The Funnel Effect


I grew up in a valley. The Sacramento valley is not a normal valley, but rather one of the largest in the world; roughly 800 miles long and nearly 100 miles wide.

So large that most days it’s hard to distinguish it is a valley rather than a continual plain devoid of mountains in almost any direction.

The weather is often uniform, and patterns can be well predicted almost any month or season of the year, with very few anomalies.

Thunderstorms in the Sacramento Valley pass through only a few times a year, but when they do the clouds spread tremendously over the horizon in all directions.

Often enough it is only after these storms or heavy rains come and pass, clearing the air of pollutants, that mountains, 40 miles to the east, 40 miles to the west appear clearly enough to remind one that there are visible limits to one of the world’s largest bowls.


Duhok is at nearly the same latitude as my home city, and as such the climate, weather patterns, and prevailing wind direction are strongly similar. Duhok is also the same in that it is a city of a valley.

I hope this graphic conveys the geographic similarities to the two cities. Sacramento at roughly 38.5 degrees north, Duhok at 37. Both have mediterranean climates dictated by weather masses moving east from large bodies of water to the west.

The comparisons, however, end there.

Duhok’s valley is very narrow, less than three miles north-to-south, and bordered by steep, dramatic mountains with cliffs that hem in the city.  The valley narrows to a series of small passes on the east, and opens up to the Plains of Nineveh and the vast Syrian Desert to the west.

The striking difference in the physical geography between the two places leads to some weather phenomena in Duhok that I’ve hardly ever seen anywhere else in the world.

To the best of my understanding these unusual weather patterns are in no small part affected by Duhok’s surrounding geography creating a massive 15 mile-long funnel.

It seems similar enough to an occurrence in meteorological study known as Orographic Lift, where air or low-level clouds that are moving towards a mountain range are forced to rise, compress, and in their new state of greater density are often forced to precipitate.

Orographic Lifting

I make this comparison, because while Orographic Lifting is a vertical process- moisture and clouds forced to greater altitudes to drop rain- the phenomenon I’ve seen in Duhok appears to be the equivalent horizontal process, with clouds and moisture being forced laterally when a storm system is already low enough to be affected by the 3-5,000 foot peaks around Duhok.

Duhok storms
The direction of storm movement. When the storms are low (below 5,000 ft) their direction seems to be heavily dictated by the front ranges of the Zagros Mountains immediately beside Duhok, creating a narrow channel above the valley where Duhok lies.

Like the meteorological equivalent of a tsunami. As the leading edge of the storm is compressed into a reduced position of maneuverability, the result is a drastically sharp storm front that topples over itself, with a wall of reduced light and increased electrical potential caused by the forces of compression.

When I first witnessed one of these storms, the raw power was amazing.  It was around 730 in the morning on a sunny mid- November day and I was preparing to leave for school.

Most days I would check the weather and temperature with a few open windows, expecting little change as the weather had been fairly uniform since September.

The change in weather happened in a matter of minutes.  A front to the west with no immediately apparent intensity built into a wall of blackness as it approached the city.

Most striking was the abruptness of the leading edge, a cliff of black, dense, charged air.

The resulting storm completely enveloped the warm morning, casting a deep shadow on the city with no more visibility than twilight.

This same phenomenon has occurred a handful of other times, and it is never any less impressive, and almost always biblical in its apocalyptic proportions.

The tail end of a massive storm with a monsoon-like intensity

To make the most California comparison possible, these storms are roughly similar to a place called “The Wedge” at Newport Beach in southern California, where a jetty sitting perpendicular to the crashing waves famously creates abnormally large swells relative to everything else around (and naturally attracts a lot of big wave surfers too).

The wave compression creates narrow, powerful waves that are incongruent to all other swells nearby.

I should add that there’s a degree of educated guessing to this post.  The conclusions I’ve drawn are owed in no small part to what meteorology I studied in college (albeit minimal), my knowledge of the surrounding physical geography, and inferences from what I deem as being similar or equatable natural processes.

That the mountains and unusual funnel shape of Duhok’s valley play such a large part on the low-level storm systems is an idea built of some conjecture, as most storms over Duhok come at a far greater elevation, and do not exhibit abnormally intense patterns.

That said, I’ve yet to find a different idea that goes as far to explain what are among the rarest and most daunting storms I have ever seen.


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