T.S. Erika

Well we did get "Erika" named obviously the other day. My thoughts then were that if this system were able to survive, it would be a potential threat to the Southeast / Florida, and I think that theme still applies. This discussion will be brief due to time constraints, but despite Erika's lack of organization, one cannot ignore how persistent the deep convective blob has been to the east of the seemingly erratic / elongated center of circulation. I cannot recall seeing such persistent convection in such a disorganized feature, which I think speaks volumes as far as how decent this storm could have been with just a little better environment. I think more attention needs to be focused on shear at levels other than the standard 200mb-850mb level when doing analysis. It is clear there has been shear, even though the following map shows a shear pattern that while not ideal, isn't the worst by any means either.













Now, from the same site, look at what you see when only looking at mid level shear.

The color scheme obviously is different, but regardless of what anyone tell you, this makes it clear that there has been detrimental shearing going on (duh... when LLC and MLC cannot co-locate, that is typically why), just more focused in the mid levels.

So what about the future? Well, I think this still has a tough road ahead, as to me the shear pattern doesn't look all that great ahead of it the next few days, but it's not so bad to prevent the storm from growing some if the LLC can reform under the persistent deep convection. If this does not occur, the storm may stay on a westward path and face possible death by Hispaniola. A reforming would allow a farther north path and a much better chance at survival, perhaps even substantial growth if it can reach the Bahamas in about 4 days, when shearing should be less. Model trends have come north versus yesterday overall, though I think the GFDL and HWRF are way too agreessive on intensity.

Bottom line, if we don't get the LLC under the deep convection, Erika is in trouble. If we do, it still has a fight for a few days, but could get going more if it survives the next 3 days and winds up in the Bahamas, in which case there would actually be a hurricane threat for Florida or somewhere a up the Southeast Coast. The next 24 hours should tell us a good deal more in order to make a better assessment.

With Danny Gone, Eyes Turn to Next System

So Danny was essentially a non-event, which wasn't a surprise, but I had figured it would keep its "named" status longer than it did, even though it wasn't a purely tropical system. In any case, he's gone, so we're left with tracking the system east of the Lesser Antilles, which looks close to if not already at tropical depression / storm status at this time, so a classification could take place by NHC later today or tonight. The environment through tomorrow or maybe Wednesday could be good enough for some steady development, though it is close, as it will be on the eastern edge of a pretty hefty shear zone. After mid-week, the environment doesn't seem to be very favorable to me, as the upper low currently causing the shear probably doesn't move away faster than the storm is moving, and add to this the fact that by the weekend, there may be a piece somewhere in the southern U.S. or Southeast left behind in the wake of the current cool trough to also add some shear to the mix. It seems that some are of the opinion that if this system survives and gets toward the Bahamas this weekend, then it is off to the races intensity wise, and I'm not sure that is the case. Mind you, that does NOT mean it can't be a hurricane at all, but comparisons to storms like Andrew, or even 2004's Frances seem premature by a long shot, as the pattern to me does not look nearly as favorable, as both of those storms had better upper air ridges to the north, noted by the 588 height line at 500 mb extending way farther into the U.S. Point here is that on the edge of ridges, you have to watch these little "garbage" upper air features that can dance around, and that needs to be considered when trying to figure out future intensity as well as of course track. I have posted the European model shear map at day 6 as an example of this. Despite a decent upper ridge in western Atlantic, there is a little weakeness on the western side, and as you can see on the bottom left image, assuming we do have "Erika" in the Bahamas this weekend, the environment is not ideal. Now, you say, well the model could be dead wrong. Sure, it very well could, but most models generally agree on the position of the ridge, which means we have to watch for these subtle weaknesses given the strong trough departing the East.

So all of that said, first off I'm not sure if this thing will survive the trek into the Bahamas (I'm assuming that is the general direction it should go, as the ridge should keep it from escaping out to sea before getting that far), but if it does, the enviroment to me does not scream major hurricane, but at the same time, there is the risk of downplaying it too much, as a minimal hurricane still is a formidable foe if you have to deal with it, and this system will have a hard time "escaping" out to sea, so the odds favor either 1) getting torn apart by shear in the coming days, or 2) a move toward the U.S, probably Florida focused, so it does bear watching of course. My discussion here is more geared toward some of the rumblings I have heard about this possible being the next "big one". I think it has quite a fight on its hand to get to that status. In any case, it will be interesting to track, as the fact that it has been slow to get going has allowed it to be more of a potential player than I figured it may be from last week.

