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Karachi, Sindh -- Is This the End of the Rain?

Sep 13, 2011; 2:00 PM ET

A SECOND-STRAIGHT YEAR OF MAJOR FLOODING

Major flooding has once again hit Pakistan, this time almost exclusively in the state of Sindh. Sindh suffered in the great flood of 2010, mostly owing to the bursting Indus River rather than from local rainfall.

Hundreds of thousands of people in Sindh are suffering. More than a million acres of agricultural land, crops and all, are under water.

A LOOK BACK AT THE SUMMER OF 2011

Best that I can tell, based upon weather records, it has been an exceptional summer of weather in Pakistan.

For one thing, some areas, such as Karachi, got off to a slow start with little rain falling in June and even in July.

What is more, whereas the north returned to mostly near-normal rainfall following the catastrophic flooding cloudbursts of 2010, delayed rains came with abnormal intensity across Sindh beginning on Aug. 10-12.

At this time, the first flooding downpours left 245 mm at Mirpur Khas, 295 mm at Badin and an almost unthinkable 436 mm at Mithi. Data are from the Pakistan Meteorology Department (PMD).

Following some late-month rainy outbursts, August ended with 300 to at least 600 percent of normal monthly rainfall in the south and east of Sindh.

Karachi got through the early August downpours with only 11 mm, and the city ended the month with 61 mm--near normal, but far too little to make up for the June-July shortfall.

September has had almost daily outbreaks of thunderstorms, some bearing heavy falls of rain, throughout Sindh.

Highest rainfall as of Sept. 13 has more than matched that of August. Mirpur Khas has another 603 mm, and the tally for Mithi reached 632 mm as of Sept. 10; since then, data are missing.

Now, September marks the normal end of the summer rains, borne on the South West Monsoon, which usually withdraws southeast of the border by the second week of the month. So there should be no shock in learning that much of Sindh has already tallied 1,000 to more than 2,000 percent of historical average rainfall for the month. Exceptional, indeed.

For Karachi Airport, rainfall through Sept. 13 was 162.2 mm versus 10.1 mm historical average, according to the PMD. Tacking on the 61.5 mm from June-August, seasonal rainfall (thus far) comes to 223.7 mm. Data from the PMD show normal rainfall for the four summer months to be 142.9 mm, by my reckoning. That would be 157 percent of normal summer rainfall within five weeks.

However, the results elsewhere in Sindh are staggering beyond belief. Roughly 107 cm within little more than four weeks at Mithi! This is 42 inches in a land that satellite imagery suggests is made up of sand hills, little more than sand dunes stabilized by sparse vegetation.

I do not have a climatological average rainfall for Mithi, but it cannot be too far from 25 cm, which would be among the higher seasonal falls in Sindh.

The story is much the same for Mirpur Khas, where summer rainfall was at least 866 mm (34 inches).

Drawing once again from the PMD data tables (June1-Sept. 13):

Badin -- 643 mm (June-September normal 197 mm)

Chhor -- 565 mm (normal 194 mm)

Hyderabad -- 409 mm (normal 127 mm)

Nawabshah -- 644 mm (normal 115 mm)

These are not final amounts. Hopefully, I have done the adding correctly.

WHY THIS SUMMER?

It would be rewarding, personally, to be able to flesh out the "why" and "wherefore" of the abnormal weather, but I do not have any explanation.

Individually, any one of the flooding cloudbursts would not have been altogether unexpected, even though the heaviest falls were exceptional. It seems enough to say that some rare convergence of factors sparked (unprecedented?) repeated exceptional outbursts, yielding what must be, for at least parts of Sindh, the highest seasonal rainfall in the historical record.

IS IT OVER?

Thunderstorms hit Sindh with flooding downpours on Sept. 13, 2011.

Tuesday's cloudbursts have faded away. Now, numerical forecast models show a scenario of mid-level drying that, beginning Wednesday, will result in much less rain going forward. It could be that this is the last significant rainfall of the season. Or, maybe, there are still a few hit-or-miss downpours.

I will venture to say that the worst of the rain is now over. I pray for the waters to now recede, and for the people of Sindh to be comforted and returned to their homes.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com