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31
Aug

Isaac Remnants…Watching Atlantic

The remnants of Isaac are rolling slowly into Missouri and will begin to stall and turn back southeast over the weekend. This will pull the winds from the Gulf over the Southeast, and especially near the core over the KY/TN region by Sunday, spreading showers and storms back into the northern Gulf States to NC.  By Monday, much of the Southeast will have southerly flow and the remnants of Isaac will be washing out, but it appears it could be in tact enough to still offer a small severe chance as it turns southeast, and gathers moisture once again. The rain amounts won’t be too big, but some areas near the circulation center in Ky to VA (APPS area) especially could get good totals Sunday night through Tuesday.  By then, the attention turns to the Atlantic right off the Southeast Coast as some models develop a weak upper low.

Here’s a look at Isaac and look at the sharp contrast with the strong subsidence and dry air around it.

Next week is in limbo, especially late week. First we don’t know where the Upper low off the Southeast will go.  Then, just east of it is “Leslie” which looks to be a major hurricane possibly. There will be a ridge to the north, so basically it will continue west , then eventually northwest, so every one on the East Coast has to be alert for this right now, but most models so far are bringing a deep trough in just in time to spare the Southeast, offering up a possible big hit from Leslie in New England.  There’s plenty of time to watch this, and recall that models are terrible at 5 days out on hurricanes usually.

Right now I’d say theres a good chance that the new trough picks up and absorbs Leslie fully but its hard to pin point where just yet. If that happens, expect a major long wave shift, and one that brings down the first widespread shot of Cool Fall-like Canadian air, right after Leslie wraps up into the trough…but thats about a week to ten days away.

30
Aug

Isaac’s Remnants To Roll North/Northwest, Then East To Apps

High pressure is building over the top of Isaac as you can see all the dry air (red) to the north, and this high will build southeast toward the Carolinas on Thursday and into Saturday, as Isaac’s remnants roll around this high.  Inflow from the Gulf will help build daily showers in GA and Al, and far nw SC and sw NC, but further east VA and most of NC and KY to east TN will be dry a couple of days as Isaac rolls around the ridge.

Radar this morning shows Isaac moving north/northwest slowly, which is drenching La, and central to south MS, moving into Arkansas.

The models are in good agreement that the remnants will move north then northeast over the weekend, before washing out somewhere near the Ohio Valley to Northeast early next week. This will allow decent southerly flow and a weak frontogenesis event to form (front attaching to Isaac) and spread showers and storms back into the Southeast, mostly from northern MS, AL, TN, GA and the western Carolinas by late Sunday but especially into Monday. Portions of VA and KY could be closer to the leftover spin of Isaac and receive decent rain totals if there is still enough spin left in the storm. You can follow the core of the storm seen by the higher shades of QPF as it travels through Mo, Ill, Ind.

So far, this storm has dropped nearly 2 feet of rain in the New Orleans Metro, much as predicted.  So far this month, 17.38″ of rain has fallen at New Orleans International, most of it from Isaac.  There are still bands to go.  New Orleans set back to back daily rainfall records as well.

This radar analysis shows over 20″ has fallen just west of New Orleans downtown in the last 2 days.

A new Tornado Watch until 3 PM CDT for portions east of the circulation.

 

29
Aug

Wednesday Morning…Isaac Making Landfall Approx. 3:30 AM CDT

At 3:30 CDT (4:30 edt) Isaac is still a hurricane Category 1 with 80 mph and is slowling working inland just southeast of Houma, LA.  This track is placing New Orleans on the northeast eye wall, and is lashing the city with heavy rains and high winds….the only saving grace is the fact the storm never strengthened to what it could have been, sparing the city slightly, as this is the absolute worst possible track a Hurricane could take to devastate the city of New Orleans.

Also, tornado warnings are popping up as expected with landfalling storms. Several counties in southern MS have TOR warnings now, and this will be a feature through much of southern MS and LA today as the storm works west and then northwest.

The track of the storm is still similar to my last call map, taking it toward northeast Texas then north into Missouri then just south of Chicago and probably back southeast toward the Ohio Valley or TEnnessee Valley this weekend.  As for rain totals, the best will follow Isaac, and southeast LA, with up to 15″ maybe 20″ in localized spots.  But as the storm slowly begins to pick up speed in the Plains, the amounts will lessen with time.  For the Southeast, the ECMWF totals from a couple of days ago looks greatly exaggerated. Some places in NC, SC, GA and TN won’t get a drop from the remnants of Isaac. (or any at all from southerly flow), but scattered storms and showers will arrive next weekend, mostly toward the TN Valley, but it will be very scattered except for the immediate spin around the remnant low.   Otherwise, today and Thursday will see a few showers each afternoon near the front in southwest NC and much of SC to north GA, but mostly dry in TN, VA and KY. and most of NC.