Danny Update... Next Feature Flares Up in Eastern Atlantic

Danny still doesn't look the greatest, though to me this isn't a surprise, as I've always felt a minimal hurricane was the highest potential max intensity for this thing all along. The center of circulation still has not seen convection wrap around it, and it wouldn't be a shock to see it reform farther east where the convection is deeper, which would mean the risk for an official landfall is much less. Even with the track I had, which was near Hatteras to Cape Cod, this was not really gonna be a big deal where most people live in the I-95 corridor, as rain from interacting with the incoming cool front was really the biggest "threat". However, it does look like the track I had will need to be nudged a bit to the east, and at this point, any landfall is probably relegated to around Nantucket and that's about it. All in all, this will be a storm that got talked about quite a bit by some, but will go down as something that in the grand scheme of things is quite insignificant.

But fear not all you tropical enthusiasts, as the next system may be forming in the eastern Atlantic, as we do have a wave that has flared up nicely, and is in an evnvironment that right now isn't too bad, so in the next few days, we could have Erika on the map. My guess right now is that this will have a hard time ever being a threat to the U.S, given that we will likely have at least one weak upper low dancing underneath the Atlantic ridge, which will probbaly act to guid this storm north of the Lesser Antilles, and then it would probably get steered back out to sea given the strong upper trough headed into the eastern U.S. next week, which probably will split and send a piece tailing into the Southeast. But obviously we're talking a long way out here, and plenty of time to watch this one.

We Have Danny!

The system discussed yesterday has just been updragded to Tropical Storm Danny, as it has finally developed an established low level circulation, and the shear pattern has improved quite a bit versus 24 hours ago. The center of circulation is not embedded underneath the deepest convection, which until that occurs will limit how fast this can ramp up, but it's a big improvement. As for the future of Danny, I don't have a lot different to add to what I stated yesterday. My guess is that the strongest this can get is a category 1 hurricane, and my best guess at track is still toward eastern North Carolina (I think the upper ridge holds this farther west than the GFS model and it's cousins, the NHC hurricane models and GFDL), affecting Hatteras the most, then moves northward along the East Coast, perhaps making another "landfall" (assuming it is still a tropical entity, which I think it should be, enough to keep classified as Danny... we'll see) in southern New England as the next upper trough is focused back in the Midwest this weekend.

While not a "major" system, it could make things interesting right along the coast, though into the big cities of the East, I still think heavy rain is really the only notable threat here. I guess the track I have laid out would put New York and Boston at a higher risk for more periods of tropical storm force wind gusts, but still there I tend to think rain is a bigger issue than wind (keep in mind I mean the metro areas, not right along the shores of Long Island or over to Cape Cod).

This also puts us actually a little ahead of schedule for the 4th named storm, which typically occurs around September 1st... interesting given the slow start to the season!

The Hiatus Is Over - Tropical Threat to East Coast?

Obviously it has been a long while since I posted anything here, mostly due to welcoming my second son into the world at the end of June, and obviously being pretty occupied on the home front since then. And of course there have been the usual commitments to the real job as well. But I am going to try and get back in the mode of updating periodically here, as we are headed for the more exciting time of year for many weather enthusiasts, which is the run up to the winter season!

But for now, it is still summer (which FINALLY came to the eastern U.S. this month), and we are still in tropical mode as well, even now with a threat to the East Coast perhaps! All eyes are on "Invest 92", an area of disturbed weather north - northeast of the Lesser Antilles, which is heading to the west-northwest currently. As of now, conditions are not all that favorable for development, at least not very quickly, but should improve over the next day or two, and I do think we'll have Tropical Storm Danny out of this. Now, where does it go? Well if you believe the U.S. models, it will turn harmlessly back out to sea. But other models say not so fast, and with good reason in my opinion. The GFS model seems pretty quick to develop this, and perhaps a bit north of where the true low level center will eventually wind up. Because a more developed system can be tugged north by any weak upper features, the GFS, by virtue of being faster with development, sends Danny-to-be off into the westerlies much faster, and stays well offshore. But given that the shear is not that favorable right now, I'd lean toward a slower development curve, and a path farther west. A pretty potent trough will dive into the Midwest this weekend, and that should mean we have enough ridging downstream in the western Atlantic, which also leads me to believe a farther west path, closer to the other modeling. This says to me that "Danny" has a much greater shot to impact the East Coast than Bill ever did, though I don't think this system gets as strong. It could organize enough to reach hurricane status, but the incoming trough should start adding enough shear to make it a tropical storm up the coast, so not the best of weekends at the coast, but where most people live in the I-95 corridor, it is probably more a rainmaker. What else will need to be looked at is the potential for the storm to interact with the incoming front and enhance rainfall even more, perhaps leading to some flooding concerns.

