Obviously severe weather can happen all year round, but for the Delaware region most of the threat is usually contained in the late spring and summer months. A ‘Severe Thunderstorm’ is one that produces winds 58 mph or stronger and/or hail 1 inch in diameter or larger. Below shows the probability of severe storms in the continental U.S. based on 30 years of climate data. Each frame is one day from March to August.
Majority of the significant threats are wind related and flooding that usually accompanies strong thunderstorms. Tornado activity in the region is not frequent but can occur. A majority of these storms are usually at the low end of the Enhanced Fujita Scale (EF0-EF2). The EF Scale rates the strength of tornadoes in the United States and Canada based on the damage they cause.
The Storm Prediction Center
The Storm Prediction Center (SPC) is part of the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP). Located in Norman Oklahoma, their mission is to provide timely and accurate forecasts and watches for severe thunderstorms and tornadoes over the contiguous United States. The SPC also monitors hazardous winter weather and fire weather events across the U.S. and issues specific products for those hazards. The SPC uses a suite of products and multiple of specialists from lead forecasters, mesoscale forecasters, outlook forecasters and etc. that continuously monitor the continental US for the potential for severe damaging weather events. (For more info on the SPC go here –> About the SPC)
Risk Categories Associated with SPC’s Outlooks
Here is an example of a Day One Outlook issued by the SPC and definitions of the categories.
The Difference Between Watch and Warning
WHAT IS A WATCH ?
Understanding the purpose of a watch is important and should not be confused with a warning. A warning means that hazardous weather is occurring at the moment / imminent and you should take actions to protect yourself. Below is a full list of categories issued by the SPC and NWS Offices.
What can we look forward too.. well its complicated :
Look at the big Picture ENSO
Let us begin to look at the larger state of the climate based on El Nino-Southern Oscillation (ENSO) Phase. We are currently trending in a La Nina state with the potential of that diminishing as we head thru Winter Months. With waters cooler in the Pacific Equatorial here is a generalistic look at what we usually see during these periods.
Now there are multiple on-going factors that need to be taken in consideration, and obvious La Nina conditions can differ with other factors that are in play. Forecasting long range are ‘best guess’ based on what current conditions are likely to be.
Here is a reminder of the 2022 – 2023 Winter Outlook from CPC: (Click either pic to go to the NOAA CPC Page for more detail)
NOTE That the above Climate Forecast is just that, and typically there are cases that could be dismissed as not 100% accurate over time. There have been plenty of La Nina seasons where our regions have seen greater then average snowfall.
Modiki El Nino: Not A Concern for 2022-2023 Season
Modiki El Nino Is when portions of the ENSO are actually cooler then normal on the West of South America. This usually drives colder temperatures for the East and Mid Atlantic.
CURRENT SST ANOMALY MAP
Take note of the above average temperatures near the Mid-Atlantic along with a very evident La Nina Storms without sufficient cold air mass especially with winds from East to West mean snow difficulties especially along the Coastal Plain.
Other major factors are what we call teleconnection patterns. Teleconnection refers to a recurring and persistent, large-scale pattern of pressure / circulation anomalies that spans vast geographical areas in the atmosphere.
So lets try to go through and give you a graphical representation of each, and try to explain how a -NAO -AO and +PNA are the best set up for a Mid-Atlantic / East Coast for winter storm setup.
Below is a look at characteristics of a Negative / Positive Arctic Oscillation (AO)
You can see here in a negative phase that the cold in the stratosphere is basically displaced into Canada and North America.
Here is a graphical representation of a North Atlantic Oscillation (NAO) and its general effects:
A Negative NAO is also sometimes referred as the Greenland Block , East Based NAO because high pressure establishes itself there allowing for the strongest flow of cold into the Mid Atlantic. West based NAO where high is positioned move over Canada is little less favorable.
… and Finally A Look at the Pacific North American (PNA) Pattern
Image by Steve Tracton (2010)
Positive PNA is also sometimes referred to as a ‘zonal flow’ usually brings milder conditions from the west straight along to the east.
So wait then, why did we see snow then here in December of 2013 where the patterns didint match any of these and we still got good snow fall totals ???
There is another pattern called the East Pacific Oscillation (EPO)
The EPO is the high altitude wind flow over the Eastern Pacific which is influenced by the ocean temps.. When the EPO is in a positive phase, there is usually troughing on the West Coast, while milder air engulfs the inland and Eastern part of the country. The positive EPO limits troughs in the East. When the EPO is in a negative phase it has the opposite effect on the East Coast where a -EPO encourages a northwesterly flow from Canada into the Eastern part of the U.S, allowing for cold air to intrude, but without the assistance of a stronger -AO or -NAO we end up with more transient shots of cold air that usually support snow more west of the coastal plain as we saw in 2013.
