Ahead of #Irma ‘water is literally being sucked out of Tampa Bay’

When a hurricane approaches, there is storm surge that piles up water, but when it is out at sea, especially in shallow waters, the vacuum effect of the low pressure of the storm can suck water away from the shores. Offshore winds also play a big role. Such is the case here. This photo, taken by Dana Young and posted on Twitter, shows the effect.

She writes:

Hours before Irma hits, the water is literally being sucked out of Tampa Bay. I took this photo at the end of my street. This was at Albany and Bayshore 15 min ago.

Others are observing the same thing:

The same thing happened in the Bahamas when #Irma approached there:

The danger here is that once winds reverse and the eye gets closer, the water comes rushing back as dangerous storm surge.

See this graph of Sea Level from Naples:

irma-naples-sea-level-surge

Advertisements

107 thoughts on “Ahead of #Irma ‘water is literally being sucked out of Tampa Bay’

    • “When you see the sea retreating, head for the hills!”

      Well, Yes. However in this case as is too often the case with sound advice, there’s a minor problem. The nearest hills are somewhere near Atlanta, GA and the roads in between may be a bit congested. It also can be a bit difficult to fold up your 3br-2bath residence and load it in the trunk of your car.

    • Please Sir; but isn’t that the way hurricanes are supposed to work ??

      The hotter molecules at the tail end of the M-B energy distribution, get up and go to be whisked away by the winds, leaving the sea surface colder.

      G

      • Correct. A tsunami is a rolling wave triggered by a sudden displacement of a large volume of water. The Hurricane is a much slower and near stationary movement of water from outer rim to central low pressure zone. It will likely move at the same speed as the hurricane, but it may well cause significant tidal surge and flooding.

    • It’s similar to the tsunami effect. A tsunami may first suck out the water and then return with a vengeance. Therefore the warning to head for the hills.

      • Not tsunami effect but more like a seiche effect. When a long (in time), strong wind blows across a long (in distance) stretch of water it can push a large amount of water to the end of the reach of water. I’ve seen this on lake Michigan. I hear it can be more dramatic on lake Erie. A long blow of a strong west wind along the long axis of the lake can inundate docks at the east end of the lake. When the wind stops blowing,the water flows back to the other end of the lake.

    • Tsunami-like but different dynamics. The difference may be academic to anyone crazy enough to venture out onto the exposed seafloor. I suspect that a strong swimmer might be able to handle the return of the ocean, but you’d have to be stark raving nuts to try that.

      Also, I have some doubts about the storm “sucking” water out of the bays. On paper, it can happen, sea level in the center of the storm rises about 1cm for each millibar below 1013mb. But there is a vast area to draw the necessary water from. I suspect the wind is the major driver.

      • Don K – September 10, 2017 at 11:57 pm

        I suspect the wind is the major driver.

        Shur nuff, Don K, ……. and I am 100% positive that your “suspecting” was 100% correct.

        With hurricanes, the powerful offshore winds push the water away from the shoreline.

        With tsunamis, the powerful forces (earthquakes/landslides) that causes a horrendous uplift of ocean water will create a “void”, thus causing the water to rush away (or be sucked away) from the shoreline to fill that “void”.

      • Correct, Don.

        Pressure is not enough for several feet of change. No doubt there is an effect, but not 3 meters as we saw in Naples.

        Several years ago we had a good storm in the Panhandle and Mobile Bay drained out to the Gulf due to the north wind of the storm. TV folks went nuts.

        Grew up here on the Gulf and have been thru stronger storms than Irma. Our sea floor gradient is much different than the south Florida Atlantic contour. Even here in the Panhandle, some places resemble south MS and LA while other sections are like Lauderdale. In our county and next one we have 60 feet or more elevation within a half mile of the shore. The sea floor resembles that same countour, so no 25 foot storm surge as we saw at Waveland, Pass Christian, et al with Katrina.

        Gums sends….

      • Well,to be a bit persnickety, it is all caused by pressure: atmospheric pressure and dynamic pressure (from the wind). How can wind effect force, except by pressure?
        The observed area can be relatively calm because the wind is acting on the water a bit more offshore and less disturbed by the local shoreline and its construction. As that offshore water gets pushed further away from shore by the wind pressure, the closer to shore water behind it will flow out to account for the void created by the wind propelled water.

  1. Since the wind at this is coming from the easterly direction, which means the water is being blown away from the shore, why is this news?
    My grandfather, growing up on the Miss. coast, told a story of his childhood of a storm that went in to the east so the winds came from the north. It blew the water from the shallow shore area back so that haven’t his young friends went walking out apparently 100s of yards from shore. They were picking up seashells and junk dropped from boats.
    When the winds shifted they had to run for the shore to save their lives to stay ahead of the returning tide.