So the bottom line is that we should see Danny out of this, and my best guess right now would be a storm moving close to or into eastern North Carolina this weekend, then northward up the coast, probably as a tropical storm, presenting heavy rain concerns up the eastern seaboard, with most of the significant wind issues right along the coast.

First Tropical Storm of Season?

Well we are almost through the first month of hurricane season, and so far have not had much to discuss. This is not entirely unusual, as many Junes do in fact wind up quiet. But we have a system now in the western Caribbean Sea that I think has a shot at becoming our first named storm of the season. The first image below is the satellite picture of the Caribbean as I type this, and I have posted the link for this above the image, since the image itself shown here is not one which will update, so by the time you read this may be old!

In any case, it looked better earlier, but is not in an ideal environment right now to develop. It should continue to drift northwest, perhaps passing just east of the Yucatan Peninsula of Mexico this weekend. Wind shear will be gradually subsiding some as well, so it is possible that by Monday it is able to organize into Tropical Storm Ana.

Where would it go from there? Well, a fairly strong trough will dig into the eastern half of the nation, which probably has enough influence to turn whatever is in the Gulf toward Florida. This path would not be one that would allow any storm to strengthen much though, as wind shear is forecast to increase in the northern Gulf by Tuesday in response to the incoming eastern trough. See the second image below for the forecast shear, valid Tuesday evening (courtesy of the fine folks at MDA!). Values greater then 20 knots are certainly unfavorable. This means that, while possibly holding on to "named storm" status, this would be pretty much just a rainmaker for Florida, as it could not possibly intensify much with this pattern in place.

The other option is that the trough does not pick up whatever is there early next week, which would probably mean a path more toward south Texas or Mexico given the ridge that would be to its northwest. But the environment could be a little more favorable for development on this course. I'd rate this as less likely than option one discussed above though. At least we have something to watch!

Carribean Satellite:

http://www.ssd.noaa.gov/goes/east/carb/avn-l.jpg

Record Heat in Houston!

While June has not been a hot month at all for many locations, the heat has certainly cranked down here in Houston. The last 2 days have climbed above 100, and should again today. In fact, yesterday's 104 degree high set the all-time June record here. Then we have this morning's low of 84, which also broke the June record for highest minimum, and tied the all-time mark for any month. The stat of the day: Our low down here this morning was hotter than the hottest high in New York City all month long! It's a neat stat, but should not be valid after tomorrow, as New York City should finally get above the 84 mark.

What was odd about the 104 here yesterday is that we were able to achieve that without a 500 mb ridge of at least 5940m in intensity. That is hard to pull off, but the fact that much of this area has seen no measurable rain for 31 days is helping that, as with no moisture in the ground, all of the sun's energy goes into heating the air rather than some of it getting used up in evaporating moisture.

Looks like, barring something strange, this will be a top 3 hottest and top 3 driest June on record here. Hopefully we won't follow the trend of the other 2 hottest Junes on record, being 1980 and 1998, and July of those years also went on to be hot (especially in 1980). Unfortunately for those of us down here though, it is hard to forecast anything other than "above normal" for Texas in July given the pattern we have in place.

Blocking is King

The term "atmospheric blocking" is something often used exclusively in the winter season, as it is typically a more influential feature to look out for during the cold months. I, however, personally think it doesn't get enough play in the summer. Sure it isn't as strong of a signal, but can still have quite an influence. Don't believe me? Well, the Arctic Oscillation has been quite negative the entire month of June so far, indicating more high latitude blocking. So below, I have posted first the map of June's anomalies to date (image courtesy of the fine folks at MDA), and second, the map showing the typically pattern when blocking in prominent in June. I'll let you be the judge here, but it looks clear cut to me that it can play quite a role. Also, the astute one may notice a lot of years in the second composite come from years where we either were heading hard into el nino or already had one in progress. Coincidence? I tend to think not!

