Northwest Florida Weather (1-3-2017) - A 4-Letter Word, and A Word of Caution

After dealing with severe weather on Monday (which included 4 fatalities in Rehobeth, Alabama), we are looking ahead to the next system. Unfortunately, this system is incredibly complex, and brings with it the 4-letter "S"-word that causes uproar in the South and strikes fear and joy alike in the hearts of its residents.

That's right... SNOW.

12Z (6 AM CST) run of the GFS valid for 6 AM Saturday morning showing precipitation type and rate. Image from TropicalTidbits.com

12Z run of the GFS showing accumulated snowfall through 12Z (6 AM CST) Sunday. Image from TropicalTidbits.com

Now, if you've been browsing Twitter or Facebook, you may have seen an image similar to one of the images I posted above. Unfortunately, many see this map and take it at face value. However, there are several things you need to consider before taking this map for what it's worth. Don't get me wrong, maps like this are useful, but only if they're used correctly.

It's Not All Snow

One big problem with the GFS is that it cannot tell the difference between snow, sleet, freezing rain when totaling up snow accumulation. So, it's hard to know exactly how much snow will fall, how much sleet will fall, or how much ice will accumulate. Thus, totals are often inflated more in these messy mixed-precipitation events. To determine our precipitation type (abbreviated P-Type from here on), we have to look at one of my favorite things, a skew-T.

Skew-T taken from the GFS model near Montgomery, Alabama, for 6 AM Saturday. Thin red line is the temperature through the atmosphere, and the thin green line is the dew point profile. This skew-T (and the next 4) is from pivotalweather.com, with my annotations drawn.

So, allow me to explain this as briefly as I can. We have to start in the mid-levels of the atmosphere to see if there is enough moisture to produce snow, sleet, etc. We look for where the temperature is between -12 degrees Celsius and -17 degrees Celsius (snow growth region), since that is the optimal ice crystal growth area. If that has enough moisture, then we can assume that ice crystals can/will form. In Montgomery's case, it's completely saturated in the snow growth region. Proceeding downward in the atmosphere, we look for any layers that are above freezing (0 degrees Celsius) that could melt the ice crystal. In this case, there aren't any. Next, we look at the surface temperature to see if it's below/at/above freezing. For Montgomery, the GFS says that it is below freezing. Thus, the ice crystal never melts, and the P-Type is likely snow.

This skew-T is from Evergreen, Alabama, valid at 6 AM Saturday. As with Montgomery, the snow growth region is forecast to be completely saturated. Further down in the atmosphere, there is a slight warm layer that is above freezing. This will allow for some melting, but not enough to fully disrupt the ice crystal. It then passes through a sub-freezing layer, which refreezes the partially-melted crystal. The surface temperature is forecast to be below freezing. All things considered, the likely P-Type is sleet (ice pellets).

This skew-T is from Andalusia, Alabama, at 6 AM Saturday. As with the previous 2 soundings, the snow growth region is completely saturated. However, there is a deeper warm layer that warms to about 1 or 2 degrees Celsius. This may be enough to completely melt the ice crystal. It then passes through a shallow sub-freezing layer. If it only partially melts, it may refreeze and fall as sleet. If not, then it will either be freezing rain or just rain. The surface temperature is forecast to be at or just above freezing. If the surface temperature is at freezing, then the likely P-Type will likely be sleet (if it refreezes just above the surface) or freezing rain (if it melts completely). If the surface temperature is above freezing, then the P-Type will be plain old rain

Crestview and Destin are very similar to each other on the skew-T's. Both have lower moisture in the snow growth region. If anything forms, ice crystals in both locations pass through a substantial warm layer, which will melt any ice completely. Both soundings have little to no sub-freezing layer, so no refreezing will occur. Also, both locations have forecast temperatures above freezing. So, according to this, the P-Type for both locations would be (a very cold) rain.

So that covers precipitation type, but there are two more things that I want to cover.