    • people unfamiliar with the effect will get into trouble. Few years back 20 or so Chinese workers picking cockles at low tide drowned at Morecambe Bay in North West England.

    • Hunter,

      Hurricanes do both…suck water up and push it away. No one said it was “news” except you. It’s nature. It’s fascinating. And since i will likely never witness it, I’m glad those who have are sharing the images.

      • Hurricanes “suck up” by the barometric depression. Gravity ensures it will flow back afterwards, not the hurricane “blowing” it back !

      • Aphan,
        You are correct. I came across dismissive and did not intend to do so.
        It is an amazing effect.
        When the sucked up water, something like a foot per barometric inch, is released along with thecwond driven surge it will be fantastic and deadly.

      • @ greg – you are wrong ; gravity does return the water and depending on the direction of the wind that will also force it – so the hurricane can blow it back..

      • I’ve seen it on Mobile Bay, both from tropical systems, and also from a strong north wind following cold fronts in the winter. My observation is that it is mostly a wind event.

    • NO, that is entirely different. An earthquake can cause a sudden drop in the sea floor, this leads to water rushing from both sides to fill the void. When the insushing water has filled the gap there is still horizontal momentum in opposing directions which causes a wall of water to build up. This flows back out as a tsunami.

      It is, in effect, a reflected wave.

      Storm surge is gradual build up due to the barometric depression. This both builds and passes slowly. There will be NO tsunami , simply a slow return to normal sea level.

  2. Naples is different from the other west coast cities – it has by far the greatest expected storm surge – 15 feet. But Tampa Bay has a somewhat constricted entranceway and the bay itself is quite large.
    I predict that although the coastline surge may reach 8 feet, it will dimish as you move into Tampa Bay itself. The Weather Channel, in its continuous attempts to portray disaster looming (keep watching, stay “informed”), has rigged up an visual illusion that shows water reaching to the second floor of a house – what they claim would happen with a 12 foot surge. Small problem here – not even beach houses are situated right at the water’s edge on the coastline.

      • 12-15 no fantasy! Tell that to the people in Mississippi that went through Katrina! A casino ship ended up on top of 3 story hotel! Look it up! Then tell me 12ft is fantasy!

      • IIRC storm surge at Pass Christian, MS has reached 8 meters (25ft) twice in modern times — Camille in 1969, and Katrina in 2005. Pretty sure it overran some of the keys completely in the Labor Day 1935 storm. Often causes significant trouble along the Mid-Atlantic and New England coasts during hurricanes and Noreasters.

      • Cyclone Mahina had a storm surge of 44 feet…

        Storm surges with cyclones are very dependant on their track. Actually what the Bahama’s encountered is what is called a “negative surge” and irma’s track was ideal to create this negative surge.

        Actually the huge destruction of Haiyan in Tacloban demonstrated very well how a negative surge can mislead and really cause a “tsunami like effect” if topography does allow it. haiyan was first blowing the water out of the bay at full eyewall strength and then after th eye passed at full eyewall strength allof the sudden back into the bay.

        the funnel shape of the bay actually did amplify this effect to the extreme of course, and the exact at peak strength and track to do this trick were just all the “exactly right” parameters to create this effect.

        like that the exceptional surge of cyclone Mahine had all the same ideal parameters combinend to creat world’s highest storm surge recorded.

      • irma’s path was actually “storm surge friendly” in the way that it could not generate a massive surge. it has to be able to “funnel the water” and for that it had to follow a track like Wilma did.

        a track that parallels ihe coast is usually creating less stormsurge but over a wider area; a lot of people forget that then nearly half of the cyclone is over land

  3. LOL “They” failed miserably on predicting the path, yet the talking heads on TV are saying with complete certainty that “lots of taxpayer dollars will be needed, and the damage will be $200 Billion. That’s $600 for every man woman and child in USA. I am not willing to chip in so that people can live in flood and hurricane zone because they are too mamby pamby to deal with colder climates.

    • Or because they bought sub-prime housing on a sub-prime loan?

      Well , get them through the storm before we get into who pays for a new house ;)

      • After Sodom et al burned, spiking CO2 and causing regional global warming, all the signs told Pharaoh that it’s “real, here and dangerous”. Even after locusts, frogs, and flies proved AGW, Pharaoh stood firm and kept the old energy system (slaves), refused to go renewable (Sphinx pharts). He sounds like a denler.