Some Bootleg June Stats

Interesting how so far, this summer (yes I know I'm calling it summer, as it is in the meteorological sense beginning June 1) has started off on the cooler side in most areas, other than for me down here in Texas... Yuck! I stole an idea from the easteruswx.com weather board, and went back and looked at some stats on 90 degree days in June for a few of the big cities in the East to see when the last time there was a June without a 90 degree day. There was a thread on this board about the last time New York has had a June without hitting 90, and I went back and looked at Philly and Boston as well. The reason I chose these sites is that they have not had a 90 so far this month, and do not seem likely to for the next week or perhaps two, taking us into late June. So if this idea is right, the window of opportunity would be getting pretty small. In any case, the last time Boston failed to get 90 in June was back in 1998. For New York, it was 1996, and for Philly you have to go back to 1982! It has been awhile indeed. This, it is possible we could get all the way into July, having had the hottest weather of the last few months in the East occur in late April rather than May or June!

In some ways, the lack of heat isn't a big shock considering the developing el nino and the impacts that such an occurrence tends to have on the global pattern, but even in similar years, you usually get a brief spike or two somewhere, so we'll see if we get on before the month is done.

Racing Toward El Niño

The last couple of months has certainly brought about a rapid warming of the tropical Pacific waters, terminating the two year la nina event (yes the nina was interrupted for a bit last summer, but quickly returned). Now the focus is on what looks to be an oncoming el nino as we haed through this warm season and into next fall / winter. Of course nothing is a lock in weather, but given how rapidly the warming has occurred, and the time of year, it seems the move toward el nino will be tough to fight off, and a high end weak to moderate event is possible. Looking just statistically, if we reach the critical +0.5 above normal threshold in nino region 3.4 by June or even July, a moderate nino is the most likely, and even strong nino becomes more likely than weak. So from a probability standpoint, moderate has highest odds, then strong, folowed by weak, and lastly neutral. Again, this is only looking at the stats, not subsurface, PDO, or anything else. The state of the PDO, while it will rise in the next few months, in my view should help fight off attempts for any "strong" event, though something like 1972 cannot be ruled out. Looking at the subsurface, we appear to at least as warm or warmer than any of the devloping moderate ninos at this stage of the year, at least the ones in which we have data for. Thus, a moderate nino would appear to be the most likely call right now.

This of course would mean a less active hurricane season in terms of numbers than we have seen in most of the last 10-15 years if correct, but where the storms go is still the important factor anyway. There is always too much made of the number of storms, though to be fair, it is tough to predict who will see the most impacts from landfalls in a seasonal forecast, regardless of what anyone will tell you.

Anyway, in looking at the Spring pattern, we see a lot of things are very typical of a year in which we are seeing a developing nino. I know some have felt the nina ruled the roost for much of Spring, or that we haven't seen a lot of true nino effects yet, but the following two maps to me say otherwise. The first map shows the upper air anomalies for this Spring (Mar-May, as far as I plotted last week), and the second one is a composite of all Springs when we were heading toward a nino from a nina or neutral state. I think a lot of the major anomaly centers match up well, but you can be the judge.

Late Spring Doldrums

Haven't posted in awhile, partially due to some mostly uneventful weather recently, and also focusing more on research. There was actually some noteworthy items this week though. An "unexpected" surge of heat came into parts of the Plains and Upper Midwest this week, sending Minneapolis to 97 degrees on Tuesday, May 19th, marking the earliest on record that they have hit a temperature that high. There was a solid front to the north though. In fact, at 5pm that day, temperatures just in Minnesota ranged from 34 up in the northeast to 100 in the southwesern part of the state! Unreal contrast for any time of year but especially in mid to late May! Wednesday was impressive as well. Ashland, WI saw a morning low of 33, yet hit 90 that afternoon. Try dressing for that weather! Or you could have been in Sky Harbor, where the temperature moved from 46 to 86 in 20 minutes, topping out at 88, and then falling back to 45 just 40 minutes after that peak! I would have loved to be outside there during that event. The Lakes are still cool, so when the wind was off the lake, they were stuck in the 40s, but for 90 minutes or so, the wind turned SW and brought in the much, much warmer air that sat just inland... wild stuff, but can happen when you get shallow cold layers like this that quickly mix out.

