Gulf of Mexico water temps to have big impacts on severe thunderstorms this spring

The northwestern Gulf of Mexico is still recovering from the February Arctic intrusion that impacted Texas. As of early-March, water temperatures are well below average. The below average water temperatures will undoubtedly have an impact on convection and severe thunderstorms west of the Mississippi throughout March.  

Current Gulf of Mexico Water Temperature

The Gulf of Mexico waters are an important variable in convection and severe thunderstorms for areas east of the Rockies. Generally speaking, when the Gulf of Mexico water temperatures are above average, this leads to more instability for convection and severe thunderstorms by supplying the atmosphere with added moisture and warmth. Instability acts as fuel for thunderstorms, and many times, the greater the instability, the stronger the thunderstorm if other variables are favorable. Thus, the added moisture and warmth bolsters instability, creating increased severe thunderstorms. 

Research shows the warmer the Gulf of Mexico water temperatures, the more hail and tornadoes occur throughout March, April, and May. With the water temperatures running below average in the northwestern Gulf of Mexico, it is possible this will have implications on convection and severe thunderstorms throughout the month of March due to the decreased availability of moisture and warmth added to the atmosphere. This may lead to less intense convection or a decrease in tornado and large hail frequencies during the month of March for areas west of the Mississippi River. It should be noted: severe thunderstorms are still possible throughout March but the frequency and intensity may be impacted. Areas farther east into Dixie Alley and the Southeast will likely not see a decrease in thunderstorm intensity and frequency as Gulf of Mexico water temperatures are above average in the eastern-half of the Gulf.

Above average temperatures are forecast for the region throughout March so this will allow the Gulf of Mexico water temperatures to slowly recover, possibly returning to average or even climbing above average by April, which could lead to an increase in severe weather during April and May.  

March Temperature Outlook

Significant Winter Storm To Likely Impact Parts of the Southeast Late Week

snowfall map

Synopsis

A potent shortwave will dive southeastward across the Rockies and enter the Southern Plains on Wednesday. The feature will develop into a closed low on Thursday over the Mid-South, triggering the development of a surface cyclone along the Gulf coast the same day. By early Friday, the system will reach the Georgia/South Carolina coast and trek up along the Southeast coast on Friday.

This system has a chance to bring a round of accumulating snowfall on Wednesday to far eastern Oklahoma and Kansas, northwestern Arkansas, southern/western Missouri and areas northward on Wednesday. A snowstorm will impact parts of the Southeast late Thursday into Friday, potentially including far northern Alabama and Georgia, eastern Tennessee, far southeastern Kentucky, far southern Virginia, Upstate South Carolina, and western/central North Carolina.

Forecast Discussion

As the low strengthens late Thursday into early Friday, a warm nose will attempt to works its way into southeastern Tennessee, northern Georgia, northern South Carolina, and western North Carolina. However, the passage of the strong mid-level closed will offset the magnitude of warming that otherwise would have occurred in the low levels. Strong frontogenesis across northern Georgia, upstate South Carolina, and central North Carolina could provide the necessary forcing to bring the freezing/melting level close to the surface in those areas. Evaporational cooling will also initially lower temperatures at and just above the surface. Despite lackluster cold in place across lower elevation regions in Georgia, the Carolinas, and even Southeast Tennessee, the dynamics of this storm system may actually ‘make up’ for it. Plus, the system will pass during a timeframe when temperatures are normally colder anyway (at night and early morning!).

We have quite an interesting scenario taking shape for the end of the week. The surface low on Thursday into Friday will take the classic track that favors significant winter weather across the Southeast. However, the pre-existing air mass across the region will only be marginally cold. Although colder air will get wrapped around the backside of the storm system, even it will be marginal. As a result, most regions across the Mid-South and western half of the Southeast region will likely just get a nasty, cold rain on Thursday.

Snow accumulation forecast for late-week winter storm

Snow Accumulation Forecast (Attempt #1)

  • I included a 5–10+ inch accumulation zone in the mountains of Georgia, South Carolina, North Carolina, and Tennessee, where soil temperatures are already relatively cool and low-level temperatures should be sufficient for snow (or a rain to snow transition).
  • I expect noteworthy accumulations to fall across the Cumberland Plateau, far northern Alabama, northern Upstate South Carolina, and western central North Carolina. A transition of rain to snow will likely occur as the mid-level and surface low wraps around colder air.
  • Far southeastern Kentucky and lower Virginia could get accumulating snow; however, if the surface low jogs slightly south, most precipitation will remain south of the area.
  • I outlined a region in pink, where this storm system could potentially bring unexpected accumulating snowfall. I currently have included the northern metro of Atlanta in this zone. Again, strong forcing will need to offset the very marginal air mass in place. Otherwise, expect a cold rain.
  • I expect only a cold rain across the rest of the Southeast and Mid-South.

