Subsequent Hurricane Irma Update

Major Hurricane Irma has just been upgraded back to a Category 5 storm with maximum sustained winds of 160 mph. It has been throwing forecasters for a loop as we try to figure out what it is going to do and where it is going to go. Well, now that we are closer to the event, models are able to represent the storm more closely to what will actually happen, and they are doing so with much more confidence and consistency allowing forecasters to zone in on the target zone.

Track Shift

Irma was always going to hook to the north; that was a fairly confident forecast for meteorologists. The issue arose with when and how sharp of a turn. At this point, the hope for Florida is that Irma has direct interaction with Cuba, that meaning the eye of Irma drifts over land so that friction with the surface as well as a change in wind shear can weaken this monster storm. If Irma does make landfall on Cuba, then Florida might see a category 3 or 4 version of the storm. However, if Irma continues on its westnorthwestward path, missing Cuba altogether (although effects from winds and rain will still affect Cuba and are affecting Cuba now), then with the fuel from the extremely warm (almost 90F!) waters south of Florida.

Where is Irma going?

As the cone suggests, our best forecast is that Irma will ride straight up the Florida peninsula, making its own stop at Disney World while the parks are closed down for 2 d
ays, and continue up through Atlanta, GA and into Tennessee. This is the best forecast we have for now with Hurricane Irma.

How Strong will it be?

Irma will be making landfall in south Florida as a Major Hurricane, meaning Category 3 or stronger. The main threat is if Irma does not make landfall over Cuba and continues to strengthen as a Category 5 prior to impact with the Florida Keys.

If Category 5

If Irma makes landfall as a Category 5 Hurricane, then it will remain a major hurricane likely until crossing into Georgia before being downgraded to a Category 2. South and Central GA will experience hurricane force winds (winds >74 mph) and South Carolina and North Carolina will experience tropical storm force winds (winds >35 mph). Then, Irma will be weakened to the point of a depression prior to entering Tennessee. Keep in mind... these are maximum sustained winds discussed here.

Gusts are a different story: Gusts in Florida could still reach 200+ mph... it would be devastating to all structures and vehicles in its way. Georgia could experience gusts exceeding 130 mph, SC gusts > 75 mph, and eastern and central NC gusts higher than 50 mph (while western NC like Asheville could see gusts exceed 70 mph). Tennessee will still likely see a breezy rain storm with gusts possibly exceeding 40 mph.

If Category 3/4

If Irma makes landfall as a Category 3, however, after interacting with the land and terrain of Cuba, then it could weaken enough to be categorized as a tropical storm prior to the central pressure exiting Florida. If this happened, then Georgia, the Carolinas, and Tennessee would receive little more than a windy rain storm.

***Currently (11:00 EST Friday, 09/08/2017) Irma is making a westward shift into Cuba, potentially bringing to fruition the Category 3 and preferred case for the United States***

What will happen along the coast?

East Coast

The east coast of Florida, GA, SC, and south NC will still receive wind, rain, and some storm surge from the power of the winds, however flooding will not be nearly as bad from the ocean itself. There is still a possibility of flooding from rain flowing downstream post-event, but surge will not swallow the coastline like what happened in Sandy or Harvey.

West Coast

The west coast of Florida, however, will receive more significant surge. While the strongest quarter of the storm, typically the Northeast quadrant of the storm, will not be shoving the Atlantic inland trying to gain real estate east of I-95, the southwest quadrant of Irma will still have an effect on the west coast as Irma moves further north. Cape Coral, Sarasota, and Tampa will likely all receive more significant storm surge now that the westward shift is being realized.

To the right I have posted an image from the RadarScope (copyright) application with the Miami, Florida radar image. At 9:58 CDT the outer rain bands were quite visible on the Miami radar.

