After a night where there were a few hints that Tropical Depression 19 may have been knocking on the door of Tropical Storm strength, it remains a Tropical Depression this morning. Though, it likely won’t be one for long. It is slated to be a Tropical Storm by tomorrow.
Right Now
Here is a look at the Water Vapor imagery of the Gulf. The red circles are identifying the two tropical systems worth watching in th Gulf. I’ve added in some arrows (magenta) pointing out the wind direction in the mid-levels. This is providing a bit of the steering current. The whitelines would be the “gateway” north for the system given the current overall setup. The red circles are identifying the two tropical systems worth watching in the Gulf.
On a slightly more zoomed-in view over on the infrared, you can see how the convection around the center has really blossomed overnight.
There is also some good venting occuring on the east side of the system.
The wind radii estimates show some collection of higher wind speeds on the northern side of the system.
From the NHC
Before we get into any model data,though, I want to start with the latest from the National Hurricane Center…
SUMMARY
LOCATION…25.6N 81.5W
ABOUT 40 MI…65 KM SSE OF NAPLES FLORIDA
MAXIMUM SUSTAINED WINDS…35 MPH…55 KM/H
PRESENT MOVEMENT…W OR 280 DEGREES AT 9 MPH…15 KM/H
MINIMUM CENTRAL PRESSURE…1004 MB…29.65 INCHES
DISCUSSION AND OUTLOOK
At 1100 AM EDT (1500 UTC), the center of Tropical Depression Nineteen was located near latitude 25.6 North, longitude 81.5 West. The depression is moving toward the west near 9 mph (15 km/h), and a turn toward the west-northwest is expected later today. A west-northwestward or northwestward motion with a decrease in forward speed is then expected during the next couple of days. On the forecast track, the center is forecast to move over the southeastern and eastern Gulf of Mexico later today and Sunday, and then move over the north-central Gulf of Mexico Sunday night and Monday.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts. Strengthening is expected when the center moves over the Gulf of Mexico, and the depression is expected to become a tropical storm later today or tonight, and continue to intensify Sunday and Monday. The system is forecast to become a hurricane by late Monday.
The estimated minimum central pressure is 1004 mb (29.65 inches).
HAZARDS AFFECTING LAND
WIND: Tropical storm conditions are possible in the watch area in the Florida Panhandle by Sunday night. Wind gusts to tropical-storm force are possible across the southern portion of the Florida peninsula today.
RAINFALL: Tropical Depression Nineteen is expected to produce total rainfall of 3 to 6 inches with isolated 8 inch amounts over the Florida Keys through tonight with 2 to 4 inches and isolated maximum amounts of 6 inches across southern Florida and the western Florida coast to the Tampa Bay metro area. This rainfall will produce flash and urban flooding across southern Florida and prolong high flows and ongoing minor flooding on rivers across Central Florida.
The depression is expected to produce through Tuesday rainfall of 3 to 6 inches with localized amounts of 8 inches along the Gulf Coast from the Florida Peninsula to southeast Louisiana Sunday and 2 to 4 inches farther inland over far southern Alabama, Mississippi and southeast Louisiana. This is expected to be a slow-moving system
that will likely continue to produce heavy rainfall and considerable flooding near the central Gulf Coast through the middle of next week. Flash, urban and rapid onset flooding along small streams and minor to isolated moderate flooding on rivers is likely.
SURF: Swells are expected to spread northward along the west-central coast of Florida and the Florida Panhandle during the next couple of days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
TORNADOES: A tornado or two is possible today and tonight over southern Florida.
FORECAST POSITIONS AND MAX WINDS
INIT 12/1500Z 25.6N 81.5W 30 KT 35 MPH
12H 13/0000Z 26.2N 83.0W 35 KT 40 MPH
24H 13/1200Z 27.1N 84.8W 40 KT 45 MPH
36H 14/0000Z 28.0N 86.4W 50 KT 60 MPH
48H 14/1200Z 28.7N 87.6W 60 KT 70 MPH
60H 15/0000Z 29.3N 88.5W 65 KT 75 MPH
72H 15/1200Z 29.8N 89.1W 70 KT 80 MPH
96H 16/1200Z 30.6N 89.9W 55 KT 65 MPH…INLAND
120H 17/1200Z 32.0N 89.5W 30 KT 35 MPH…INLAND
KEY MESSAGES
1. The depression is forecast to strengthen to a hurricane early next week as it moves across the northeastern Gulf of Mexico, and there is an increasing risk of life-threatening storm surge and dangerous hurricane-force winds from southeastern Louisiana to the Alabama coast. Residents in these areas should closely monitor the progress of this system and updates to the forecast, as Storm Surge and Hurricane watches will likely be issued later today.
2. The depression is expected to produce flash flooding across portions of southern Florida and prolong existing minor river flooding across central Florida through Sunday. Flash, urban, and minor to isolated moderate river flooding is likely across portions of the central Gulf Coast Sunday through Tuesday.
3. Tropical storm conditions are possible by Sunday night in portions of the Florida Panhandle, where a Tropical Storm Watch is in effect. Wind gusts to tropical-storm force could occur over portions of the southern Florida Peninsula today.
Model data
When looking at the forecast data, I know everyone wants to see the spaghetti models. They are a quick and easy way to get a good idea about where a system may head. But there are some “under the hood” things you may be interested to look at first, to give you a better idea about which spaghetti model – or cluster of models – is more likely to be accurate.
Sure, I could simply tell you which one is which, but what is the fun in that?!
First thing I want to show is the 500mb vorticity map from the 00z GFS for Monday afternoon. The big red splotch just off of the Mississippi and Alabama coast is Tropical Depression 19 – likely a Tropical Storm by that point.