Please stayed tuned for subsequent forecasts on this potential winter storm. Don’t forget to download our Southern Snow app. Our app provides you with snow forecasts from both Firsthand Weather AND your local National Weather Service office. Check it out!

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Significant severe weather outbreak possible Saturday

Forecast Discussion: A strong shortwave is currently sweeping across the Four Corners region, which has induced the development of a surface low pressure system over the southeast Colorado/northeast New Mexico border. As the strong shortwave closes off into a mid-level low pressure system, the surface low will move into southwestern Kansas over the next few hours. A frontal boundary is currently stalled out across central Missouri, lower Illinois/Indiana and along the Ohio River in Ohio/Kentucky. A very moist environment exists south of the frontal boundary at and near the surface. As the surface low treks across Kansas tonight and tomorrow morning and into Missouri/Iowa late Saturday afternoon, the stalled front will begin moving northward as a warm front, replacing the dry airmass to its north with moisture-laden air. Throughout the day Saturday, surface dew points will increase across southeast Iowa and over the remainder of Illinois, Indiana, and Ohio.

surface analysis

Isentropic lift occurs when warmer air pushes up and over a colder airmass, which can generate precipitation. Isentropic lift, along with embedded weaker shortwaves, will continue to generate rainfall along and north of the soon-to-be warm front tonight into tomorrow morning across much of the lower Midwest. If you take a look at the Storm Prediction Center’s (SPC) severe weather risk area for Saturday, they have an enhanced and moderate risks extending from far northeast Missouri and southeast Iowa into northern/central Illinois, and northwestern Indiana. Please be aware that conditions in the morning (6-8am CT) may not feel like a severe weather day across the enhanced/moderate risk areas. Since the warm front will have not moved through much of the region at this point, temperatures will be somewhat chilly, especially with the rain falling. However, as the warm front surges northward, low-level moisture (humidity levels) will increase rapidly into the afternoon hours.

severe weather forecast

The surface low will move into western Iowa by mid-afternoon, strengthening further as it moves into the region. The region positioned just east of the surface low, ahead of the cold front, and south of the warm front will have the greatest risk of dangerous severe weather, as outlined in the SPC forecast. Rainy weather in the morning hours should move out quickly enough to allow for sufficient daytime heating at the surface. As the mid-level low approaches from the west, mid-level temperatures will cool, which will increase instability within the atmosphere. Surface-based instability allows air parcels (bubbles of air) near the surface and within the low levels of the atmosphere to begin rising. Surface heating and the addition of moisture makes those low-level air parcels buoyant. By cooling the mid-levels of the atmosphere, this ensures that the rising air parcels will remain warmer than the surrounding environment, allowing them to keep rising. This strong rising motion in the atmosphere on Saturday will result in deep thunderstorms developing across the risk zone, which will cause an increased risk for very large hail.

Tornado Risk: The enhanced and moderate risks also have been issued due to the tornado risk tomorrow. Within the treat zone, winds will flow from the southeast at the surface but will veer to the southwest with increasing height. We call this vertical wind shear. The position of the surface low relative to the mid-level low and shortwave will cause this turning of the winds with height. Given higher instability and vertical wind shear, tornadoes, some of which could be EF-2 or stronger, are expected. In fact, long-track tornadoes are possible. Keep in mind that the tornado risk extends southward into the Mississippi Valley ahead of the cold front as well; however, the tornado probabilities across that region will stay comparatively lower.

Chicago Tornado/Hail Risk: You might notice that the SPC only has Chicago under a slight risk; however, residents should watch the forecast closely tomorrow afternoon into the evening. The 18z NAM model is slower with moisture return across the Chicago area. By 5pm CT, the model projects dew points to only be in the mid to upper 40s. To the contrary, the HRRR model guidance has consistently projected dew points to be in the upper 50s or 60°F around the same time in downtown Chicago and well into the 60s in the western and southern metro. Timing matters a lot. If the low levels moisten sooner in Chicago, this could increase the tornado risk across the city, especially in the western and southern metro. Which model do we pick? That’s a tough question, especially when they’re trying to iron out intricate details. From what I can tell, the NAM model keeps conditions a bit cloudier across northern Illinois into the afternoon and even has storms moving through a little earlier than the HRRR model does. On the other hand, the HRRR has more daytime heating across the area, which would likely allow the warm front to advance northward more quickly. In effect, this would give developing and passing storms a much more unstable environment to work with. Honestly, I wouldn’t be surprised if the SPC bumps up the risk across areas closer to Chicago in their next update.

NAM model dew points
HRRR model dew points

Please continue to monitor the situation closely throughout the day tomorrow. These forecasts are never perfect, which means that you should expect some forecast modifications tonight and tomorrow morning.  

