DISCUSSION: Climatologically there are seemingly only two seasons in Hawaii, these being summer and winter. While there are over 10 climate zones experienced in Hawaii, it can be apparent that summer is often May through October with Winter from November to April. Much like the Eastern Pacific portion of the United States the winter is often the wet season for Hawaii, diminishing the coveted trade wind weather and bringing a slew of cold fronts and/or troughs of poor weather with increased precipitation, often posing major hazards to the area.
President’s Day and its week are expected to see some of this wet and typical weather for mid- winter season. The island chain is under a rather slow trough located at the surface with an upper-level disturbance bringing in round after round of thunderstorms to the islands. These unstable conditions are bringing widespread lightning, thunderstorms, and flash flooding to the island especially in windward location of the islands. With some winds out of the south, the chain has been experiencing unsettled weather associated with this moisture plume bringing increased possibilities for water spouts, thunderstorms, and lightning.
The National Weather Service Honolulu (NWS) has issued a flash flood watch for the entire state, as moderate to heavy rain falls. In addition, the NWS has issued a winter weather advisory for the Big Island summits (Mauna Loa and Mauna Kea) as snow is expected to fall with this system. Due to the precarious nature of this forecast, moisture will remain in the area as this unstable weather will be supported by a trough, and a developing upper level low. As the trough evolves into a closed low over the next day or so, heavy precipitation will persist, the atmosphere will become increasingly unstable and the NWS has indicated, “updraft strength becomes sufficiently strong to support the development of small hail and funnel clouds.”
Diagram 2, current analysis for the Skew-T diagram has indicated K-index of 33 a moderate potential for convection, total totals at 53 indicating widely scattered severe storms, as verified by radar, however Lifted index only -4 indicating marginal instability. Overall there’s increased potential for convective action and flash flooding but no determination for extreme instability regarding the slow-moving trough. This wet pattern is expected to stick throughout the week, with at least some marginal chance for precipitation each day.
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© 2018 Meteorologist Jessica Olsen
DISCUSSION: It is important for the National Weather Service to issue weather-related warnings to the public for their safety. A new type of snow warning called a “snow squall warning” can be issued, as of January 3rd, 2018, by the National Weather Service. A snow squall is a sudden, short period of heavy snowfall accompanied by strong winds and occasionally lightning. During this time, snow accumulation may be substantial.
Snowstorms and snow squalls are much different. A snowstorm can be predicted days in advance. They are typically larger in scale and affect more area than snow squalls. Also, the likelihood of an accumulation is always greater with snowstorms than with snow squalls. Although accumulation is less with a snow squall, the sudden reduced visibility from sudden heavy snowfall causes danger to travelers. Snow accumulation is typically around 1 to 2 inches of snow with visibility that can be less than one quarter of a mile and is expected to last less than an hour.
According to the National Oceanic and Atmospheric Administration (NOAA), the new warning can be issued in the following NWS offices: Buffalo, NY; Detroit, MI; Cheyenne, WY; Pittsburg, PA; State College, PA; Binghamton, NY; and Burlington, VT. These warnings are first sent from the Advanced Weather Interactive Processing System (AWIPS) to the National Weather Service (NWS) as a code. For example, “SQWBUF” is the Buffalo, NY snow squall warning code. If the weather forecast office in Buffalo, NY was to receive that code, the NWS would then issue a snow squall warning to the public for that area. The NWS has given advice if a snow squall warning is issued in your area:
1. Consider avoiding or delaying travel until the snow squall passes your location.
2. If you must travel, use extra caution and allow for extra time.
3. Rapid changes in visibility and slick road conditions may lead to accidents.
It is crucial that the public is notified as soon as possible. According to The Weather Channel, research indicates many highway pileups are attributed to snow squalls each winter season. For example, on March 20, 2017, there was a 30-car pileup on Interstate 81 in Schuylkill County, PA that killed one person. Similarly, there was a 50-car pileup on February 13, 2016, in Lebanon County, PA that killed three people. These are just a couple examples of some of the highway accidents associated with snow squalls. They create low visibility and slippery road conditions that cause tires to lose traction on the road. Most of the time, snow squalls create minor snow accumulations as opposed to greater totals dropped by snowstorms.
NOAA states that they can now better predict short-term weather events with the new GOES-16 satellite as well as, recent improvements in Doppler-radar, and more accurate and detailed weather models. Some of the short-term weather events which can now be detected quickly include snow squalls, thunderstorms, and tornadoes. With this new technology, the NWS can alert the public in a timely manner and reduce snow squall related accidents. (Credit: NOAA, The Weather Channel)
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©2018 Weather Forecaster Brittany Connelly
A Mythbusters Report: Is it Harder to Breathe in Cold Weather? (Fleet Feet Sports, Very Well, American Lung Association)
Image: Man breathing in cold weather per Fleet Feet Sports.