Stay tuned to your local meteorologists for the most up-to-date information. The same key messages apply, and it is recommended that coastal Floridians evacuate, and take your pets with you. DO NOT LEAVE YOUR PETS BEHIND. It is very sad to hear about pets, let alone human beings, being left behind in storms such as these. They are helpless, and after some of the things I saw in the Harvey aftermath, people can be cruel beings. Please take ALL of your FAMILY MEMBERS with you. They love you unconditionally, and we can all learn a thing or two from that kind of love the Lord commands. Be safe all, and God bless.

Katia, Jose, and Irma... Oh My!!!

'Tis the Season

The tropics are alive and well as we have reached the peak of hurricane season, and it's not going to stop soon. Currently there are three named storms in the Atlantic basin: Hurricane Irma, Hurricane Jose, and Hurricane Katia. Hurricane Katia will spin up some moisture and head down into central Mexico providing some much-needed rain down there. I will discuss Irma and Jose further below.

Major Hurricane Irma

Hurricane Irma has been catching the nation's attention for almost a week now. Riding the wake of Hurricane Harvey, which just spent a week parked over southeast Texas dumping 7-day record-breaking rainfall totals of over 60" and producing catastrophic flooding, Irma has been forced on a more westward path, alerting the Caribbean and United States of the raw power of God's creation. Tuesday afternoon (18Z 20170906), Air Force Reconnaissance recorded wind data on their flight, including max sustained winds exceeding 185 mph.

The Caribbean Islands are experiencing Category 5 hurricane Irma now and the next island to receive a direct hit will be will be Haiti and the Dominican Republic. Some islands, including Barbuda and St. Martin, have basically been destroyed... In Barbuda, all cell phone towers have been knocked over, the reinforced steel bent and twisted from the strength of the winds.

One aspect of this storm to keep in mind is its relation to the Synoptic, or large-scale environment. High pressure building into the Great Plains is forcing Irma on a more westnorthwestward path, however as the trough ahead of it lifts out into the northern Atlantic, Irma is expected to make a sharp turn to the northnortheast. It has already begun heading more NW than earlier, and models now have major hurricane Irma running up the east coast, potentially making landfall in Miami on Sunday morning/afternoon.

Georgia and the Carolinas are currently in the line of sight for Irma, however northern Hispanola, the Bahamas, and Florida reside in the immediate path. Much destruction has already occurred in the Caribbean, and although Irma has weakened slightly, more is to be expected with the now max sustained 180 mph winds. I have pictured to the left the most updated ensemble projections for the path of Hurricane Irma of the ECMWF (European Model, top) and the GFS Ensemble (American long-range Model, bottom). Irma is expected to cut back, but even now the models are not sure where exactly it will go. Whatever the case may be, the Bahamas and South Florida need to be preparing for the worst. Below I have also shared NOAA's main points regarding the devastation capable of Irma. 

Here's what to prepare for (Irma edition):

High winds: While flooding remains a threat, the strong wind capable of toppling buildings and tossing automobiles like matchbox cars is the real threat initially. Keep in mind, 180 mph is about how fast planes fly when landing or taking off. It is about three times that of highway speed, and this powerful wind is capable of moving/uprooting/toppling just about anything. Even if this storm weakens as it moves up the coast and veers toward the Carolinas, as some model runs would suggest, places like Asheville, NC could experience hurricane-force wind gusts exceeding 75 mph.

Flying debris: Piggybacking off of the high wind potential, debris will be carried by winds. These winds can be equated to those found in an EF-4 tornado, which tends to flatten anything in it's path. The straight-line winds in a hurricane do not have quite the devastating effect of those found in an EF-4 solely because the pressure differential is much greater in a tornado, because it is a smaller cyclone of rotation, but nevertheless the winds can flatten structures and fling debris through the air with ease.

Power outages: Cause and effect from the first two potential hazards leads us to the third hazard to prepare for, and that is widespread power-outages. While Irma will likely move quickly up the coast, the sheer strength of the storm will blow over power lines and possibly even ruin substations and power stations depending on their location... In this case, millions of people could lose power for an extended period of time while power companies work extra overtime in order to get everyone back on the grid. Make sure you have supplies prepared in the event of extended power outages.

