Tropical Weather Update - October 31, 2020

October 31, 2020

Happy Halloween! It's also a full moon today, called the Blue Moon. The area of interest I mentioned on Thursday was designated Invest 96L on Friday and it now has a 90% chance of development over the next 2 days. 

So the question is, where is it going to go? Right now the models are in two camps. The HWRF, Euro, UKMET, Canadian, ICON (German), and ACCESS (Australian) models all take 96L into Central America as do most of the spaghetti models. The majority if not all of the Euro ensembles take it into Central America as well. From there a few members bring a system back north around next Wednesday or Thursday but I can't tell if it's the same storm or the models picking up on something new although they may be hinting at some agreement with the GFS. The GFS has the storm stall in the southwest Caribbean for a few days and then brings it north across Cuba next Friday and then into Florida. The GFS ensembles have the same general solution, although there may be a few weak members that take the storm into Central America. So I guess there really aren't two camps, the GFS is sort of a lone ranger.

Spaghetti Models:

Euro Ensembles:

GFS Ensembles:

All the models that take the storm into Central America have the storm racing into the coast on Monday or Tuesday while the GFS slows it down and stalls it in the Caribbean. It would seem like maybe the GFS is out to lunch on this and shouldn't be trusted but I don't think that's the case. I could easily dismiss the operational GFS, but with the majority of the GFS ensembles in agreement that has me paying attention. The GFS ensembles were the first to pick up on what ultimately happened to Zeta. I missed it because I didn't understand what it was showing at the time. When Zeta came northwest then I realized what I had been seeing. This version of the GEFS has been fairly reliable this year, so with a signal this strong I think it needs to be considered as equally likely as the other solutions. Either way we'll know in a few days, we'll have to watch to see how the models change as well.

That is it for today. Get out and enjoy the cool weather!

Chris

New Tropical Development Likely in the Caribbean

October 29, 2020

I hope everyone fared well with Zeta. Zeta was 1 mph away from a category 3 storm at landfall, not what was expected at all. Real quickly this morning, I wanted to let you know that the NHC has designated another area in the Caribbean that has the potential for development. It first showed up yesterday and this morning chances for development are up to 60% over 5 days. It's a bit too early, but I think we're looking at similar track possibilities as we were seeing early on with the system that became Zeta.

Let's give this a few days to see how it evolves and then we'll take a better look at it.

Chris

Tuesday Night Update on Tropical Storm Zeta

October 27, 2020

Time got away from today me a little bit but I wanted to provide an update on Zeta mainly to focus on the hazards we may experience over the next day to day and a half. Zeta is pretty close to being locked in to making landfall somewhere near the Mississippi Delta tomorrow evening. The forecast is for Zeta to make landfall as a category 1 hurricane but it could make a run at category 2 strength. Zeta will be fast moving and the center of the storm will be well out of the area by Thursday morning with some effects lingering until midday.

Damaging winds is the obvious hazard for those near the landfall point. Keep in mind we'll see gusty winds well away from the center of the storm.

Tornadoes will be possible for some areas near the coast from Wednesday overnight into Thursday. There's a 5% chance of tornadoes for the area to the east of the landfall point through the western Panhandle and into southern Alabama with a 2% area indicated just beyond that. The graphics below are a bit old as of the time I'm writing this so don't rely on them as an exact forecast and keep alert for tornado watches that may be issued for your area.

Storm surge is another hazard. Below is the peak surge forecast for Zeta. Keep an eye out for this to change if the track shifts a little or the intensity changes. This caught quite a few people off guard with Sally, although a track shift of that magnitude is not expected at all.

As mentioned Zeta will be a fast moving storm so flooding isn't expected to be a widespread issue. All the same these storms can dump a lot of rain so be prepared if you're in a flood prone area.

That is all I have for this evening. If the tornado threat changes significantly I'll let you know, otherwise this will likely be my last update for Zeta. This weekend we'll take a look at what the tropics may have in store for us in November.

Have a good rest of the week, a great weekend, and a Happy Halloween (it's also a full moon...). Once Zeta and our next cold front clear the area the weekend should be a nice one.

