Local Forecasts

There are 153 posts filed in Local Forecasts (this is page 2 of 16).

Latest Spaghetti Plot: Entire Gulf Needs To Remain Alert

Firsthand Weather is keeping a close eye on the Gulf of Mexico this week as the remnants of Tropical Storm Harvey move into the southwestern Gulf. Impacts to the United States are looking more likely–especially for Texas then there’s the potential the remnants may impact additional Gulf States (Louisiana, southern Arkansas, Mississippi, Alabama, and Tennessee), so I wanted to provide a brief post on the latest spaghetti plot with you all.

The National Hurricane Center (NHC) is monitoring the remnants of Harvey (currently crossing the Yucatan Peninsula), and is giving the low a 70% of tropical cyclone development over the next 48 hours and an 90% chance of tropical cyclone development over the next five days. The current analyses show decent spherical vorticity, light environmental shear ahead of the system in the Bay of Campeche, and above average sea-surface temperatures. This should allow the remnants to develop into a tropical cyclone by Wednesday afternoon. It is possible the NHC may label this as a Potential Tropical Cyclone by the afternoon hours today, which would allow local National Weather Service offices to begin issuing weather products (watches) on this system.

Numerical guidance has begun trending further northward over the past few runs. This has shifted the potential track from northern Mexico, more towards the Texas coast. This means the entire Texas coast needs to keep a close eye on future forecasts as confidence continues to increase.

On to the spaghetti:

So what exactly are spaghetti plots? Spaghetti plots are what meteorologists refer to when multiple numerical weather models are shown together. This creates a spaghetti like appearance because the individual model tracks are all plotted on the same image. These plots are important because they can give some insight into where a tropical system may track.

Here is the latest spaghetti plot for the remnants of Tropical Storm Harvey that’s heading towards the Gulf of Mexico. The 12Z guidance is clustering a landfall along the mid-Texas coast. This is a drastic shift northeastward over the past 24 hours. Guidance will continue to need to be assessed to determine if future shifts (northward or southward) are possible.

If you live along the Texas coast, you need to prepare now for potential tropical cyclone impacts. This is a precautionary measure in case impacts are felt late in the week. The other Gulf States should keep a close eye on this system, too, because it is possible it may phase and get pulled into Louisiana and Mississippi.

See yesterday’s article about the remnants of Harvey!

Texas and Southeast Tropical Cyclone Threats?

Firsthand Weather is keeping a close eye on the tropics this week. There are two systems that may impact two separate regions across the United States this week.

Northern Mexico and Texas: Remnants of Harvey (Caribbean)

The first area we are monitoring is the Caribbean, which is where the remnants of Tropical Storm Harvey reside. The National Hurricane Center (NHC) is monitoring the remnants of Harvey, and currently is giving the low a 50% of tropical cyclone development over the next 48 hours and an 80% chance of tropical cyclone development over the next five days. The current analyses show decent spherical vorticity and light environmental shear. The main hindrance from immediate development is the speed at which the low is moving and the close proximity to land. There is likely not enough time, before the system crosses land, to undergo intensification into tropical cyclone status. This intensification may occur later in the week (more details below).

Area Being Monitored (NHC)

850mb Current Vorticity (University of Wisconsin)

Current Environmental Wind Shear (University of Wisconsin)

The remnants will move across the Yucatan Peninsula on Tuesday and cross into the Bay of Campeche (southwestern Gulf of Mexico) by Wednesday morning. While the remnants will likely remain below Tropical Depression/Tropical Storm criteria before moving across the Yucatan, heavy rainfall, rough seas, and gusty winds are possible across this area.

As the remnants move into the Bay of Campeche, environmental conditions appear to become favorable for development into a tropical cyclone. Global numerical guidance is indicating a steering pattern that may be favorable for a northwestern movement. The latest GFS and European have a general landfall between Tampico and Brownsville around Friday. This position would wrap in rich moisture into southern Texas and generate rough seas along the coast. With a cold front likely draped somewhere in the vicinity (southern Texas/central Texas), a flooding scenario could set up. The future intensity of the remnants and how much of a northerly component these remnants will take remain uncertain, but close monitoring is required.

