***Tropical Weather Mode.***
This blog will take on a bit different format than you are accustomed to seeing, and it will remain this way until further notice. This blog will provide comprehensive & detailed information regarding Tropical Storm Isaac. It also includes a video, so be sure to click the link below to watch that. I will also link it on facebook. See the discussion & my official forecast below.
You always hear me say it when there's a storm threatening the Gulf..."can't sound the all clear just yet, and we'll continue to monitor the storm until it makes landfall". Boy, does that ring true this go-around! If you have been following along with me since Isaac's inception late last week, then you know it was originally expected to make landfall at mid-week in the Florida Panhandle. Well, my how things have changed (or at least we expect them to based on the current prognostications from the models.) Sure, a Florida landfall is still well within the realm of possibility, but what seems more likely is a hit closer to home. How close? When and what intensity? These are the questions we will answer with this discussion.
I hope everyone has indeed enjoyed this last weekend of August, but also heeded the advice I gave on Friday to keep one eye on Isaac. On this Sunday night, it is time to become vigilant but at the same time not panic in any way, shape, or form. We have been through this before, and this will certainly NOT be anything like what we endured 7 years ago, and probably not even 4 years ago. Every storm is a different entity, and Isaac has certainly proved that. He was originally forecast to be a hurricane on Thursday or Friday while approaching Hispaniola, but it never made it. Well, it still hasn't as of the 4p.m. advisory, however, that could change within the next 24 hours. The current satellite representation shows that Isaac is trying to get better organized with convection trying to wrap all the way around the center as it pulls away from the Florida Keys and enters the SE Gulf of Mexico. It will be interesting to watch to see if Isaac can get his act together to even reach hurricane status. Regardless, the system in whatever capacity it is has to go somewhere. The National Hurricane Center has traditionally been conservative with their forecasts, and anytime an adjustment is made it is typically done gradually. I think this is generally smart, just in case models zip back into the original thinking, It is always key to hone in on consistency with forecast models, especially when dealing with tropical entities.
Isaac still has some things going against him that are so far, thankfully, keeping him from strengthening much. The forward speed, dry air intrusion, and some Southerly wind shear have all been impeding on Isaac's development on his journey through the tropical Atlantic thus far. However, as he pulls away from the Florida Keys overnight, he will certainly be in an environment that will be more than favorable for further strengthening. Most of the Gulf of Mexico is an area of high oceanic heating content right now, though not on the levels as it has been in some previous years. Thus, the official forecast calls for strengthening & we should have Hurricane Isaac sometime late Monday. Modest strengthening is the key word here it would appear. The intensity forecast calls for a category 2 at landfall, and this is plausible. However, forecasting intensity is always a harrowing challenge, and it could be stronger than that if all the ingredients come together right over Isaac. It could also just as easily stay a weaker system, and only be a category 1 at landfall just the same. As important as it is to try and figure out intensity, it is more important that you don't focus just on the black line in the official forecast. This is a large storm, and it will affect a wide area regardless of where it goes.
Speaking of where it goes....this is looking more like a Louisiana storm. This should be the state's most significant storm since Hurricane Ike & Gustav in 2008, even though Ike actually made landfall in Texas. You remember what it did to SW Louisiana. The latest official forecast track shows landfall near Pass Christian or Bay St. Louis, MS early Wednesday morning as a category 2 storm with 100 mph winds. However, I believe, given the recent trends of the most reliable models the official track will be shunted further West & ultimately end up somewhere in Louisiana. It seems most likely to me that landfall will occur late Tuesday/early Wednesday between the Mouth of the Mississippi River & Morgan City. SE Louisiana seems like the bullseye at this point. Though, I should mention here, while the most reliable American model (GFS) is a left-biased model, it has also been the best performing model this season & can't be ignored. The GFS track shows a formidable hurricane approaching the SE coast near Grand Isle or Barataria Bay Wednesday morning, and then sliding NW essentially paralleling the coast, and eventually moving completely inland over SW Louisiana with the circulation center passing near or over Lake Charles Wednesday evening. If that tracks verifies, then the Lake Area will certainly experience strong tropical storm conditions, and depending on how fast the storm moves & how fast it weakens, hurricane conditions are possible. On the other hand, the European model (ECWMF) has landfall in the vicinity of Mobile on Wednesday & as a stronger category 3 or 4 storm. One historical note here, Wednesday is the 29th, and that is the date of expected landfall. It will be 7 years to the day since Hurricane Katrina completely devastated SE Louisiana and the Mississippi Gulf Coast. The NHC has basically taken an average of these models & split it down the middle with landfall in the aforementioned area. The worst of the weather with Isaac should be from Lower Acadiana on towards New Orleans. Keep in mind, the forecast that I produce below will be subject to change. I would be surprised if the forecast track isn't shifted further Westward tonight, and I would also expect additional watches/warnings to be issued either with the 10p.m. advisory or the 4a.m. advisory. As it stands right now, Hurricane Warnings are hoisted from Morgan City to Destin, FL. An inland Tropical Storm Warning is in effect for the Baton Rouge Metropolitan Area as well.