28
Aug

Isaac To Make Landfall As Category 1 Early Wednesday

He’s still not an official Hurricane, but the latest satellite and buoy data shows he’s on the verge, and some slight strengthening is likely just before it hits southern Louisiana either very late tonight or early Wednesday.  It should be a weak category 1 storm, but the big deal with this system for LA is going to be flooding rains, not so much wind.

The models are in good agreement that Isaac will crawl across the southern Coast of Louisiana and slowly work northwest toward eastern Texas. This is not the official track from NHC however, as NHC has it going almost due north, northwest, however I disagree with that track. I think he will follow the diagram below. Here’s how I see the remnants of Isaac going.  A ridge will form to the north and roll east toward Ohio West VA and the CArolinas by late week and weekend, as Isaac rolls around this ridge to the west through northeast Texas up into Oklahoma then into Missouri,  possibly getting as far north as very near Chicago. Keep in mind, this will be remnants, where Isaac is an extratropical Low pressure, capable of a small but heavy band of rain.

 

The longer out in time, the harder it is to forecast TS remnants, as they can wander around for days without really being picked up by the flow.

For sensible weather, still lots of heavy rain around the core of Isaac, maybe 12″ to 16″ of rain in parts of the LA bootheel and southern to central LA over the next few days.  Further east, the front will interact with moisture in the Carolinas and Georgia, especially around northern GA and much of SC…but further north in TN and Va, not much rain.  Once Isaac gets further northwest, his inflow will increase Gulf Moisture in the Southeast, but there will be spotty showers that can’t be nailed down yet, but the models have decent amounts of rain fall totals in the Southeast in general the next week or so, but some areas won’t get much, others will get several inches.  Just a generally soupy airmass will encompass the Southeast thanks to good southerly Gulf flow.

On an anecdotal note, none of the models should be taken as exactly strict guidance on Tropical Storms when they move inland..it’s very possible a week from now we will still be talking about the remnants of Isaac wandering about “somewhere”.  That somewhere could literally be anywhere between Kansas City Chicago and Atlanta to DC.  There’s been many tropical systems that wobble for even up to two weeks once inland.

 

27
Aug

Monday Morning Isaac Update…Getting More Agreement

After looking at the data recently, this is looking like a big flood event for Louisiana and southern Mississippi. For now the storm is still fighting dry air and other issues, but the storm will become a hurricane before reaching shore, and the trend is very clear…its going to stall.

The reason is the big closed Heat Ridge over the Rockies.  The storm won’t be able to cut much further west because how that ridge will act like a wall, and further east it probably won’t get picked up by the front, so the only real option is to sit and spin somewhere near New Orleans.  The GFS is still showing this, but ECMWF is still drifting this slowly north. The most recent NAM also has been trending toward a stall over Louisiana coast.

As the circulation comes around the east side, it will slam into the front dropping through the Carolinas and northern GA starting Tuesday and really beefing up on Wednesday and Thursday. The front there will stall, with northeast and east winds from the High in the Lakes helping to develop upslope into the Appalachians. Right now, thats another area of my heavy rain setup.  The models have really been showing this for days, with the winds around the high and moisture from Isaac’s outer feeder bands all aiming at the Southern Appalachians. In between, the rain could be showery and spotty, but some good amounts in Alabama and central GA as well, as this may break into two main areas of lift and rain

1)  Around Isaac itself

2) Ga and Carolinas, especially northeast Ga and southwest NC, where several inches could fall.

The biggest deal looks like flooding and winds coming to New Orleans area, starting Tuesday night, unless the storm takes a west jog , or a north jog, barely sparing the city.

If the storm finally moves north, by late week, there could be a closed high building over VA/NC and the GFS actually shows 594 heights, which is pretty hot for this time of year.  Meanwhile Isaac remnants could work north on the west side of this new eastern heat ridge.

 

I’ll have another update soon.

Rain totals per 12z GFS:

96 hour totals (notice the 15 to 20″ of rain near New Orleans, thanks to a stall)

 

26
Aug

Still No Solid Certain Track For Isaac

The spread is from northeast TX coast to the extreme western Florida panhandle. The new 00z NAM came in just east of Mobile and slowed down to a stall in southeast Alabama, which is the furthest east of any guidance, and would be a big southeast Rainmaker (shows 15″ of rain near Montgomery). Right now, it looks too far east.  But like I mentioned, this is about whether or not the trough captures the storm, or totally bypasses it, or “attempts ” to pick up it up, only to relenquish its grip and allow it to jog back west. So over the next 2 days there could be a period where it looks like its turning north, only to resume a west northwest trend again. Its’ that close, and it’s just utterly impossible to know for sure which way for sure this is going.