GFS 850mb Vorticity (Friday Morning)

European 850mb Vorticity (Friday Evening)

Spaghetti Plot

Southeast (Florida): Invest 92 L (Atlantic)

The second area we are monitoring is the Atlantic (near the Bahamas), which is where a broad area of low pressure resides. The NHC is monitoring the low and currently is giving the low a 10% of tropical cyclone development over the next 48 hours and an 40% chance of tropical cyclone development over the next five days. The current analyses show a non-symmetrical/elongated vorticity, but environmental wind shear is light. Low-level convergence is also weak currently.

Area Being Monitored (NHC)

850mb Current Vorticity (University of Wisconsin)

Current Environmental Wind Shear (University of Wisconsin)

There is less confidence with this broad area of low pressure, which is visually displayed in the latest spaghetti plots. The timing and movement are big questions. The GFS shows this area of low pressure developing into a weak tropical cyclone (Tropical Depression). The European is not as bullish with tropical development, but shows a low developing with an upper-level trough off of the East Coast. Both scenarios indicate deep moisture being pulled into Florida, which will aid in heavy rainfall.

GFS 850mb Vorticity (Friday Evening)

European 850mb Vorticity (Friday Evening)

Spaghetti Plot

Firsthand Weather will keep a close eye on these two systems over the next few days. As confidence increases in the movement and intensity forecasts, we will provide updates.

Cooldown Coming To Southeast

A change in the upper-level pattern will lead to a noticeable cooldown for the Southeast by mid-week, which will continue into the upcoming weekend. This pattern change has been consistently advertised on the global models, thus, confidence is high in this scenario.

The upper-level changes will send a cold front through the Southeast by mid-week. Behind the front, drier and cooler air will advect into the Southeast; temperatures will be 5-10 degrees Fahrenheit below average from Thursday through the weekend. Highs will drop into the low to mid 80s, with lows dipping into the 60s–a few 50s are possible across the Tennessee Valley by Friday morning. Along with cooler temperatures, humidity levels will decrease, which will make for very comfortable afternoons. The only exception is for areas closest to the coast and Florida. The cool front’s momentum will slow and will struggle to provide much relief for these areas.


GEFS 2m Temperature Anomaly August 24th-29th

GFS Friday Morning Lows

Enjoy the break from the heat!

Cold And Wet Winter Ahead According To Farmers’ Almanac

Enjoy cold and wet weather during the winter? Well, you’re in luck according to the 2018 Farmers’ Almanac, which is predicting a cold and wet winter for much of the continental United States (outside of the West Coast). This is based on a 200-year-old formula used by the Almanac.

According to the Almanac, the Northeast should prepare for cold and snow. Cold and wet conditions will extend further south than the Northeast, too, which may place much of the South in a favorable region for above average wintry precipitation. The Northern Plains can expect cold and snow during the winter, but this region will experience more moderate (near average) temperatures compared to average. The Pacific Northwest will be drier than normal, while the Southwest will see precipitation near average with mild temperatures.

2018 Winter Outlook (Farmers’ Almanac)

Here’s a regional breakdown based on the Almanac:

Southeast:
Temperatures: Below average
Precipitation: Above average

Northeast:
Temperatures: Average
Precipitation: Above average

South-central:
Temperatures: Average
Precipitation: Above average

North-central:
Temperatures: Average
Precipitation: Average

Southwest:
Temperatures: Average to above average
Precipitation: Average

Northwest:
Temperatures: Average
Precipitation: Below average

This is not Firsthand Weather’s 2018 winter outlook, and this does not necessarily represent our views on the upcoming winter season. Firsthand Weather will have a winter outlook out in a few weeks, so keep checking back for details!

Modelcasting versus Forecasting: Why you can’t just use models

Modelcasting has become a big issue in the meteorological world.   Cell phone apps, websites, and even some forecasters simply look at what each individual run of the model shows them and makes that their forecast.  This has led to large changes in some forecasts and led many of you to ask us why the forecast in your local area has gone from rain, to snow, back to rain and then back to snow 22 times in the past 5 days only for the sun to be shining the day of.