Chris

TS Zeta Update - Monday October 26, 2020

October 26, 2020

As of the 8 a.m. advisory Zeta is nearing hurricane strength with 70 mph winds. Zeta should become a hurricane shortly and to continue to strengthen as it approaches the Mexican coast. The current forecast has it losing strength over land and then regaining hurricane strength in the Gulf. It's possible we could see Zeta around category 2 strength at its strongest and then weakening some before landfall. The track guidance has consolidated well but there's still a little uncertainty regarding when the storm will start its northward turn and then later its turn to the northeast. Regarding the spread, it's possible that a stronger storm will have a more eastern track and a weaker storm a more westward track. That's not set in stone, but something to be aware of if you're in the vicinity of the forecast cone.

My forecast on the 21st where I didn't think we'd see a lot of rain from the first front was a bust! I don't know what happened where you all are, but I think I got nearly 2" of rain! Zeta is obviously our most immediate concern but we can expect another front to move through around Thursday with at least some rain, although it's hard for me to distinguish rain from a departing Zeta and this front. I expect we'll see some cooler weather follow the front into the weekend, getting temps down to about where they should be this time of year just in time for Halloween.

Looking long term in the tropics, there are strong signals that we'll see another storm develop about where Zeta did during the first week of November. Let's get Zeta past us first, and by then we'll have a better idea what might happen a week and half from now.

That's it for this morning. Have a good Monday.

Chris

Update on Tropical Storm Zeta

October 25, 2020

TD 28 was named Tropical Storm Zeta at the 2 a.m. EDT advisory overnight. The track forecast is no longer showing the hard right turn over the middle of the Gulf but the landfall possibilities are still in the same general range from Louisiana to the Florida Panhandle. Zeta is expected to be near hurricane strength for its first landfall on the Yucatan Peninsula late Monday. It is forecast to remain a category 1 storm for most of its trek across the Gulf and is expected to weaken prior to landfall sometime on Wednesday, although the NHC notes that this weakening phase can be difficult to predict.

The HWRF, which again has been fairly accurate this year, shows Zeta becoming a strong category 2 storm before hitting the Yucatan so that will be something to watch for. Even though this model has a stronger storm initially it brings Zeta across the Gulf and into the Mississippi Delta as a tropical storm. This is just one run from one model but it'll be interesting to see if it verifies. The HWRF has been flopping around a bit as it tries to get a hold of the situation so I don't have a lot of confidence in this yet. You can see other intensity models below. The NHC's intensity forecast is near the consensus of this guidance. Note that so far no model is indicating rapid intensification or a very strong storm at landfall.

That's all for this morning. The good news is that I don't think we're going to see a major impact as we have seen several other times this year. That being said some folks along the northern Gulf Coast are going to get yet another storm.

Have a good day.

Chris

TD 28 Forms in the Northwest Caribbean

October 24, 2020

Invest 95L was upgraded to Tropical Depression 28 at 4 p.m. CDT. The forecast cone outlines the general trend we were seeing from the models earlier. One change from this morning is that the intensity guidance has increased a bit and the NHC shows TD 28 becoming a hurricane about 3 days from now and then weakening as it approaches the coast later in the week. The NHC's discussion does mention uncertainty with both the track and intensity forecast, with the current intensity forecast perhaps being on the high side.

Have a good evening.

Chris

TD 28 Forms in the Northwest Caribbean

October 24, 2020

Invest 95L was upgraded to Tropical Depression 28 at 4 p.m. CDT. The forecast cone outlines the general trend we were seeing from the models earlier. One change from this morning is that the intensity guidance has increased a bit and the NHC shows TD 28 becoming a hurricane about 3 days from now and then weakening as it approaches the coast later in the week. The NHC's discussion does mention uncertainty with both the track and intensity forecast, with the current intensity forecast perhaps being on the high side.

Have a good evening.

Chris

Update on Invest 95L

October 24, 2020

Invest 95L is up to 90% chance of development this morning. When the NHC speaks of development, they mean the chance that a tropical cyclone may form. It doesn't indicate anything about how strong the storm may get, etc. A tropical depression is the first stage in the tropical cyclone lifecycle and this is what the 90% chance is forecasting the potential for.

Getting back to 95L, Levi Cowan of Tropical Tidbits provided a good explanation last night of what the future may hold, you can watch it here: https://www.youtube.com/watch?v=pJjq_dHzvfI. In short, he mentioned that there's quite a bit of uncertainty on where the storm may go. However, that was over 12 hours ago and many models seem to be consolidating around a general track. You can see various models below, but the basic idea is that a high pressure will form in the western Atlantic that the storm will steer around. That's why you see a tight jog to the left and then a slow curve back to the right. When Levi made his discussion yesterday, there was still the possibility of a strong storm forming quickly and moving off to the northeast only to be hooked back to the west into the Gulf. That may be completely off the table now. I'd like to see this trend hold for another 12-24 hours to feel better about it. Regardless of the general trend, notice that there's quite a bit of spread even in the short term. That's to be expected for a storm that hasn't really formed a well defined structure yet, each of the members have their own guess when and where that will occur and that's why the spread is so wide.