Run-to-Run Inconsistency

An animation showing the last 12 runs of the GFS valid for 12Z (6 AM CST) Saturday. Animation from TropicalTidbits.com

One thing we meteorologists look for is some form of consistency in the models from run-to-run. The more it stays the same, the more confidence we can have in the forecast. Over the last 12 runs (3 days), the system that is forecast to impact the Southeast this weekend has jumped all over the place from run to run, which raised questions about what would actually happen. Only in the last few runs has it become more consistent, and confidence has increased a bit. Being 4 days out, changes are still possible, so we can't take any one run of any one model and run with it. We have to watch for consensus among the models and consistency within the models.

Know Your Sources

With the advent of social media, anyone (and I mean anyone) can get online and post a picture of a computer model. However, the difference is the explanation behind it. Now, I know some people who post these things are truly fascinated in the weather and possibly want to pursue their dreams. I know that they want to be like the meteorologist he/she admires. I think all of us meteorologists were there at some point, trying to mimic what our favorite meteorologist did. Others, however, do it for the hype behind it. They try to get as many likes or shares on Facebook and Twitter as they possibly can by using clickbait and over-exaggeration to get people to see it and believe them. I recommend that, if you see a post that you aren't sure about, ask a meteorologist who will have more insight on the situation. I can guarantee you we are looking at the same things you are and that they are. Just be careful who your sources are. I wrote a piece on this a while back when talking about the tropics, but it still applies. Read it here.

So, for the TL;DR (too long; didn't read). It looks increasingly possible that wintry weather could impact the Southeast. However, be wary of model snow maps as they are not always what they seem. Also, know your sources, and make sure you trust them enough to provide you with important information.

I do not think we will see much, if any, wintry precipitation in Northwest Florida at this time. If any were to occur, I think it would likely be in the form of freezing rain, especially closer to Century and Jay. The GFS Ensembles valid at Eglin AFB, Florida, only gives a 5% chance of measurable freezing rain (shown below). But, the forecast can (and probably will) change, and I will update my Facebook and Twitter to account for any changes.

from: http://www.emc.ncep.noaa.gov/mmb/cguastini/gefs/EMCGEFSplumes.html

Definitely Active in the Tropics

We've had quite a bit of hype from several sources about former-Invest 99L, but shortly after we got a tropical depression upgrade in the Florida Straits (more on that later), articles like this started popping up.

And this comes from a reputable news source! Several meteorologists, storm chasers, and others quickly squelched this article, and NBC Nightly News quickly removed the tweet. But this just shows you, watch where you get your information from! Even reputable news sources are guilty of posting these articles. It's a classic example of fearmongering and clickbaiting. Just beware! You can read my post about over-hyping here.

Now that that's out of the way, let's move forward with the tropics, as there really is a lot going on.

Our first stop takes us to the central and eastern Pacific. Why out here? Well there are potential threats to Hawai'i over the coming days. We will start with the closes storm to Hawai'i.

MAJOR HURRICANE MADELINE

This is Madeline churning over the central Pacific. Here's the latest from the National Hurricane Center:

SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.6N 145.5W
ABOUT 630 MI...1015 KM E OF HILO HAWAII
ABOUT 825 MI...1330 KM E OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...966 MB...28.53 INCHES

Madeline is a Category 3 Hurricane moving to the west-northwest. A Hurricane Watch is in effect for the island of Hawai'i. Gradual weakening is expected, and Madeline is expected to pass near the island of Hawai'i as a gradually weakening hurricane.

Models are a bit spread as Madeline approaches Hawai'i. Right now, if it makes landfall, it would likely be on the island of Hawai'i. But there is a good amount of guidance that takes it further south. Either way, heavy rain, gusty winds, and increased surf are possible with Madeline.

MAJOR HURRICANE LESTER

This is Hurricane Lester in the eastern Pacific, well away from any land right now. Here's the latest from the National Hurricane Center:

SUMMARY OF 200 PM PDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...18.0N 130.5W
ABOUT 1375 MI...2210 KM W OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...951 MB...28.09 INCHES

Right now, Lester is a strong Category 4 major hurricane. Intensity forecasts show that Lester will start to weaken as it approaches Hawai'i, but still keeping it a hurricane. The projected path brings it closer to Hawai'i in 5 days as a hurricane.