Maden Julian Oscillation – MJO can be a strong influences to extreme events our weather. Though we usually talk about this during hurricane season and tropical development it can have a profound influence during the winter including Arctic air outbreaks during the winter months.
MJO is large propagating area of tropical convection (showers and thunderstorms) that has a strong influence in Jet Stream patterns. Patterns can cycle from 40-50 days and travel eastward across the tropical equator. The MJO is classified in Phases as it moves through each of the regions as dictated in the forecast below. We usually see effects in regions 7 8 & 1. The further away from the circle the stronger the effects. (Circle is sometimes categorized as the Circle of Death because the effects are minimal.)
Current MJO Forecast
Generalistic Look at the MJO and its effects in each phase.
Sudden Stratospheric Warming (SSW)
A Sudden Stratospheric Warming (SSW) of the atmosphere refers to a swift jump in temperatures in the stratosphere and its impact on the Polar Vortex. The infamous Polar Vortex is a large gyre of extremely cold air that usually circumducts the Arctic Circle. When a strong sudden warming event occurs it causes the Polar Vortex to split and drives these vortices ( 2 or 3) of arctic air Southward. When this occurs, the Jet Stream gets enhanced and sets up a strong pattern for Cold and possibly Stormy Events for the East and Mid-Atlantic.
Image Courtesy of @WeatherProf Jeff Berardelli in Article from CBS Located Here
Water Temperatures – This early into the year, water temps usually dont help us on the coastal plain that much. It is usually not till we get more into the heart of the winter season when water temps get cooler and have a less dramatic effect on potential snow storms.
Finally Storm Track – Inland storms also favor snow to West and rain to the East, with a South to South West wind bring warm temps during the storm, and then cold air as the system moves out with slight chance of snow on the back-end.
Okay so what are we seeing today that may be indication that white winter is coming… ( or NOT coming) ?
Reminder : we want to see -AO -NAO and +PNA
The above teleconnections are really relative right now of cool and possibly snow event in the Mid-Atlantic in December. If the patterns remain persistent and a more significant cold pattern develops (such as some arctic intrusions with some really cold temps as we head into mid December. Alternatively, we could see more warm weather during the second half of 2022-2023 season.
Though we are not in the heart of winter yet, we still have a way to go and we recommend you prepare for it in any case. Make sure you have a Winter Kit for your vehicle including warmers, de-icers, extra blankets, shovel etc.
Today we thought we take you into the different climatological and environmental aspect of Hurricanes and what effects them in today’s post we will cover SAL and Wind Shear two factors that occur specifically in the early part of the season but are not limited to that timeframe.
Saharan Air Layer (SAL) –is an elevated layer of Saharan Air and Mineral Dust and occurs during the late spring through early fall over extensive portions of the North Atlantic Ocean between the Sahara Desert, the West Indies, and the United States.
SAL is a dry air mass driven off of Saharan Desert and can sometimes be abundant with dust as seen in the above figure. Dry air will definitely suppress thunderstorm development and weaken tropical cyclones causing downdrafts to occur around the storm. Below are two images of impacts of Sal.. first showing the current Sal and the second a Water Vapor Loop also showing the extent of Dry Air in the Atlantic basin.
One thing to Note.. Dry Air is not just a Africa Component, it exists across the globe and is just as effective in degrading tropical cyclone and thunderstorm development.
A perfect example of that is in June of 2020 with tropical storm #Cristobal where further increase of development was hampered due to significant amount of dry air (yellow) was to the West of the system and it was being pulled into it and hampered any last minute intensification.
One of the benefits of having dust in the atmosphere is that it promotes fantastic evening sunsets.
SAL is usually prevalent during the early part of the Hurricane season but begins to relax as we get into late July, but its not always the rule. We have seen seasons where SAL has basically shut down any development in the MDR ( Main Development Region) for almost the entire season.
Here is a Satellite view of current SAL conditions in the Atlantic:
Wind Shear –
Wind Shear – is a change in wind speed with height. Strong upper level winds destroy the storms structure by displacing the warm temperatures above the eye and limiting the vertical accent of air parcels. Hurricanes will not form when the upper level winds are too strong.
Tropical cyclones are heat engines powered by the release of latent heat when water vapor condenses into liquid water. Wind shear hurts tropical cyclones by removing the heat and moisture they need from the area near their center. Shear will also distort the shape of a hurricane by shearing it (blowing the top away from the lower portion), so that the vortex is tilted. A tilted vortex is usually a less efficient heat engine–the delicate balance of inflowing low-level winds and outflowing upper-level winds that ventilate the storm gets disrupted.