Hurricane spaghetti models:

GFS ensembles:

Euro ensembles:

UK ensembles:

Moving on to intensity, so far we're not looking at anything too concerning. You can see the intensity guidance below and most of the track plots above are color coded for intensity. I think the wind shear in the Gulf may be a bit too strong to allow for a lot of strengthening but since we're probably not going to see a landfall until Wednesday or Thursday there is time for that to change.

To summarize all of this, I think we can be fairly certain the the Gulf Coast somewhere from the TX/LA border to the Florida Big Bend will be impacted by a storm that could range from a messy rain maker to maybe, stretching it a bit here, maybe a category 1 hurricane. Again this could evolve but right now I'm not overly concerned about a major impact just yet, let's see what the next 24-48 hours brings.

Have a good Saturday.

Chris

Tropical Development Possible in the Caribbean - Could Move Into The Gulf

October 23, 2020

The yellow area in the Caribbean (which is now orange) has now been designated Invest 95L by the NHC and they are now indicating a 50% chance of development over 2 days and 60% over 5 days. This changed fairly quickly overnight, going from a 30% chance at 8 p.m. EDT still headed to the northeast, to 40% headed north and then east at 2 a.m., to what you see now. Needless to say I'm a bit caught off guard.

None of the models are showing any strong development yet. I think the NHC upped the chance for development based on a much stronger presentation on satellite that occurred overnight. You can see the system below. 

Looking at the models, the GFS brings a messy system across the Gulf towards Mississippi, Alabama, and the Florida Panhandle late next week, what it shows probably wouldn't be much more than a tropical depression. The Euro splits this energy to the west and east with one piece going out into the Atltantic and another going towards Louisiana also as a messy system late next week. The GFS ensembles mostly show the previous solution, a weak system going across Cuba to the northeast into the Atlantic with a few members showing tracks towards the northern Gulf Coast, again no strong development is indicated. The Euro ensembles have nearly all its members still showing the northeast track with maybe 2-3 members showing weak tracks towards the northern Gulf Coast and 1-2 more towards Mexico. So right now none of the models are excited about this, including the UK and Canadian. I will caution that we'll probably see some changes in the models later today and through the weekend. Now that this is an invest the the models will get a better look at, so it's possible that everything I described above showing very little development could be due to the models just not seeing the system yet.

The good news is that conditions in the near term don't look that favorable. 95L is in a somewhat favorable environment at the moment, but as it moves into the southern Gulf it will encounter stronger wind shear which should limit development until maybe midweek. After that conditions may get better but we're too far out to know. The Caribbean is still plenty hot but the Gulf is a bit cooler. All the same there's probably enough energy to support a fairly strong storm if the wind shear dies down and it can sneak up to the north in between fronts. You can see the heat potential below.

Unfortunately this is something we're going to need to watch. Hopefully it doesn't blow up quickly in the Caribbean as that could change things. I don't think that's likely, but given how fast it changed overnight we need to watch it. We'll know a lot more over the next 24 hours but it'll probably be early to mid next week before we have a good feel for what's going on, assuming it is able to develop.

Have a good Friday and a great weekend. I'll send out another update by tomorrow.

Chris

Tropical Development Back on the Board for the Caribbean...

 October 21, 2020

Well, that was short-lived...I didn't think we'd see something this soon. The NHC has a yellow area again, 20% chance of development over the next 5 days. I think this is the same thing that I mentioned this morning that the UK and Canadian models were seeing. The GFS and Euro still aren't showing much, even the ensembles. I think if it does anything it'll move off to the northeast as shown.

Nothing to get excited about at this point, I just want you all to know it's there.

Chris

Tropical Weather Update - Wednesday October 21, 2020

 October 21, 2020

There's good news in the tropics this morning, the NHC has dropped the yellow area in the Caribbean off the 5-day outlook. The surface weather map for the tropics does show a low pressure in the northwest Caribbean but development is no longer expected in the near term. The Euro got this one correct I think as it consistently showed nothing happening. The GFS, which showed a storm forming run after run for well over a week, finally dropped the idea of development a few days ago. There are still a few GFS ensembles showing development but they're in the minority. As a side note, and because it's there, Epsilon, located east of Bermuda, is no threat to the US.