Discussion: The 2017-18 winter season has extended its hand for Arctic air to have an extended stay in the Continental U.S. (CONUS). On January 19th, the NWS Weather Prediction Center’s Extended Forecast Discussion (issued at 11am EST) explains how below average temperatures are shifting from Central and Eastern U.S. to Western U.S. Already by next Friday, temperatures in the West are forecasted to be 5 °F – 15 °F below normal.
When spending long periods of time outside, people have found it harder to breathe and have even experienced a burning sensation. There’s a common myth that the colder it is outside the harder it is to breathe. Well that’s wrong! In actuality, the cold temperatures are not solely to blame for trouble breathing outside. Rather, the fact that cold air is much drier than warm air, and therefore has a lower relative humidity is the primary culprit. When inhaling dry air, cells that line the trachea give up their water supply to warm your body temperature to 98.6 °F and bring the relative humidity of the air to 100% before entering your lungs. This process can dehydrate and irritate trachea cells causing shortness of breath, burning in the lungs, wheezing, or coughing. This is especially true for people who suffer from chronic lung disease, asthma, bronchitis, or even Chronic Obstructive Pulmonary Disease (COPD).
Here are a few tips to remember for breathing outside when the next shot of Arctic air blasts your area:
Stay up to date on what’s happening this winter here.
©2018 Weather Forecaster Amber Liggett
On January 11-12, a potent storm system brought heavy sleet and snow to parts of the southeastern United States. Preliminary reports from the National Weather Service offices in Memphis, and Paducah indicated snowfall totals of between 1 and 4 inches with some locations receiving up to between 6 and 7 inches across northwest Tennessee, and west Kentucky. The meteorological term, deformation zone, is solely responsible for the excessive snowfall totals. These deformation zones are common across parts of the southeastern United States, and can ultimately produce large snowfall totals.
A deformation zone is an area of converging air, whereby atmospheric stretching occurs. This stretching is often a result of multiple air streams flowing toward each other, then subsequently diverging, or spreading out after they converge. Under the deformation band, heavy precipitation can fall resulting in heavy snowfall rates and totals. The enhanced precipitation is a result of increasing divergence aloft, and an increase in the temperature gradient, a process referred to by meteorologists as frontogenesis. The deformation zone is usually found to the west or northwest of the area of surface low-pressure. They are usually found with an orientation of north-to-south or northeast-to-southwest. An important challenge to meteorologists is forecasting the location of these deformation bands, and associated snowfall amounts within them.
In the early morning hours of January 12, an area of surface low-pressure developed under favorable upper level dynamics across central Mississippi. This area of low-pressure moved northeast into eastern Tennessee and Kentucky before crossing the Appalachian Mountains. As the surface low was in the processes of forming, precipitation was ongoing across parts of the southeastern United States. As the colder air mass moved into the area, a graduate transition to freezing rain and sleet occurred. In the mid morning hours on Friday, an eventual transition to all snow occurred as the surface low to the east slowly deepened (i.e., increased in intensity with respect to its minimum central pressure) with time.
As the surface low moved to the northeast, a favorable area of heavy snowfall was becoming increasingly likely over western Tennessee and on over towards west Kentucky as the deformation zone formed. As mentioned above, these deformation bands can produce excessive snowfall rates, and eventual snow totals. That is exactly what happened, as snowfall totals ranged from 4 to 7 inches in the deformation zone. Although, 1 to 2 inches of those storm totals could be in the form of sleet, it goes to show the power of the deformation zone as well as and the associated atmospheric dynamics which are involved.
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©2018 Meteorologist Allan Diegan
DISCUSSION: As the blizzard of 2018 continues to impact New England, the above video captures some of the impacts felt in northeast New Jersey. Snow, while light at this time, was heavy at times during the morning and into the early afternoon hours with gusty winds. This can also be represented below (Aviation Weather Center) in the 18Z METAR from Newark International Airport which is reporting blowing and heavy snow, low visibility, winds gusting over 30 mph, and temperatures in the low 20's.
This monster of a storm’s central pressure dropped to a minimum of 950 mb, via WPC’s surface analysis. This was strong enough to drop the pressure around northeast NJ to approximately 984 mb, represented by the picture below of my hand-held barometer. (The thinner hand is the current pressure reading, the thicker hand was the previous pressure the last time the barometer was adjusted).
As mentioned and shown, the winds were gusting throughout the storm which caused blowing and drifting snow. Drifts exceeded a foot in some areas, while snow totals were in the 8-inch range. Below is a picture of such a snow drift.