The craziness in the Upper Midwest is gone, leaving things kinda blah again since the system in the Gulf is just a rainmaker (and was / still is a hefty one in parts of Florida!). Hard to believe the month of may is about over, and we're about to begin meteorological summer as well as the hurricane season! But will the developing el nino (or so it appears to be developing) squash any chance for noteworty extremes in both cases? It could. Most of the best-fit analogs are not hefty in the total number of named storms department, suggesting mostly numbers in the 9-12 storm range. That would not mean a dud of a season though, since it just takes one to make a season memorable. As for the summer, the consensus seems to be for a relatively benign (or near normal) summer for much of eastern U.S, perhaps even below normal in some places, with warmth favored in interior West. We do have to be cautious of the 2002 analog though, which is arguably the best match to what has actually been happening this Spring globally and overall in North America, and that turned out to be a fairly hot summer nationally, so this is not a slam dunk. It does appear the el nino is for real though, perhaps going moderate by fall / next winter.

Incoming!

Haven't posted for awhile, as I figured I'd leave the hurricane talk near the top for a bit, but had to throw this in here today, as we're witnessing one of the more impressive thunderstorm complexes I have seen in quite some time rolling across Missouri and headed into northern Arkansas and western half of Tennessee and Kentucky. These "MCS"s (mesoscale convective systems) are common in the spring when you get impulses in the upper levels interacting with a very warm, moist (and thus unstable) air mass, but this one has been exceptionally strong, with gusts estimated as high as 100 mph when it passed through eastern Kansas this morning. Baseball size hail and a couple of tornadoes have occurred as well in Missouri. Just glancing at radar / satellite imagery, you'd think a hurricane was moving through the region! What is also fascinating is that some of the strongest winds have actually occurred behind the strongest line of thunderstorms, as high as 85 mph as much as 30 minutes after the worst of the thunderstorms has passed! Very wild and impressive stuff! I've seen plenty of damage reports coming in from the affected areas, so hopefully everyone stays safe who is in the path of this over the next few hours.


Here is an image from around 8:00 central time this morning. Wow!

Hurricane Season Just Over a Month Away!

Hard for me to believe, but we're steamrolling toward the start of another hurricane season. June will be here before you know it, and speculation about what type of season we will see is of course in full swing. The consensus seems to be for a near to slightly above normal year in terms of the number of named storms, though expected by most to be one of the quieter seasons we have seen in recent years, which of course have tended to produce more storms, or at least have more swirls named. The two big reasons citied for this are 1) cooler water in the Atlantic, and 2) a possible shift toward an el niño pattern.


The cooler water in the Atlantic should not surprise anyone, as we have had two years of la nina (though it rested last summer) hammer away at it. For those not aware of this, la nina tends to, over time, spill over into the Atlantic and result in stronger trade winds which can cool the waters of the tropical Atlantic. I have posted an image below of years at this time which followed two years of la nina (using the MEI, which is always my measure of ENSO) to show the tendency toward this cooler tropical Atlantic.















Compare to actual SST anoms shown here:

http://weather.unisys.com/surface/sst_anom.html

Now, given that we do not appear to have entered the long term negative AMO state yet, and the fact that la nina is fading away (or arguably has faded away), the waters could easily recover some, so this is not the end-all factor to look at here. In fact I'd be surprised if they don't recover some in the next few months, but probably not nearly enough to compete with the warmth of the waters in many of our super-active years.