Looking farther out to next week and into November tropical development in the Caribbean is still possible. Below is the two week tropical hazards outlook and you can see a moderate area for development highlighted in the southern Caribbean for the second week. Models aren't showing a lot, although both the UK and Canadian models seem to develop something near the Bahamas late this weekend that then moves out to sea, maybe some energy from an old front. I think that area in the Caribbean is being highlighted mostly because this time of year favors development in that area and conditions will be generally favorable off and on.

Looking at the weather in the US, we'll have a front move in overnight on Friday. Rain chances will increase starting late Thursday and will last through Saturday. Sunday and Monday look nice and then we'll see another front come through Tuesday with maybe some rain. Rain totals don't look high from either system. Temps won't change much through the next 7 days but it looks like we may see a third front towards the end of next week that could bring some cooler air.

I'll get more into this in a future update but La Nina conditions are expected to persist through the winter and this typically means we will see mild, if not warm, and dry conditions in the southeast.

Have a good rest of the week. If things stay quiet you probably won't hear from until next week so if that's the case have a great weekend.

Chris

Tropical Weather Update - Thursday October 15th, 2020

October 15, 2020

There are three areas that the NHC is watching for tropical development as shown below.

Area #1 right over the Lesser Antilles has been watched for a few days, it is Invest 93L. I haven't mentioned it because it's not expected to be a threat to the US and you can see that the NHC gives it 0% chance of development, it'll mainly be a rainmaker for the islands. Area #2 east of Bermuda may try to develop but I think that's a long shot. Both the GFS and Euro spin it up into what is probably more of a subtropical storm than a tropical cyclone but they stop short of full development. Even if it were to develop I think it would be difficult for it to get too close to the coast this time of year, especially as far north as it is, although the Euro shows it getting close to the North Carolina coast next weekend. It's something to keep an eye on if you're on the East Coast but for now I don't think it's a threat.

Area #3 is what we need to watch. We've known about the potential for development in that location for more than a week and now that we're closer it has been identified by the NHC. The GFS and many of its ensemble members have been excited about this area for a while. The current run develops a storm late next week and takes it northeast across Jamaica and eastern Cuba and then across the Bahamas out into the Atlantic. Most of the GFS ensemble members support this general idea but there are a few members that bring it more north across western Cuba leading to a South Florida landfall next weekend or early the week of the 26th. The Euro has been consistently the opposite, the most it shows is a broad circulation that drifts west a bit in the Caribbean. The Euro ensembles are equally bearish, although many members do eventually pull a very weak system to the northeast similar to the GFS track. From what I can gather the consensus is that the Euro is just failing to see the potential for development again as it has done so many times this year. We know conditions will be favorable for development as indicated by the GFS so it's a bit of a disappointment that we're not seeing this from the Euro.

Right now all we can say is that we're likely to see development in the western Caribbean mid to late next week. I don't think we'll see a track west or too far into the Gulf as a north-northeast track is favored this time of year with the fronts that are sweeping through on a regular basis. We're way too far out to rule out anything but I'd say the main threat areas are from western Cuba through to Tampa over to eastern Cuba and Hispaniola through to the Bahamas. We'll probably have a better idea early next week.

In other news we should see a mostly rainless cold front push through today and overnight that'll bring cooler air. Our next shot at rain will be early to mid next week but right now I don't think we'll see much.

Have a good end of the week and a great weekend, it should be a nice one.

Chris

Last Update on Delta and 7 Day Outlook

October 8, 2020

This will likely be my last post about Hurricane Delta. The storm is strengthening and is expected to make landfall tomorrow evening as a strong category 2 or category 3 hurricane. Unfortunately it looks like it will heavily impact the people that are still just beginning to recover from Laura.

Below is the severe weather outlook through Sunday morning. The details will change over the next few days, but expect there to be damaging wind and tornado threats as Delta approaches the coast and heads inland. No specific hazard probabilities are given for day 3 (Saturday) but I expect we'll see 2-5% wind and tornado areas when the day 2 outlook is issued for Saturday late tonight. The threat is expected to diminish as Delta's wind weakens but we could see this expand into Tennessee for Sunday overnight to Monday morning but that's unclear at this point.