The truth is, just as our knowledge of what the weather will do is imperfect, a computer’s knowledge of what the weather will do is just as imperfect.  A human forecaster can use logic to look at a map and realize that something doesn’t make sense.   A computer has rigid equations and programs and follows them to the letter.  It doesn’t matter to the computer if its showing the worst storm ever known to man, if that’s what the programs and equations say goes there, then the computer puts it there.

As trained forecasters, meteorologists are supposed to know better.  We know the model has biases, that the model has errors.  We are well aware that the model is just downright bad at forecasting certain storm evolutions.  This brings me to newly formed Tropical Depression 8, probably better known to many of you as Investigation area 99L.  A little while back in the comment section on an article about then Tropical Storm Franklin, I was asked about TD8 and how the Euro model was showing a stronger system than other models.   I explained then that the GFS was very weak in forecasting the type of system that 99L was and continues to be, with even the 06Z run this morning continuing to show barely any development of TD8 as we’ll see down below.

Reality against the Machine

The image above is the model forecast for early this morning.   The current NHC data shows that TD 8 has a minimum central pressure of 1011 mb while this model data shows a minimum pressure of 1014 mb.  As you can see from the image, it also doesn’t show much convection.

This is where a meteorologist needs to know their models and how those models do and don’t work.  We here at Firsthand have been looking at this system for Tropical development for days and first mentioned that the system might develop in this area in an article back on August 8th.  We did this despite models like the GFS not showing any development because we know of the models weakness and added value to the model based on our own meteorological knowledge.  This added value by the meteorologist is essential in any forecast.  We head to the image below for another example.

modelcasting

This image, which is the model forecast for Monday afternoon, shows no major closed circulation.  Based on the previous image, this image would even indicate that TD 8 is weakening.  However, the forecast from the National Hurricane Center doesn’t call for weakening.  The forecast expects that TD 8 will have been a Tropical Storm with winds between 50 and 60 mph.  Do you see that Tropical Storm on this image?   I certainly don’t.  Modelcasting this storm would be a disaster if you happened to be on a cruise ship in that area.

Finally,  this image shows what’s supposed to be a tropical system on Tuesday the 14th.  The forecast during this time period calls for a strengthening Tropical Storm with the NHC forecast heading up to 65 mph and nearing hurricane strength.   That type of forecast simply isn’t here on this model and it wouldn’t be on any app that uses this model for it’s forecast.

This same logic seen here with this forecast for TD 8 can be applied to many other scenarios.  Whether its the development of a winter storm, a major outbreak of severe weather, or even something as simple as the morning temperature, The data that goes into and comes out of computer models allows us a much better idea of what the weather is going to do, but that data and the programming that goes into creating those models is only as good as our understanding of that data and programming.

Modelcasting with a computer can solve a lot more equations, but if the equation itself isn’t perfect then the answer to it isn’t going to be perfect either.   The difference is that meteorologists who use the data as a tool, instead of just modelcasting and outright using the data, can understand what when the tool isn’t giving you the right answer.

 

Robert Millette

First Atlantic Hurricane Of 2017

Franklin has continued to intensify throughout the day and has become the first hurricane of the 2017 Atlantic Season. Hurricane Franklin has maximum sustained winds of 75 mph, and will move west towards the coast of Mexico overnight. Tropical Storm Warnings and Hurricane Warnings have been issued for parts of eastern Mexico.

Coastal Watches/Warnings and Forecast Cone for Storm Center (NHC)

Significant flooding, dangerous storm surge, and strong winds are the primary impacts for Mexico overnight into tomorrow. Mountainous regions of Mexico may see upwards of 15-20″ of rainfall, which may lead to dangerous mudslides and flash flooding. Coastal regions will see strong winds exceeding 70 mph as Franklin makes landfall tonight.

NAM Forecast Rainfall Totals Through End Of Week

NAM Forecast Surface Winds This Evening

Franklin will not directly impact the United States, but southern parts of Texas may see increased wave activity and rip currents through Thursday.

