Here Comes the Wind Again (Anchorage, Fairbanks: closing, live, retired)

[globetraveler]

Originally Posted by Glitch

Actually, the storm surge associated with hurricanes is caused by extremely low pressure. The low pressure in the atmosphere actually lifts the water up. While we experience hurricane force winds, there is no associated low pressure system to create a storm surge.

That's not entirely correct. The storms that roll across here are caused by low pressure and some of them have had pressures as strong as hurricanes. Last years November storm that slammed Nome had a pressure of 945 millibars, that's the same pressure you would see with a strong Category 3 hurricane. Hurricane Issac had a pressure of 984 millibars, however the storm two weeks ago had a pressure of 975. This storm has a current low pressure around 980 millibars.

The difference is in a hurricane, the winds flow around the central eye. With a normal low pressure system, the winds flow from a high pressure area to a low pressure area. If the high pressure area is very close to the low pressure area, or if the pressure difference is large, the winds get very strong.

While low pressure from a Hurricane will have an impact on storm surge, it only amounts to about 5-10% of the surge. Thee action of high winds piling up water and pushing it towards shore amounts to typically more than 85% of the surge. The last component are waves pushing water inland faster than it can drain off, otherwise known as wave set-up. Wave set-up is typically 5 - 10% of the surge.

Storm surge is normally associated with hurricanes, but any low pressure can produce storm surge is the winds are strong and the geography is correct. The March 1993 "storm of the century" that blasted the eastern half of the US. While most of the people remember this storm for the epic snow amounts, in Florida, there was a storm surge of 12 feet, which resulted in 7 deaths. During the Nov 2011 storm that hit Nome, the storm surge and high tide rose seas about 10 feet above normal water levels.

Storm surge - Wikipedia, the free encyclopedia
The Storm of the Century
Surge peaks in Nome, still rising elsewhere: 2011 Bering sea storm | Alaska news at adn.com

[Moose Whisperer]

Correct. From the NWS Website:

Storm surge is produced by water being pushed toward the shore by the force of the winds moving cyclonically around the storm. The impact on surge of the low pressure associated with intense storms is minimal in comparison to the water being forced toward the shore by the wind.

Storm Surge Overview

As globetraveler points out, these storms that hit South Central rountinely fall into Hurricane force as defined by pressure. The alltime low pressure recorded on my weather station was ~964 mb during the Nov 10 2009 storm, which equals a Cat 3 Hurricane on the Saffir-Simpson Scale. However there was no mention of a storm surge during that storm a far as I recall, or any other of our storms here for that matter. Damage is almost always caused either by high winds, or flooding due to swollen rivers and heavy rain.

[Glitch]

Originally Posted by globetraveler

That's not entirely correct. The storms that roll across here are caused by low pressure and some of them have had pressures as strong as hurricanes. Last years November storm that slammed Nome had a pressure of 945 millibars, that's the same pressure you would see with a strong Category 3 hurricane. Hurricane Issac had a pressure of 984 millibars, however the storm two weeks ago had a pressure of 975. This storm has a current low pressure around 980 millibars.

The difference is in a hurricane, the winds flow around the central eye. With a normal low pressure system, the winds flow from a high pressure area to a low pressure area. If the high pressure area is very close to the low pressure area, or if the pressure difference is large, the winds get very strong.

While low pressure from a Hurricane will have an impact on storm surge, it only amounts to about 5-10% of the surge. Thee action of high winds piling up water and pushing it towards shore amounts to typically more than 85% of the surge. The last component are waves pushing water inland faster than it can drain off, otherwise known as wave set-up. Wave set-up is typically 5 - 10% of the surge.

Storm surge is normally associated with hurricanes, but any low pressure can produce storm surge is the winds are strong and the geography is correct. The March 1993 "storm of the century" that blasted the eastern half of the US. While most of the people remember this storm for the epic snow amounts, in Florida, there was a storm surge of 12 feet, which resulted in 7 deaths. During the Nov 2011 storm that hit Nome, the storm surge and high tide rose seas about 10 feet above normal water levels.