One excellent web site to diagnose current wind shear values is the University of Wisconsin CIMSS site. They compute upper level winds by looking at cloud motion from satellites. A mean low level wind, averaged over a layer between 925 mb and 700 mb (1500 feet to 10,000 feet), is subtracted from a mean upper level wind, averaged over a layer between 300 mb and 150 mb (30,000 to 45,000 feet). If a tropical cyclone is present, the winds due to the circulation around the storm are removed, so that one can just look at the environmental wind field the storm is embedded in.
On April 7th, 2022 Colorado State University’s Phil Klotzbach (@philklotzbach) and team released their extended Hurricane Forecast for 2022.
“Current weak La Niña conditions look fairly likely to transition to neutral ENSO by this summer/fall, but the odds of a significant El Niño seem unlikely. Sea surface temperatures averaged across the eastern and central tropical Atlantic are currently near average, while Caribbean and subtropical Atlantic sea surface temperatures are warmer than normal. We anticipate an above-average probability for major hurricanes making landfall along the continental United States coastline and in the Caribbean. As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season, regardless of how much activity is predicted.”
This forecast was delivered by Phil at the 2022 National Tropical Weather Conference and can be found here:
Be ready for hurricane season. Today you can determine your personal hurricane risk, find out if you live in a hurricane evacuation zone, and review/update insurance policies. You can also make a list of items to replenish hurricane emergency supplies and start thinking about how you will prepare your home for the coming hurricane season. If you live in hurricane-prone areas, you are encouraged to complete these simple preparations before hurricane season begins on June 1. Keep in mind, you may need to adjust any preparedness actions based on the latest health and safety guidelines from the CDC and your local officials.
Good Morning.. A very active pattern continues for the Delaware and Eastern Shore over the next week or so. Confidence level for any specifics mentioned below is low ;however, guidance has been extremely repetitive on the chance of some ICE Events for portions of Central and Northern Delaware along with the Eastern Shore.
Overview Today a low pressure system off the Carolina’s will move East and out ot sea. The precipitation shield associated with this may spark the conversational snow in the most Southern regions of the state. No accumulation is expected.
Saturday another low will slide North and there is the potential of a Wintry Mix moving into the region from morning hours especially in the South. This should spread North eventually affecting all of Delaware.
Precipitation continues thru Sunday and there will be a greater chance of Sleet along with Freezing Rain especially for North Central and Northern Delaware. The wintry mix should change to rain for our Southern region.
As it stands right now per the latest forecast discussion precip is expected to be on the lighter side. Advisories may be issued where freezing rain is more prevalent.
Confidence on where the ice / freezing rain will develop is low.
While we may have a break on Monday a larger low pressure system will make its wayin on Tuesday making for a very tricky forecast.
Look at the GFS ‘Total Accumulated’ Ice ** NOT A FORECAST **
The take away from all this is that there’s a possibility again of a wintry mix and models have been more consistent with more freezing rain but this could very well be all rain in areas as well.It will depend on the placement of the low. and its movement thru the region.
Another System is to affect the region Thursday – Friday time frame. Right now it does appear that we may be the ‘warm sector’ for this event but,this will need to be monitored as well.
We just want folks to be aware that the potential is there for Ice Events and as we mentioned earlier even the potential of low liquid equivalent ( such as Sunday) there is the potential of impacts.
In regards to Tuesday even though the models have been bullish on a more significant ice event this is not a forecast. We feel that it cant be dismissed as a threat and that you should at least be aware and monitor NWS Mount Holly’s website for more information as we move through the weekend.
Sent: Tue, Aug 25, 2020 1:03 pm Subject: Fwd: August 4th Additional Report 1 of 3
Good Day.. we didn’t receive any acknowledgement of our last email.. but we did happen to meet with Neal Dukes last week. After our initial conversation I became little curious that on August 4th during Isaias little after the 9am time frame, wind event at my residence might have been related to Neal’s report.
(Our apologies for the multiple notes, for some reason I’ve had issues trying to compile, save and send)
A.Cedar Swamp Road Approx 2.4 Miles in From Route 9 (Flemmings Landing Rd) Environment: Wooded Area Surrounded by Marsh Damage: Full Tree Damage Either Totally Fallen or Broken Half to 3/4 Way Down. Fall Direction: North West Between 310° and 318° Length of Path: Approx .14 of a Mile Width of Path: Approx 20 Yards (Difficult to determine due to environment)
We were not able to look at any other areas within the path line due to marsh areas and farm roads that were cabled closed; however, aprox. 5 or so miles NW from the damage we did see trees down around the corner of our residence in the area of Coleman’s Christmas Tree Farm on Route 9
Again our apologies for the 3 separate notes on this issue but for some technical issues would not allow me to compile, save, and send this in one note.