But the bottom line is from Northeast TX coast to Pensacola and all immediate inland locations need to keep watching this, for some parts of that entire area will most definitely feel the effects (that is, unless Isaac goes west, then southwest–not likely, but not impossible with a big ridge in the Rockies and western Plains)

It’s a rather unique setup, with no clear steering mechanism, but the big ridge isn’t going anywhere too soon, so thats why all models stop Isaac to a near stall near southern Louisiana…further making this worse than if it kept on moving.

The new 00z GFS just coming in looks like it maintains a hit directly on New Orleans…so that model is being consistent since the big switch it made.

Right now is the time to monitor the satellite and radar closely (soon we won’t have much Radar since it will be in the Gulf) but already a central dense overcast has developed nicely, and the storm is organizing fast with strong multiple feeder bands spiraling in, no shear, a huge warm body of water and a slow steady speed…all good factors for strengthening.  Some Hurricane models take Isaac to CAT 4 in southern Louisiana, which is a devastating hit there. With such slow speed, and the angle of this impact regarding how Katrina came due north, that means this will be a long lasting side swipe for Southeast La, and probably the worst possible case for landfall. Hopefully it doesn’t get to that point, but it very well could.

For the Southeast in GA and the CArolinas, rain will fall from outer fringes of the bands and some upslope….but if GFS is right, then it won’t be that big of a deal. If NAM turns out right with its recurvature, then its an entirely different ball game, but I can’t make that call yet.

 

26
Aug

Isaac Update Sunday Afternoon

The latest trend in the globals still doesn’t do much to lead me to believe one specific area is at risk for this storm. Now we’re coming down to just watching the satellite and radars as much as possible and using the short range Models such as NAM , and RAP.

The ECMWF is landfalling in Mobile and heading north. This would be a big hit from just east of New Orleans to the western Fl. panhandle.  The GFS is further west , hitting all of Southern La. very hard with flooding rains + high winds, maybe a cat 2 or 3 storm.  It also nearly stalls the storm, possibly and effect of feeling the weakness left behind in the TN valley trough.  The latest RAP and satellite presentation is eye opening though..as well as 4km 18z NAM run.  Both are going much further north, nearly due north on the RAP in its latest run, which runs every hour.  I don’t know if this is a trend, or a blip.  We will have to monitor this kind of thing.

This forecast has a much bigger cone for landfall, and NHC made a note of that in their latest briefing. Thats’ because it all boils down to whether or not the front or trough in the TN. Valley will affect Isaac….some models and ensembles say it will, and others say not so much, so this leaves the forecaster with a big headache. The door is open to all possible areas from Texas to the Florida panhandle, literally, even at this late stage of the game. Thats’ just the way it has to be on this one.

One thing is certain, it’s beginning to get very organized and strengthening is extremely likely now.  The upper anticyclone on top of the outflow is about as perfect as it gets, very little shear and its moving over a warmer body of water…all pluses for strengthening, the only question is to what degree?

If the short range models keep up with this sudden hooking northwest then north, toward the FL panhandle, then the Southeast from the extreme eastern parts of Miss. to most of Alabama and most of GA and the Carolinas are in for a major rain event.

If the globals like GFS and to a lesser degree ECMWF are right, then the eastern parts of the Southeast won’t be nearly as affected. There is a huge range of what could happen. It all boils down to where and when the north turn begins.  Like I said a few days ago, it may start to feel the effects and draw north some, only to lose the effects or pull, and then cut back northwest again, just before it appears to be making landfall.  This is something to keep in mind. Talk about threading the needle, this is a tight one!

I’ll post again soon on the possibilities, but a big area from east Texas to the FL panhandle has to be on their toes.  Also for the folks in GA and CArolinas not to write off what the GFS was showing the other day, with the major rain totals…it could still happen if the north hook occurs early enough. Same for Louisiana, even though the odds are this is “probably” headed your way, there’s no guarantees of anything in tropical systems ..just be prepared.  None of the models are really handling this too well, with a lot of waffling, so thats a sign of just how extremely difficult this one is to forecast.

Here’s a look at the RAP model at 5H just a couple hours ago..notice the inset lower left corner is starting point, and how the hook occurs in the next 18 hours.  The latest run is even sharper with the hook north, but it’s way too early to know if this will be right.