Now, I want to briefly discuss what is going on here...As in why the big shift in the models? We have been under the influence of high pressure for the better part of the last now. It has come and gone all summer, as we have been back and forth between very wet or very dry. Our original thinking was that a late summer trough digging into the Mid-West would dip down far enough along the East Coast, and tug Isaac Northward towards the Florida Panhandle with the ridge holding firm across the Northern Gulf. However, the other possible scenario was that the trough wouldn't dig as far, and the ridge would begin to weaken across the Northern Gulf, and if the system was weaker it may result in a further Westward track. Last week, all models were consistently opting for the first scenario, so that forecast seemed logical. However, models begin to diverge at the end of the week leaving us with an unusually high risk of uncertain even with all the meteorological knowledge and understanding. At first, I was rather reluctant to shy away from the Florida Panhandle solution, but when the consistency returned on Saturday with the models shifting Westward there simply was no choice. I feel we are getting close to the time now when looking at models won't matter so much. It will soon by just a matter of going by storm behavior to try and nail down this forecast.
My official forecast will call for Tropical Storm conditions to be experienced across all of SW Louisiana with hurricane conditions possible towards Lafayette & New Iberia. Besides wind, rain will be the issue & whoever is to the right (East) of the center of circulation (eye) will likely receive upwards of a foot of rain, perhaps more in the Tuesday-Thursday time frame. There will be a storm surge as well to the right of the center & let's not forget about the tornado threat as well. Tornadoes are always possible with a tropical cyclone on the North and East side. Initially, there won't be much weather at all in the Lake Area as we will remain on the better side of the storm. It wouldn't be until Wednesday morning that we would see any effects, maybe some extreme outer rain bands Tuesday evening or overnight Tuesday. Winds will noticeably increase as the day progresses Tuesday, but we'll have an offshore wind, so the air will actually be a little drier. North winds around 20-30 mph are expected for Tuesday, with winds increasing into the 35-50 mph range for Wednesday based on the current forecast. As I have said, I do believe they'll be a bit higher than that in the Lake Area, but I will play it conservative for now based on the current NHC forecast. Also, 2-5" of rain is possible across SW Louisiana, a little more towards Acadiana. The tornado threat may be non-existent here unless something like the GFS track comes to fruition. Tide levels will likely rise at least 1-2', but surge should not be much of an issue at this time in Cameron Parish based on this forecast. All in all this will be a close call, if it doesn't end up being a direct hit. I will have my official forecast outlined for you shortly, but first it is prudent to look at some model guidance here. I also want to include the latest satellite & radar data, and then I will conclude with the official forecast track from the NHC.
Let's first take a look at the latest satellite imagery. There you see Isaac off the SW Florida Coast.
You can see the center of circulation on the Key West, FL radar. A link is provided.
http://radar.weather.gov/radar.php?rid=BYX&product=N0R&overlay=11101111&loop=yes
Here are the latest tropical model runs.