  4. A hurricane ‘pushes’ water ahead of itself. On the east side of Florida, there is storm surge because the winds are driving water into the land. Those same winds are blowing across Florida, and pushing water out to sea on the west side. As the hurricane moves north, the circulating winds will again blow, but this time from the west, pushing water back to land where it was blown away earlier. There is a high tide due soon also, so all the water that drained out will return, plus the tide, plus the storm surge itself which will pile even more water on the west side. The low pressure point, itself, has little to do with the water that is pushed around by a hurricane. It is simply the center point, but has little wind and little ability to move water.

    • Barometric pressure moves water. That is why there is an “inverse barometer” correction for sea level.

      A depression is an area of low pressure. Outside that area there is normal 1 bar ( or possibly a high pressure system ) which is exerting downward pressure on the ocean surface. This is independent of surface winds in or outside the eye of the storm.

      max depression of Irma is about 955 mbar ie -45mbar from a std atmosphere. That is about 18″ of water column. So as a static system away from land simply the barometric pressure would cause 18″ of storm surge.

  5. http://www.ndbc.noaa.gov/show_plot.php?station=npsf1&meas=w10m&uom=E&time_diff=-4&time_label=EDT

    10m wind speed at Naples is now dropping indicating the eye is moving over and peak w/s is past.

    It peaks at 32 knots ( 40 mph ) . Half the entry level wind speed of a cat 1 hurricane. You don’t want to go out and walk the dog but it is not as dramatic as all the news channels try to make is seem with claims of cat4 130 mph winds.

    That is NOT what people have to deal with at ground level.

  6. Forth Lauderdale (holiday resort north of Miami) or at least major part of it, has lost electric power, as just confirmed by a text message from a visitor in the area. Couple of webcams I was monitoring (refereed to in my previous comments) have gone blank and no data from the local weather station for over 3 hours,
    Presumably no electricity means no water, no (electricity) cooked meals, by tomorrow some of refrigerated food may be unusable etc, but the most important there may be fear of looting in the deep darkness of the night.

    • I have to imagine that they intentionally choose to cut power for scenarios such as this? I can’t imagine they want to risk electrocution and electrical fires during flood scenarios and so choose to cut power to the city when they detect the risk is near?

      I really have no idea as I’ve never been in a hurricane or flood but at least that seems a logical chance for the grid operators to take in the case of a major storm or flood. Perhaps those in the know can inform me better as it’s something that’s piqued my curiosity.

      • It is often done to protect transformers, Earlier during day transformer exploded in South Miami Avenue. Transformers are expensive pieces of equipment.

    • Not all that much news is getting out from areas hit by the storm days ago, but I did hear a report on CNN or NPR that the power grid in Puerto Rico has failed and that it may take weeks to fully restore power there.

    • Yes, taking the land route to Ft Meyers is not good but it’s loosing steam rapidly now. There will be a lot of damage but not the kind of $200 billion figures that have been thrown around in the last few days.

      Seems like NOAA’s tidegauge portal has gone down. Hope the insturments are still working.

    • He he. seems to be rising too fast. There must be some kind of QA software which stops transmitting data if it changes too fast. They assume its flooded. Once there’s enough confirmation it appears to come back.
      Shame it blocks the whole dataset rather than just the suspect data.

      Having dropped to about 5kt, the wind it picking up: coming out of the eye.

      • Nooo, it’s updating correctly – it’s called a ‘surge’ for a reason. Maybe your tin-foil hat is on too tight to understand things you haven’t been through.

      • Nooo, it was not updating at all , as I reported. After a while it comes back, presumably after it gets enough readings that are consistent for the automatic QA to accept that it is happening and is not a data glitch. I have no problem with it rising fast but apparently NOAA QA thinks it is wrong and blocks it.

        The interface is badly written since it then refuses to show any data at all , even the stuff that was previously known to be good.

        We now have a good trace of the storm surge:

        It maxed out at about 5ft above the normal predicted tide level which at that time was around the mean sea level. So peak storm surge was about 5ft. Just under the bottom of the 6-12 ft range Gov Scott was given to announce to the public.

        As I said yesterday, the talk of 12 to 15 ft was a fantasy ( or based on assumptions of Irma building back up to cat5 maybe : equally unrealistic ).

  7. How could a low pressure do anything but raise water? An east wind however would have no problem blowing water away from the west coast of Florida, and that is obviously what has happened. –AGF

  8. I remember going to see Prof Julius Sumner Miller when I was young, and the one key takeaway I recall from the night is that there is no such thing in physics as “suction”. There are just pressure differentials with matter from a point of high pressure providing a “pushing” force towards a point of relatively lower pressure.

    He demonstrated it by placing the inlet of a vacuum cleaner between two suspended spheres and we observed the two spheres being pushed together by air on the outer surfaces. I have adopted JSM’s pedantry on the topic.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s