Its time to start comparing model runs with actual satellite and radar representation.

26
Aug

Isaac Update…Sunday Morning (Big Changes?)

Could Isaac be going further west than official NHC track?  All of the models have trended west in the last 24 hours, except ECMWF (the Euro) has trended east last two runs.  The breakdown:

GFS …on 12z, 18z, and 00z…all runs now have not allowed Isaac to feel the front, and instead allow Isaac to cruise northwest right into New Orleans.  This is the model that for days always had a close call with the front, but ended up recurving into the Florida Panhandle

NAM…both it and its High Resolution 4km version all have recently trended much further west toward central Gulf Coast

ECMWF…For days it was the westernmost guidance, until 12z Saturday, when it made an abrupt switch to a recurvature in Florida Panhandle and recurvature through Southeast.   The latest run 00z, has the storm coming inland around the border of Fl/Al and moves it slowly due north, flooding most of Albama, Georgia and much of South Carolina to southern NC and southern Tennessee.

Short Range models like RAP…are just now seeing this storm come into their 18 hour view…and so far, they too are not feeling the effects of the front, instead allowing Isaac to head out more into the central Gulf, not curving north in the Eastern Gulf.

So the vast majority of the models are starting to allow the front to NOT capture or have that much of an effect on Isaac.

The bottom line is as always, allow plenty of room for error on close calls, and this is  a super close call with only a few hours of timing and a few miles (in the big picture) of what could be a big change in track.  Also, the more time the storm spends in the lower or central Gulf, the chances of a much stronger hurricane go up.

I’m going to wait until 12z Sunday before shifting my track substantially further west….but when the most accurate model of the last 20 months switches its position (GFS) it certainly makes me scratch my head and not want to go against it’s trend…

There are still about half the ensembles and hurricane models showing a recurve, and half not.  It’s like driving a big SUV down the road, and you see a curve coming up.  With all the momentum of the vehicle, the tendency is for inertia to keep the vehicle in a straight path, unless someone grabs the wheel and makes it turn.  That someone could be the front (or not).  Remember the motto on tropical forecasting:  These types of storms the models don’t deal with for 95% of the year, and forecasting them is hit and miss thanks to a lot of complicated things.  So, what is usually a good model for most of the year, could easily end up being totally off on a tropical system…and it’s no real detriment to the validity of that model. Same for a bad model getting a forecast right…no real credit can be attributed.  Tropical Systems are notoriously hard to forecast.

So check back after 1 PM Sunday for my latest thinking on the track…but so far, I’m leaning toward a much further west landfall near Mobile to New Orleans unless the GFS and short range NAM show some strong signal of recurvature toward points east. Either way, the Gulf Inflow in the entire Southeast will bring rains, and possibly a lot of it.  But a strong storm hitting New Orleans for example would allow higher pressure to settle down east of the Mountains and not have much affect in central and North GA and most of the Carolinas (like GFS)…so track and trajectory means a lot right now, and we’ll know soon if the storm is allowed to cruise more west or cuts northward sharply, like the official NHC track.

25
Aug

Hurricane Isaac Full Update Saturday Aug 25

He’s not yet a Hurricane but will be in a couple days near the Key’s and then explosively deepen just west of Tampa in the Eastern Gulf.  By now you’ve read all the “model war” hype and my stance has always been clear:  On Tropical Systems, you allow plenty of leeway and room for error or critical judgement, simply because Hurricane Models and the Global models don’t handle these unique phenomenon well. Not yet. Unlike the 99% of the remainder of the year when we’re dealing with cold core systems and shortwaves and baroclinic processes in the mid latitudes, this leaves plenty of error for the models (and actual model forecasts) since the science is not quite there yet, like we are with storms the remainder of the year. Therefore, you put your best guess using synoptics, patterns and history and gather what you know about Meteorology to calculate your guess, no matter if you’re working for the National Hurricane Center or if you’re  too reliant on the weather models…in the end, excuses don’t matter….results do!  Too often Forecasters on TV and elsewhere on the Internet “blame the models” for a flip-flopping forecast.  That’s not really doing justice to the science, instead its a way of copping out as a Forecaster.

So, here’s the breakdown. The 12z GFS ran a few miles west of where it had been going all week.  A surprising move but it could be a burp…remember the model is run 4 times a day.  Unlike the ECMWF which is run twice daily.  The ECMWF now has switched strongly east, after going to the Yucatan, Texas, the Central Plains, the Ohio Valley and New Orleans, today’s run has it where the GFS has been clustered all along, that is the Panhandle of Florida, with a recurvature inland through Georgia and the Carolinas.