Major Early-Season Winter Storm Becoming More Likely But Uncertainty Remains

In my last article, I primarily discussed the big picture and detailed the regions that could be at risk for wintry precipitation this weekend. We’re now getting to the point that we can begin discussing precipitation-type; however, we won’t be releasing accumulation maps until later in the week. Let’s get right into things.

The surface low will develop and trek across southern Texas Friday into early Saturday. This feature will strengthen as it moves across the lower Gulf coast states over the weekend and then off or along the East Coast late weekend/Monday.

The models have recently begun to project another shortwave feature swinging across the Great Plains and then phasing (combining) with the southern stream system moving eastward from California. This could result in a stronger surface low, especially as it approaches the East Coast, and given these trends, I fully anticipate that most of the southern right quadrant of the U.S. will receive heavy precipitation this weekend. The Weather Prediction Center graphic below shows this quite well in their days 4-5 forecast that covers Friday night through Sunday night. Of course, some of these areas will be getting snow and/or ice (or a combo), so for example, an inch or two of rain equates to quite a lot of snow if an all-snow event occurs for a given location. For the regions that manage to be on the snowy/icy side of this system, I expect a significant, early-season winter storm event.

weather prediction center forecast

Let’s start from the Four Corners region and the Southern Plains and then work our way eastward. I’ll reference the latest operational European model, and then tell you what I agree and disagree with.

The swath of snowfall accumulations shown to occur from New Mexico to the Texas panhandle and over northern and central Oklahoma and Arkansas look well-placed. Most of Texas (outside of the panhandle), Louisiana, and most of Mississippi (expect possibly the northern part of the state) should only experience a cold rain.

Southern Plains winter storm forecast

Tennessee, the northern third of Alabama/Georgia, and the Carolinas poses the greatest forecast challenge. Strong high pressure will be located to the north, as discussed in my last article, but the low pressure system will deepen as it crosses the Gulf coast states. Additionally, cold air damming will establish itself along the east side of the Appalachians, which will allow cold air at and near the surface to spill into western and central North Carolina, northern South Carolina (including the Upstate), and northeast Georgia. Places such as Atlanta, GA and Chattanooga, TN will likely be placed relatively close to the cold rain/frozen precipitation line.

Given the latest trends in surface low strength, warm air will likely get advected over the colder air at the surface; thus, a transition from snow to ice (sleet/freezing rain) will probably eventually occur across some locations. Since I anticipate the presence of this warm nose aloft, I currently am not ruling out the possibility of an ice storm somewhere across northeastern Georgia, South Carolina, and across central parts of North Carolina. Colder air will be deeper across western North Carolina and into Virginia; thus a significant snowstorm will be more probable across those locations. The latest European model depicts this well. It has the heavier snowfall totals across northern Upstate SC, western and central NC, and southern Virginia. The European model is a bit more bullish on snowfall totals south of I-85 across northeast Georgia and the Carolinas than I would be at this point, but that’s because I believe ice could cut back on total snowfall amounts in those areas. The Atlanta area needs to cautiously monitor the latest forecasts, even though I believe the main event will be to your north and northeast. BUT, it only takes a ‘little’ snow and ice to cause a big mess. That currently is my biggest uncertainty with this forecast.

Southeast winter storm forecast

The European model is a bit more generous with snowfall accumulations into southeastern Tennessee than the GFS model (and the Firsthand Weather forecast, for that matter) has been. I have higher confidence that snowfall accumulations will occur in northern Tennessee and southern Kentucky, due to the availability of colder air. However, I continue to monitor southern Tennessee closely. That’s still a very tough call.

I expect only rain along the southern half to two-thirds of all Gulf coast states from Mississippi eastward. In fact, there could be thunderstorms within the warm sector of this system.

To summarize, the big story will be the swath of snow that falls from parts of the Southern Plains/Southwest eastward into parts of Tennessee and Kentucky. The biggest story will likely be the significant winter storm that unfolds across parts of the Carolinas, northeast Georgia and Virginia. Determining the exact cut-off between frozen precipitation and cold rain remains extremely challenging. For those located along and near the southern edge of potential accumulations, please be aware that significant modifications to the current forecast may need to be made over the next couple of days.

Please continue to follow Firsthand Weather on Facebook, and please follow us on Instagram if you haven’t already. We will have an accumulations forecast later this week.

What’s All Of This Talk About A Southern Winter Storm Next Weekend?

Is it really that time of year again already? For most of us, we skipped fall and went straight into winter last month. Although wintry precipitation has already impacted parts of the United States, the first legitimate chance for a winter event farther to the south will come in about 6 or 7 days. The goal is never to address local-scale specifics in the long-range, but we can begin discussing the pattern that could support a winter storm. This allows us to establish an initial framework by looking at the big picture first, and then we can build upon that foundation with specific details in the coming days.