Could The Total Solar Eclipse Generate Convection?

On August 21, 2017, a total solar eclipse will occur from coast to coast across the United States. This will be the first time since the county was founded that a total solar eclipse will only be visible from the United States, and it will be ninety-nine years since a total solar eclipse has swept across the entire country from coast to coast.

The areas that see a total solar eclipse will go into complete darkness during the afternoon hours (see if you will see a total solar eclipse and at what time HERE). The areas that witness complete darkness during the afternoon hours will see temperatures quickly drop due to the sun being obscured. This could impact the atmosphere a generate isolated convection if other atmospheric variables are favorable.

Cool air from areas witnessing the total solar eclipse could push outward towards areas where afternoon temperatures are not as heavily impacted by the eclipse. This cool air would act as a boundary and force air to rise, and in return convection may develop if there is no convection inhibiting layer of air above the surface. Of course, this is a hypothetical scenario since these events do not occur frequently, and many other atmospheric variables could influence whether convection develops. Nonetheless, it will be fun to keep an eye to the sky on the 21st for more than one reason!

Severe Storms Possible This Afternoon-Tonight

Severe thunderstorms are possible across much of Oklahoma and northern Texas this afternoon–continuing through the overnight hours. Many of the local lakes and camping areas are packed with people celebrating the holiday, so it will be important to remain alert throughout the rest of today. The region was heavily impacted by severe storms yesterday. Wind damage was common across Oklahoma and northern Texas. Here is a look at the severe weather reports from yesterday.

Storm Reports From Yesterday (Storm Prediction Center: SPC)

These same areas will see severe thunderstorms again this evening. The SPC has a slight risk of severe thunderstorms for much of Oklahoma and northwestern Texas. There is even an enhanced risk for much of western Oklahoma and far northwestern Texas.

SPC Thunderstorm Outlook For Today-Overnight

The main threat is damaging wind. This threat will be enhanced as a thunderstorm complex evolves and rapidly advances southward. Winds associated with this thunderstorm complex may exceed 70mph. A secondary threat is large hail. This is why the SPC has a Severe Thunderstorm Watch through 11:00PM CDT.

Severe Thunderstorm Watch In Place (SPC)

It is possible this watch may be extended further southeast with time. Latest high-resolution short-range models are showing the thunderstorm complex that is currently developing in northwestern Oklahoma will advance through most of Oklahoma and northern Texas.

Future Radar Early Morning (3km NAM)

Please remain alert if you’re camping tonight. Damaging wind is not the only threat. Frequent cloud to ground lighting and flash flooding is possible for all of Oklahoma and northern Texas.

Tropical Storm Cindy

Tropical Storm Cindy Information

The National Hurricane Center (NHC) has officially classified the low in the Gulf of Mexico as a Tropical Storm Cindy. This system has sustained winds of 45mph and is stationary–a continued northwest movement is expected overnight. Tropical Storm Warnings are in place for the entire coast of Louisiana and parts of the upper-Texas coast, which includes Houston, Texas. The areas in the Warning vicinity will see very heavy rainfall, dangerous sea conditions, gusty winds, and a storm surge threat where the tropical storm moves inland (more on the impacts below).

Projected path of the center of Cindy

What are the main threats and who will be impacted?

Large impacts are and will continue to be felt from the Florida Panhandle to the upper-Texas coast through much of the week. The biggest threat with Tropical Storm Cindy is heavy rainfall in these areas. The center of Cindy will likely intersect land in Texas, but due to environmental wind shear, the system is lopsided. Thus, much of the precipitation is well east of the center of Cindy. Coastal areas will see 8-14″ with locally much higher amounts (potentially isolated 14-24″ near the Louisiana and Mississippi coasts). Areas further inland across the Gulf states (parts of Florida, parts of Georgia, Alabama, Mississippi, Louisiana, southern Arkansas, and eastern Texas) will see heavy rainfall, too. The flooding threat will be enhanced for the inland areas of eastern Texas, Louisiana, and southern Arkansas Thursday into Friday as Cindy, then the remnants, move northward. The metro areas of Houston (especially the eastern side) and New Orleans will have an enhanced flash flooding threat due to the impervious surfaces throughout the metro. Dangerous and catastrophic flooding could be observed due to rainfall in coastal areas.