Flooding: The final hazard I want to rehash is the possible of catastrophic flooding. This storm will not park itself over one location for a week as did Harvey, but the strength of the wind will cause massive storm surge along the coast, especially between Charleston and Wilmington should the current path come to fruition, and heavy rainfall further inland will flow down the narrow river basins overrunning banks potentially flooding downstream neighborhoods as we saw with Hurricane Matthew last year.

Hurricane Jose

Even just 24 hours ago, Jose was "supposed" to be a fish storm and curve back out to sea. Mother nature had a different idea in mind. The prevailing easterlies are proving to be an effective mode of transportation for Hurricane Jose, and now it is expected to take a more northwestward path. The danger now lies with the northern Caribbean islands which just got decimated by Hurricane Irma... and that danger is that another Hurricane will be making its visit in likely before the end of the weekend. There are reports that 90% of structures and automobiles have been destroyed on the Island of Barbuda, and now there is a possibility of another Hurricane, possibly Major Hurricane, wreaking additional havoc less than a week later. Hurricane shelters and other shelters alike were demolished from the record-breaking winds of Irma, and now another storm poses a threat to the Caribbean.

Essentials

Below is a list of items which would be necessary for survival should the above situations occur, those including flooding, widespread power outages, and wind damage.

1. Bottled Water
2. Canned Foods
3. Flashlight with extra batteries
4. External Phone Charger/Battery Pack
5. Some means of receiving updated information in the event of a power outage (i.e. phone, battery-powered weather radio, etc.)
6. Tent, sleeping bags, and other essentials for sleeping outdoors should residential structures become damaged to a point of endangering those residing in them.
7. Safe location away from the coast/coastal waterways

Not all of these may be possible, but now that NC and SC are both in a state of emergency, I highly recommend taking the necessary steps to prepare yourself and your loved ones for the worst, obviously praying and hoping for the best. The death toll has begun in Barbuda with already 6 people being proclaimed dead, and that number will only rise as conditions clear behind the storm ahead of Jose and damage can be assessed. Please do not take this storm for granted, as it is a life-threatening storm capable of catastrophic damage.

Evening Storms and Overnight Severe in NC

We have an interesting situation setting up with good potential for a severe outbreak in the Southeast, including North Carolina. A trough with a strong jet streak upstream is becoming negatively tilted. In layman's terms, that means that it is increasing in strength rapidly and gaining atmospheric potential to unwind in a severe way.

Here's the situation: Storms will be forming and rolling through around dinner time. These storms, for central North Carolina, will more likely be our normal thunderstorms than not. The main event will come in the wee hours of Thursday morning and last into the morning commute (3:00 a.m. until 7:00 a.m.), making anything severe that much more dangerous due to the lack of available light for observation. Soundings indicate the possibility for a Linear Convective System to establish itself prior to moving eastnortheastward across the state, with growing potential for isolated supercell formation and tornadoes.

|A Supercell Thunderstorm is one in which the main core involves a lower, rotating mass of clouds called a mesolow. This rotation allows for super strong updrafts capable of creating and maintaining hail stones larger than golf balls and in some cases larger than tennis balls, and if the conditions are right and the rotation persists, a tornado can form. There are many more factors involved in tornado formation which I will not go into at this point.|

Threats:

The imposing danger is split into 3 different parts.

1. Strong Winds: This not including tornadoes... Atmospheric sounding profiles would suggest that throughout the event, 850 and 700 mb wind speeds would produce non-insignificant damage if mixed down to the surface, and currently it looks as though with high equivalent potential temperature (theta-e) air will be mixed into the system by the Gulf with southerly winds ahead of the line. This high theta-e air mixed into the middle of the atmospheric profile will provide instability (even though the surface instability from surface heating will not due to the time of day), and mixing to the surface could occur, producing surface instability and atmospheric mixing. These winds, when mixed down, could blow at a rate of 50 or 60 mph, a speed capable of toppling trees and power lines.