Will the mid and upper-level atmosphere support an early-season winter storm across portions of the South?

The first step, especially at this point, is to look at what’s currently going on well-above the surface and attempt to determine how that pattern will evolve over time. From this, it’s possible to infer what could occur at the surface without it being necessary to look at modeled surface output at this point. A closed mid-to-upper level low pressure system was located over the central U.S. yesterday (Saturday) and has now moved northeastward over the Great Lakes. A cold front, associated with a surface low that developed in response, will push all the way through Florida by mid-week. Broad troughing will remain established over the eastern U.S., keeping an anomalously cold air mass in place.

Now, here’s the main reason I made a post on November 29th about the possibility of a winter storm. A split-flow regime is expected to become established over the far western U.S. Let me explain what that means. With this setup, the jet stream splits into northern and southern components. The northern component (the polar jet) will extend well into western Canada and Alaska, while the southern component (the southern jet) will eventually dip into Baja California. Now, check out the map I posted under this paragraph. You can see the broad trough over the eastern U.S., ridging over western Canada and Alaska, and a shortwave extending into southern California and Baja California. I drew arrows to indicate mid and upper-level flow. Do you see how the flow begins to merge back together over the central U.S.? When this occurs, this is called confluence. As this confluence occurs, this will result in sinking motion over the Great Plains and will support the development/maintenance of strong high pressure over that area. Winds flow clockwise around a high pressure system in the Northern Hemisphere, and cold, Canadian air, will wrap around on the east side of this high. There’s your cold air source.

GFS 500 mb map

This will allow another cold front to push southward, and a surface low will develop in response to favorable dynamics just to the east of the shortwave over California. As this shortwave treks eastward late week into early weekend, so will the surface low, which will probably ride somewhere along the frontal boundary. This will result in rainfall across drought-stricken southern California and the Southwest and a swath of wintry precipitation that will extend somewhere from the Southwest/Southern Plains to the East Coast.

If you were to ask me how far to the south I believe frozen precipitation will occur, in short, I’ll tell you I don’t know. But, I’ll give you some insight on this. With conditions favoring high pressure over the central U.S., I’m comfortable saying that it wouldn’t be too difficult to get frozen precipitation (snow and/or ice) as far south as parts of Oklahoma, Arkansas, and Texas. Farther eastward into Tennessee and northern Mississippi/Alabama/Georgia, it becomes a bit more of a tough call. I’m especially paying close attention to northern South Carolina, most of North Carolina, and parts of Virginia, due to the potential for cold air damming to establish itself east of the Appalachians as surface high pressure moves eastward. That’s why in our ‘best chance for wintry precipitation’ map (shown below), we currently depict higher probabilities across those locations. Of course, it should go without saying that we will have to modify this map between now and next weekend, and keep in mind that wintry precipitation is not exclusively snow. We can iron out all of those details later.

southern snow/ice forecast

Conclusion:

Again, we’re simply trying to determine how this pattern will evolve. Any unforeseen changes in that would completely throw off my current expectations for next weekend. Have fun looking at all of the snowfall projection maps, but it’s important to understand the major limitations of accumulation projections this early in the game. And no, I’m not expecting nearly 3 feet of snow in parts of South Carolina like what the European model is showing.

european model snow forecast

Be sure to follow us on Facebook for numerous updates on this event throughout this week. Also, please give us a follow on Instagram. We’re really trying to grow that account. As always, continue to check back with us daily for new updates.

A special thank you to Kimberly Gnat for sharing a picture with us of the snowstorm near Chicago late last month, which we used as the featured photo.

2018-2019 Winter Outlook

Introduction

It is that time of the year. Days are getting shorter; temperatures are getting cooler; and, many have already seen their first freeze or snow of the season. October is an important month for climatologists and meteorologists to analyze certain trends and variables from August to present to obtain an idea of what may come during the winter season. Seasonal forecasting is difficult, and an inexact science, in which many meteorologists have varying methods to generate a seasonal forecast. There are certain areas around the world we can observe to assist in providing a ‘snapshot’ of what the winter season may look like for the United States. A handful of current or predicted teleconnections and variables around the globe can aid in providing the ‘snapshot’ of the upcoming winter. A few of these are: ENSO, QBO, snow and ice cover, NAO, AO, PDO, TNH, and solar activity. A few of these aforementioned variables will be included in the technical discussion later in the article, but first, here is the 2018-2019 Winter Outlook and Snow Outlook.

Regional Discussions

A (San Antonio, TX; Houston, TX; New Orleans, LA; Tallahassee, FL; Charleston, SC; Fayetteville, NC): This region will feature an active winter. Temperatures will be below average and precipitation will be above average. Wintry precipitation will be above average for this region outside of Florida. Either way, you want to make sure you are ready for the winter. It’s so simple. Just by doing a quick search into something like ac repair chandler if your heating is broken, you’ll be able to find a professional who can help resolve this issue and get you living in a warm environment for the winter months once again. You just never know what the weather is like, as it is so unpredictable, but it is best to be safe than sorry.

