Latest update from the Hurricane Center continues the same forecast rationale but shows the turn in towards land happens a bit faster and, thus, landfall is further south - in central NJ. That's not so great for us here in DC as it likely means more rain and wind probably starting on Sunday and lasting until Tuesday.
Friday, October 26, 2012
Thursday, October 25, 2012
Sandy Threat: 5 PM Update
Here's the latest Hurricane Center update:
Not much change in the forecast rationale. This update carries the storm through landfall in New Jersey. The storm will be quite large (in areal extent) by landfall so the center isn't really a focus - this storm will effect the region from the Carolinas to the upper Northeast especially along the coast.
There are still some crucial details to sort out - and that should happen in the next couple of days. Temperatures around here on Monday and Tuesday will struggle to get out of the 40's with wind and occasional heavy rain. Snow is possible in the mountains.
All we can do is watch the models and see if anything changes but at this point, there's pretty good indications for a serious weather event in the Mid-Atlantic and Northeast early next week.
Not much change in the forecast rationale. This update carries the storm through landfall in New Jersey. The storm will be quite large (in areal extent) by landfall so the center isn't really a focus - this storm will effect the region from the Carolinas to the upper Northeast especially along the coast.
There are still some crucial details to sort out - and that should happen in the next couple of days. Temperatures around here on Monday and Tuesday will struggle to get out of the 40's with wind and occasional heavy rain. Snow is possible in the mountains.
All we can do is watch the models and see if anything changes but at this point, there's pretty good indications for a serious weather event in the Mid-Atlantic and Northeast early next week.
Sandy Trouble for the Mid-Atlantic / Northeast?
Hi everyone! I guess we're starting a bit early this year.
For the record: I expect this winter to be significantly snowier than last winter - so, if that ends up being the case, there will be lots to blog about.
First, though, there's Sandy.
In 1991, right around this time in fact, an intense low pressure system developed off the coast of Canada and moved southward because of a large blocking high pressure system. The storm became so large and organized that it actually absorbed a hurricane (Grace) and became a hurricane itself. The Perfect Storm, as it would be known, eventually impacted the Mid-Atlantic and Northeast - largely through huge surf and the resulting coastal damage. If the storm had actually made landfall, it would have been much much worse.
While this is not the same situation, we have another case where a large system (in this case, a strong cold front moving across the country) could significantly affect the track of a hurricane (in this case, Sandy). And this time, it looks like the effects on the east coast could be more direct - especially if certain model solutions verify.
Weather forecasts are fraught with conditional language. "Could", "if", "might", "chance" are the vernacular of most meteorologists and the reason - as I've often mentioned - is that the atmosphere is a hugely complex system where any small change in a particular parameter could change everything about a forecast.
That said, it seems likely Sandy will continue to move north or north-northeastward for the next 36 hours or so before curving somewhat more to the northeast. At that point, several factors will combine and how they combine is really important.
Most models now forecast Sandy's northeastward motion to accelerate on Saturday and Sunday. If the timing of the incoming cold front is just right, sometime on Sunday the accompanying trough may "capture" Sandy and that's where the problems really begin.
A couple of days ago, this "capturing" looked unlikely to happen. Now the timing and system locations look more and more like it will happen. In fact, only one model right now suggests that the storm will pass harmlessly out to sea - i.e. that the trough will miss the capture and Sandy will become what is referred to as a Fish Storm. And actually, looking at the latest model runs, I think that one has jumped on board as well.
At the same time, colder ocean surface temperatures and interaction with the trough will probably cause Sandy to begin transition to an extratropical cyclone. In technical terms, Sandy will be changing from a warm-core low (tropical system) to a cold-core low (extratropical). In practical terms, the winds at the center of circulation will begin to weaken but the wind field itself would spread out significantly from the center meaning that places well inland could have tropical storm-force winds.