The black lines (some of which I’ve made thicker to showcase where they are) are something called geopotential heights. And while I won’t spend time right now breaking that down, just know that these lines are equal lines of air pressure and can usually give you a good estimation of wind direction (the air follows the lines) and speed (the close the lines are together, the stronger the wind).
I’ve added in the magenta arrows again to show which direction the wind is moving.
Notice that by Monday afternoon the wind near Tropical Depression 19 is going to pushing and pulling at it. Perhaps nearly equally at times. That means the “current” involved with “steering” the storm will become almost balanced out according to this model run. That is why the forecast from the NHC is for Tropical Depression 19 to slow down as it approaches land. The wind that is steering it doesn’t really steer it much anymore.
This slowing is reflected in most of the models used in the spaghetti plots, too.
Notice that the lines show a “48 hour” tick just south of Panama City, meaning that by Sunday night it will be (pretty far south) off the coast of Panama City. But it takes another 48 hours for it to move from that point to near New Orleans.
This could be a problem. Because a slow moving system over the open waters of the Gulf of Mexico is likely to do two things: strengthen and rain.
Intensity forecasts this early are still not – exactly – the best. But I wanted to share it because I think it still highlights something important.
There is some spread within the data, but notice that there is some strengthening through the next 48-to-60 hours, but then it continues to strengthen and plateaus and the holds there for nearly 24 hours in some of the guidance. That is likely an indication that the system is stalled out near land, but still over water. We can estimate this because if it were on land, it would be weakening. And if it were fully over water, it would likely continue to strengthen given the favorable environment.
But in this case, it will be close to land, so ithe models suggest it should – should is the key word – be more difficult for Tropical Depression 19 to continue to strengthen.
It is interesting to note, though, that the SHIPS model does still peg Tropical Depression 19 with a 16-percent chance of Rapid Intensification during the next 72 hours.
That would put it as a Category 1 or even Category 2 Hurricane near the Louisiana / Mississippi / Alabama coastline in 72 hours.
Not a “big” chance. But also not small, either. The chances are still more than 3.1 times higher than the climatological average.
The Gulf Waters
Now, what about the water? It is warm. And TD 19 is forecast to, unlike Marco, slide around the coldest water in the Gulf.
The map above shows where the “heat content” is the highest in the Gulf. And Tropical Depression 19 will be moving over some of the most voluminously-warm waters as it emerges into the Gulf. And it will ride along the periphery of the not-as-warm waters as it moves toward Louisiana / Mississippi / Alabama next week.
The 26C isotherm that I’m always talking about has a little thumb that is poking up in roughly the same spot.
Notice the 26C isotherm doesn’t show the “not-as-warm” area quite as brightly. This is an indication, perhaps, that while the overall heat content may not be as high, it is still high enough for tropical development.
What does this mean for where I live, Nick?
Specifics are still limited, but the main concerns for everyone will be rain. A lot of rain, possibly. With flash flooding. Beyond that, people closer to the coast will also have to deal with wind and. potentially. storm surge.
Florida panhandle
Timeline: Sunday – Tuesday
1. Heavy rainfall is expected to produce isolated flash flooding from Tallahassee back to the west. Up to 10 inches of rain may be possible closer to the coastline. Up to 7 inches inland.
2. Tropical storm conditions are possible by Sunday night in portions of the Florida Panhandle, where a Tropical Storm Watch has been issued.
3. The system is forecast to strengthen to near hurricane intensity by early next week as it moves across the northeastern Gulf of Mexico. Dangerous impacts from storm surge, wind, and heavy rainfall will be possible along the Gulf Coast from the Florida Panhandle late this weekend and early next week. Residents in these areas should monitor the progress of this system and updates to the forecast, as Storm Surge, Tropical Storm or Hurricane watches could be issued on Saturday.
Lower Alabama
Timeline: Monday – Wednesday
1. Heavy rainfall is expected to produce isolated flash flooding. Up to 6 inches of rain will be possible, especially closer to the coastline.
2. Tropical storm conditions are possible by Monday and Tuesday, but not likely at this point. Continue to monitor future forecasts for more information.
3. The system is forecast to strengthen to near hurricane intensity by early next week as it moves across the northeastern Gulf of Mexico. There is a chance that tropcial storm force wind may be relegated to closer to the coastline and inland areas may not see as strong of wind.
South Mississippi
Timeline: Monday – Thursday
1. Heavy rainfall is expected to produce isolated flash flooding, despite recent dry conditions. Up to 12 inches of rain may be possible along the coast during this multi-day rain event, depending on how slowly this system moves.
2. Tropical storm conditions are possible. particularly closer to the coastline.
3. The system is forecast to strengthen to near hurricane intensity by early next week as it moves across the northeastern Gulf of Mexico. Please stay tuned for future forecasts.
Southeast Louisiana
Timeline: Tuesday – Thursday
1. Heavy rainfall is expected to produce isolated flash flooding, despite recent dry conditions. Up to 12 inches of rain may be possible in some locations.
2. Tropical storm conditions are possible. particularly closer to the coastline.
3. The system is forecast to strengthen to near hurricane intensity by early next week as it moves across the northeastern Gulf of Mexico. Please stay tuned for future forecasts.
Please know that this information may change. Perhaps drastically. So it is very important that you continue to check back for forecast updates.
The Bottom Line
If you live along the coastline between Morgan City, Louisiana and Pensacola, Florida. Or within 75 miles of the coast between those cities, please keep tabs on the forcause for future updates. The National Hurricane Center will continue to refine the forecast and the Hurricane Hunters will likely be flying into the system during the next 24 to 48 hours to get more data and make the forecasts even more accurate.
But since this system formed so recently, there are still a fair amount of unknowns.
What we do know is that this will be a slow moving system. There will be flooding in some areas. The wind will be a concern for some, too. And surge may be an issue along the coast.