B (Dallas, TX; Oklahoma City, OK; Little Rock, AR; Jackson, MS; Birmingham, AL; Atlanta, GA; Greeneville, SC; Charlotte, NC): This region will be characterized by temperatures below average and precipitation above average. This region has the opportunity for several winter storms to provide snow and ice opportunities.

C (Kansas City, KS; Omaha, NE; Rapid City, SD; Casper, WY; Billings, MT; Fargo, ND; Des Moines, IA; Chicago, IL; Columbus, OH): This region will be characterized by temperatures well below normal and snowy conditions. Several winter storms and brutal cold are possible.

D (Philadelphia, PA; New York, NY; Boston, MA; Portland, ME): This region will be characterized by temperatures below average and snow well above average. A few potent Nor’easters are possible in this region over the winter.

E (Detroit, MI; Marquette, MI; Green Bay, WI): This region will be characterized by chilly temperatures and frequent snow opportunities.

F (Denver, CO; Salt Lake City, UT; Twin Falls, ID; Spokane, WA): This region will be characterized by temperatures slightly below average and near normal precipitation. A few winter storms moving in from the Pacific Northwest are possible in this region.

G (Albuquerque, NM; Phoenix, AZ; Los Angeles, CA; San Francisco, CA; Las Vegas, NV): This region will be very bland during the winter. The “Pineapple Express” will cease to exist, thus, temperatures near to above average with precipitation below average. Far eastern areas in this region may see precipitation near average.

H (Portland, OR; Seattle, WA; Boise ID): This region will be characterized by temperatures above average and precipitation near average to slightly below average. There will be a few winter storms that move in from the northern Pacific, thus, providing beneficial snow to ski resorts in the region.

Discussion/Method

The equatorial Pacific is an important region to analyze in October. The state of this region can play one of the puzzle-pieces (an important puzzle-piece) into how the winter will shape up. There are three very important variables to analyze when looking at the equatorial Pacific: I) sea-surface temperature (SST) anomalies, II) the positioning of the anomalously warm or cool SSTs, and III) the depth of the anomalously warm or cool SSTs. As of late-October, the state of the equatorial Pacific is trending anomalously warm which is signaling El Niño conditions developing. In fact, the trade winds (normally flow from east to west) in the central and eastern equatorial Pacific have started significantly weakening. This is only reinforcing the anomalously warm temperatures that have persisted for several weeks; another sign of a developing El Niño. This is supported and is expected to continue per the majority of the models. We are currently in a neutral condition (not El Niño or La Niña); however, due to this region continuing to warm since summer, the chances of El Niño developing are increasing. The Climate Prediction Center has increased the odds of El Niño developing in the winter to 70-75%.

Current SST Anomalies

ENSO Predictions Plume

So what is El Niño? El Niño simply put a climate pattern that occurs when SSTs (in the equatorial Pacific) are above-normal for a long period of time. This climate pattern is a cycle (ENSO) in which below-normal SSTs can occur, too. When SSTs are below normal for an extended period of time in this region, the development of La Niña can occur. This climate cycle play an important role in shaping weather patterns around the entire World. Of significance, are the impacts of this cycle on the winter in the U.S. El Niño is typically associated with an extended Pacific jet stream and amplified storm track for parts of the southern United States. This can cause an increase in cloud-cover and precipitation for the southern United States In return, due to the cloud-cover and precipitation, temperatures tend to be below-average in this region. With the hyperactive storm track across the south, the chances are increased that at some point a phase between the northern and southern jet stream will occur, leading to the possibility of southern winter storms. It can also lead to above-average temperatures in northern/northwestern parts of the United States. The impacts on temperatures and precipitation, however, are dependent upon the strength of the El Niño and the positioning of the warm SSTs.

El Niño winter pattern in North America (CPC)

Based on the current trends and available data, it appears a weak to moderate Modoki El Niño may develop this winter. I am sure you’re wondering what differences, if any, are there between Modoki El Niño and El Niño. And yes, there are differences. An Modoki El Niño is slightly different than the conventional El Niño. Modoki El Niño features stronger warming, and at a great depth, of the central equatorial Pacific and cooling in the eastern and western tropical Pacific. This is what is occurring based on the latest SST anomalies. Also, notice the cooler temperatures along the West Coast of South America. This is a signature, when paired with the central warming, of Modoki El Niño.