We could be looking at practically every weather effect you can think of from a storm like this. There would be big problems with surf, coastal beach erosion and wind damage at the coast - especially at and north of the center landfall location. Winds of 70-80 miles per hour at the coast would be common - even in places like New York City and especially in Long Island and points to the north. Rainfall amounts will vary by location and I'm not sure at this point how much we'll see here but areas in the northeast will likely receive many inches of rain and elevated areas - especially in Pennsylvania and New York - could see a lot of heavy, wet snow. Tropical storm-force winds could affect the entire region which means a lot of tree damage.
Here is one of the latest model runs showing the storm position on Halloween just off of New York City:
If this verifies, this would be a historic storm - the type that gets named afterwards (and I don't mean something like "Sandy").
In some models, the storm actually does a loop before heading out to sea. During this loop is when we in the DC area stand the best chance of receiving precipitation although I think that we would see winds and clouds before then.
The time frame for effects here looks to be starting on Sunday and lasting into Tuesday night with wind and clouds initially, some rain during the curve into the coast and then, depending on what it does next, some lingering effects.
There is a lot of uncertainty as to the particulars of who-sees-what. Right now, what seems least likely is that Sandy will go harmlessly out to sea (unfortunately). Readers in the northeast and along the coast should consider making preparations soon and we'll watch this for the next couple of days to see what its going to do.
Snow is fun and big storms in the winter are fun but there's nothing fun about this one. This could be really bad - especially north of the DC area along the coast. Let's hope something changes in the next 48 hours to take Sandy out to sea.
More to come.
For the record: I expect this winter to be significantly snowier than last winter - so, if that ends up being the case, there will be lots to blog about.
First, though, there's Sandy.
In 1991, right around this time in fact, an intense low pressure system developed off the coast of Canada and moved southward because of a large blocking high pressure system. The storm became so large and organized that it actually absorbed a hurricane (Grace) and became a hurricane itself. The Perfect Storm, as it would be known, eventually impacted the Mid-Atlantic and Northeast - largely through huge surf and the resulting coastal damage. If the storm had actually made landfall, it would have been much much worse.
 |
| Satellite image of The Perfect Storm on the morning of November 1, 1991. The hurricane has already formed in the center of the circulation although NOAA elected to leave it unnamed to prevent confusion. |
While this is not the same situation, we have another case where a large system (in this case, a strong cold front moving across the country) could significantly affect the track of a hurricane (in this case, Sandy). And this time, it looks like the effects on the east coast could be more direct - especially if certain model solutions verify.
Weather forecasts are fraught with conditional language. "Could", "if", "might", "chance" are the vernacular of most meteorologists and the reason - as I've often mentioned - is that the atmosphere is a hugely complex system where any small change in a particular parameter could change everything about a forecast.
That said, it seems likely Sandy will continue to move north or north-northeastward for the next 36 hours or so before curving somewhat more to the northeast. At that point, several factors will combine and how they combine is really important.
Most models now forecast Sandy's northeastward motion to accelerate on Saturday and Sunday. If the timing of the incoming cold front is just right, sometime on Sunday the accompanying trough may "capture" Sandy and that's where the problems really begin.
A couple of days ago, this "capturing" looked unlikely to happen. Now the timing and system locations look more and more like it will happen. In fact, only one model right now suggests that the storm will pass harmlessly out to sea - i.e. that the trough will miss the capture and Sandy will become what is referred to as a Fish Storm. And actually, looking at the latest model runs, I think that one has jumped on board as well.
 |
| The official National Hurricane Center forecast (at 11 AM 10/25) shows the capture taking place on Sunday and the storm turning in towards land by Monday with potential landfall on Tuesday as an extratropical storm or hybrid. |
At the same time, colder ocean surface temperatures and interaction with the trough will probably cause Sandy to begin transition to an extratropical cyclone. In technical terms, Sandy will be changing from a warm-core low (tropical system) to a cold-core low (extratropical). In practical terms, the winds at the center of circulation will begin to weaken but the wind field itself would spread out significantly from the center meaning that places well inland could have tropical storm-force winds.
