with mean wind | | | |
| 63 km/hr or more (gale) | (No.) | 0 | -- |
| SUNSHINE | | | |
| Mean daily | (hours) | 8.0 | 6.2 |
| EVAPORATION (Mascot) | | | |
| Total for month | (mm) | 148.8 | -- |
| RAINFALL | | | |
| Total for month | (mm) | 11.6⁺ | 124.1 |
| Rain days (days of 0.1mm or more | (No.) | 7 | 13 |
| PHENOMENA | | | |
| Days when thunder heard | (No.) | 2 | 1.3 |
| Days when hail fell | (No.) | 0 | 0 |

* Highest maximum on record, previous highest 33.0° on 10/1969 and 1/1936.

⁺ Lowest April rainfall since 1896 when 4 mm and 4th lowest April rainfall on record.

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N.S.W.

TABLE NO. 6. SUMMARY OF CANBERRA CITY OBSERVATIONS FOR APRIL, 1980

| ITEM | | MONTH OF APRIL, 1980 | NORMAL OR EXTREME |
|---|---|---|---|
| PRESSURE (reduced to M.S.L.) | | | |
| Mean (9 a.m. and 3 p.m.) | (mb) | 1020.5 | 1018.7 |
| TEMPERATURE | | | |
| Mean 9 a.m. | (°C) | 12.4 | 12.1 |
| Mean 3 p.m. | (°C) | 21.9 | 18.7 |
| Mean daily maximum | (°C) | * 22.7 | 19.6 |
| Mean daily minimum | (°C) | 6.6 | 6.4 |
| Mean for month | (°C) | 14.7 | 13.0 |
| Highest during month | (°C) | 27.7 | 32.6 |
| Lowest during month | (°C) | - 1.6 | - 3.6 |
| Days 40°C or higher | (No.) | 0 | 0 |
| Days 30°C or higher | (No.) | 0 | 0 |
| Days 2°C or lower | (No.) | 2 | | |
| Days 0°C or lower | (No.) | 2 | | |
| RELATIVE HUMIDITY | | | |
| Mean at 9 a.m. | (%) | 69 | 75 |
| Mean at 3 p.m. | (%) | 36 | 48 |
| WIND | | | |
| Mean speed | (km/hr) | | | |
| Strongest gust | (km/hr) | NW/ 63 | NW/ 106 |
| Days with mean wind 63 km/hr or more (gale) | (No.) | 0 | | |
| SUNSHINE | | | |
| Mean daily | (hours) | 7.9 | 6.9 |
| EVAPORATION | | | |
| Total for month | (MM) | 98.8 | 104 |
| RAINFALL | | | |
| Total for month | (MM) | 6.2 | 50 |
| Rain days (days of 0.1 mm or more) | (No.) | 3 | 8 |
| PHENOMENA | | | |
| Days when thunder heard | (No.) | 0 | 0.9 |
| Days when hail fell | (No.) | 0 | 0.1 |
| Days of frost | (No.) | 17 | 4.9 |
| Days of snow | (No.) | 0 | 0 |
| Days of fog | (No.) | 3 | 4.1 |

* Highest April mean maximum on record.

-12-


=== Page 16 of 29

N.S.W.

TABLE 7. EVAPORATION AND SUNSHINE
FOR SELECTED STATIONS

APRIL, 1980

| STATION | EVAPORATION * MONTHLY (MM) | SUNSHINE MEAN DAILY (HOURS) |
|---|---|---|
| CANBERRA | 99 | 7.9 |
| COBAR | 105 | 9.0 |
| COFFS HARBOUR | 164 | 8.1 |
| MASCOT (SYDNEY AIRPORT) | 149 | 8.5 |
| MOREE | 179 | 10.1 |
| RICHMOND | 146 | 8.6 |
| TAMWORTH | 191 | 10.0 |
| WAGGA | 146 | -- |
| WILLIAMTOWN | 153 | 8.5 |

* Evaporation measured in Class A pan equipped with bird guard.