The other threat from Delta will be excessive rain and you can see how that is expected to evolve below. I think most of the main hazards, rain and severe weather, will stay to the west of our area.

Since I'm into animations today, here is how other weather features will progress through next week. Most notably (other than Delta of course) is the front that moves through early in the week and also at the end you can just see the next front coming down through the midwest on Thursday. We'll probably see a little bump of cooler air with the first front midweek but it is the second that has a better chance of bringing in cool air around next weekend. Below the fronts animation is our expected rainfall for the next seven days and then the seven day total, you'll see that not much rain is expected once Delta clears out.

Long term in the tropics there are still a few model signals showing possible development in the Caribbean late next week. Again there's nothing definite to speak of, but hurricane season is not yet over.

I'll let you know if the severe weather threat starts to look more concerning, otherwise I'll send out the next update Tuesday or Wednesday. For those that don't know or don't remember, all of these emails are posted to my blog: https://www.deepsouthwx.com/ with links posted on Twitter (@DeepSouthWXU) and Facebook. There's also weather links, radar, and many of the maps I used today on there. When I get to it I'll add some more stuff.

Have a good end of the week and a great weekend.

Chris

Wednesday Hurricane Delta Update

October 7, 2020

Hurricane Delta made landfall near Cozumel and Cancun Mexico early this morning, as a strong category 2 storm is my guess, and it will soon move out over the Gulf of Mexico. Thankfully, Delta's wind speed decreased steadily overnight up until landfall. Delta's future over the Gulf is about the same although models aren't showing quite as much restrengthening and the forward speed has increased a little. Delta is forecast to be a mid category three storm by tomorrow evening and to maintain this strength until it is close to making landfall on the central-western Louisiana coast around Friday afternoon.

As Delta progresses inland Friday and through the weekend there will likely be effects across much of Alabama, especially the central to northern areas, the western Florida Panhandle, and all of Tennessee. Localized heavy rain, gusty winds, and isolated tornado threats will be the main concerns. The National Weather Service will start to highlight any specific risks and risk areas over the next few days.

In the long term, we may need to watch both the Caribbean and the Atlantic off the southeast US for tropical development starting mid next week into the early part of the following week. There's no strong signals at this point but there are some hints at development in these areas. 

This will be it for me for today unless something changes unexpectedly.

Chris

Tuesday Evening Update on Hurricane Delta

October 6, 2020

Hurricane Delta is now a strong category 4 hurricane with 145 mph winds. It is forecast to continue to strengthen to 155 mph in 12 hours, just shy of category 5 strength. The NHC's forecast only covers 12 hour intervals so it's possible Delta could be even stronger at landfall, this possibility is being hinted at by several models. Only 36 hours ago, Delta was a 35 mph tropical depression. That is a 110 mph increase in a day and a half! Rapid intensification like that is extremely rare with only 1 or 2 other storms in the last 50 years gaining that much strength in such a short period of time. The forecast continues to be one where Delta weakens some after making landfall in Mexico, followed by reintensification to category 4 strength, followed by some weakening before landfall in the US. I think we may not know exactly how the final weakening phase will play out until we start to see it happen, although models are in agreement that weakening should occur. The NHC is also reporting the wind field is expected to grow in size as it approaches the coast so even with weakening this will be a significant wind and storm surge event.

The track has shifted to the west slightly again. Now that landfall on the US is within about 72 hours, the forecast cone has narrowed considerably, and I think those of us in Florida can breathe easier. The spread on the track models is about the same as or narrower than the cone (depending on the model) so we can start to feel fairly confident that landfall will be somewhere along the central to central-western Louisiana coast late Friday or early Saturday.

There's not much else to report this evening. My heart goes out to the people in Mexico, a lot of you know what it's like to experience what they are about to go through. Delta will then come close to hitting where Laura made landfall earlier this year...

Have a good evening.

Chris

Delta Now A Strong Hurricane, Continuing to Strengthen Rapidly

October 6, 2020

Hurricane Delta is a strong category 2 hurricane this morning with 110 mph winds, 1 mph away from a category 3. Yesterday I was wrong in thinking that the intensity forecast wouldn't increase beyond category 3 strength. I think the situation is changing so quickly that the models were having trouble keeping up. Delta is forecast to be at category 4 strength with 130 mph winds as it approaches its first landfall on the Yucatan Peninsula tomorrow. I think we may see this increase with the full advisory at 11 a.m. EDT. The language from the 5 a.m. EDT advisory is sobering:

"The hurricane is in the midst of a very impressive rapid intensification episode, having strengthened over 50 kt during the  past 24 hours.  I honestly don't see much that will stop it until it reaches Yucatan..."