2. Hail: The hail danger is fairly straight forward. If hail forms, it will likely cause damage. If it's large enough, it could cause window breakage and crop damage in addition to dents in the roofs and hoods of cars.

3. Tornadoes: Tornadoes can form in two of the aforemention situations... either in the isolated supercell thunderstorms, or in a piece of a multicell line that accelerates due to strong winds from aloft. One piece I did not mention about those strong winds in point 1, is that if they mix down they can aid the advancement of a piece of the line of t-storms ahead of the rest of the line. In this case, the northern portion of that advancing segment could wrap around and allow for tornadic formation. The other situation is within a supercell thunderstorm, where the rotation found in the mesocyclone (aforementioned "mesolow") extends down to the surface.

Keep all forms of social media and warning prepared for tonight, as these storms will be arriving while most everyone is asleep, increasing the danger which exists with already dangerous storms. I will be retweeting from @miscan5000 and sharing by miscan5000 on Facebook overnight to help keep updates coming. Have an awesome day everyone! Keep your eyes to the sky!

Subsequent "Winter is Coming" Accumulation Update for North Carolina

Updated information is necessary!

The band of expected highest accumulation has shifted to the northeast from earlier. Temperatures are a bit warmer aloft than expected a few days ago for this storm. The transition zone is setting up around the Triangle as it usually does with these types of systems. However, 

New Accumulation Expectations

Many respected meteorologists in the area have been seeing similar hints from the models. 

Mountains: 

Boone, Asheville, and other areas in the foothills and higher elevations can expect from 3-7"

Western Piedmont: 

Salisbury, Asheboro, Winston Salem, Greensboro, and up to Danville, VA can expect highest accumulations. Most of these areas can expect 6-10", and higher accumulations will be experienced depending on where heavier mesoscale snow bands set up. Some areas, if conditions are favorable throughout the night into the morning, could see over 12"

Eastern Piedmont: 

Durham, Chapel Hill, Hillsborough, up into Roxboro, Henderson, and down into Pittsboro and Siler City could also see greater accumulation of 6-10" with the same case concerning snow banding. 

Raleigh, Wake Forest, Louisburg, Rocky Mount, and up to Roanoke Rapids are expecting now lower totals of snowfall as there is still that warm air aloft. If dendrites form higher up in the atmosphere, then melt in that warm layer, it will not take much time to cool the atmosphere to freezing at this layer. When this happens we will make the transition to snow here. Snow totals though are backing off to 2-4" for now. We still need to see what happens with that warm layer before making another update on accumulation amounts. 

Sandhills / Upper Coastal Plains: 

Laurinburg, Fayetteville, and Goldsboro have the best chance of snow accumulation in the Sandhills which will start later than other areas once the temperature cools off. All snow is expected by daybreak, however most of the moisture will have precipitated by that point. I am forecasting up to 1-2" max in these areas.

Greenville, Oak City, Murfreesboro, and over to Elizabeth City will be on the transition zone or southeast of it. Most of the accumulation in these towns and cities will be that of sleet transitioning to rain/freezing rain. Snow that falls in these areas will begin closer to lunch and accumulations of less than 1" are expected.

Lower Coastal Plains: Most everywhere else in the quadrant east of I-95 and south of US-64 can expect mostly rain transitioning to a wintry mix late in the morning tomorrow. Very little if any snow accumulation is expected. 

Winter is Coming... But How Much? Where? When?

Happy New Year Everyone!

It is only fitting that the first post of the new year would be a snow storm, as these are arguably the most exciting for students and the most challenging for forecasters. This, in my humble opinion, is starting off 2017 correctly!

Now getting to the meat; this post is primarily going to be for North Carolina, however I will mention accumulation forecasts for other parts of the southeastern United States. In addition, there is still uncertainty among computer model members and meteorologists alike as to where the areas of heaviest precipitation will be and what types of precipitation will be experienced. I will try to sort some of that out for you all here. 

