Monday, September 18, 2017

Notes on Hurricane Irma

Hurricane Irma on September 8.
Five days ago the last remnants of what was once Hurricane Irma fizzled over the eastern U.S. Attention is now focused on dangerous Hurricane Maria, which at this writing is slamming the island of Dominca. For the most up to date information on Maria, Jose, and Lee visit the National Hurricane Center web site.

As Hurricane Irma gained strength I and many others were riveted to web sites, social media, and news programs tracking the progress of the storm. In this day of nearly instant communication of information it's not hard to get immersed in following the progress of a storm like this. Periodically I grabbed images and information to save in anticipation of a blog post or two about this storm. Irma and its aftermath has been well-documented so I won't rehash Irma's history here. What I would like to do is share some of the images and information I collected during the storm that you may not have seen.

The first land Irma slammed into was the island of Barbuda. Barbuda is one of two major islands that make up the Caribbean nation of Antigua and Barbuda in the middle of the Leeward Islands. Irma made a direct hit on Barbuda.

Here is the radar image from Guadalupe showing the eyewall of Irma over Barbuda at 0100 local time. Winds were likely gusting to 170 mph or more over the island.

Here is the series of weather observations from Barbuda for the two hours prior to the arrival of the eye.  Sustained hurricane force winds with gusts as high as 155 mph were recorded at this station on the southwest side of the island. Note that the CALM winds reported for the last two observations were not from being in the eye, but were due to the destruction of the anemometer.

Weather observations from Barbuda as Irma made landfall September 6.

This radar image at 1:30 a.m. local time shows the entire island of Barbuda in the calm eye of the hurricane.

Irma left widespread destruction across Barbuda. The island was evacuated after the hurricane moved on, leaving the island uninhabited for the first time in 300 years.

Irma's path then took it through the Virgin islands, producing destruction across St. Thomas, St. John, and St. Maarten.

Damage in St. Maarten.
Photo: Dutch Defense Ministry

Irma continued WNW and passed to the north of the Dominican Republic and Puerto Rico.

Hurricane Irma approaches Puerto Rico on September 6.

Irma was able to maintain its strength due to the very warm water in the southern Atlantic and Caribbean, especially the area between Cuba and the Bahamas. Sea surface temperatures in this region were in the range of 85°F to 90°F

Sea surface temperatures on September 6.

One interesting image is this one of all the marine traffic around Florida on Saturday, September 8, heading south and east. It's interesting to note the number of cruise ships.

Marine traffic near Florida on the morning of September 8.

After brushing along the north coast of Cuba on Saturday, September 9, Irma turned north toward the Florida Keys. The eye of the storm made landfall in the Florida Keys, east of Key West, around 8:00 a.m EDT, Sunday, September 9.

Radar image from the NWS Key West radar at 8:02 a.m. EDT September 10.

After crossing the keys, the eye of Irma was over open water and headed to another landfall on the Florida west coast. Irma made its final landfall near Marco Island, FL at 3:35 p.m. EDT on Sunday.

Radar image from the NWS Key West radar at 3:35 p.m. EDT September 10.

Hurricane Irma was certainly a storm of record. No doubt the name Irma will be retired. Philip Klotzbach, a tropical storm researcher at Colorado State University, compiled a list of of records and notable facts about Irma.
Josh Morgerman (iCyclone on Facebook and Twitter), a professional hurricane chaser, was in Naples, FL when Irma made landfall. He produced a video of his experience which you can view here.

Wednesday, September 6, 2017

Montana is Burning...

The sky over Butte, MT on September 3.
Source: Facebook
and so is Oregon, California, and Idaho.

Much of the "weather attention" is now on Hurricane Irma, still a few days away from affecting the U.S. Smokey skies from the Pacific coast to the Midwest call attention to another disaster - wildfires in the west, particularly in Montana, Oregon, and California.

Eighty-one large fires have burned 1.4 million acres in nine western states. Hot weather on Labor Day caused fires to gain thousands of acres in Montana, Oregon, & California. Of the nine western states with wildfires, Montana tops the list with 28, the largest being the Rice Ridge fire in the Lolo National Forest at 108,126 acres. Two other fires in the Miles City area are at 99,735 and 73,797 acres. Of the 28 fires (total of 574,552 acres) only one is completely contained. The Rice Ridge fire is only 2 percent contained. California (17 fires, 244,066 acres). Sadly, two fire fighters have lost their lives fighting the wildfires in Montana.