You don't see language like that very often from the NHC. The storm is expected to weaken some over Mexico, but then quickly regain category 4 strength over the Gulf. The HWRF model, which the NHC mentions in their 5 a.m. discussion as being a good performer this year, has the storm intensifying to nearly 140 mph over the open Gulf. I think we'll see the intensity forecast for this portion of the track increase as well. The storm is still expected to weaken prior to landfall, with winds forecast in the 100-125 mph range, but I think the details of this are still a bit uncertain.

The track forecast is largely the same, it did shift slightly west a little earlier this morning. I'd be surprised by a large track shift at this point and I think we'll see the landfall point narrow down this evening and overnight. Even so, if you think you may need to prepare for this storm the clock is ticking.

That's it for this morning. I'll send out another update after the 5 p.m. EDT advisory. We'll have two more model runs by this evening and more hurricane hunter data. Hopefully by then there will be a feel for what the ceiling is on the intensity.

Have a good day.

Chris

Monday Evening Update on Tropical Storm Delta

October 5, 2020

As of the 5 p.m. EDT advisory, Tropical Storm Delta is now a 70 mph storm, 4 mph from hurricane strength. The NHC is calling for rapid intensification with the forecast now up to 120 mph 36 hours from now, a mid category 3 storm. It seems the caveats on the intensity forecast I mentioned this morning are being realized. I don't expect the intensity to go up too much more at this point, but the situation is still evolving rapidly. The track forecast is a bit west with this update. The model spread has increased beyond three days, so the NHC mentioned that the uncertainty in the long term has increased as well. I think it will be this time tomorrow or late Wednesday morning before the landfall point starts to narrow down. Delta is forecast to weaken to 100 mph near landfall, but keep in mind that a 100 mph storm that was 120 mph a day before can have a larger storm surge than a storm just reaching 100 mph strength. Regardless of the exact strength, significant wind and storm surge damage is expected. 

That's it for now. The next full update will be at 10 p.m. CDT.

Have a good evening.

Chris

Monday Morning Update on TD 26

October 5, 2020

Note: TD 26 was upgraded to Tropical Storm Delta as I was writing this. While I included the correct forecast map showing the change, I didn't notice the change and thus my discussion refers to the storm as TD 26 throughout.

This morning I've had a chance to take a better look at Tropical Depression 26. The biggest change overnight has been a fairly large shift to the east for the later portion of the forecast track. The storm is expected to head northwest through at least midweek but Gamma could cause a jog to the west at some point. The NHC seems almost surprised at how good the track agreement is between the models. This is good news in light of what we've seen with other storms. There's still some uncertainty on where a strong core will form, which is expected sometime today, and also uncertainty regarding how 26 will interact with Gamma. Both of these could cause shifts in the short term track. Beyond midweek an approaching upper level trough will cause 26 to turn north and then northeast. Where 26 is when this occurs will determine the landfall point.

The intensity forecast is about the same, which shows the storm achieving category 2 strength by day 3 but then weakening prior to landfall. Near shore the Gulf has cooled a bit and this combined with the possibility of increasing wind shear is expected to cause the storm to weaken. There are a few caveats to this however. First, if TD 26 gets its act together quickly today, we could see some rapid strengthening before it has even reached the Gulf. If it can form a good core soon there's not much to limit it in the Caribbean. Second, if it is moving fairly quickly when it reaches the cooler water in the northern Gulf, it may not be impacted much by the lower temps. Third, if there is wind shear, the storm will likely be moving with the shear, this can lessen or even negate the effects it could have on the storm if the shear isn't very strong. The good news is that this morning I'm not seeing any strong model signals that show an intensity above the NHC forecast but we need to watch how this evolves.

Unfortunately the central Gulf Coast is going to be impacted by yet another hurricane. It'll be another day or two before the cone at the landfall point starts to narrow down so if you're in the cone start thinking about preparations. Keep in mind the cone only covers 2/3rds of historical track errors so a track outside the cone is always possible as we saw with Sally. We will see the track bounce around like always but I don't expect any major shifts, we all know how quickly things can change though.

That's it for this morning, have a good week and stay safe.