In the long range, the models tend to keep Lester north of the Hawaiian Islands. However, yet again, heavy rain and increased surf will be the main threats. Now, if either Lester or Madeline make landfall on any of the Hawaiian Islands, it would be the second tropical cyclone to make landfall (Darby was the first in July).

Now, let's move to the Atlantic.

DISTURBANCE IN THE NORTHWEST GULF OF MEXICO

A weak area of low pressure near the Texas coast will wander southwestward, but it should not develop. Heavy rain will be the main threat in southeastern Texas. The latest outlook from the National Hurricane Center says:

A weak trough of low pressure located just offshore of the central
coast of Texas is producing disorganized showers and a few
thunderstorms over the northwestern Gulf of Mexico and adjacent
coastal areas.  Proximity to land and only marginally favorable
upper-level winds are expected to inhibit development while the
system drifts southwestward during the next day or so.  For
additional information on the rainfall associated with this system,
please see products from your local National Weather Service office.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...low...10 percent

HURRICANE GASTON

At 4 PM CDT Sunday, Gaston became the first major hurricane (Category 3 or higher) of the 2016 Atlantic Hurricane Season. It has weakened a bit since then. Here's the latest from the National Hurricane Center:

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...31.2N 55.2W
ABOUT 570 MI...915 KM E OF BERMUDA
ABOUT 1665 MI...2675 KM W OF THE AZORES
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...NNE OR 30 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...968 MB...28.59 INCHES

Gaston is a strong Category 2 hurricane, and it's expected to slowly weaken back to tropical storm status as it approaches the Azores this weekend.

Models are in pretty good agreement through the next several days as Gaston makes that turn toward the northeast. The only threat to land could be the Azores late next week, but a lot can change between now and then.

TROPICAL DEPRESSION EIGHT

Well, Tropical Depression Eight is encountering some strong shear, leaving the system lopsided. The shear is going to help keep TD 8 in check. Right now, here is the latest from the National Hurricane Center:

SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...33.6N 74.0W
ABOUT 140 MI...225 KM SE OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.86 INCHES

Tropical Storm Warnings are in effect for the Outer Banks of North Carolina from Cape Lookout to Oregon Inlet and also for Pamlico Sound. A Tropical Storm Warning means that that tropical storm conditions (sustained winds of 39 mph or greater) are expected within the next 36 hours. However, even if TD 8 doesn't make landfall, most of the showers and storms will be on the west side of the system. Also, it appears that TD 8 will not become a particularly strong tropical storm. But, heavy rain, rough surf, and deadly rip currents will be possible for portions of coastal North Carolina.

Anything after 72 hours is the result of TD 8 losing its identity and merging with a front. But, models are in decent agreement about bringing TD 8 close to the North Carolina coast before being swept out into the far north Atlantic.

TROPICAL DEPRESSION NINE

After about 11 days of tracking this system as Invest 99L, it finally became a tropical depression Sunday afternoon after the Hurricane Hunters found that former-99L had a well-defined closed circulation. Now, that does not mean it's well-organized. It has been battling wind shear, but that is starting to subside as TD 9 moves into the Gulf of Mexico. Right now, the main thing that TD 9 is battling is some dry air. Here's the latest from the National Hurricane Center:

SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...24.0N 84.8W
ABOUT 195 MI...310 KM WSW OF KEY WEST FLORIDA
ABOUT 160 MI...260 KM WNW OF HAVANA CUBA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

