Fred rapidly intensifies; new wunderground storm surge section launched
Hurricane Fred put on an impressive burst of intensification overnight, and is now a major Category 3 hurricane with 120 mph winds. However, Fred is not a threat to any land areas for at least the next week. Satellite imagery of Fred shows the spectacular signature of a classic Cape-Verdes type major hurricane, with a prominent eye, well-developed low-level spiral bands, and high cirrus clouds denoting excellent upper-level outflow on three sides. It is quite unusual to have such a powerful system so far east in the Atlantic, and Fred is only the third major hurricane to exist east of 35W. Fred is also the strongest hurricane so far south and east in our data record. However, this type of system would have been difficult to document before satellite pictures began in the 1960s.
Figure 1. Visible satellite image of Hurricane Fred at 10:30am EDT 9/9/09. Fred was a Category 3 (120 mph winds) at this time.
The forecast for Fred
Wind shear through Thursday morning is expected to stay in the low range, 5 - 10 knots, and ocean temperatures will be about 1 - 2°C above the threshold needed for tropical cyclone formation. Given these conditions, plus such factors as the temperature at 200 mb and the amount of moisture between 700 mb and 500 mb, this morning's run of the SHIPS model computes that the Maximum Potential Intensity (MPI) Fred can reach tonight is 140 mph (121 knots), which would make it a Category 4 hurricane. This is the strongest a hurricane can get in this region of the atmosphere. Very few hurricanes ever reach their MPI, and it will be interesting to see how close Fred gets to this mark.
Shear will rise to the moderate range, 15 - 20 knots, Thursday through Friday, then increase to the high range, 20 - 40 knots, Saturday through Sunday, thanks to a strong trough of low pressure traversing the North Atlantic. This should weaken Fred to a tropical storm five days from now. The trough will also pull Fred to the northwest and then north. Most of the models foresee that this trough will not be strong enough to fully recurve Fred to the northeast and out to sea. However, another strong trough of low pressure is forecast to traverse the central Atlantic about eight days from now, and this trough should be strong enough to recurve the storm northeastward out to sea. The odds of Fred making it all the way across the Atlantic to threaten land areas appear low at this time.
Elsewhere in the tropics
A weak front is expected to move off the Texas coast Friday and linger along the coast for several days. Beginning on Friday, we will need to watch the Western Gulf of Mexico for possible development of a tropical cyclone along this front. Any storm that develops would likely move northeast or north-northeast and impact Louisiana and northern Texas coast. The models are less enthusiastic this morning about developing such a storm than they were in previous runs, and there will be some high wind shear to the west for a potential tropical system to contend with.
New wunderground storm surge section launched
The Weather Underground is pleased to announce the release of the Internet's most comprehensive hurricane storm surge web pages. The new storm surge section provides more than 500 detailed, zoomed-in storm surge maps from the official storm surge model used by the National Hurricane Center--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. I've created SLOSH model worst-case flood maps for Category 1, 2, 3, 4, and 5 hurricanes for the entire U.S. Atlantic coast, plus Hawaii, Puerto Rico, the Virgin Islands, and the Bahamas. Zoom-in maps of fifteen important cities such as Miami, New York City, Boston, Tampa, and Corpus Christi are included. To help coastal residents see how past storms have affected their region, the wunderground storm surge pages also include SLOSH model animations of the surge for more than 40 historic storms--from the Great Colonial Hurricane of 1635 to Hurricane Ike of 2008. You can access the new storm surge web pages.from our Tropical/Hurricane page, on the right side of the page under my blog box. I encourage all coastal residents along the U.S. coast to take the time to familiarize themselves with the storm surge risk where they live.
Figure 2. Sample water depth inundation image (left) and storm tide image (right), created using NOAA's SLOSH model. These Maximum of the "Maximum Envelope of Waters" (MOM) plots are for Tampa Bay, Florida, for a mid-strength Category 4 hurricane (sustained winds of 143 mph) hitting at high tide.
How to interpret the storm surge images
There are two sets of images available. The first set, titled "Maximum Water Depth", shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of ten feet above mean sea level, and the combined storm surge and tide (the "storm tide") is fifteen feet at your location, the water depth image will show five feet of inundation. The second set of images, titled "Maximum Storm Tide", shows how high above mean sea level the sum of the storm surge plus the tide reaches. Over the ocean, the storm tide and water depth images will show the same values. The storm tide images contain no information about how deep the water will be inland, and are generally less useful than the water depth images. All of these Maximum of the "Maximum Envelope of Waters" (MOM) images were generated for high tide, and thus show worst-case inundation scenarios for mid-strength hurricanes of each Saffir-Simpson Category (Category 1, 2, 3, 4, and 5). Category 5 hurricanes have never occurred in the Mid-Atlantic or New England regions, so there are no Category 5 images shown there. No single storm will be able to cause the level of flooding depicted in the SLOSH storm surge images along the entire coast. A sample set of storm surge images for a Category 4 hurricane hitting Tampa Bay is shown in Figure 2. Black lines mark the coastline, and also delineate the grid the SLOSH model used. There may be storm surge present outside the boundaries of the grid, so pay attention to where the grid boundaries are. Also, if you see a high surge modeled for a narrow waterway that goes right up to the edge of the grid boundary, don't believe it. The model puts an artificial barrier at the grid boundary, and the surge is piling up against this non-existent barrier. Empty brownish grid cells with no coloration show where no inundation is computed to occur. St. Petersburg becomes two islands in a worst-case scenario Category 4 hurricane, as shown by the brown areas surrounded by colored areas of storm tide (this did occur during the Great Gale of 1848, a Category 4 hurricane that hit the city). The tide level is marked at the bottom of the color legend, and is 1 foot in this example. The left "maximum water depth" image shows how high above each grid cell the storm tide reaches. The storm tide--the combination of the storm surge plus the 1 foot high tide--reaches as much as 27 feet above mean sea level (pink colors) near downtown Tampa (right-hand "maximum storm tide" image). The amount of inundation inland is controlled by the elevation of the land. Some of the inland regions near downtown Tampa being inundated by the 27-foot storm tide are at an elevation of 19 feet, so as much as 8 feet of inundation will occur at those locations (dark blue colors in the left-hand "maximum water depth" image). Interstate highways are the thick grey-green lines, and smaller highways are shown as dark green and light green lines. If a road is inundated by storm surge, it will not appear. County boundaries are shown in red.