Chris

PTC 26 Forms in the Caribbean

 October 4, 2020

PTC (Potential Tropical Cyclone) 26 has formed in the Caribbean. The PTC designation is given to systems that are expected to be TCs (tropical cyclones) soon so that the NHC can start issuing advisories for them before they are "officially" TCs. It is expected to become a tropical depression and then a tropical storm in the next 24 hours. Four days out it is forecast to be a category 2 hurricane with 100 mph winds with some weakening possible prior to landfall. You can see the forecast cone below. I haven't had a chance to dig into the forecast, but I understand there's good confidence in the track out to 3 days with increasing uncertainty beyond that.

Since Gamma is still out there I've included the cone for it below, but I think PTC 26 is considered the greater threat to the US at this time. It'll be interesting to see how these two systems in the Gulf will interact with each other.

Here's the 5-day tropical outlook. The yellow areas in the Atlantic aren't expected to be threats to land. 

I'll send out a better update on PTC 26, soon to be named Delta, tomorrow morning.

Chris

Tropical Weather Update

October 2, 2020

Synopsis: I wrote a bit more than I thought I would, so here's a summary: The first system will probably develop into a tropical depression or tropical storm and *could* be a threat to southwest Texas next weekend or the following week, it could also just dissipate over land. The second system needs to be watched also but there's so much uncertainty that it might be mid week before we have a better idea what will happen, if it even develops. Outside the tropics the weather should be mostly nice and boring in the deep south through the coming week.

Here's the 5-day tropical outlook:

The northwest Caribbean continues to be the area to watch for tropical development. The area we've been watching all week now has a 90% chance of development and it is expected to become a tropical depression or tropical storm today or tonight. The future of this system is a bit uncertain. If the storm stays weak in the near term, as is expected, it will continue to move slowly west-northwest and then more westerly. If it were to somehow strengthen significantly, steering currents for a stronger storm could pull it to the northeast across western Cuba and south Florida. As I mentioned, this is not expected. If we go out a few more days to mid week what happens depends a lot on land interaction with the GFS and ECMWF split nicely between two scenarios. The GFS hooks the system to the north around the Yucatan Peninsula and into the Bay of Campeche, avoiding nearly all land interaction. The GFS then has a hurricane form that moves off towards the US/Mexico border late next week or weekend. The Euro takes the system squarely across land where it dissipates over Central America. These aren't the only possibilities but they represent the spread of possible outcomes fairly well. Regarding which will occur is uncertain and depends on where the storm center forms and how strong it is before it gets near land. There is also a front draped across the area with dry air to the north, any developing system is going to have to fight off this dry air.

The next tropical wave, now located more or less south of Puerto Rico has a 30% chance of development over 5 days as it continues west. The general consensus is that this system has the greater potential down the road but a lot of uncertainty remains. Levi Cowan of Tropical Tidbits mentioned last night that this wave could actually split with one piece going north of the Greater Antilles and another going west through the Caribbean. He called the overall situation with this "complex." The current run of the GFS doesn't develop this at all. Because it develops the first system, the outflow from that storm creates unfavorable conditions for the second wave. The Euro brings the second system into the Bay of Campeche late next week where it starts to develop, that is where the model run ends at 240 hours out. As mentioned it has the first system dissipating so favorable conditions are left behind. The ensemble guidance is a bit hard to interpret because there are many runs of two different systems in the same vicinity at the same time. The Euro ensemble has 51 members and the new GFS has 31 so with two systems there is a lot going on looking at one map. The Euro ensemble generally supports the operational model keeping the first system weak and developing the second system in the southwest Gulf. The GFS ensemble has both strong and weak solutions for the first storm so looking out mid to late next week the Gulf is a mess of potential solutions between both systems. It might be mid week before we start to have a better idea what is going to happen and we need to see what the first system does to forecast the next system.

Up here in the mid-latitudes we should have fairly benign weather through most of the coming week (assuming nothing tropical comes our way...). Near the coast we could see some rain Tuesday or Wednesday as some tropical moisture gets pulled up from the Caribbean. Temps should warm by mid week and then we may see a dip by the end of the week and possibly some rain as a front comes through. As a follow up, the last two days where there was a chance of severe weather were a bust. On 9/24 there wasn't a single storm report. On 9/28 there was one wind report in eastern Tennessee.

That's all I have for today. I'll send out another update in the first half of next week. Have a good Friday and a great weekend.

Chris