This leads us to the ENSO state. A lot of models are on board with a move toward el nino as we move through the next few months, and the SSTA link above shows some warmer waters starting to show up in the tropical Pacific already. But it isn't always the actual ENSO state that is important, but rather, which way the trend is going. For example, the shift out of a nina pattern can be led by the atmosphere itself, meaning some nino-like characteristics can be present before an actual nino is seen or declared. Thus, in some cases, a weakening nina can have similar effects as an actual nino. So, regardless of whether or not we go into an official nino by later in the hurricane season, these factors would seem to support less activity than what we have averaged this decade (even removing the massive 2005 season total). The farther we get on the nino side of the spectrum, the less activity I'd expect. I'm not sure we move far enough into a nino to get a year quite as quiet as 2006 though, as somewhere between warm-neutral and weak nino seems a better guess to me right now (MEI somewhere in the 0.2 to 0.6 range?). In addition, it is worth pointing out that all these guesses as far as number of namded storms is kinda pointless in a sense, as it only takes one big one to make the season memorable, and really, it is very tough to pinpoint where storms will go, as they depend on the pattern present at the time of formation, so no matter what, everyone needs to always stay prepared if you live near the coast. The consensus of 11-13 named storms from most outlets I have seen is pretty tough to argue with though.

What could allow for more activity? Well should the waters warm more solidly and the atmosphere jolt back toward la nina, then we could see more than the consensus calls for, so that is where to look in the next couple of months. Typically it is late spring / early summer when ENSO "decides" its course.

Vacation Done... Back to Weather

The worst part about vacations is that they have to end. I think I found my new favorite city in Zurich, Switzerland. What a fabulous place, from the scenery, to the easy access to public transportation, and just an all around good place to relax. Rome was nice as well, and even though I'm not Catholic, being in the Vatican as the Pope delivered his Easter Sunday message was quite an awesome experience.

It helped that the weather was absolutely beautiful... very warm with sunshine every day we were there. In fact, temperatures were running a good 12-15 degrees above normals on most days. We expected to need a sweater and light jacket on some days based on normal temperatures for time of year, but that wasn't the case at all (and no I had not spent a ton of time trying to forecast what it would be like haha).

But now things are back to the normal routine. It looks anything but "normal" though in the eastern U.S. this weekend into early next week, with a very impressive (for late April) surge of warmth that will bring a chance for at least a couple of days of 85-90 from the Carolinas all the way up to perhaps Boston. The good news is that this time of year does not bring much in the way of humidity, so it won't be as bad as the same temperatures in say, June through August. Still, highs 15-20 above normal for the time of year is pretty warm, so for those of you living in these areas, enjoy your early taste of summer!

Vacation Time!

Haven't posted in awhile, as I've been preparing for my vacation to Europe. I will depart later today and return next weekend. Fortunatley the weather where I am going looks mild, albeit cooler than I'm used to this time of year down here in Texas.

Last week's severe weather event (talked about last time I actually posted) went about as planned. It just was not the setup for a major outbreak. Maybe I'll do some case studies or something at some point in the future as far as some key things to look for, for those who aren't already aware.

We had some wild stats from the Plains the other day. Gage, OK had a morning low of 14 Tuesday, but rose to 82 in the afternoon! Try dressing appopriately for that kind of day!

Anyway, I don't see a major outbreak of severe weather on the horizon the next few days, but some smaller scale events are possible per SPC's discussions. We may have to wait for the end of the month or early May for a more favorable overall synoptic setup, assuming continued progression of current Madden-Julian wave. These waves will also help play a role in the state of ENSO in the coming months, which of course has big implications on summer and even next winter (yes I know many are already wondering about that!).

I'll be back to posting after my trip.

Severe Weather Update

I don't have a lot to change from yesterday's thoughts as far as the overall gist of the current severe weather situation. This just isn't looking like a major outbreak of tornadoes to me, which is a good thing of course, but again, does NOT mean you let your guard down if you are in the risk areas. I have posted the current radar (as of this typing) below, and you can see a lot of storminess already out there. Moisture is sufficient as is shear, but the oreintation of the trough incoming is not prime for a huge tornado producer in my view (see yesterday's post), and you can already see the linear nature of the storms in Mississippi. We'll have to watch for any isolated storms ahead of this line, along with spin-ups in any bowed out sections or breaks in the line. Damaging straight-line winds will certainly be a threat with these storms. We also have a lot of activity in Florida, with some threat for tornadic cells, though I would think with the clustered nature, straight-line winds would be more of an issue as well. So all in all, the categorical risk on the SPC map below looks good now that they've cut back on the moderate risk some, though I still think the probabilities for tornadoes may be a bit high, with risk for damaging wind gusts perhaps not high enough in the moderate risk zone. It's been a neat storm to track, and hopefully no one will get a major hit here out of this.

Should be more threats to monitor in the South over the next week or two.