The blizzard of 2018 was certainly an impressive storm here in northeast New Jersey. While the brunt was felt along the Jersey shore and across southern New England, this will definitely be remembered for not the snow totals, but the incredible and persistent winds and record cold to follow.
Stay tuned for the latest on this and the next snow storms this year here!
©2018 Forecaster Joseph DeLizio
DISCUSSION: Winter Storm Grayson has been pummeling the eastern seaboard of the United States these past few days with blizzard conditions, arctic cold temperatures, and storm surge. There is an enormous amount of detail surrounding Grayson, so let’s start with the formation:
Grayson started off as a winter storm January 2nd. From there, it rapidly transitioned into a Nor’Easter through a process meteorologists call bombogenesis. Bombogenesis, also known as explosive cyclogenesis, refers to a pressure drop of 24 millibars in 24 hours. This storm dropped 59 millibars in 24 hours, generating huge amounts of wind and energy. The reason this storm is so unprecedented is that we rarely see bombogenesis this extreme.
Grayson has left historical impacts all along the east coast. Some of them being: Savannah, Georgia and Charleston, South Carolina breaking one-day snowfall records, it produced the first measurable snow in Tallahassee, Florida, in over 28 years, wind gusts in excess of 70 mph were reported in the Outer Banks of North Carolina, white out conditions and heavy snowfall in New York City and the tristate area, and finally Storm surge, high winds, and blizzard conditions in New England.
Perhaps the most destructive part of this storm is occurring in New England, where bone chilling temperatures, combined with storm surge, flooding, high winds, low visibility, and heavy snow are halting life. The high winds and flooding is bringing ice shards into the streets making it difficult for the National Guard to help residents. Power outages are also a major concern and a race against time for the National Guard. Evacuations are underway in the areas most affected by this storm. The following days after Grayson will bring temperatures unheard of in the past 100 years to the Eastern United States.
Grayson will absolutely go down in the record books as one of the most intense winter storms the U.S has seen in a very long time. For more information on winter storms, be sure to click here!
©2018 Meteorologist David Tedesco
Sources: The Weather Channel
DISCUSSION: A low pressure system currently off the coast of Georgia is expected to strengthen and move up the east coast over the next few days. The expected impacts of this storm on the northeast are described in the GWCC article here. However, the storm is already having impacts in the southeast where winter weather usually is not experienced. For example, freezing rain and ice were reported on bridges in south Georgia this morning, prompting travel issues, and it snowed briefly in Tallahassee, FL for the first time in 28 years. This storm system is expected to impact essentially the entire eastern seaboard of the U.S. as indicated in the figure above. The figure shows areas under various winter storm watches, warnings, and advisories. Specifically, the pink color indicates winter storm warnings, white indicates winter storm advisories, and blue indicates a winter storm watch. Red indicates regions under a blizzard warning. All of these areas are either currently experiencing freezing rain, sleet, and/or snow (i.e., winter precipitation) or could be soon. Freezing rain leads to a coating of ice that can easily pull down trees and power lines, and the high winds associated with this storm system could also lead to power outages. The continued frigid cold that is expected after passage of this storm system may make power outages especially dangerous. So, if you are in the path of the storm system, it is important to be prepared (e.g., have an emergency kit prepared) in case power is lost and travel isn't immediately possible.
To learn more about other interesting winter weather stories from around the world and to keep up to date on this particular storm system, be sure to click here!
©2017 Meteorologist Dr. Ken Leppert II
DISCUSSION: As all eyes turn to a massive storm system eyeing portions of the Mid-Atlantic into the Northeast, arguably the most dangerous feature with this storm will be the extreme cold as the storm exits the region. Above is a snap shot from this morning’s 12Z NAM model (courtesy of WeatherTap) valid Thursday at 1PM which shows the intense low-pressure system, sub 960mb on this model run, off the NJ and LI coast in the Atlantic. This model is forecasting this system to have impressive sustained winds across coastal regions of NJ, all of LI, much of CT and much of coastal New England experiencing sustained winds 25-45 mph with higher gusts as this Nor’easter bombs out. There is a threat for power outages in these locations which is always a risk to safety. This storm will pull down extremely cold air from southeastern Canada elevating the danger of this situation.
The above image is the 12Z NAM (WeatherTap) representation of the actual air temperatures on the morning of Saturday January 6th. These extreme cold temperatures, along with the howling north and northwesterly winds advecting this frigid air into the region will make the temperatures feel well below zero (image below same time frame). This of course is a dangerous situation for any locations that lose power and do not have heat.