-13-


=== Page 17 of 29

145 150

50 25 10 0.4 0.4 0.4 0.4 10 25

Murwillumbah

Lismore

Tibooburra

Mungindi

54

Moree

50

48

52

Warialda

50

Inverell

Glen Innes

Yamba

53

Grafton

Bourke

Walgett

56

Narrabri

Coffs Harbour

46

55

Armidale

51

25

Gunnedah

Tamworth

Coonabarabran

Smoky Cape

Wilcannia

Cobar

Nyngan

50

Port Macquarie

Broken Hill

Scone

Manning Heads

49

Dubbo

61

47

Ivanhoe

Mt Hope

50

65

Mudgee

Cessnock

100

Newcastle

Orange

25

Forbes

Bathurst

Wyong

SOUTH

Hillston

Katoomba

Richmond

PACIFIC

Cowra

OCEAN

50

Wentworth

75 25

SYDNEY

(TASMAN SEA)

67

Griffith

Taralga

50

Hay

25

Leeton

68

Port Kembla

Euston

Junee

70

Goulburn

25

100

100

Balranald

Wagga

Wagga

CANBERRA

Jervis Bay

Deniliquin

Holbrook

50

Tocumwal

69

10

50

Kiandra

Moruya Heads

50

Kosciusko

Rainfall

25

Bega

below 0.6 mm

Bombala

10

10

Eden

10

145 150

NEW SOUTH WALES

MAP 1. RAINFALL FOR APRIL, 1980.

ISOHYETS. (millimetres)


=== Page 18 of 29

FOR NEW SOUTH WALES

QUEENSLAND

SOUTH AUSTRALIA

48

Bourke

51

Nyngan

50

Condobolin

75

Leeton

Junee

Holbrook

Kosciusko

(Based on monthly totals from Telegraphic Rainfall Stations)

VICTORIA

Murwillumbah

Yamba

Coffs Harbour

Smoky Cape

Port Macquarie

SOUTH PACIFIC OCEAN (TASMAN SEA)

Newcastle

Wyong

Richmond

SYDNEY

Port Kembla

Jervis Bay

Moruya Heads

Bega

Eden

for NEW SOUTH WALES

Very much above average

Above average

4-7 Average

Much below average

Very much below average

MAP 2. DISTRIBUTION OF DECILE RANGE NUMBERS OF RAINFALL NEW SOUTH WALES APRIL, 1980.


=== Page 19 of 29

Higher than 1°C. above normal

Within 1°C. of normal (±)

Lower than 1°C. below normal

MAP 3. MAXIMUM TEMPERATURES FOR APRIL, 1980.


=== Page 20 of 29

Higher than
1°C. above normal

Within 1°C. of normal (±)

Lower than 1°C. below normal

MAP 4. MINIMUM TEMPERATURES FOR
APRIL, 1980.


=== Page 21 of 29

# DAILY WEATHER MAPS

1000 K (00 GMT)

1-30 April 1980

Dates are ringed left-hand corner of each map.

### LEGEND

Isobars are drawn at 4 mb intervals

Cold Front
Warm Front
Occlusion


=== Page 22 of 29

1012

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=== Page 23 of 29

16 17
18 19
20 21
22 23


=== Page 24 of 29

1012
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XH
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24 1016 1012 1008 1004
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1000 996 992 988 984
980
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LX

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26 1004 1000 996 1000 1004 1008 1012 1016 1020
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=== Page 25 of 29