Radar, followed by SPC risk map:

Severe Threat for Tomorrow, 4/2/09

Now that we are closer to tomorrow's threat, we can hone in a little more than I did the other day. First off, check the first map below which shows SPC's risk areas for tomorrow. We still have a lead shortwave which veers winds in its wake tomorrow, and keeps the low level jet a little on the weaker side, though probably not as weak as last week's system saw initially. Still though, despite the veered LLJ, the surface winds look to have a more southerly component, which would give a decent 0-1 km shear vector, which for a tornado outbreak is the most important shear layer. I agree with SPC's moderate risk, but despite robust moisture and more than sufficient instability progged, you can color me skeptical on this being a "major outbreak" of tornadoes. I will preface this comment though by saying that if you live in the risk area, be ready! This stuff can be tricky and you don't want to be caught downplaying an event that has any potential to turn out serious.

But I will look to the past some here. The second map below is the progged 500 mb map for tomorrow afternoon. Note the strong, but sharp, and already trying to tilt negatively, shortwave headig toward the South. My reason for some skepticism is that such a pattern looks conducive for storms to fire early, and with stronger forcing due to tilt of trough, we get many storms that can more easily cluster together rather than discrete storms which in a sheared environment can be more of a tornadic problem. If you look at historical data, many (but to be fair, not all) of the big outbreaks in the south occurred with a trough that had a larger base and / or was actually more of a positive tilt variety. Why? Well, since the South almost always has a lot more moisture to work with, positive tilt means forcing isn't as strong, but still strong enough for isolated / discrete storms to fire. The third map below is from 4/7/06, which was one such major outbreak, but I could provide other examples.

In any case, as mentioned, I agree a moderate risk is warranted. I don't see it being a high risk day, or at least verifying as one at this time, and think the tornado threat will be confined mostly to initial storms in western half of moderate risk area, and then become mostly a wind / hail threat rather quickly, with spin-up tornadoes mixed in the clusters still a possibility. We're still 24 hours away though, so small scale details can still change, so stay tuned! Maps referred to above follow:

Basketball > Weather... Maybe More Interest Thursday?

Well, internet issues again didn't allow me to post Friday as I had planned, but it looks like in an overall sense, the Friday - Saturday severe weather event did not live up to what some models had been portraying, which of course is good news for those that were in the path of the storm. As such, the weekend wound up a good one to watch some hoops. My forecast for a UNC title still is alive at least, though I only got half of the Final Four correct this year.

Anyhow, with basketball on a break until the weekend, it is back to searching for threats in the current weather pattern. The next notable threat I see is on Thursday, and interestingly enough is in many of the same areas that were under the gun back on Friday. The pattern seems to want to repeat itself to some degree, with a series of lows coming out of the Rockies and into the Plains, then heading to the Mid-Atlantic, and that is what looks to occur Thursday and Friday of this week. I have two maps below. The first is the 500 mb forecast off the NAM valid Thursday afternoon. Yeah the NAM is not known for being stellar beyond like day 1, but other models generally agree on this setup. The second map shows the 2 meter dewpoints progged for the same time period, along with the lifted index. Obviously there should be no major concerns as far as lack of moisture is concerned. But once concern that may limit the potential here is similar to what happened back on Friday. Note the white circle I have placed on the 500 mb map. Right now, models show this lead impulse taking some of the "energy" away from the second system back in the southern Plains. I put "energy" in quotes because it's an over simplification, but the net result is that this lead system again weakens the 850 mb gradient, and we wind up having to wait until later in the evening to get the low level jet to crank again, and with it being tucked close to the parent trough coming out of the southern Plains, it would seem to imply that the tornado threat would be limited mostly to a 2-3 hour window, and storms may wind up clustering rather quickly after that. SPC has highlighted an area basically from New Orleans to Jackson, MS eastward into the Southeast in their day 4 assessment, though my guess is that will wind up needing to cover all of LA and MS. Greatest threat to me looks to be in LA, MS, and AL, and I could see this being a moderate risk day at the present time, but of course this far out will need to be refined as the event draws nearer. SPC also highlighted a risk this weekend in parts of OK and TX into the lower Mississippi valley, but this hinges on how much moisture can get back into the region in the wake of the Thursday storm, so will have to assess this one later on.