The sections below in order include a description of the main meteorological factors contributing to this situation, my forecast for precipitation accumulation and location, and the hazards and impact associated with the outcome (as well as the class cancellation forecast should it be necessary). While I understand many are only concerned with the forecast, I encourage all of you to read the why associated with this system. It is a very complicated system with many uncertainties and ultimately we as meteorologists will not know exactly what will happen until it happens with this storm. As Nate Johnson, meteorologist and Executive Producer at WRAL-TV put it today on the radio, "there's a lot of 'bust' potential with this storm". It's not easy to predict the future, but it's possible to prepare for what may happen.

Setup / Meteorological Factors

Model Forecast Temperatures Overnight Friday Night

Model Forecast Low Temperatures Sunday Morning

Cold Air: Cold air is being forced into the south by the Canadian high pressure system in conjunction with an upper-atmospheric ridge (area of high pressure higher up in the atmosphere), and is banking up against the eastern side of the Appalachian Mountains as a result of the Coriolis Force, or the apparent right turning of objects and fluids in the northern hemisphere (and left turning in the Southern Hemisphere) as a result of the earth's spinning on it's axis. This cold air has another role: aiding in accumulation. The 4" soil temperatures in the Piedmont and Coastal Plains are much too warm at this point to be conducive to accumulating frozen precipitation, however cooling temperatures over the next few days will bring these temperatures to a more manageable temperature. On Monday, soil temperatures in the Triangle were around 50 degrees Fahrenheit. However, by late Friday night into early Saturday morning, cold air and some already fallen precipitation will assist the ground temperature to reach that desired (or dreaded) freezing point. 

Model Forecast Low Temperatures Monday Morning

Moisture: As this ridge has been building, an area of low pressure is being forced around it. This low pressure last weekend had not yet crossed onto the Continent and was still out over the Pacific Ocean. As this low pressure center progresses, it is expected to travel over the Gulf of Mexico, cross over Florida, and proceed northwest along the coastline while remaining at sea. The importance here is that winds flow counterclockwise around the low's center, meaning that as the center is located over the warmest water in the Gulf and the Gulf Stream, winds to the north will be flowing toward the continent carrying moisture-rich air parcels. 

Atmospheric Ascent / Lifting Mechanism: In order to receive precipitation from that moisture, some sort of lifting mechanism is needed to force those air parcels upward in the sky where they can cool and condense into liquid precipitation from water vapor. The setup we have for this weekend includes at least two lifting mechanisms: orographic, and atmospheric. The orographic lifting mechanism resides in the mountain range. As the wind blows toward the mountains, it has nowhere to go but up, and rises over the range allowing the moisture in the air to cool. Atmospheric lifting will occur as surface air is forced toward and over the "cold dome". That dome of cold air is created and maintained by continental surface winds originating from the north/northeast (in VA, NC, SC, and GA) continuing southward and turning into the Appalachian mountains.

Precipitation-Type / Timing / Accumulation

P-Type and Timing:

Precipitation Type Model Guidance through 7:00 a.m. EST Saturday

Precipitation Type Model Guidance through 1:00 p.m. EST Saturday

At this point it looks like the main swath of precipitation will run through the eastern Piedmont and western Coastal Plains of NC angled northeastward from Greenville, SC up through Norfolk, VA... essentially following the I-85 corridor. A gradient of accumulation will likely develop on either side of this corridor. Due to warmer temperatures at the onset of the precipitation, p-types will likely begin as rain in the afternoon across the board with the exception of the higher elevations to the west. After a couple hours, the precipitation will likely shift over to a mix of snow, sleet, and freezing rain. Temperatures will be cooling off very rapidly, and less than a couple hours later around dinner time or slightly after we will begin seeing the transition to snow. Snow will be the main precipitation type for the Coastal Plains and Piedmont for Virginia, North Carolina, South Carolina, and Georgia. Those living on the coast will likely experience a mix of sleet and snow due to slightly warmer temperatures through the duration of precipitation.