# NEW SOUTH WALES

145 150 155

Murwillumbah

Lismore

Tenterfield

Goodooga Mungindi

54

58

57

Moree Warialda

Yamba

52

Glen Innes

Grafton

Inverell

Tibooburra

48

53

Walgett

30

56

Narrabri

59

Bourke

Coffs Harbour

Armidale

55

Gunnedah

Coonamble

46

51

Tamworth

Smoky Cape

Coonabarabran

60

Port Macquarie

Nyngan

64

Wilcannia

Cobar

Dalkeith

Scone

Manning Heads

Gloucester

61

Dubbo

62

Broken Hill

Bobadah

Mudgee

Jerrys Plains

47

50

65

Newcastle

Mt. Hope

Condobolin

Ivanhoe

Orange

Wyong

Forbes

Bathurst

Katoomba

SYDNEY

Hillston

Cowra

63

67

66

REFERENCE TO METEOROLOGICAL DISTRICTS

Wentworth

75

68

Taralga

Port Kembla

46 WESTERN (FAR NORTHWEST)
62 CENTRAL TABLELANDS (N)

Griffith

47 WESTERN (LOWER DARLING)
63 CENTRAL TABLELANDS (S)

Goulburn

48 WESTERN (UPPER DARLING)
64 CENTRAL WESTERN SLOPES (N)

Euston

Hay

Leeton

73

70

49 WESTERN (SOUTHWEST PLAINS)
65 CENTRAL WESTERN SLOPES (S)

74

Junee

50 CENTRAL WESTERN PLAINS (S)
66 METROPOLITAN (E)

CANBERRA

Jervis Bay

51 CENTRAL WESTERN PLAINS (N)
67 METROPOLITAN (W)

Moulamein

Wagga Wagga

Adelong

52 NORTHWEST PLAINS (W)
68 ILLAWARRA

72

69

53 NORTHWEST PLAINS (E)
69 SOUTH COAST

Deniliquin

Holbrook

54 NORTHWEST SLOPES (N)
70 SOUTHERN TABLELANDS (GOULBURN - MONARO)

Moruya Heads

Kiandra

55 NORTHWEST SLOPES (S)

Tocumwal

Cooma

56 NORTHERN TABLELANDS (W)
71 SOUTHERN TABLELANDS (SNOWY MOUNTAINS)

57 NORTHERN TABLELANDS (E)

Kosciuszko

71

Bega

58 UPPER NORTH COAST
72 SOUTHWEST SLOPES (S)

59 LOWER NORTH COAST
73 SOUTHWEST SLOPES (N)

Bombala

60 MANNING
74 RIVERINA (E)

Eden

61 HUNTER
75 RIVERINA (W)

145 150


=== Page 26 of 29

N.S.W.

such occasions, and at times are as high as 375 millimetres, but falls in excess of 500 millimetres per month are rare.

While flooding of all coastal rivers has occurred in May, apart from the Murray and Murrumbidgee systems inland rivers are very seldom affected directly. However water from heavy rains earlier in the year usually takes many months in its course to the sea down the Darling River system, so that flooding can occur from this cause.

During May, although inland and coastal districts experience average day temperatures varying between 19°C. in the south and 21°C. in the north, the Tablelands report readings below 15°C. and as low as 7°C. in the south.

On the tablelands night temperatures are usually below 1° in the south and seldom above 5°C. in the remainder. In consequence in these regions frosts are common and fairly extensive particularly in the more elevated regions. Over the rest of the State minima usually vary from about 7°C. in the west to 10° to 15°C. on the coast.

Serious bushfires occur during May only when dry conditions have been experienced in preceding months.

-5-


=== Page 27 of 29

N.S.W.

TABLE 2. DAILY RAINFALL - SELECTED STATIONS - FOR APRIL, 1980
(FROM TELEGRAPHIC REPORTS)
(AMOUNTS OVER 1.0 MILLIMETRES ROUNDED TO NEAREST MM)