Wildfires in the northwestern U.S. as of September 5.

In Oregon, there are 19 active fires encompassing 353,029 acres and none are contained. Almost half of that acreage is one fire - the Chetco Bar fire in the Siskiyou National Forest. The Chetco Bar fire is 167,513 acres and is only five percent contained. The Eagle Creek fire straddles the Oregon-Washington border and is now burning more than 30,000 acres.

Eagle Creek in Oregon.
Photo credit: @tristanCF on Twitter

So far this year 47,094 fires consuming 7.8 million acres.It's the most fires since 2011. but so far third in acreage as of this date behind 2015 and 2012. There is still a long way to go. For the ten-year period from 2006 through 2016, the was an annual average of 50,129 wildfires and an average of 5,458,817 acres affected. For 2017 there are fewer fires but a 14 percent increase in acreage as of September 5.

GOES-16 loop of wildfires in western Montana and Idaho late on September 3.
Source: NOAA

At first glance one might think that the fires are just burning grasslands and forest. However, much of that grassland in some areas is grazing land  In Montana, for example, the impact from the fires will be long-lasting. Fires have burned thousands of acres of grazing land. The price of hay was already 30 to 40 percent higher or more because of the drought. Donated hay may help ranchers make it through this year, but there is next year to worry about. In some cases the fires will have impacts for years to come, as ranchers may have to sell off cattle to survive. Cattle have perished in the fire, and others that survived may be affected by heat and smoke inhalation. or burned hooves from walking over smoldering ground. In addition to the grass and trees, an estimated 1400 miles of fencing has been destroyed, costing an estimated $15 million to replace.  It has been estimated that 80 to 100 percent of the acreage affected by the Lodgepole Complex of fires in east-central Montana suffered a complete loss of grass, most of which was grazing land.

Fires in and around Glacier National Park in northwestern Montana have destroyed one structure and threatened others. Firefighters lost the battle to protect the Sperry Chalet on August 31st as the Sprague fire spread into the area.

The Sperry Chalet main building ablaze in Glacier National Park.
Photo credit; National Park Service

Moisture conditions coming into the summer were not bad in Montana. At the end of the May much of the eastern third of Montana was classified as D0 (Abnormally Dry). By the end of June drought had intensified and D3 (Extreme Drought) was established in northeastern Montana. At the beginning of August D4 (Exceptional Drought) covered the northeastern quarter of Montana. As of last week Extreme to Exceptional Drought covered almost 40 percent of the state.

The lack of rainfall has been well-documented by our Montana CoCoRaHS observers.There have been lots of gray dots on the Montana map the past few months. The CoCoRaHS observer at MT-LC-14 Helena 2.0 NNW has measured only 1.36 inches of rain since June 1st. There have been only eight days with measurable rain, and 0.79 inch is the largest daily amount. The observer also measures evapotranspiration, and the water balance since June 1st (precipitation minus evaporation) is -21.26 inches.

The observer at MT-LN-6 Troy 26.9 NNE has tallied only 0.97 inch of rain since June 1st, and today commented that this marks "63 consecutive days with no measurable rain." (the number is actually 52 days - the last measurable rain, 0.01", was on July 16).

Many CoCoRaHS observers are reporting low visibility from smoke and even ashfall. Ash was falling in Seattle Tuesday morning morning, the first time since Mount St. Helens erupted in 1980. Ash was also reported in Portland, OR.

Smoke from the western fires is causing serious air quality issues in the west with visibility reduced to less than a mile in some locations. The smoke has also hazed the skies over the Plains and Midwest making for some spectacular sunrise, sunsets, and coloring the moon orange.

The combination of dry and hot weather this summer has exacerbated fire conditions from Montana to the Pacific coast. Dryness increased across the west during the summer, while the heat has been fairly persistent especially in the Pacific Northwest south through California.

Some showers could move through western Washington, Oregon, and perhaps Idaho by the end of the week which may help a little. However, most of Montana will remain dry.

Quantitative precipitation forecast for the three-day period ending at 6:00 p.m. MDT Saturday, September 9, 2017