12:45 PM | The day of reckoning has come for Comet ISON

[Image courtesy spaceweather.com taken yesterday from the Canary Islands, eastern Atlantic Ocean]

Discussion

On Thursday, Thanksgiving Day, Comet ISON will make its closest approach to the sun flying through the sun’s atmosphere little more than a million kilometers above the solar surface. At closest approach, the core of ISON could rise by as much as 5000° Fahrenheit – a life or death challenge for an icy comet. No one knows if it will survive.

But if ISON makes it out alive, it could provide a great show to the naked eye and possibly even live up to its billing as the “Comet of the Century”. On Friday, professional and amateur astronomers will be searching for the comet as it comes around the sun and then between Thanksgiving and Christmas, it will fly over the North Pole – potentially, a very nice holiday comet.

What makes ISON quite special is that it is a lone traveler originating from a giant population of comets at the very edge of the solar system – the furthest reaches of the sun’s gravity. The distance from the Earth to the sun is an “astronomical unit” or AU. Pluto, as an example, is 40 AU from the sun. Comet ISON began its journey 100,000 AU away from us in a place called the Oort cloud which contains billions of icy, rocky objects. Detected comets from the Oort cloud are quite rare – probably only a handful per century.

For all of human history – at least a million years according to NASA – this comet has been heading towards the sun. We’ll know beginning this Friday, after coming within a hair of the sun, if Comet ISON survives and is ready to put on a great show for us during the month of December.

12:00 PM | *Coastal storm threat continues for the middle of next week*

Discussion

The latest (12Z) run of the Global Forecast System (GFS) computer forecast model has backtracked somewhat from its previous couple of runs with respect to a potential significant midweek coastal storm in that it now phases a strong northern system with a potent southern system at a slower pace which allows the storm to form slightly farther to the east. There is still plenty of time to go; however, for this particular model to get back to a sooner phasing of energy and other forecast models do suggest that there will be a quicker phasing of these waves resulting in quite a rapidly intensifying coastal storm by the middle of next week – just in time for pre-Thanksgiving Day travel time period. The GFS forecast model is, in fact, known for a southeast bias with respect to coastal storm tracks so I wouldn't be surprised if it were to shift the track back to the west and we’ll monitor it closely. [12Z GFS 500 mb forecast map (above) showing both systems is for next Wednesday morning, courtesy weather.cod.edu)

The overall synoptic pattern shaping up for next week certainly suggests that there is potential for a significant coastal storm. First, a strong system will be moving eastward in the northern branch of the jet stream and it will be associated with an influx of fresh cold air. Second, a potent upper level low will be crossing the Gulf of Mexico and once this fresh cold air mass interacts with the southern system, rapid intensification of low pressure should take place near the Mid-Atlantic coastline. In addition, if you then throw in copious amounts of Gulf of Mexico moisture that will be available, this potential storm could turn out to be quite a precipitation producer even including thunderstorms in the vicinity of the low pressure system.

As far as precipitation-type is concerned, climatology is indeed one factor against snow in the I-95 corridor this time of year; specifically, with regard to the still-warm Atlantic Ocean waters. While odds do favor rain along the coast and inland back to the I-95 corridor big cities, it is still a close call and, if the phasing is just right, snow could be the result around here or perhaps there may be a “rain changing to snow” scenario. Accumulating snow is quite possible just to the north and west of the big cities in the colder higher elevation locations. Stay tuned.

7:00 AM | **Brutal cold on Sunday some 20+ degrees below normal**

6-Day Forecast

Today

Mostly cloudy, milder, a few showers likely, highs near 60 degrees

Tonight

Mostly cloudy, cool, chance for showers before midnight, lows in the low 40’s

Saturday

Becoming mostly sunny with increasing winds, highs in the low 50’s that may be reached in the morning

Saturday Night

Partly cloudy, colder, windy, mid 20’s

Sunday

Bitter cold for this time of year more than 20 degrees below normal; partial sunshine, windy, very cold with a snow shower or two possible, highs in the low-to-mid 30’s