We could be looking at practically every weather effect you can think of from a storm like this. There would be big problems with surf, coastal beach erosion and wind damage at the coast - especially at and north of the center landfall location. Winds of 70-80 miles per hour at the coast would be common - even in places like New York City and especially in Long Island and points to the north. Rainfall amounts will vary by location and I'm not sure at this point how much we'll see here but areas in the northeast will likely receive many inches of rain and elevated areas - especially in Pennsylvania and New York - could see a lot of heavy, wet snow. Tropical storm-force winds could affect the entire region which means a lot of tree damage.
Here is one of the latest model runs showing the storm position on Halloween just off of New York City:
If this verifies, this would be a historic storm - the type that gets named afterwards (and I don't mean something like "Sandy").
In some models, the storm actually does a loop before heading out to sea. During this loop is when we in the DC area stand the best chance of receiving precipitation although I think that we would see winds and clouds before then.
The time frame for effects here looks to be starting on Sunday and lasting into Tuesday night with wind and clouds initially, some rain during the curve into the coast and then, depending on what it does next, some lingering effects.
There is a lot of uncertainty as to the particulars of who-sees-what. Right now, what seems least likely is that Sandy will go harmlessly out to sea (unfortunately). Readers in the northeast and along the coast should consider making preparations soon and we'll watch this for the next couple of days to see what its going to do.
Snow is fun and big storms in the winter are fun but there's nothing fun about this one. This could be really bad - especially north of the DC area along the coast. Let's hope something changes in the next 48 hours to take Sandy out to sea.
More to come.
Sunday, February 19, 2012
South south south.
As you probably know by now given the forecast trends, the storm track has continued to shift south bringing less and less snow and less cold air to our region.
What looked like a bullseye 3 days ago has become another disappointment in this unusual winter.
I expect to see some snow later this afternoon and evening but certainly no important accumulations.
Guess we would have been better off asking the first model what was going to happen rather than depending on the GFS.
With the further-south track also comes less cold air so any precipitation will likely start as rain and change to snow.
What looked like a bullseye 3 days ago has become another disappointment in this unusual winter.
I expect to see some snow later this afternoon and evening but certainly no important accumulations.
Guess we would have been better off asking the first model what was going to happen rather than depending on the GFS.
With the further-south track also comes less cold air so any precipitation will likely start as rain and change to snow.
Thursday, February 16, 2012
The Return
Both of me, and possibly of SNOW!
I've been conspicuously absent from this blog since, well, August when Irene came along and flooded everything. Actually, it was Lee that flooded everything but Irene didn't help.
In any case, there hasn't been much to blog about this winter - certainly no one wants to read a blog about the 1/2 inch of snow that's likely to fall on any given day.
But this weekend looks like the first (last?) real chance at a real snowstorm. If it happens, and the models hold, it looks like we might be in the bullseye for this one which makes it fun, too. At least it gives me something to write about.
Let's start where we always do: the models.
Sorry.
The GFS at 57 hours (10 PM Saturday night) shows a pretty good storm organizing in the southeast US. Note the blue line indicating the freezing point for this particular part of the atmosphere. We want to be north of that line and at this hour, we're right on it. That's a good thing.
Also a good thing? That high pressure area in the Great Lakes that will be moving east and bringing cold air to our area which should make for fewer precipitation issues (snow vs. rain vs. sleet).
At 75 hours, early afternoon on Sunday, the main event should be in full swing around here. This shows moderate to heavy precipitation in our area and that we're well to the north of the freezing line. The potential for significant accumulating snow exists. But the storm track means everything and we're still more than 3 days from this model time.
At 78 hours, late afternoon Sunday, we're still in the thick of it. The storm looks to slide off the coast, right along the freezing line so this likely means not much for our Northeast neighbors but a possible bullseye for us.
By Sunday night the storm is moving away, precipitation ends from west to east and our storm is done.