Wintry Accumulations:

Accumulations will likely not be as high as many of the shared pictures have shown, and to be completely honest there is still a decent chance of some areas to the northwest in NC and southeast in SC who will not see precipitation at all. That being said:

Deep South: Places including Northern Alabama and Mississippi could see a trace to some measurable accumulation around 0.5". There are also chances for a wintry mix in southern Mississippi and Central Alabama.

Southeast: Northeast Georgia could receive up to between 1-2", and areas in Northwest South Carolina could receive between 2-3".

East: The range I am forecasting now for Southwest to Northeast North Carolina is a main swath of between 3-5" with some areas possibly seeing 5-6" with a gradient up to the Northwestern NC foothills of 0.5-1", increasing again to into the higher elevations with between 2-3" in places like Boone, Grandfather Mountain, and Asheville. It is looking like the Virginia Beach area and Norfolk area will receive part of that main swath so probably 2-3" in areas up there.

Coastline: I want to do a special accumulation forecast for the coastline because it is likely that those living between Charleston and the Outer Banks (at this point at least) will receive some accumulating freezing rain. I am not sure how much, however some model representations approximate up to 0.5" of freezing rain accumulation in places of extended freezing precipitation. This will provide grounds for power outages (as I will mention in "Hazards").

Hazards

1. Slick Roads: Whenever we get wintry precipitation, the roads fail to remain clear of drivers, and in the case of snow drifts, pedestrians as well. At first, rain will aid in the road surfaces cooling, however after the temperature drops to below freezing, that layer of water will quickly become a layer of ice. Be mindful of how much time you spend on the road as it is unsafe for yourself and others.

2. Wind: While there should not be too many instances where the wind will blow rapidly, gusty conditions at times cannot be ruled out. In the cold and potentially freezing precipitation, this could spell power outages. Power outages in the cold could cause many health issues.

3. Biting Cold: Not only are we going to be below freezing for the majority of the precipitation event, but after the precipitation comes to a halt the temperature will drop even more quickly. The sky will clear on Saturday afternoon into Saturday evening, and cold air advection (the movement of cold air from location to another, in this case from Canada down to NC) and radiative cooling, or the process of longwave electromagnetic radiation being emitted from the earth's crust and released into the atmosphere, will work in tandem to cool the temperature into the single digits. There is a possibility that we will wind up setting some new low temperature records, and possibly even a few lowest highs. The American weather model even has us getting down below 0 degrees F without including wind chill. It is going to be very, very cold.

4. Hypothermia/Frost Bite: When it gets this cold, it does not take long before your body begins to slow down and show signs of frost bite or hypothermia if you have been exposed to cold water. I have posted here the National Weather Service Windchill Chart. After some model analysis, we can expect wind chill values throughout Sunday into Monday to drop into the single digits with possible values below 0. When it gets this cold, a time of only 30 minutes is necessary before frost bite affects exposed pieces of the body. If your power goes out, be sure to have a supply of candles and blankets ready to keep your living spaces lit and warm.

5. Bursting Pipes: This is usually not a hazard for us in the Southeastern United States, however with an air mass as cold as this one is expected to be, make sure you have your faucets dripping at night.

Class Cancellation Forecast

Unfortunately, church will likely be cancelled on Sunday, however I would recommend having your quiet time even so.

I have a hard time believing that classes will resume for the Spring semester on Monday, January 9. Temperatures will be so cold that we will be experiencing a hard freeze during the middle of it, and anything that has a special opportunity to melt will freeze again on Saturday and Sunday Nights.

I believe that because of warming weather Tuesday will not be a complete snow day, but a half day.


That is all I have for you right now! Get your bread, milk, and be sure to fill up your cars with gas! I hope everyone has  a great couple of snow days and stays safe!