El Niño SST anomalies (JAMSTEC)

Modoki El Niño SST anomalies (JAMSTEC)

This type of warming and cooling pattern in the tropical Pacific alters the normal winter pattern in the United States and has different implications than the typical El Niño on temperatures and precipitation. Instead of the Southwest seeing an increase in rainfall, as expected with El Niño, Modoki El Niños can cause an increase in temperatures and lack of precipitation in this region. This is depicted in our winter outlook in which we are forecasting the Southwest to see a warm and dry winter. An increase in storminess and cool temperatures can occur for South-central and Southeastern parts of the United States during a Modoki El Niño. This active storm track from Texas across the Gulf Coast states and up the East Coast is also depicted in our winter outlook.

El Niño temperatures (JAMSTEC)

Modoki El Niño temperatures (JAMSTEC)

El Niño precipitation (JAMSTEC)

Modoki El Niño precipitation (JAMSTEC)

The North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), are crucial teleconnections to take into consideration during seasonal forecasting–-especially during the cool months. The NAO, which can be hard to forecast outward more than a few weeks in advance, has large implications on winter seasonal outlooks—-especially for areas east of the Rocky Mountains. Throughout much of the year, the NAO and AO have been positive but the strong positive phase of these teleconnections has begun to relax and dipped to negative levels. A more neutral or negative phase of NAO allows a high to build near Greenland, which tends to lead to cooler temperatures for parts of the eastern United States due to a dip in the jet stream across this region. SST anomalies distribution across the North Atlantic Basin is looking increasingly favorable for the NAO to go neutral or negative during the winter. Research shows a link between SST anomalies and NAO in which a certain pattern of SST anomalies across the Atlantic Basin can increases the likelihood of the NAO dipping to a negative phase. A negative phase of the AO also aids in ushering chilly air for parts of the eastern and southern parts of the United States due to the circulation around the North Pole becoming weak, thus, can allow chilly air to move southward at times. When these two teleconnections (NAO and AO dip to negative values, the atmosphere will eventually respond, and very active weather will establish across parts of the South and the Mid-Atlantic/New England. Ensembles show the NAO and AO remaining neutral with negative dips at times during the winter, which will lead to large winter storms at times from the Southeast up the East Coast.

Current SST anomalies (North Atlantic)

Negative NAO Pattern Implications On Surface Temperatures

Negative AO Pattern Implications On Upper-Levels

The Pacific Decadal Oscillation (PDO) is important to analyze, too. The PDO has a warm and cool phase. What is unique about the PDO is that the warm and cool phases can last 20-30 years–-this is much longer than your ENSO cycles that last half a year or up to almost two years. The PDO also has an influence on the strength of ENSO. When the PDO is warm, higher heights develop over Alaska and the northwestern Pacific, which can dislodge cold air over Canada and usher it southward into central and eastern parts of the United States. The PDO is in a warm phase, which will have big impacts downstream–leading to lower heights across the eastern United States. Alaska has observed impacts from this “warm blob” so far this Fall. Many records have been broken across the state for the warmth and lack of snow that have occurred thus far. This will likely continue through the winter season.

Warm PDO SST anomalies

Another important factor to take into consideration is the snowcover across Siberia and other parts of the Eurasian continent, snowcover across western and central Canada, and the Arctic sea ice extent. While the snowcover was not abundant in parts of Siberia, it has begun to increase over the past couple of weeks, and the snow cover continues to build in eastern Canada and advance southward in central Canada. This will allow for cold air to build and become well established, followed by an eventual equatorial movement at times during the winter.

Current Snow and Ice Cover

Taking into consideration some of the phases of the aforementioned teleconnections and current global features, here are a few analog years that may give a good snapshot of what this winter could look like. Weak to moderate central based El Niño years were selected to generate temperature and precipitation anomaly composites to help form the framework of the winter outlook. Please note, no two years exactly parallel one another. This is what the analog years chosen showed for the winter:

Temperature Anomalies

Precipitation Anomalies

2018-2019 Winter Outlook Conclusion

The 2018-2019 winter will feature below average temperatures for southern and eastern parts of the United States. Above average temperatures are expected for the the Pacific Northwest. Precipitation will be above average for southern and eastern parts of the United States. The above average precipitation will lead to seasonal snowfall totals above average across the Southern Plains, Southeast, Mid-Atlantic and the Northeast. Please keep in mind, if your region is in an area with above average temperatures, this does not mean wintry precipitation will not occur.

Hurricane Willa’s Remnants Will Have Large Impacts From Gulf States And Up The East Coast

Hurricane Willa is getting closer to the west-central coast of Mexico and should make landfall within the next few hours (Tuesday evening). Willa should retain major status until landfall. Willa will begin to weaken and lose its tropical characteristics as it moves across the higher terrain of Mexico into Texas but the remnants will remain well established to have large impacts from mid-week through the weekend for parts of the United States.