Monday

Mostly sunny, brisk and still very cold, upper 30’s

Tuesday

Partly sunny, cold, chance for rain or snow at night, low 40’s

Wednesday

Cloudy, cold, rain and/or snow likely, low-to-mid 40’s

Discussion

A strong cold front will usher in an Arctic blast over the weekend and this air mass will be the coldest so far this season. The front will generate some shower activity around here from today into the first half of tonight, but then skies will clear on Saturday as winds begin to pick up in intensity. A snow shower or two can occur tomorrow night as the bitter cold air pours into the region and Sunday will flat out be a brutal day for this time of year with high temperatures struggling to reach the freezing mark and there will be strong northwest winds up to 30 mph generating even lower wind chills. The unusual cold will continue on Monday and then attention will turn to a storm pulling out of the Gulf of Mexico region by later Tuesday as it heads towards the Mid-Atlantic coastline. This storm could throw some rain and/or snow into the region by the middle of next week before yet another Arctic outbreak reaches the east coast in time for Turkey Day. Odds favor rain along the I-95 corridor and snow in the higher elevations just to the west and north of the big cities, but it is still a close call and ultimately it could evolve into a rain changing to snow scenario around here. Stay tuned on this storm coming next mid-week...just in time for the Turkey Day travel.

7:00 AM | An Arctic invasion arrives for Sunday and Monday; another cold blast should arrive in time for Turkey Day

6-Day Forecast

Today

Mostly cloudy, cold, highs near 50 degrees

Tonight

Mostly cloudy, not as cold as recent nights, maybe a shower towards morning, lows in the low 40’s

Friday

Mostly cloudy, milder, chance for showers, upper 50’s

Friday Night

Mostly cloudy, chilly, showers likely, mid 40’s

Saturday

Clouds and showers early then partial sunshine and becoming windy, temperatures may peak during the morning hours in the low 50’s

Sunday

Partly sunny, windy, very cold, maybe a snow shower, low-to-mid 30’s

Monday

Mostly sunny, still very cold, near 40

Tuesday

Mostly cloudy, chance for rain or snow, cold, mid 40’s

Discussion

A strong cold front will usher in an Arctic blast over the weekend and this air mass will be the coldest so far this season. The front will generate some shower activity around here from early Friday into early Saturday, but clearing is likely Saturday afternoon as the winds pick up in intensity. By Sunday, the Arctic chill will be firmly entrenched in the region with high temperatures doing no better than the low-to-mid 30’s (normal high at DCA is now 57 degrees) and strong winds will cause even lower wind chill values. The unusual cold will continue on Monday and then attention will turn to a storm pulling out of the Gulf of Mexico region by later Tuesday as it heads towards the Mid-Atlantic coastline. This storm could throw some rain or snow into the region by the middle of next week before yet another Arctic outbreak reaches the east coast in time for Turkey Day.

Video

httpv://youtu.be/RNdd8AdlstQ

7:00 AM | *Cold again today and an Arctic invasion for Sunday and Monday*

6-Day Forecast

Today

Mostly sunny, brisk and cold, highs in the upper 40’s

Tonight

Mostly clear, cold, lows in the low 30’s

Thursday

Partly sunny, chilly, low-to-mid 50’s

Thursday Night

Mostly cloudy, cold, upper 30’s

Friday

Mostly cloudy, cool, chance for showers at night, mid-to-upper 50’s

Saturday

Clouds and showers early then becoming partly sunny and windy, highs in the low-to-mid 50's may be reached in the morning as PM temperatures could drop

Sunday

Partly sunny, windy, very cold, mid-to-upper 30’s

Monday

Mostly sunny, very cold, upper 30’s

Discussion

Cold high pressure will continue to control our weather today and temperatures will hold at well below normal levels. There will be some modification in temperatures later this week as another cold front approaches the region and it’ll help to pump in slightly milder air ahead of it. That cold front is likely to spread some shower activity into the region on Friday night and early Saturday. Following the front, very cold Arctic air will flood the Mid-Atlantic region for Sunday and Monday. In fact, this will be the coldest air of the season so far and temperatures are likely to hold in the 30's for highs on both days. Looking ahead, a storm will pull out of the Gulf of Mexico region by mid-week and heads towards the Mid-Atlantic coastline. While odds favor rain around here, higher elevations to our north and west could indeed get some accumulating snow out of this system by mid-week.