In closing I just found this a tad too much of a coincidence that these were in-line and would thought we should share.,
OUR THANKS TO NEAL DUKES for providing us remote access and drone coverage of the area.
On August 3rd, 2020 Hurricane Isaisas makes land fall at Ocean Isle Beach, NC as it accelerated to the North toward the Delmarva.
Tropical Storm Winds Along with potential of Locally heavy rain anywhere between 3 to 6 inches with local possibilities of even 8+ were forecasted for the region.
“As Isaias tracked to the NNE through the area early Tuesday morning, a north-south oriented surface boundary set up on the north side of the storm (just to the east of I-95). On the east side of the boundary, winds were mainly out of the SE with temperatures in the upper 70s-around 80F and surface dew points in the mid to upper 70s. To the west of the boundary, winds were generally out of the north with temperatures and dew points in the upper 60s-around 70F. “
“As the storm’s structure evolved, the strongest winds were maintained on the east side of the storm. Numerous wind gusts to strong tropical storm force were measured especially in New Jersey, Delaware, and eastern Maryland, with a few hurricane force gusts reported. In addition, several tornadoes occurred along and east of the storm track. Meanwhile, west of the storm’s center, very heavy rainfall occurred, with the greatest amounts over eastern Maryland, southeast Pennsylvania, and the Lehigh Valley region. Widespread rainfall totals of 4 to 7 inches were reported with a few amounts in excess of 7 to 8 inches. This led to both severe flash flooding as well as significant river flooding.”*
*National Weather Service Mount Holly
At: 2020-08-04 08:50 UTC 04:50 Local We received our first Tornado Warning in SE Sussex County.
From there on we had multiple report of and warnings in Kent Count, Delaware Eastern Shore of MD and finally in New Castle County Delaware which was around 09:21 am Local.
NOUS41 KPHI 061959
Public Information Statement
National Weather Service Mount Holly NJ
359 PM EDT Thu Aug 6 2020
...NWS DAMAGE ASSESSMENT RESULTS FOR TROPICAL STORM ISAIAS TORNADOES...
.Kent and New Castle County Delaware Tornado...
Start Location...Dover in Kent County, Delaware
End Location...Middletown in New Castle County, Delaware
Date...August 4, 2020
Estimated Time...8:55 AM EDT to 9:25 AM EDT
Maximum EF-Scale Rating...EF1
Estimated Maximum Wind Speed...105 mph
Maximum Path Width...200 yards
Path Length...29.2 miles
The tornado touched down in the vicinity of the Eagle Meadows
Apartment Homes on Sorghum Mill Road in Kent County then moved
across Route 10. It tracked nearly parallel to South State Street
through Anneville, the south side of Dover, where significant tree damage occurred, including some treetops shredded from Poplar Lane to the neighborhood around Steele Road. It was here where some roof damage occurred to some homes especially due to fallen trees, however a garage was significantly damaged on Dyer’s Tree Farm. The tornado then crossed over Route 13 near the Eden Medical Center and very near the William Henry Middle School. A couple sections of the school’s roof were blown off along with some tree damage nearby. A warehouse adjacent to the school had a few sections of its metal walls torn off and a couple of tractor trailer trailers flipped onto their side. The tornado then crossed over Walker Road at Route 15 then to Westminster Village at Dover near the intersection of Route 15 and College Road.
The tornado then tracked northward just east of Cheswold where
the damage may have been more sporadic before moving through the
east side of Smyrna where more notable tree damage occurred. A 96
mph wind gust was measured at a Delaware Department of
Transportation weather station located on Route 1 just north of
Smyrna as the tornadic circulation passed by. From here, the
tornado continued nearly parallel to Routes 1 and 13 on the east
sides of Townsend and Middletown in New Castle County. Numerous
trees were snapped or uprooted along portions of Blackbird Landing Road and Gum Bush Road in Townsend with some damage to roofs. A garage at a residence on Blackbird Landing Road was destroyed. The tornado then damaged homes in Middletown along Spring Hollow Drive. In this neighborhood, some homes had roof material and siding blown off with numerous trees uprooted. Several garage doors were blown out. One home had an entire side wall blown out, although construction appeared to be poor. One picture showed a home with a missing exterior corner wall on the second story. The tornado may have started to dissipate between Mount Pleasant and Glasgow in New Castle County, however it is possible the tornado track extended into Cecil County, Maryland. Doppler radar data showed a continuous and well defined rotational signature and a tornado debris signature.