| DATE | TIBOOBURRA | BROKEN HILL | BOURKE | BALRANALD | CONDOBOLIN | NYNGAN | WALGETT | MOREE | BARRABA | TAMWORTH | ARMIDALE | TABULAM (MUIRNE) | LISMORE | COFFS HARBOUR | TAREE |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | | | | | | | | | | | | | | | |
| 2 | | | | | | | | | | | | | | 1 | |
| 3 | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | |
| 5 | | | | | | | | | | | | | | | |
| 6 | | | | | | | | | | | | | | | |
| 7 | | | | | | | | | | | | | | | 11 |
| 8 | | | | | | | | | | | | | | | |
| 9 | | | | | | | | | | | | | | | |
| 10 | | | | | | | | | | | | | | | |
| 11 | | | | | | | | | | | | | | 0.8 | 3 |
| 12 | | | | | | | | | | | | | | | |
| 13 | | | | | | | | | | | | | 0.2 | | |
| 14 | | | | | | | | | | | | | 0.2 | 4 | |
| 15 | | | | | | | | | | | 2 | 7 | 9 | 4 | |
| 16 | | | | 2 | | | | | | | | 0.4 | | 17 | |
| 17 | | | | | 10 | | | | | | | 0.2 | 0.6 | 4 | |
| 18 | | 0.8 | | | | | | | | | | | | 6 | |
| 19 | 2 | 15 | | 8 | 1 | | | | | | 0.2 | 0.2 | 3 | 5 | |
| 20 | 12 | 3 | 2 | 7 | 7 | 3 | 4 | | | | | 5 | 11 | 2 | |
| 21 | 9 | | 3 | | | 3 | | | 0.4 | | 0.4 | | 2 | | 4 |
| 22 | | 2 | | 1 | | | | | | | | | | | 1 |
| 23 | 37 | 42 | | 24 | | | | | | | | | | | |
| 24 | 3 | 5 | 10 | 16 | 13 | 8 | 6 | 4 | 2 | 2 | | | | | 0.6 |
| 25 | | | | | | | | | | | | 6 | | | |
| 26 | | | | | | | | | | | | | | | 12 |
| 27 | | | | | | | | | | | | | | | |
| 28 | | | | | | | | | | | | 0.8 | | 2 | 2 |
| 29 | | | | | | | | | | | | | | | |
| 30 | | | | | | | | | | | | | | | |
| 31 | | | | | | | | | | | | | | | |

-7-


=== Page 28 of 29

N.S.W.

TABLE 2. DAILY RAINFALL - SELECTED STATIONS - FOR APRIL, 1980
(FROM TELEGRAPHIC REPORTS).
(AMOUNTS OVER 1.0 MILLIMETRES ROUNDED TO NEAREST MM)

| DATE | NEWCASTLE (MARYVILLE) | MUDGEE | BATHURST | COONABARABRAN | DUBBO | SYDNEY | LIVERPOOL | WOLLONGONG | BEGA | CANBERRA CITY | PERISHER VALLEY | WAGGA | COOTAMUNDRA | NARRANDERA | HAY |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | | | | | | | | | | | | | | | |
| 2 | | | | | | | | | | | | | | | |
| 3 | | | | | | | | | | | | | | | |
| 4 | | | | | | | | | | | | | | | |
| 5 | | | | | | | | | | | | | | | |
| 6 | | | | | | | | | | | | | | | |
| 7 | 2 | | | | | 1 | | 13 | | | | | | | |
| 8 | | | | | | | | | | | | | | | |
| 9 | | | | | | | | | | | | | | | |
| 10 | | | | | | | | | | | | | | | |
| 11 | | | | | | | | | | | | | | | |
| 12 | | | | | | | | | | | | | | | |
| 13 | | | | | | | | | | | | | | | |
| 14 | | | | | | | | | | | | | | | |
| 15 | | | | | | | | | | | | | | | |
| 16 | | | | | | 0.4 | | 2 | | | | | | | 3 |
| 17 | | | | | | | | | 2 | 0.2 | 3 | 4 | 4 | 9 | 1 |
| 18 | | | | | | | | | | 5 | 4 | | | | |
| 19 | | | | | | | | | | | 0.4 | | | 4 | 3 |
| 20 | | | | | 0.4 | | 0.2 | | | | 2 | 2 | 2 | 17 | 1 |
| 21 | 6 | | | | 0.4 | 5 | | | | | | 1 | | | 1 |
| 22 | 3 | | | | | 0.2 | | | | | | | | | |
| 23 | 0.4 | | | | | | | | | | | | | | 8 |
| 24 | | 4 | 3 | 1 | 3 | 0.4 | 2 | 0.2 | | 0.8 | 4 | 27 | 19 | 30 | 23 |
| 25 | | | | | | | | 0.2 | | | | | | | |
| 26 | 6 | | | | | 4 | 1 | 2 | | | | | | | |
| 27 | 0.2 | | | | | 0.2 | | | 0.6 | | | | | | |
| 28 | | | | | | | | | | | | | | | |
| 29 | | | | | | | | | | | | | | | |
| 30 | | | | | | | | | | | | | | | |
| 31 | | | | | | | | | | | | | | | |

-8-


=== Page 29 of 29

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