Maps referred to above:

Severe Weather Threat Today... In My Backyard!

Occasionally I get to write about weather in my own area, and today is one of those days. It's a tricky situation (always is down here regarding severe weather chances), but there is a risk of severe storms in parts of Texas and over into Louisiana later today and tonight, and yes, a couple of tornadoes are possible. This morning's cold front pushed farther south than expected though, but is heading back north as I type, which means warmth and moisture is back on the increase in southeast TX. We already have a severe thunderstorm watch in central Texas, mostly for hail. What to watch for later is 1) How much does the low level flow increase? And 2) Does the cap erode in SE TX, allowing storms to root in the boundary layer? Models show the low level jet increasing to over 30 knots later this evening just to my east, which is sufficent to get severe storms. Along and to the west of the LLJ axis is where the best tornado threat should be, provided the cap weakens enough. I see SPC almost pulled the "moderate risk" trigger here, and I can see that, but I feel that, given concers about the cap, a high end slight risk is the way to go. Sunshine has poked out here though, so we'll see what happens late afternoon into early tonight, which is when "prime time" would be.

A more significant outbreak of severe weather is still possible Friday and Friday night in far eastern TX into AR, LA, and MS. I still find it hard to imagine such a strong upper level storm like the one that is coming out of the Rockies (which will be a hefty late season snow producer from eastern Colorado into KS, OK, and parts of MO) can clash with such a warm, moist air mass without some fireworks. My guess right now is that SPC will go moderate risk in tonight's day 2 outlook for this event. As mentioned yesterday, this threat carries into the Southeast Saturday, still with some tornado potential.

And now we have a few models that show another storm around the middle of next week which could be a severe weather producer in the same areas, along with another snow threat from eastern Colorado into Kansas and perhaps parts of Oklahoma. Lots to keep track of here the next few days, so stay tuned!

BTW, here is today's tornado risk map courtesy of SPC, which I have no major disagreements with.

More Severe Weather On the Way

Yesterday went about as I expected... not a huge outbreak, but unfortuantely I did read that there were a few injuries. Here are yesterday's reports:














Looking ahead, there is no rest for the weary, as severe weather season seems ready to take off as we move through the next couple of weeks. Each of the next few days we have chances for severe weather, all the way to Saturday. I don't want to downplay the next couple of days (which could include strong to severe storms in my own backyard tomorrow into tomorrow night), but clearly the most glaring feature on the maps the next few days is Friday into Saturday. The current system moving into the Midwest is not able to push far enough south to really "clean out" the warm, moist air mass in place, which will allow the late week storm to have a lot of "juice" to work with. Here is the GFS valid Friday afternoon, which is one of the more ominous model depictions:















That's a pretty potent upper level system coming out of the central / southern Rockies, which by the way will be an impressive snowstorm from Denver out into parts of Kansas and perhaps up into Nebraska then the Upper Midwest for this time of year. The GFS also has a sufficient low level jet in place across the lower Mississippi Valley. Take note also of the vort max shown over the TN / KY region. That is a key also, as subsidence in the wake of this feature may allow sunshine to maximize destabilization from eastern Texas into AR / LA / MS ahead of the main upper low, though again, this model solution is probably the most ominous, but all models show what could be a dangerous storm in these areas (again maybe down toward me, though capping usually squashes the threat here for the most part... we'll see), though some other models do not depict much of a low level jet in place. While the GFS may be overdone, it's hard to see how such a system at 500 mb wouldn't generate enough of a LLJ for some severe weather (you don't need a 40+ knot LLJ anyway), especially with the warmth and moisture in place. Anyway, can't really get too specific yet other than this, but everyone from eastern Texas across the South will need to keep an eye on this, and the threat may extend into the Southeast Saturday.

Longer term, numerous models show a trough more or less anchored in the means near the Rockies, so we probably are not done with severe threats after this week, provided enough warm, moist air stays in place. We also may see a trough hanging around off the Northeast as well, but if you recall the image I posted a long time ago (I'll have to dig it up again) that showed the "optimal" tornado pattern, you often see this. The reason is that such a setup leads to higher pressure in the East, with a south to southeasterly return flow in the middle of the nation, and this keeps low level flow backed enough to maximize directional wind shear. Bottom line... We probably will have a lot to watch in the next week or two at least.