Downpours Hit Western Arabia Last Week

Mar 22, 2011; 12:04 PM ET

HEIGHTENED AWARENESS FOLLOWING TWO DEADLY FLOODS

A few readers of this column have asked me as to weather in western Arabia, especially Jeddah, following numerical forecasts (now expired) showing substantial rainfall in western Arabia. The valid period for these forecast actually ended last week. Downpours did indeed happen here.

Although I do not have any good information as to how much rain fell in/near Jeddah, I do know that Makkah got somewhere between 50 and 75 mm within about two days, when all was said and done (according to our database).

Google Maps.

I have no information as to any flooding, but the rain may well have been heavy enough to spark flash flooding.

The trigger for the rain seems to have been a mass of humid air from the southern Red Sea that destabilized enough to breed thunderstorms as far north as west-central Saudi Arabia.

LATEST FLOODING IN AUSTRALIA

I do not recall hearing of so much flooding, over such a far-flung area, as I have witnessed (via weather data, news media) since late last year in Australia. Every state has been hit in some way, albeit none more so than Queensland, which is said to have had its wettest year on record in 2010.

Flooding has hit the far north and northwest of Western Australia. Flooding has hit Darwin, Northern Territory, swathes of South Australia, Victoria and even Tasmania.

The latest outburst of flooding hit an area that, of late, seemed to have been spared any unusual rain. Coastal New South Wales southward from greater Sydney seems to have been spared the soakings, being “shadowed” by westerly/northwesterly wind flow downcast from the Great Dividing Range.

Indeed, Sydney itself seems to have had a hot, dry summer.

Anyway, Sydney got a good soaking late last week with rain continuing through early this week. Between Sydney and eastern Victoria, meanwhile, rainfall reached as high as 398 mm within 24 hours according to the Australian Bureau of Meteorology (BOM). Other amounts were 200 to more than 400 mm within three days as of Tuesday between the eastern slopes and the coast.

I believe that tropical moisture was thrown back against the eastern slopes behind a cold front, whereupon it was wrung out as flooding cloudbursts.

CHANGING SEASONS BRING END IN SIGHT

The direct overhead sun has, as of last Sunday, shifted across the equator to the Northern Hemisphere, betiding the end of the “big wet” across tropical and sub-tropical Australia. Still, several weeks of rainy season do lie ahead for coast Queensland to the the Top End of Northern Territory. Then, too, there is the potential for tropical cyclones, none of which seems to be in the making at this time.

ELSEWHERE

The latest tropical cyclone, dubbed Cherono, has now dissipated at sea over the western south Indian Ocean.

If there is another candidate for tropical cyclone formation within the next day or two, it would be a tropical wave east of the Fiji mainland.

Things have quietened over the Indian Subcontinent, although there have been some soaking rains lately in the far northeast. Looking forward, the far northeast (maybe with stretches of Bangladesh) will have above-normal rainfall during the next one to two weeks if numerical forecasts are on target.