A sizable snow pack is forecast by the NWS and the latest model guidance for much of New England. Since snow is a good emitter of infrared radiation, during the nighttime hours more radiation is able to escape out to space much quicker than if there was no snow cover, allowing these temperatures to really drop during the overnight. Such extreme nighttime lows will produce very dangerous wind chills as discussed above.
Just how impactful can a deep snowpack be to low temperatures? The surface analysis above from December 8th 2013 at 12Z is a perfect example. There was over a 20 degree temperature difference in two locations in the Pacific Northwest. Eugene, Oregon, with a few inches of snow cover shown is resting at -9 degrees F and Portland Oregon, with little to no snow cover is sitting at 13 degrees F. This highlights the concern across areas that receive snow and high winds from this system in the Northeast.
A dangerously cold situation will impact the Northeast later this week into the weekend. Be sure to follow GWCC and click here for the latest on this Nor’easter, the snow cover, and the cold air following!
©2018 Forecaster Joseph DeLizio
Year in and year out there is always an interest across the United States and the world for matter regarding whether or not there is a decent chance of there being a White Christmas. Being as though it is Christmas Day and millions of people living in more than a dozen cities spread across the United States have already experienced a White Christmas here in 2017, it is always interesting to understand more about why the percentages of there actually being a White Christmas varies so much in going from north to south across the nation.
It is important to acknowledge the fact that the verification of there being a White Christmas is contingent upon there being snowfall cover on the ground during the period between Christmas Eve and Christmas Day and/or there being a verification of new snowfall accumulating during that same period of time. More often that not, the reason why the odds of there being a White Christmas is due to the predominant storm track in place across a good portion of the lower 48 states. From year-to-year, this average national storm track position obviously varies based on the influences from various global climatic teleconnections such as the El Nino Southern Oscillation. Having said that, based on the fact that we are currently under the influence of a Central Pacific Ocean-based La Nina event. Thus, the typical storm track position during a typical La Nina Winter is roughly positioned along a track from the Pacific Northwest and southeastward towards the Southeastern United States.
Nonetheless, as with any national climatic tendencies based on trends tied to seasonal climatic variability, there is always subs-seasonal variability associated with where low-pressure systems enter various parts of the contiguous U.S. For instance, over the past 48 to 72 hours, a relatively weak "Alberta Clipper" low-pressure system entered the U.S. and progressed east-southeastward towards the North-Central U.S. before heading towards the interior Northeastern U.S. Upon reaching the greater Mid-Atlantic coastline, the system transferred its energy towards the area just offshore from the Delmarva Peninsula before moving off to the northeast with time. As a result, this system delivered mostly rainfall to the greater NYC metro area. However, more inland locations across New York and up towards New England all witnessed a White Christmas. Hence, areas which typically have less than a 40% chance of witnessing a White Christmas got that and more today in some cases.
It just goes to show that dreams can come true when the atmospheric storm track and timing decides to play along with the hopes and dreams of younger generations who anticipate this time of year all year long.
To learn more about other neat winter weather stories from around the world, be sure to click here!
©2017 Meteorologist Jordan Rabinowitz
Understanding What Forces Different Types of Wintry Precipitation (credit: National Weather Service)
DISCUSSION: As we are heading deeper into the 2017-2018 Winter season, it is always important to bear in mind what factors come into play when it comes to forecasting for winter weather events. One of the first questions which should always be asked when it comes to anticipating any variety of winter weather event is to what extent (i.e., both with respect to vertical and horizontal difference) there is cold air in place. In addition, the other major issue pertains to if there happens to be warmer air (i.e., above-freezing air) at the surface and/or above the surface. If there is warmer air above the surface, this can often lead to either icing events, mixed precipitation events, or even sleet events. The main difference is determined by the exact presence as well as depth of the relatively warmer air.
If there is warmer air present through the depth of the precipitation all the way down to the surface, this leads to the occurrence of an all-rain event. However, when there ends up being a shallow layer of colder air very close to the surface, this quite often leads to the occurrence of a freezing rain event due to the fact that rain falling through a somewhat warmer layer above the surface reaches a below-freezing layer very close to and/or right above the surface of the Earth which leads to the rainfall freezing upon contact with the ground. Thus, this leads to what are most commonly recognized as destructive freezing rain events. The other relatively common possibility is for the "frozen layer" of the lower part of the atmosphere to be substantially deeper than that observed with the freezing rain scenarios which leads to sleet events where rain freezes well above the surface. This leads to ice pellets which can often have quite a high impact since upon reaching a frozen surface, they can adhere to the surface and create a dangerous situation as well. The message to be taken from all of this is that all-out snowstorms are not the only issues to be concerned about when it comes to winter weather events.
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©2017 Meteorologist Jordan Rabinowitz