Hurricane Katrina made landfall just south of Ft. Lauderdale, FL around 7pm this evening with sustained winds to 80mph and gusts between 90-95mph. It has moved in a general southwest fashion ever since then, taking it into the heart of the Everglades, and moved a bit quicker than forecast as well. This is what some models were calling for, notably the GFDL, but not quite as extreme as its solution from last night and earlier today. There are two confirmed deaths thus far with the storm, an estimated 1,000,000 people without power, and still another landfall ahead for this storm.
An analysis of the overall synoptic situation shows that it is largely unchanged from that forecast Tuesday night. (For those who did not see it, I do refer to it a couple of times below, so please glance over it at http://flhurricane.com/blog.php?met=Clark, the second option in the list.) The trough in the west is moving towards the east right on schedule -- perhaps just ahead of the forecasts from 24-48hr ago, as shown in a comparison of the model output and analyses -- and is at or just above the intensity forecast at that point as well. Its impacts are borne out in the 850-400mb steering flow pattern progression from the Univ. of Wisconsin website over the past 24hr -- the ridge in the east centered over the ArkLaTex region has remained in place, but has become much flatter (i.e. extends less to the north, from up into the NE 24hr ago to only in the SE now) over that time period. It is slightly stronger than forecast; this is the primary reason why the storm is being forced a bit towards the southwest. This southwest motion should continue for the next 6-8hr, followed by a gradual turn towards the west-northwest as it approaches shore. It should be offshore within about 6hr but should parallel the shore for some time thereafter.
A track over the Everglades is going to result in the wind profile of the storm becoming flatter -- in this case, meaning that the wind field won't change much in intensity away frm the center -- but not losing a lot of its intensity. Certainly, the short time over land and the intensity of the storm at landfall will keep the circulation vigorous above the surface. Given the warm marshes of the Everglades, moist conditions from recent rains, and proximity to water, the mechanisms are in place for the storm to somewhat maintain itself over land for a brief period of time. At this point, the storm will likely emerge offshore somewhere near or south of Everglades City tomorrow morning as a 50-55kt tropical storm, with feeder bands extending well east of the center. While the storm may have made landfall several hours ago and is moving into south-central Florida, the rain event for the entire S. Florida region will not end for another day or two. Locally heavy rainfall amounts -- over 10" -- are possible, largely in areas that are already running above normal for rainfall, resulting in the potential for flooding.
From there, the storm should begin to slow down as the ridge in the ArkLaTex moves westward and the trough continues to move eastward. Signs of this are already present, with an upper-low near Baja California beginning to move westward; it is only a matter of time before the ridge begins to do so as well. With the trough on or slightly ahead of schedule and slightly stronger than forecast, plus the storm a bit ahead of schedule, I do not see major changes needed from my forecast from Tuesday. This forecast is largely an update of that forecast, primarily for intensity purposes and to narrow down the landfall region just a bit.
Over the course of the 12-36hr time span, this system should move relatively slowly in the SE Gulf of Mexico about 100-150mi offshore. This will keep the west coast blanketed with rain and gusty winds through Friday and Saturday. During this time, it will be gradually turning towards the north and northwest in advance of this trough. A slight acceleration will be felt -- albeit not a large one, as the main extent of the trough is expected to be somewhat removed to the north; think the gradual acceleration seen with Irene with this one -- as the storm heads for the general vicinity of the central Florida panhandle. I expect landfall in the 72-96hr time period, likely towards the middle part of that region, not too far from the NHC forecast position. This, as noted before, is largely the same as the forecast on Tuesday night and shifted only slightly further east.
Model guidance is starting to come into better agreement with each other and some of the better models have remained fairly consistent with their solutions over the past few runs. With landfall approaching that 3 day window, where track errors have been largely minimal over the course of the past couple of seasons -- and even smaller with some of these landfall storms -- confidence in the forecast begins to grow around this time. Still, it is not a certain forecast, as timing issues could still send the storm 50 miles further east or west of a projected area.
The higher intensity and overall very well organized circulation expected to emerge into the Gulf of Mexico bodes ill for the northern Gulf coast. The same holds for the very warm waters found across the Gulf -- generally 30C (86F) or higher across the entire region -- and forecast low shear values. The worst-case scenario brings this storm off-shore as a moderate tropical storm, takes a little time to spin up again, and sees it rapidly intensity much like Dennis did a little over a month ago. Unfortunately, the best case scenario at this time is not much different than this. Extrapolating the NHC intensity out to landfall form the 3 day point and maintaining continuity brings the storm ashore just below major hurricane status. Models and the NHC have both been trending upward in intensity forecasts and many of the parameters towards rapid intensification appear favorable once it emerges out into the Gulf. At this time, I do not see any reason to disagree with the NHC forecast; if anything, I would err slightly higher on the intensity. This brings a potential category 3 hurricane to the central Florida panhandle overnight Sunday into Monday morning.
To repeat: the potential is there for a major hurricane to make landfall on 75 miles either side of Panama City, FL within 72-96hr. Current forecasts place it just below major hurricane intensity at that time and those seem reasonable to follow at this time. The projected landfall window is largely the same as before, only tightened a little on the west side from Mobile over to just east of Pensacola. Residents of the area to the MS/AL border and over to Cedar Key, FL should watch this storm closely in case anything changes.
To residents over the Florida panhandle: start getting prepared now. Watches will likely be issued for the coastline late tomorrow or early Saturday, with warnings likely to follow soon thereafter. Many areas in the region have either recently gone through two major hurricanes (Ft. Walton & points west) or are limited in their ability to handle such a storm largely because it is a rare event to see (Panama City & points east). There are many residents spread out over rural areas and many people located in high-density population centers throughout the region. Being prepared now will save you a lot of time and hassle in the days ahead. At this point, you should just be watching the storm and starting to make preparations; it is too early to be putting any plans into effect. Stay tuned to NOAA Weather Radio and your local authorities for the latest on the situation into Friday and Saturday.
If you have any questions or comments, please feel free to send me a PM or ask on the boards in the appropriate folder/thread. I will be around through the weekend to provide further updates as needed, as will the other meteorologists here at the CFHC. The next update of this forecast is planned for tomorrow night or early Saturday morning, assuming no drastic changes between now and then.
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