The National Hurricane Center notes that a Tropical Storm or Hurricane Watch may be required for a portion of the Florida Gulf Coast. Now, TD 9 actually took a dive to the west-southwest Sunday evening as it was interacting with Cuba. Most of the time, land is not a good thing for tropical cyclones. But sometimes, it can help the circulation a bit. With the friction caused by land, TD 9's circulation was able to tighten up on the southern side and convection to flare up on the southern side of its circulation. This allowed for TD 9 to move a bit more to the west-southwest. But, it has since started moving toward the west. Eventually, TD 9 is expected to turn more toward the northwest and then to the north. Then, a cold front (the same one expected to sweep away TD 8) will cause TD 9 to turn toward the northeast. Where and when all these turns occur will ultimately determine where TD 9 will make landfall. The current forecast from the National Hurrican Center calls for a strong tropical storm to make landfall somewhere between Port St. Joe and Sarasota.

These are the possibilities of seeing tropical storm force winds (sustained winds greater than or equal to 39 mph). Right now, the best chance looks to be between Port St. Joe and Tampa. Again, a lot can change between now and Thursday (when this could make landfall).

Let's look at the models and see what they're saying:

The one thing that models agree on is that TD 9 will eventually turn toward the northeast, but they greatly differ on when that turn will occur, so the models are really spread from Pensacola to Fort Myers. Again, still need to watch this system anywhere in Florida.

Let's look at our two most reliable models (GFS and ECMWF):

This is the 12Z (7 AM CDT) run of the GFS from Monday morning. This run is generally in the middle of all the guidance, but may have trended a touch north with a landfall southwest of Perry as a tropical storm. Again, this is just one run of one model. But let's look at the ECMWF.

The ECMWF is stronger than the GFS, but essentially the same track. However, the ECMWF, like the GFS, also has trended just slightly more west and north compared to the last run. And this slight shift westward can be seen in our model ensembles.

Ensembles (in this case, the GEFS) are the same model (in this case, the GFS) run with slightly different initial conditions. These alterations in the initial conditions help provide a range of possibilities. On the map above, all of the tiny red numbers near the Florida Panjandle are different positions for TD 9. There is a bit more cluster near Panama City and Apalachicola. This is just something to monitor as we go forward in time.

Note that even a strong tropical storm can cause storm surge issues in the Big Bend of Florida. That area is one of the most storm surge prone areas in the United States. The storm is likely to be lopsided due to some shear, so most of the impacts will be felt on the eastern and southeastern side of the system. Heavy rain, gusty winds, dangerous surf, elevated tides, some storm surge, and deadly rip currents are all possible threats which will be fine tuned as we move forward.

TROPICAL WAVE COMING OFF OF AFRICA

There is a pretty strong tropical wave coming off the coast of Africa into the tropical Atlantic and moving near the Cabo Verde Islands. This is the latest from the National Hurricane Center:

A tropical wave is expected to move offshore of the west coast of
Africa tonight.  Conditions are expected to be favorable for gradual
development of this system later this week while it moves westward
at 15 to 20 mph over the tropical Atlantic.
* Formation chance through 48 hours...low...near 0 percent
* Formation chance through 5 days...medium...50 percent

The above animations are the GFS (top) and ECMWF (bottom) out to 7 AM CDT September 3rd. Both models generally agree that this wave (probably will be designated Invest 92L) will move westward across the tropical Atlantic. However, it is way too far out to speculate what will happen beyond 5 days.


Now, remember to get all your information from official sources (NOAA, NWS, NHC, etc.). You can find detailed information about watches and warnings from your local National Weather Service office here. The latest tropical cyclone information (and where I got several of the graphics in this blog) can be found here. Follow the direction of your local officials and emergency management for preparation tips and evacuation information (if it becomes necessary). Make sure your emergency preparedness kit is stocked at all times.

Also, credits to Levi Cowan's website for the model graphics.

All Aboard the Hypetrain! Misleading Posts and Clickbaiting

You've NEVER seen this before in your lifetime! Chances are, you have; but it got your attention. While scrolling through your news feed or your timeline, you have probably seen (and clicked on) these "clickbait" articles - you know, those ones where you have to click through 20 pages just to find out what the article was actually about. Well, those articles are usually nonsense and are nothing that directly affects you. But what about the weather?