Special thanks is extended to Kent County and New Castle County
Emergency Management, trained spotters, and the public for their
extensive assistance with this survey.
First all let us preface this by stating we are not running around screaming red alert or the sky is falling, however; with the recent releases of multiple Hurricane 2020 forecasts from the likes of Colorado State, North Carolina State, The Weather Company (IBM), WeatherBell, and etc., the outlooks could be well stated as concerning.
We will try to explain why we may see an above average hurricane season and in turn why it could also be a hyperactive one as well. We will examine what you may want to be doing now and as we enter Hurricane Preparedness week in May.
Overview: ENSO (El Niño-Southern Oscillation)
In its simplest terms, all severe weather is mostly based on how a parcel of air rises in the atmosphere and develops into a thunderstorm. This is not any truer then in the Tropical environment where rising motion along with the an abundance of fuel ( above normal sea surface temperatures), and lack of wind shear, can ultimately allow these thunderstorms to thrive and develop into the monster storms we call Hurricanes.
What is ENSO (El Niño / La Niña) ??
The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. El Niño and La Niña are the extreme phases of the ENSO cycle; between these two phases is a third phase called ENSO-neutral.
In general, warm El Niño events are characterized by more tropical storms and hurricanes in the eastern Pacific and a decrease in the Atlantic, Gulf of Mexico and the Caribbean Sea. The increased wind shear helps to prevent tropical disturbances from developing into hurricanes.
La Niña is a climate pattern that describes the cooling of surface ocean waters along the tropical west coast of South America. Alternatively, wind shear characteristics are opposite a El Niño typically yielding more tropical cyclones in the Atlantic and fewer in the Pacific where wind shear is greater.
Example of shear a) El Niño vs b) La Niña based on Westerly Winds. Note that in ‘a)’ there is much greater zonal winds especially as we enter the upper atmosphere. This would typically cut-off thunderstorm tops and hamper further development.
Right now temperatures are running above normal across a large portion of Niño areas, Gulf of Mexico, and MDR (Main Development Region)
Warmer Sea Surface Temperatures:
“(Knaff 1997), when the Azores High is weaker than normal, Atlantic trade winds are also weaker than normal. These weaker trades inhibit ocean mixing and upwelling, thereby causing anomalous warming of tropical Atlantic SSTs. These warmer SSTs are then associated with lower-than- normal sea level pressures which can create a self-enhancing feedback that relates to lower pressure, weaker trades and warmer SSTs during the hurricane season (Knaff 1998). All three of these factors are associated with active hurricane seasons.” – (Via Colorado State Tropical Extended Range 04.2020 Forecasthttps://tropical.colostate.edu/media/sites/111/2020/04/2020-04.pdf)
Although Niño areas are warm currently, looking at that from a surface perspective is little deceiving. There are cooler waters are trying to make there way to surface and should progress over next several months. The following graphic depicts water temperature and its corresponding depth. (Note all the cold water edging its way to the surface eroding away at the warm waters in the Pacific.)
Looking ahead from July forward most guidance is suggesting ENSO will most likey be Neutral to La Niña for the heart of the hurricane season. The unknown is how strong this oscillation will be and how its effects will ultimately power the season overall but, as you can see with already warmer then average water in the Atlantic, combined with a ENSO forecast that will most likely help augment an above average hurricane season.
So am I Going to See a Hurricane Where I Live ?
Fact is, no one knows… we are trying to take a somewhat generalist approach here in terms of educating and understanding what might come. The amount of statistical work ( including all the predictors which we haven’t even begun to discuss) going into these forecasts are just amazing, however; they do not constitute a ‘sure thing’ !
Effects of these storms are extremely variable based on multiple factors that account for a hurricanes size, wind field, storm surge, rainfall, steering, and of course geographical and demographic influences.
“The probability of landfall for any one location along the coast is very low and reflects the fact that, in any one season, most U.S. coastal areas will not feel the effects of a hurricane no matter how active the individual season is.”
Its a game probabilities and possibilities as it were, with that though comes the reality that 2020 hurricane activity might be about 140% or plus the average season. Statistically that could mean a greater chance of a land-falling hurricane to the United States especially in the Gulf and South East States.
Going through an active Hurricane Season on heels of already disastrous world wide pandemic is obviously not what we want to see yet, as in any risk there are steps you can take to mitigate and manage. There are multiple tools and programs established through FEMA and NOAA to make a plan. Use the preparedness time in May and June to develop/enhance or review your plan.