Wednesday, September 15, 2004

Wednesday morning update:

I have no major changes to the details posted below on expected storm impacts. I am concerned that the northern turn has still not happened. Time is running out for New Orleans, it seems likely that landfall winds will reach or exceed 140 mph. NHC began pointing out last night that Ivan is expected to remain a hurricane for 12 or more hours after landfall.

So that's the sedgway into the headline for the past couple days:


First a general storm update:
As of 5am Wednesday, Ivan is a still a strong Category 4 storm. No one should get hung up on the word "weakened" as tossed around by the Hurricane Center. I think that is a misnomer to use with the general public, for it seems to imply a much less stronger storm, which is not the case at all. Whether the winds are 140 or 150, my house would still get obliterated.

Satellite imagery, which you can view by clicking on the loop link, shows the storm beginning to entrain some dry on it's left flank. This may serve to lower the wind speed a bit, and disrupt the eye, but the unintended consequence of that is we'll see the wind field expand. If the storm loses it's ability to keep those intense winds tightly clustered around the eyewall, then the unraveling begins. Unfortunately that whole process is starting too late for there to be any benefit from it on the Gulf Coast.

This reduction in strength may be temporary, as NHC discussions indicate that the storm will cross a warmer region of surface waters. If anything, the warmer water may serve to negate the "weakening" trend, thus holding the storm at a strong Category 3 or minimal 4.

The purpose of the title is to draw attention to what will happen if Ivan heads for the mouth of the Mississippi. I strive not to be a rabid alarmist, but I cannot underline enough how dangerous a situation this can be for New Orleans and the Sound. The area truly at risk for a major environmental and human catastrophe is Mobile Bay. Storm surge of 10-15 feet will surge up the bay, creating the "Bangladesh Effect" as the bay narrows to a funnel shape farther inland. This forces the water to splay outward, flooding hundreds of square miles of bayside property. Accuweather has a set of graphics to explain the massive impacts of Ivan.

I have found some alarming reports from the New Orleans Times-Picayune. Either the hurricane center has upped the ante in the last hours, or someone in the press is gunning for higher ratings. Read this story for yourself. Apparently official forecasters somewhere have alluded to the possibility Ivan could re-strengthen to Category 5 before landfall. Maybe they are "just saying that" to scare enough people to leave the city. At last report, all major highways leading out of New Orleans are jammed bumper to bumper for miles in any direction.

The NHC admits this will be a strong Cat 3 at landfall, if not a 4. The sheer size and strength of the storm is breath-taking, as it is 30% larger and stronger than Frances. Hurricane force winds extend out 115 miles, this is a far wider wind field than Frances ever projected. To top that, tropical storm force winds extend out a whopping 260 miles from the center. Camille and Charley, by contrast, were both very compact storms.

The Tuesday CBS and ABC evening news reports stated that New Orleans, despite being under a hurricane warning, is not issuing a mandatory evacuation because "the city does not possess the resources to enforce such an order." So city officials are being as vehement as they can be in encouraging a voluntary departure from the city.

Despite the fun and intrique in following these fascinating works of nature, they remain a chronic claimer of lives, prepared or unprepared. If you have family anywhere along the Miss. Sound or in New Orleans, I urge you to encourage them to obey evacuation orders and leave as soon as possible.


Tuesday afternoon
(Left on the post for archival purposes)

Rip currents will be noticeable along the entire eastern Gulf from the Keys to the LA/Texas border. With many schools closing on Tuesday throughout the eastern Gulf coast, parents should be cautious of their children “going to the beach” one more time as rip currents will be unexpectedly strong. Upper-level cloud outflow will cover most of Florida’s peninsula and reach the northern gulf coast by nightfall. Mandatory evacuation orders will be issued for all coastal areas inside the hurricane watch area. Residents of New Orleans should especially evacuate early, as the Causeway and Route 10 east is likely to be closed due to surge flooding starting on Wednesday

Wednesday morning
Waves will increase in intensity, and large swells will accompany a slowly increasing wind from the east and southeast reaching 40 mph by noon. Tides Tuesday night were already running 2 feet above normal at the Mississippi Delta. The effect of an easterly fetch over the Sound will slowly begin to drive water into Lake Ponchartrain and into intracoastal waterways and inlets. Storm drains will overflow well in advance of the storm. Thunderstorms and scattered downpours of rain will begin in earnest by afternoon. Swells and tidal surge will begin to flood low-lying areas, with increased wave action throughout the day. Waves of 5-10 feet will begin impacting the Florida panhandle and intracoastal waterways of Alabama and Mississippi.