Storm surge - Wikipedia, the free encyclopedia
The Storm of the Century
Surge peaks in Nome, still rising elsewhere: 2011 Bering sea storm | Alaska news at adn.com

I stand corrected.

[AK-Cathy]

Not piling on Glitch but storm surges (combined with a high tide at the time) in Juneau during the 1984 Thanksgiving storm caused at least part of the over 2 million dollars damage from that storm. I was working in the airport tower that day watching the dial barometer move visibly and rapidly downward. The winds picked up to the point that the huge panes of glass were clacking together though our evacuation speed was "sustained" 80 knots, we were getting gusts rather than sustained wind. When we got the higher gusts to 95 we decided to abandon the tower after proper notification and moved downstairs to flight services. As we left a small atrium window in the stair area blew in.

Airplanes were rolled up all over the airport. Passenger jets were rocking hard. I lived on Auke Bay on high ground but when I got home, boats and docking were piled all over the shore. Rain and possibly blowing surf was driven into my living room approximately 3 feet from a tiny crack under the front door. It was a real eye opener. Unlike hurricanes which have backsides, this thing lasted only about 10 hours and was over but it made a real mess everywhere.

[warptman]

In Florida they are called Hurricanes, in Alaska, we call it Friday.

[globetraveler]

Originally Posted by Glitch

I stand corrected.

Nah - I'm just kinda of a weather nerd.

[Moose Whisperer]

More:

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1145 AM AKDT MON SEP 17 2012

AKZ101-111-121-125-131-135-145-171-180600-

...ANOTHER ROUND OF STRONG WINDS AND HEAVY RAIN LIKELY TUESDAY
AND WEDNESDAY FOR SOUTHCENTRAL ALASKA...

ABUNDANT MOISTURE WILL SURGE NORTHWARD TOWARDS THE GULF OF ALASKA
COAST AS A SERIES OF STORM SYSTEMS IMPACT SOUTHCENTRAL ALASKA
TUESDAY AND WEDNESDAY. FIRST A FRONT WILL MOVE THROUGH LATE TONIGHT
AND TUESDAY PRODUCING WIDESPREAD HEAVY RAIN. A MORE POTENT LOW
PRESSURE SYSTEM WILL THEN FOLLOW SHORTLY BEHIND THE FRONT AND
IMPACT SOUTHCENTRAL IN THE TUESDAY EVENING THROUGH WEDNESDAY TIME
FRAME. THERE IS A LIKELIHOOD OF ANOTHER ROUND OF WIDESPREAD HEAVY
RAIN AND STRONG WINDS WITH THIS SYSTEM.

WITH SEVERAL LOCAL RIVERS AND STREAMS ALREADY AT OR NEAR MINOR
FLOOD STAGE LEVEL ACROSS THE SOUTHCENTRAL REGION...MORE FLOODING
IS PROBABLE TUESDAY NIGHT THROUGH THURSDAY.

STRONG WINDS ARE ALSO A POSSIBILITY TUESDAY NIGHT INTO WEDNESDAY.
HOWEVER...BECAUSE THERE IS A LOT OF UNCERTAINTY IN THE EXACT TRACK
OF THE STORM SYSTEM IT IS DIFFICULT TO PINPOINT THE LOCATIONS AND
WIND SPEEDS AT THIS TIME.

CHECK BACK FOR THE LATEST FORECASTS AND STATEMENTS AS THE WEEK
PROGRESSES FOR THE LATEST INFORMATION ON THIS DEVELOPING STORM.

[AlaskaNana]

Originally Posted by warptman

In Florida they are called Hurricanes, in Alaska, we call it Friday.

Ya always put the good ones out there when I can't rep ya. Oh well. Alteast know I appreciate the effort

[Moose Whisperer]

So far I've got high gusts of 74 mph recorded on my station within the last few hours. Power is out, transmitting on generator power. Hard to stand up outside. The driving rain is now starting to seep in around my windows. I just heard that flights are being diverted away from the ANC Airport. Also looks like I'm about to lose a tree in the yard.

I've got some videos uploading to youtube right now - I'll post in a bit.

[Moose Whisperer]

Shot this out in the back yard, though it doesn't look as bad as it really is.


Anchorage wind 9/19 - YouTube