As the remnants move into Texas, deep moisture will stream northward throughout Texas into eastern New Mexico and Oklahoma. This will aid in heavy rainfall for this region with the greatest flood threat occurring in central and southern Texas, which has recently been inundated with rain. Widespread 1-3″ amounts are possible in eastern New Mexico and central and southern Texas with isolated 3-4″ amounts in central Texas near the Hill Country (see Fig. 1).

Fig. 1: 7-day rainfall forecast

The remnants will move out of Texas on Wednesday, merge with a shortwave, and begin to slowly intensify across the northern Gulf by Thursday. This will aid in thunderstorms and heavy rain for the Gulf States (from Louisiana to Florida) for late week. The low will then move off of the Southeast coast by late Friday and begin a north-northeastward forward movement off of the coast of the Carolinas. At this point, the low will begin to interact with an approaching cold front and deepen fairly quickly by Saturday morning as it spins off of the coast of the Mid-Atlantic. Heavy precipitation (see Fig. 1), rough seas and strong winds up to 30-60 mph (see Fig. 2)) will be possible for parts of the Mid-Atlantic and Northeast through the weekend. While coastal areas will see heavy rain (2-4″ are possible), areas further inland may see snow.

Fig. 2: Wind forecast Saturday evening

That is right, snow is possible as the nor’easter wraps in enough cold air for a transition to a heavy, wet snow. The best chance for snow will occur in interior parts of the Northeast down into the higher terrain of West Virginia. These areas may see a few inches of wet snow with several inches possible in the higher elevations of the Appalachians. Please keep in mind, we are a few days out so the snowfall forecast will likely need to be adjusted. A couple degrees cooler or warmer will have large impacts on accumulations and precipitation type.

Flooding is possible in Texas from this storm, which will impact travel. Turn around, don’t drown. Travel implications are also likely in parts of the Mid-Atlantic and Northeast due to wind and precipitation. With trees still having leaves on them, this increases the likelihood of them being overwhelmed for either wind or snow. This will increase the chances of power outages in this region over the weekend.

2018-19 Winter El Niño?

October is an important month for climatologists and meteorologists to analyze trends and variables to aid in providing an idea of what may come during the winter season. There are certain areas around the world we can look to, to provide a ‘snapshot’ of what the winter season may look like. One area of significance importance is the equatorial Pacific. The state of this region is a large piece of the winter outlook puzzle. There are three very important variables to analyze when looking at the equatorial Pacific: I) sea-surface temperature (SST) anomalies, II) the positioning of the anomalously warm or cool SSTs, and III) the depth of the anomalously warm or cool SSTs.

As of mid-October, the state of the equatorial Pacific continues to trend anomalously warm, which is signaling El Nino conditions developing (see Fig. 1). In fact, the trade winds (normally flow from east to west) in the central and eastern equatorial Pacific have started significantly weakening. This is only reinforcing the anomalously warm temperatures that have persisted for several weeks; another sign of a developing El Niño. This is supported and is expected to continue per the majority of the models (see Fig. 2). We are currently in a neutral condition (not El Niño or La Niña); however, due to this region continuing to warm since June, the chances of El Niño developing are increasing. The Climate Prediction Center has increased the odds of El Niño developing in the winter to 70-75%.

Fig. 1: Current SST anomalies (Tropical Tidbits)

Fig. 2: Models ENSO predictions (IRI and CPC)

So what is El Niño? El Niño simply put a climate pattern that occurs when SSTs (in the equatorial Pacific) are above-normal for a long period of time. This climate pattern is a cycle (ENSO) in which below-normal SSTs can occur, too. When SSTs are below normal for an extended period of time in this region, the development of La Niña can occur. This climate cycle play an important role in shaping weather patterns around the entire World. Of significance, are the impacts of this cycle on the winter in the U.S. El Niño is typically associated with an extended Pacific jet stream and amplified storm track for parts of the southern U.S. (see Fig. 3). This can cause an increase in cloud-cover and precipitation for the southern U.S. In return, due to the cloud-cover and precipitation, temperatures tend to be below-average in this region. With the hyperactive storm track across the south, the chances are increased that at some point a phase between the northern and southern jet stream will occur, leading to the possibility of southern winter storms. It can also lead to above-average temperatures in northern parts of the U.S. The impacts on temperatures and precipitation, however, are dependent upon the strength of the El Niño and the positioning of the warm SSTs.

Fig. 3: El Niño winter pattern in North America (CPC)

Based on the current trends and available data, it appears a weak (to possibly moderate) El Niño may develop by winter. It should be noted, the strength of El Niño does not necessarily reflect its impacts on global weather patterns that develop. The type of warming and cooling pattern in the tropical Pacific alters the normal winter pattern in the U.S. and has different implications on temperatures and precipitation. Historical weak El Niños have produced these temperature and precipitation anomalies in the lower-48 (see Fig. 4 and Fig. 5):

Fig. 4: December-February temperature anomalies

Fig. 5: December-February precipitation anomalies

While the aforementioned figures show below-average precipitation across parts of the southern U.S. during a weak El Niño, El Niño that tend to be on the strong side of weak (close to moderate) lead to wetter conditions in this region.