It should be noted, this system will stream deep moisture into parts of Georgia and South Carolina thus enhanced rainfall rates along a stalled boundary. Also, heavy rain may impact Tennessee and parts of the Southeast later in the week into the weekend as the remnants of Cindy move eastward.
Potential rainfall accumulations map through this week (NCEP)

Cindy landfall, and tornado and wind threat

The cyclonic flow around the low will also allow for sea water to ‘pileup’ causing flooding for areas just above sea-level for Louisiana and Texas through Thursday morning. The storm surge will be around 1-3 feet where Cindy intersects land, which is likely between Galveston, Texas and Port Arthur, Texas. This land intersection should be late Thursday morning. The latest NAM is showing a land intersection close to the Texas-Louisiana line, but this should occur about 25-50 miles west of this state lines per the NHC.

3km NAM predicted radar (shows Cindy landfall Thursday morning in Texas)

Right now, it appears Cindy will impact land as a moderate to strong tropical storm. Secondary threats are gusty winds between 30-60mph along the upper-Texas coast and western Louisiana coast and an isolated tornado threat for much of Louisiana and Mississippi.

Wind speed probability Map

Tornado potential tonight (greatest threat area outlined in pink)

Tornado potential Wednesday (greatest threat area outlined in pink)

Tornado potential Thursday (greatest threat area outlined in pink)

Please do not disregard the flood threat along the coastal regions of the Gulf, and do not cross roads that are covered in water. Updates will be provided throughout the week.

BREAKING: NHC Classifies System as Potential Tropical Cyclone

Potential Tropical Cyclone

The National Hurricane Center (NHC) has officially classified the low in the southern Gulf of Mexico as a Potential Tropical Cyclone. This system has sustained winds of 40mph and is moving towards the north at 9mph. Tropical Storm Warnings have been issued for parts of the Louisiana coast and Tropical Storm Watches have been issued for parts of the Louisiana coast and upper-Texas coast as the system is expected to continue a north to northwesterly motion towards the Louisiana/Texas coastline.

So what is a potential tropical cyclone?
This is a new classification the NHC uses to provide more detailed guidance on systems that are not yet tropical depression or tropical storm strength, but have a high chance of becoming a tropical storm or hurricane within the next 48 hours and impact land. This new classification system allows for National Weather Service offices to issue Tropical Storm Watches/Warnings in advance.

Projected Path of Potential Tropical Cyclone

Wind speed Probability Map

Large impacts will be felt from the Florida Panhandle to the upper-Texas coast from tonight through Thursday. The biggest threat is heavy rainfall in these areas where coastal areas will see 6-12″ with locally much higher amounts (potentially isolated 12-20″ near the Louisiana and Mississippi coasts). Areas further inland across the Gulf states (Florida, parts of Georgia, Alabama, Mississippi, Louisiana, and parts of Texas) will see heavy rainfall, too. The metro areas of Houston and New Orleans will have an enhanced flash flooding threat due to the impervious surfaces throughout the metro. This is not a hype forecast or to create panic, but catastrophic flooding could be observed due to rainfall in coastal areas.

Potential rainfall map through this week (NCEP)

The cyclonic flow around the low will also allow for sea water to ‘pileup’ causing flooding for areas just above sea-level for Louisiana and Texas. Secondary threats are wind (depending on the strength of the system) and isolated tornadoes. The latest guidance is indicating this system may become a strong tropical storm–borderline hurricane. This will be addressed in a future article, as well as the impacts as this storm moves inland. Keep checking back for updates!

12km NAM near-surface winds (Tuesday afternoon)

12km NAM predicted radar (Tuesday afternoon)

12km NAM near-surface winds (Wednesday evening)

12km NAM predicted radar (Wednesday evening