Video

httpv://youtu.be/FD8NHWZrW6w

7:25 PM | UPDATE: New launch time is 8:15PM

Discussion

T-1 hour and counting. New launch time is 8:15 p.m. EST

6:45 PM | UPDATE: Launch currently on hold at T-1 hour

Discussion

T-1 hour and holding. The range team continues to troubleshoot issues at the tracking site in Coquina, NC. The launch window runs until 9:15 P.M.

2:30 PM | Another rocket launch tonight at Wallops Island, Virginia could put on a spectacular show

Discussion

The last time there was a rocket launch at Wallops Island, Virginia it made for quite a spectacular sight throughout the Mid-Atlantic region and there is another opportunity this evening for one more great show. An Orbital Sciences Minotaur I rocket is scheduled to lift-off tonight at 7:30 PM from NASA’s Wallops Island Facility and the weather conditions are looking quite favorable as the current gusty winds are likely to diminish by early tonight and the skies are mostly clear. The nighttime launch could light up the sky for millions of observers along a wide swath of the east coast from Maine to Florida and inland as far as Michigan, Indiana and Kentucky according to the Orbital Sciences visibility map (above).

The launch will be the second of a Minotaur from Wallops in the last three months and this one will set a record of 29 satellites launched from a single rocket. The primary payload is the Air Force Space Test Program Satellite-3 spacecraft, a mission that will measure different aspects of the space environment. The launch also will be part of the FAA’s certification process for the Minotaur rocket.

In addition, the rocket will deploy 28 “CubeSats” or nano-satellites and carry two non-separating tertiary payloads. Among the “CubeSats” being launched is TJ3Sat, the first satellite built by high school students to be launched into space (Thomas Jefferson High School in northern Virginia). The Minotaur I is a four stage rocket capable of boosting up to 1300 pounds into low-Earth orbit.

The launch will be carried live at this web site beginning at 6:30 PM: http://www.ustream.tv/channel/nasa-tv-wallops. In the Philly and New York City metro regions look near the horizon in the southern sky at launch time and, if in the DC area, look to the southeastern sky.

7:00 AM | Cold for the next couple of days then some modification; more cold air arrives later in the weekend

6-Day Forecast

Today

Clouds early then becoming mostly sunny, windy and cold, highs in the low 50's

Tonight

Mostly clear, cold, lows in the upper 20’s

Wednesday

Mostly sunny, brisk and cold, upper 40’s

Wednesday Night

Mostly clear, cold, low-to-mid 30’s

Thursday

Partly sunny, chilly, low-to-mid 50’s

Friday

Mostly cloudy, cool, chance for showers at night, mid 50’s

Saturday

Mostly cloudy, cool, chance for showers, mid-to-upper 50’s

Sunday

Partly sunny, windy, cold, upper 30’s

Discussion

Cold high pressure will spread eastward from the Central Plains over the next couple of days and this will keep us below normal through tomorrow. Temperatures will modify slightly on Thursday and then another cold front should approach the region at the end of the week and even colder air is likely to arrive by the second half of the weekend.

1:15 PM | Sudden brightening last week of Comet ISON gives some hope for a great show

Discussion

Comet ISON is nearing its closest approach to the sun and it surprised many astronomers by suddenly brightening quite significantly late last week. If that trend continues, it could make for a sight visible with the naked eye in the low east-to-southeast horizon in the pre-dawn sky very soon, and it could last through January. If the comet is torn apart; however, there might only be a bright flash visible to Earth and then nothing more.

The comet’s recent outburst of activity has done more than simply brighten the comet. Whatever exploded from the comet’s core created a spectacularly long tail that is estimated to be more than 16 million kilometers from end-to-end. The tail of the comet now stretches more than 7 degrees across the sky which is almost as wide as the bowl of the Big Dipper (image courtesy of spaceweather.com). Physically, ISON’s tail is about 12 times wider than the sun so when the head of the comet plunges into the sun’s atmosphere on November 28th, Thanksgiving Day, more than 15 million kilometers of the comet’s tail will still be jutting into space behind it.

Because so much gas and dust is spewing from the comet’s core, it is impossible to tell what caused the outburst in activity late last week. Is this a short-lived event or the beginning of a more active phase? It is possible that the nucleus has become completely fragmented and, if so, it will be several days before we know for sure. Stay tuned.