Some amateur meteorologists or weather enthusiasts ("social media-rologists" as they've been coined) have started making very flippant posts in recent years. Now, that's not to say ALL of these pages are untrustworthy, but it's becoming more common. Even reputable weather sources utilize these "hype" titles ("44 Million People Are At Risk for Tornadoes"). It's becoming harder and harder to tell who actually is a professional meteorologist, and who is just an over-enthusiastic middle schooler that wants to get as many fans as possible. This is especially true when it comes to the page's name. You've got actual pages such as the US National Weather Service (which you should definitely like and follow) or pages such as Red Goat Alert Weather Service of Meteorology that you probably shouldn't trust. (Sorry if you have a page with this title.)

"But, they provide weather for my hometown."

Sure, they may do so, but so do trustworthy sources, such as your local news station and your local National Weather Service office.

"But they provide warnings for storms."

Okay, now, are they issuing their own warnings? Or, are they using National Weather Service warnings? NWS data is the ONLY official source for watches, warnings, advisories, etc. Even news stations strictly utilize NWS for these alerts. If your weather page that you like is issuing their own warnings, that's a big red flag.

"But they told me that a hurricane is going to strike in 11 days."

This is a HUGE red flag! I came across this post this morning on Facebook. The post has since been deleted due to (deserved) backlash from several notable meteorologists and public alike. Chances are (much like this example above) they posted a picture of one model run with a Category 4 hurricane striking either a major city or where you live more than 7 days out. Really, anything past 5 days is not really reliable, and beyond 7 days, it's usually better to lean toward climatology. Also, the models are going to change every time they run. This is the case with the current system in the Atlantic - Invest 99L.

As of 11 AM CDT, the National Hurricane Center (another page you should like/follow) gives 99L a 10% chance of becoming an organized tropical cyclone during the next 2 days, and a 50% chance during the next 5 days. While that means that there is a 50% chance of developing, that also means there is a 50% chance of it NOT developing. Plus, it's still a good 4 or 5 days away from approaching any land whatsoever.

UPDATE: as of 1 PM, the 5-day formation chance was upped to 60%.

Now, there is one thing that the models do agree on, it will likely move west toward the Lesser Antilles. The models also do show that it could possibly become somewhat organized. After 5 days or so, the models widely diverge, both in track and intensity. And when I said widely, I meant anything from Mexico to the Canadian Maritimes. BUT, there is one thing to note: it's not yet an organized system yet. The models typically don't have a good handle on disorganized entities. Not to mention, some models have it too organized or too disorganized to begin their run. All of that and much, much more plays into how a model progresses forward with a storm.

Right now, all you should be doing is monitoring. Don't make a big deal about this unorganized system, yet. Maybe once it gets into the Caribbean, that's when you can start watching it more closely, and hopefully the models will have a better handle on what this system may or may not be,

Regardless of where it moves and how strong it is (or if it even develops), you should always be prepared for a hurricane. Even if a hurricane doesn't strike you, these supplies can also come in handy in other weather situations (thunderstorms, flooding, tornadoes, etc.) or even just a power outage.

All this to say, watch who you get your information from. In general, on Facebook and Twitter, look for the little blue check next to their name. That typically means that they are verified and are trustworthy. Now, that's not always the case (the example I posted toward the beginning actually had a blur check by their name), but it is true more often than not. Official news agencies, official meteorologists, and government agencies are the best sources to follow.

Stay prepared, stay calm, and stay informed.

Useful links:
National Weather Service
Website: http://www.weather.gov
Facebook: http://www.facebook.com/NWS
Twitter: http://www.twitter.com/NWS

National Hurricane Center
Website: http://www.nhc.noaa.gov
Facebook: http://www.facebook.com/NWSNHC
Twitter: http://www.twitter.com/NHC_Atlantic & http://www.twitter.com/NHC_Pacific

FEMA Disaster Preparedness
Website: http://www.fema.gov/disaster/4085/updates/building-supply-kit-your-family