Firsthand Weather is in the process of developing its 2018-2019 Winter Outlook but I wanted to give some insight into one of the pieces of the puzzle we analyzing for the winter season. Firsthand Weather’s 2018-2019 Winter Outlook tentative release date is October 26th, 2018!!

Snoklahoma: Snow In The Forecast For Parts Of Oklahoma, Texas And Kansas

It is only October but snow is in the forecast for parts of Oklahoma, Texas and Kansas by late this weekend. The strongest cold front of the season will move southward into this region by late-weekend. Behind this cold front, the temperatures with the Canadian airmass will be at or below freezing for much of Kansas, the Panhandle of Oklahoma and northwestern Oklahoma, and the Texas Panhandle.

A potent shortwave trough will dive south out of the Rockies, along with warm-air advection well-above the surface, will lead to the development of precipitation late Saturday into Sunday. Precipitation initially will fall as light rain but forecasted soundings show (see Fig. 1) a transition to snow is expected throughout the day on Sunday into early Monday (see Fig. 2 and Fig. 3).

Fig. 1: Forecast sounding in Texas Panhandle

Fig. 2: Future radar (Sunday afternoon)

Fig. 3: Future radar (Monday morning)
Guidance indicates frontogenesis developing Sunday, which will act to increase precipitation rates. This will lead to banded snow features in which moderate to heavy snow may fall at times late Sunday. Several inches may fall within this area of frontogenesis, which guidance indicates will be from southwest to northeast out of the Oklahoma Panhandle into central Kansas. Lighter snow amounts will fall to the east and south of this area (see Fig. 4).

Fig. 4: Forecast snowfall totals
Travel will likely become dangerous in areas that see the heaviest snowfall late Sunday into Monday morning.

Big Cool Down On The Horizon

A decent cold front will move through central parts of the country late this week into the weekend. The sub-tropical ridge that has kept temperatures across the Southern Plains and Southeast above average recently will begin to move eastward as a trough moves in from the west. This will send a cold front south on Thursday and the front will continue its southward progression into the weekend. The front should move through Nebraska and into Kansas on Thursday into Friday, and through Oklahoma and northern Texas on Friday into Saturday. Tomorrow, along the cold front, a few severe thunderstorms look possible due to forecasted instability and shear values (see Fig. 1).

Fig. 1: Thunderstorm outlook map for Thursday

The front should stall across northern Texas and western parts of the Mississippi and Tennessee Valleys as it feels the influence of the ridge. This will keep temperatures warm for much of the Southeast outside of Arkansas, northern Louisiana, northwestern Mississippi and western Tennessee (cooler temperatures are in the forecast for other parts of the South/Southeast later in the extended period so keep reading for details on the cooler temperatures). Temperatures behind the cold front will be well below average for much of the Southern Plains and Midwest late this week and weekend (see Fig. 2 and 3).

Fig 2: Friday afternoon temperature anomalies

Fig 3: Saturday afternoon temperature anomalies

It should be noted, deep moisture will move into New Mexico, Texas and Oklahoma from Thursday into Saturday as the trough nears. This moisture will stream into this region from the Gulf of California where a Tropical Depression is located this afternoon. The increase in moisture will lead to increased rainfall, which may lead to flooding in parts of New Mexico, Texas and Oklahoma. Isolated areas in Texas and Oklahoma may see 2-6″ (see Fig. 4). The increase in precipitation and cloud-cover should keep afternoon temperatures below average even before the front moves through on Friday (see Fig. 2 and 3). High temperatures late this week into the weekend should be in the 60s and 70s for Oklahoma and 80s for most of Texas.

Fig. 4: Rainfall forecast through 7 days

Looking ahead to next week, a more amplified trough appears to usher in a reinforcing shot of cooler air. The cooler air will first be felt across the Northern Plains early next week, followed by the Southern Plains by mid-week, then eventually parts of the Southeast by late week into next weekend. Far Southeastern parts of the United States (Florida, eastern Georgia, South Carolina, and eastern North Carolina) may miss out on the coolest fall-like temperatures from this front but temperatures should still decrease. For other parts of the South, this will be the first significant cold front of the fall season. High temperatures will be well below average (see Fig. 5). It is too early to forecast high and lower temperatures with much confidence but right now it appears highs may be in the 60s and 70s with lows in the 40s and 50s behind this front. Locations further north will see temperatures much cooler than this.

Fig. 5: Temperature probabilities days 8 through 14