Wednesday night
Winds along the coast will be sustained to tropical storm force first from the southeast, moving to the north, with hurricane force winds arriving by nightfall. Outer rain bands will begin to impact an area 100 miles on either side of Biloxi, MS. With a hurricane wind field of possibly 100 miles in diameter, the extreme northern areas ahead of landfall will experience these winds first. With such a slow northward movement, areas from New Orleans east to Pensacola may be in for a long duration of strong winds, possibly 12 hours or more. Tidal surges of 4-8 feet will begin flooding the coast, with waves of 10-15 feet on top of that. Localized areas inside the landfall zone may see surges near 20 feet.

Thursday morning
By this time, the entire northcentral and northeastern Gulf is bearing the full brunt of this storm, as southerly winds outside the eye push water onshore for hundreds of miles, affecting areas from Cedar Key in the northern Florida’s gulf coast, across the entire panhandle and over the entire Miss. Sound. If Gulfport and Mobile are in the bullseye, then a storm surge of possibly 15 feet or greater will inundate the coast for a mile or more inland. Waves of 20 to 30 feet will accompany the surge, virtually oblitering almost anything in the path of this force. The area affected may be over 100 miles of coastal, and inland for several miles. By contrast, Andrew's greatest destruction in south Florida was confined to an area roughly 25 miles in diameter. That was still catastrophic, but the geography of Mississippi Sound enhances the effect of storm surge.

Thursday afternoon
The hurricane makes landfall as a strong Category 3 with winds just under 130 mph. Hurricane force winds will extend out over a hundred miles to the north and east of the center, and near 100 miles to the west. North winds on the west side of the storm may drive some water in Lake Ponchartrain south towards New Orleans, where we hope the levee and pumping system can withstand the constant pressure over a period of 24 hours or more, plus 5 to 10 inches of rain.

Total catastrophic damage will occur within the radius of the eyewall, which may be 20 or more miles in width. Mobile homes are completely destroyed, roofs blown off most other structures, massive tree blow downs, and major window damage to large buildings. Coastal structures will be nearly destroyed and major structure damage is inflicted on most inland homes within 10 miles of the coast. The worst damage will be on the eastern side, where the combined effect of a south wind, storm surge and waves will just about erase some towns and barrier islands from the map.

Thursday night
Ivan moves inland ever so slowly, as there are no significant steering currents to rocket it north as did Charley. Areas within 150 miles on either side of the storm receive torrential rain for 12 hours or more, with amounts possibly up to 10 inches. It is just frightening writing this stuff. It almost seems like it is more for a fictional script of some Hollywood disaster movie.

The weakening storm will be downgraded to tropical storm by midnight Friday, but it will still pack winds near hurricane force and a broad area of heavy rain encompassing Alabama, Georgia and Tennessee. By the time remnants reach the Memphis to Atlanta region, it should be further downgraded to a depression. The terribly sad part is that areas that were hardest hit by Frances will get pounded again. Flooding rains will continue up the Appalachians through Sunday, drenching areas that just received 10-20 inches of rain from Frances. The federal government is starting to realize this could be an inland flood of historic, unparalleled porportions in the southeast. It will be the Tennessee Valley's Agnes for those of you who were in that disaster of 1972. I hope that you are mentally prepared to see one of the largest swaths of total destruction that you have ever seen in your life save for 9/11. It will be difficult to look at the TV for the Friday morning news and see what Ivan will have left behind.

Saturday - Sunday - Monday
The remnants of Ivan will "get stuck" in the Appalachians, as the jet stream is well to our north in Canada, and there are two highs on either side of the storm blocking motion east or west. So it will just sit and meander around Knoxville, TN dropping unholy amounts of rain. We should not discount the effect that eventual south winds will have on Virginia and the Chesapeake Bay.

Residents along waterways and tidal areas even in Maryland are encouraged to keep a close watch on tide changes depending on the strength and location of the storm’s remnants. “Silent surges” of 2 or more feet are possible as south winds restrict the outgoing high tide. Rainfall over Virginia, Maryland and Pennsylvania may equal that which was observed with Frances… 4 to 6 inches is not an exaggeration.

AFTER IVAN’S TERRIBLE TOUR IS OVER….the Gulf Coast has about a week to prepare for… Hurricane Jeanne. And then the East Coast has about 10-12 days to prepare for Karl.

I am not making this up just for ratings sake. By the time you read this, Jeanne will be a hurricane bearing down on Puerto Rico. It is projected to follow a path similar to Frances for the short term, with a turn to the west over the 5 day term. If it gets into the Gulf and crosses the Florida straights between Cuba... LOOK OUT TEXAS and LOUISIANA. It is not over yet.

And behind Jeanne... way over by Africa, is what will become Karl over the next 2-3 days if not sooner. This area of disturbed weather has the look and feel of Gloria from 1985. And she formed right about this time in about the same place. All indications are that the upper air pattern is set up for at least the next 2 weeks to deliver any westward developing storms directly to the U.S. mainland.

You can bet I will be watching that one closely as September 20-30 has historically been prime time for Mid-Atlantic and New England landfalling major hurricanes.

The next update will be later tonight after the 8pm advisory.

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