We have the new advisory as of 10p.m. hot off the presses from the National Hurricane Center. As I expected, it has shifted further West once again, but still not as far as I think it will ultimately be. It just represents the trend. The official track takes Isaac inland between Grand Isle and Buras and right over New Orleans and Lake Pontchartrain and then over the Northshore into Mississippi as a decaying storm Thursday. Landfall is still forecast to be late Tuesday night/early Wednesday morning as a category 2 storm. Notice, that everyone from Lake Charles Eastward is now in the cone of error. There has been no change to the Hurricane Warnings as of yet. Here are the specifics.
Tropical Storm Isaac...10p.m. Sunday, August 26, 2012
Latitude: 24.2 N
Longitude: 82.9 W
This is about 75 miles WSW of Key West, FL & roughly 605 miles SE of New Orleans.
*A Hurricane Warning remains in effect from Morgan City to Destin, FL. Watches/Warnings will likely be extended Westward & more than likely include SW Louisiana early Monday. (the 4.a.m. advisory).
Winds: 65 mph w/ higher gusts. Isaac has strengthened little today, but a slow strengthening process is expected to begin Monday & Isaac may become a category 1 hurricane late Monday. Isaac is forecast to be a category 2 hurricane with 100 mph winds at landfall. Tropical storm force winds extend outward to 205 miles mainly to the NE of the center. Tropical storm force winds are still being experienced across the Florida Keys & lower South Florida.
Movement: WNW @ 14 mph. The WNW motion should continue through tonight into Monday w/ a gradual turn to the NW expected during the next 24 hours along w/ a reduction in forward speed. It will approach the Northern Gulf Coast on Tuesday with landfall expected likely somewhere in coastal Louisiana late Tuesday or early Wednesday.
Pressure: 993 mb. or 29.32"
Tropical Storm force winds will approach the Louisiana coast late Monday & hurricane conditions will begin sometime on Tuesday spreading NW across South Louisiana it would appear Tuesday night into Wednesday.
Now, based on all of this here is my official forecast.
*This forecast is highly subject to change.*
Tonight...Mostly Clear. Low 74. Light E wind.
Monday...Partly Cloudy with a 20% chance of scattered showers & thunderstorms. High 95. Winds increasing as the day goes on. NE wind 10-20 mph & gusty.
Monday Night...Partly to Mostly Cloudy with a 30% chance of tropical showers. Low 73. Breezy. NE wind 15-25 mph & gusty.
Tuesday...Partly to Mostly Cloudy with a 40% chance of tropical squalls. High 88. Tropical Storm conditions possible by the evening hours. NE to E wind 20-30 mph & gusty.
Tuesday Night...Tropical Storm conditions possible. Mostly Cloudy with a 60% chance of tropical squalls from rain bands associated with Isaac. Low 77. NE wind 30-40 mph with higher gusts.
Wednesday...Cloudy & Windy w/ Tropical Storm/Hurricane conditions possible. High 86. East wind 40-50 mph w/ higher gusts. Chance of rain 80%.
Wednesday Night...Tropical Storm and/or Hurricane conditions possible. Tropical rain squalls & very windy. Low 80. SE wind 30-45 mph w/ higher gusts. Rainfall totals could exceed 5" from Tuesday into Thursday.
Thursday...Conditions improving but still Cloudy & Windy with lingering tropical squalls. High 88. SE wind 20-40 mph w/ higher gusts. Chance of rain 60%.
Thursday Night...Mostly Cloudy with a 30% chance of showers & thunderstorms. Low 76. SE wind 10-15 mph.
Friday...Back to normal. Partly Cloudy with a 20% chance of showers & thunderstorms. High 93. SSE wind 10-15 mph.
Friday Night...Partly Cloudy. Low 76. Light SE wind.
Saturday...Mostly Sunny to Partly Cloudy. High 93. SE wind 10 mph.
Saturday Night...Mostly Clear. Low 75. SE wind less than 5 mph.
Sunday...Partly Cloudy. High 94. SE wind 10 mph.
Stay tuned for more...my next blog update will be Monday evening.
Have a good night, try to get some rest & God bless!
-DM-
No comments:
Post a Comment