Twenty years ago on this date
On September 9, 1989, satellite imagery detected a strong tropical wave with plenty of spin and heavy thunderstorm activity moving off the coast of Africa, just south of the Cape Verdes Islands. The satellite analyst at the National Hurricane Center duly noted the tropical wave, the 35th such wave to move off Africa that year, in his tropical weather discussion. No one could suspect that the routine-looking tropical wave would eventually grow to become Hurricane Hugo--the costliest Atlantic hurricane of all time.
Jeff Masters
Reader Comments
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Is that the green blob?
Well, shoot. I was just talking about our weather. Yeah, doesn't look too bad. Hoping you don't get too much rain, since your area can flood easily. I'm glad Greg is mentioning the possibility. At least people will know either way. He is really trying to stay on top of things this year. I have to give him credit for that.
Thanks, again. :)
oh ok, thanks Tampa, so, Cowboys vs. Bucs sunday.... hmmm ;)
no problem! :D
Yeah. I agree. Its good to know one way or the other instead of "Panic when I tell you to Panic!" Geesh. Definitely better this year. Lol
Have a good night.
Lol. My dog's been a mental case since she went through Humberto. She freaks out if a drop of rain hits the house. She's a baaaaddd dog. Lol
BY SATURDAY...A WEAK SURFACE LOW IS FORECAST TO DEVELOP ON THE
TAIL END OF A DISSIPATING BOUNDARY OVER THE WESTERN GULF OF
MEXICO. THIS LOW SHOULD MOVE NORTHEASTWARD OVER THE WEEKEND AND
SHOULD MOVE INLAND SOMEWHERE NEAR THE TEXAS/LOUISIANA BORDER. AS
THE LOW MOVES TOWARD THE AREA...STRONG MOISTURE ADVECTION AHEAD OF
THE LOW WILL HELP INCREASE CONVECTIVE COVERAGE THROUGH THE
WEEKEND. WILL CONTINUE TO CARRY LIKELY POPS ACROSS THE WHOLE AREA
THROUGH THE WEEKEND...WITH LOWER THAN NORMAL HIGHS DUE TO LIMITED
INSULATION.
A Snorky. Half Schnauzer half Yorkie. Lol she looks like a lil old man with her salt and pepper coloring.
Just for aviation. And to change pops for tonight. No discussion tho.
Ya the BUCS should blow them out....you think?......LMAO...gonna be a rough year in Tampa im afraid.....but, you never can tell!
Marine Weather Discussion
--------------------------------------------------------------------------------
000
AGXX40 KNHC 100622
MIMATS
MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
222 AM EDT THU SEP 10 2009
MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.
GULF OF MEXICO...
EASTERLY WINDS HAVE INCREASED SLIGHTLY TO 10-15 KT ACROSS THE
SOUTHERN WATERS ENHANCED BY TROUGHING OVER THE NW CARIBBEAN AND
MEXICO. CONSEQUENTLY...SEAS HAVE BUILT TO 2-4 FT...HIGHEST OVER
THE W PORTION WHERE THE FETCH IS MAXIMIZED. A WEAK PRESSURE
PATTERN OVER THE SOUTHERN CONUS AND N GULF IS RESULTING IN LIGHT
WINDS AND LOW SEAS...10 KT OR LESS WITH 1-2 FT SEAS...OVER THE
NORTHERN WATERS. GFS AND ECMWF ARE NOW IN AGREEMENT IN SHOWING
TROUGH DEVELOPMENT OVER THE W GULF FRI. BOTH MODELS SHOW THE
TROUGH LIFTING NORTHWARD TOWARD THE N GULF COAST WITH LOW PRES
DEVELOPING ALONG THE TROUGH FRI NIGHT. GFS DEVELOPS THIS LOW
NEAR THE TEXAS COAST WHILE THE ECMWF'S LOW PLACEMENT IS ABOUT
180 NM TO THE EAST. WILL TAKE A MIDDLE GROUND IN TEXT AND
GRAPHICS. BOTH SOLUTIONS SHOW A DEVELOPING WARM FRONT E OF THE
LOW BY FRI NIGHT WITH THE LOW AND FRONT MOVING N OF THE AREA BY
SAT NIGHT. I PLAN ON KEEPING FORECAST OF SE TO S 10-15 KT WINDS
S OF THE FRONT AND E 10-15 KT N OF THE FRONT. HOWEVER...WINDS
COULD BE STRONGER IF LOW PRES BECOMES BETTER DEFINED...AS
SUGGESTED BY THE NAM.
Hmmmm? Looks like either you or me Ice. Lol. ;)
Good night Ice. But why is the nam and gfs showing it at 72 hours and the ecmwf on 168 hrs???
Night BT .:)
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