Friday, October 30, 2015

Cyclone Chapala to Make Very Rare Arabian Peninsula Strike, Up to 20" of Rainfall with Disastrous Flooding Possible; Atacama Desert Floral Profusion; and D.C. Area Rainfall Stats

A church seen beneath the vibrant fall colorful leaves of a large tree in Burke, Va., October 29, 2015.

Photo by Bruce Sorrell that appeared in this CWG entry.


While I didn't get a chance to post another entry last night -- it was already 1AM by the time I would have started, and I was quite tired, I would like to update the blog now with a weather-related posting.

I am re-posting this entry, in part, because I have to note a remarkable weather event as described in excellent detail in this Capital Weather Gang entry:

Cyclone Chapala among strongest storms on record in Arabian Sea, targeting Yemen

By Angela Fritz
Capital Weather Gang
11:03AM EDT October 30, 2015

Source link.

Caption: Cyclone Chapala is forecast to make landfall in Yemen as an extremely rainy Category 1 (Meteosat)


The rapidly intensifying Cyclone Chapala is spinning westward through the northern Indian Ocean, challenging the strongest storm on record in the Arabian Sea, and threatening just the third hurricane-strength landfall on record for the Arabian Peninsula. Though the storm is expected to weaken before landfall, more than 20 inches of rain are in the forecast for the incredibly arid region.

Chapala formed as a tropical depression on Wednesday, and since then has quickly strengthened into a powerful cyclone. The storm rapidly intensified from wind speeds of 65 mph to 155 mph in just 24 hours from Thursday to Friday. Since then, the storm has weakened slightly to 150 mph, but remains the equivalent of a strong Category 4 hurricane.

Cyclone Chapala is only the first storm this year that has managed to reach hurricane-strength in the region. Though reliable satellite records over the northern Indian Ocean only go back to 1990, Chapala is the strongest storm in the Arabian sea since Super Cyclone Gonu in 2007, the only Category 5 storm on record in the basin. Gonu's powerful winds maxed out at 165 mph.

The official forecast suggests Chapala will strengthen to Category 5 status on Friday, reaching wind speeds of at least 160 mph and eventually making landfall in Yemen -- or possibly Oman -- as a Category 1. But Chapala will have a lot to get through in order to reach that intensity -- there's a lot of dry air to overcome, and cyclones rarely maintain hurricane strength as they approach the very dry peninsula.

Even if Chapala weakens significantly over the weekend, it will still come ashore packing strong winds and high waves that the region is not necessarily accustomed to. More importantly, it will bring a significant amount of rain to an extremely arid region. Global forecast models are suggesting as much as 20 inches of rain could fall over Yemen, enhanced by the region’s mountainous coastline. According to the U.K. Met Office, this region typically gets less than 4 inches of rain per year.

Cyclone Chapala forecasted track showing a landfall on the Arabian Peninsula. Source: Weather Underground


For comparison, Cyclone Gonu weakened to a Category 1 as it passed by the Arabian Peninsula to the north in 2007. But the cyclone's strong winds, big waves and heavy rainfall still managed to do $4.4 billion in damage to Oman and the United Arab Emirates.

Cyclones in this region are not uncommon -- on average a few weak to moderately strong storms spin up each year. However, landfalls in this region are rare. According to the Weather Channel's Michael Lowry, there’s no record of a hurricane-strength storm making landfall in Yemen back to 1945. And, if Chapala maintains hurricane strength at landfall, it would only be the third hurricane on record to make landfall on the entire Arabian Peninsula.

This tweet from Michael Lowry shows the tracks of Gonu (2007), Phet (2010), and Chapala (2015 - 5AM forecast today) on the left and on the right, a model output of forecasted precipitation (without caption).

Tropical cyclones are known as just "cyclones" in the Indian Ocean, but they’re the same kind of storm as typhoons or hurricanes. The Indian Meteorological Department is responsible for tropical cyclone warnings in the North Indian Ocean.

End of CWG entry.


I looked up the 6Z 10/30/2015 operational GFS for the Africa region to find the forecasted precipitation totals. Here is the image:

This is the precipitation totals for the region through hour 147 / valid 9Z 11/5/2015.

Quite astonishing.


As for other unusual weather, here is another CWG entry about all the rainfall in the Atacama Desert as a result of the major warm ENSO ("El Niño") event underway. Back in late March, Antofagasta -- which averages just 0.07" of rain a year -- had 0.96" of rain in a single day. A slurry of muddy flood waters killed at least 9 people.

The rains have caused the lovely pink (mauve?) malva (mallow) flower to bloom across the Atacama Desert in a display not seen in 18 years (in the 1997-98 El Niño event).

Oh, and frickin' Death Valley, Calif., had 0.55" of rain on Oct. 5th, a new 24-hour record rainfall for the month of October, and this was followed by more rain on Oct. 16th.


Rainy, mild, autumn evening at the edge of Lafayette Park along H St NW, Washington, D.C., 6:34PM Oct. 28, 2015.

I was walking from McPherson Square Metro after work to Old Ebbitt Grill, where I met LP at the Old Bar for dinner. Later, we went to No. 9, where we met Gary.


Back home here in the Baltimore/Washington region, the three-day rainfall from a low pressure system that was the very indirect "ghost" of Hurricane Patricia ranged from 1/4" to as much as 4" with the highest totals in Frederick County, Md.

NWS Doppler radar-estimated rainfall totals for the extended Metro D.C. and Baltimore areas for Oct. 28, 2015.


The three-day totals at the four regional climate stations were as follows (with the bulk falling on Oct. 28th):

KDCA: 0.68"

KBWI: 0.70"

KIAD: 1.99" (with 1.97" on the 28th, a daily record)

KDMH: 0.39"

The monthly totals through Oct. 29th are:

KDCA: 3.04" (-0.13")
KBWI: 3.40" (+0.29")
KIAD: 3.95" (+0.92")
KDMH: 2.41" (-0.47")

Note: KDMH does not yet have a full 30-year official NWS climate base period.

The region is below normal since Sept. 1st but above normal for the year because it was so wet through June.

It might rain again on Sunday into Monday. Next week is forecasted to be warm with temps. around 74F as a large ridge dominates the Eastern U.S. and a trough is over the Western U.S. There is still no sign of an Eastern U.S. polar vortex regime.

At this point, it does not look like an early winter here.

OK, that's all for now. My next planned update will be tomorrow (Saturday).


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