If you’ve followed my forecasting for the last couple of years, either in weather forums or FB or the website, you’ll notice my talk of how many times this type of thing has happened. Since Christmas snowstorm of 2010 in the Southeast, all through the Spring of 2011 (historic season!) all through Summer, and now on to this Spring and Summer, almost all of the significant weather events that had a disparity between the GFS and ECMWF on the days 4 through 7 panel , ended up with ECMWF caving into a version similar to GFS in the end. Today’s Isaac storm is another example. I have been studying models my entire life since becoming a Meteorologist in 1992, and most of the time the GFS model has had severe problems that are dutifully noted, such as being too supressed, too cold, overdeveloped and with a Southeast bias especially in a split-flow or Winter time Supressed storm track (and this really shows up when blocking occurred). However, since the Christmas Storm 2010, the pattern has changed or the model has been tweaked (unsure of last tweaking) so that it’s vastly outpeforming in each season since then, and thats well over a year and a half now. I’ve relied heavily on this subtle change instead  of coasting happily on the ECMWF former coattails.  As a forecaster, we’re compelled by Science and Observation, not charts, numbers or verification charts which can be misleading.  Who knows if the old guard is changed once we enter into another El Nino supressed Winter, it will be interesting to see if the GFS reverts back to being it’s old self, way too supressed and full of phantom snows and cold air. But for now, if you’ve studied and paid attention for the last 18 months, and read my forecasts you’ll notice I put out alerts very early on, relying heavily on a various methodology that includes a lot of tools in forecasting, and in the end, come up with something very close to what GFS operational portrays.  All of the derecho’s, Severe Outbreaks, tornado outbreaks, cold waves, heat waves, blocking events, cold air damming episodes, all the main longwaves, pattern changes, cutoff lows, almost every conceivable weather event in the Southeast, the GFS has shown since the start of 2011 and eventually the ECMWF came on board. Almost every MCC or MCS that formed I was able to forecast out to 5 and 7 days from occurrence using the subtle cues and synoptics of GFS, whereas no other model showed it…and it worked! This is true for the Midwest, Southeast and MidAtlantic.

With all this said, it’s not to bash or praise any model really, but to notice some differences that make a difference here in the real world…that is YOU, and what you, your family and your business can expect, from as far out as possible and with as much accuracy and attention to detail as possible.  Generic forecasting and blantantly following models (and consequently blaming them) does you no good….does Meteorologists no good as well.

 

Here’s my best call so far on Isaac.  I think the models are correct in starting the strengthening process near the Keys and especially in the Eastern Gulf of Mexico, but obviously the big question is where does he make landfall? So far most guidance still clusters around the Florida panhandle, and I agree with that.  Beyond this , it gets harder to make a call, so I’ll have another update when or if things change ( or by Sunday—-whichever comes first).  There are two options: One is that it recurves, like the vast number of GFS runs show (but today’s run didnt’ recurve).  The other option is for it to slowly drift north or northwest, ala ECMWF.  Both are possible.

In percentages, I would lean toward a recurvature right now.  Several reasons make WxSouth lean this way

1) A wet Alabama to Carolinas

2) All Summer long, except the heatwave, there’s been a graveyard of fronts around the Southeast and TN Valley to NC.

3) Weak upper low near Florida, helping to pull Isaac north initially today (more so than most models showed)

4)  Climatological tendency for Florida Panhandle storms to hook north/northeast.

 

If you have any interests along the Gulf Coast, especially from New Orleans, east bound, take a special long hard look at what you need to do to prepare.  Waiting until the last minute when a Category 3 storm is approaching is too late.

In the end, it’s possible this storm stalls. There’s no guarantees on any track. Remember my rule of Tropical Forecasting: Lots of leeway and a gracious plenty room for error! These are unique systems and don’t always follow the rules as we know them.  If it stalls,  there will be catastrophic flooding.  Right now it’s possible it begins to get picked up, but doesn’t fully, in which case a worse-case scenario unfolds quickly along and north and northwest side of the circulation.  So if that storm tracks from Florida panhandle to Macon , then along and north of the track would be hit hard, including eastern Alabama and Atlanta to most all of the Southern Appalachian Mountains.  A further north track would still hit Mountain Chain with strong upslope flow, but not nearly as much rain for the rest of the Carolinas, but dumping a lot of rain in the Great Tennessee Valley. All these are possibilities, but I’ll continue to monitor it and do expedient updates.

25
Aug

Will Have Full Update on Saturday after 12z Models

Check back around 2 PM  for the latest on Isaac and where the heaviest rains could be.

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