Of course, the question is "how much?"
For now, I think the concentration should be on whether the models hold for another day. If these runs don't change much and the other models fall into line, this looks like the real deal. The ECMWF has been flip-flopping between a more southerly track and a more northerly track. The southern solution means less precipitation for us so this all bears watching.
For now - the probability exists, I'd say better than 50%, for a significant snowstorm with 3+ inch accumulations starting late Saturday night and ending Sunday night. The possibility for more exists of course but this is the highest probability range for now.
Just for fun: the GFS "clown" map:
which shows us just outside of the 4-6 inch range or so. These aren't all that accurate this far out except to show the path and pattern of the snowfall.
Stay tuned.
I've been conspicuously absent from this blog since, well, August when Irene came along and flooded everything. Actually, it was Lee that flooded everything but Irene didn't help.
In any case, there hasn't been much to blog about this winter - certainly no one wants to read a blog about the 1/2 inch of snow that's likely to fall on any given day.
But this weekend looks like the first (last?) real chance at a real snowstorm. If it happens, and the models hold, it looks like we might be in the bullseye for this one which makes it fun, too. At least it gives me something to write about.
Let's start where we always do: the models.
Sorry.
The GFS at 57 hours (10 PM Saturday night) shows a pretty good storm organizing in the southeast US. Note the blue line indicating the freezing point for this particular part of the atmosphere. We want to be north of that line and at this hour, we're right on it. That's a good thing.
Also a good thing? That high pressure area in the Great Lakes that will be moving east and bringing cold air to our area which should make for fewer precipitation issues (snow vs. rain vs. sleet).
By 66 hours, the storm is really getting wound up. It's phasing (or phased) with northern stream energy from the jet stream and is beginning the turn up the coast. Notice that we're in the freezing zone by this point. It's too early to tell how the precipitation will start, but if these model forecasts hold, the major portion of it should be snow.
At 75 hours, early afternoon on Sunday, the main event should be in full swing around here. This shows moderate to heavy precipitation in our area and that we're well to the north of the freezing line. The potential for significant accumulating snow exists. But the storm track means everything and we're still more than 3 days from this model time.
At 78 hours, late afternoon Sunday, we're still in the thick of it. The storm looks to slide off the coast, right along the freezing line so this likely means not much for our Northeast neighbors but a possible bullseye for us.
By Sunday night the storm is moving away, precipitation ends from west to east and our storm is done.
Of course, the question is "how much?"
For now, I think the concentration should be on whether the models hold for another day. If these runs don't change much and the other models fall into line, this looks like the real deal. The ECMWF has been flip-flopping between a more southerly track and a more northerly track. The southern solution means less precipitation for us so this all bears watching.
For now - the probability exists, I'd say better than 50%, for a significant snowstorm with 3+ inch accumulations starting late Saturday night and ending Sunday night. The possibility for more exists of course but this is the highest probability range for now.
Just for fun: the GFS "clown" map:
which shows us just outside of the 4-6 inch range or so. These aren't all that accurate this far out except to show the path and pattern of the snowfall.
Stay tuned.
Friday, August 26, 2011
Here Comes Irene
I've decided to post a rare non-winter blog entry because of the impending hurricane here on the East Coast. As usual, the post will be more concerned with effects in the DC area since that's where I live.
Irene is currently a Category 2 hurricane. She has weakened a bit in the last day or so and has maximum sustained winds of 100 MPH placing it just inside Category 2 status (which begins at 96 MPH). The intensity will likely not change significantly before landfall in extreme eastern North Carolina - probably in the vicinity of Cape Lookout tomorrow morning.
Two things to remember:
- This storm is large. So is the extent of the rain and wind fields. For this reason, its projected path offshore is still close enough to the coast to cause problems for us.
- However, the cut-off between significant rain and just a few showers is usually pretty sharp with hurricanes passing to our east. If the storm follows the current forecast track, I'd guess that we'll get significant rain in the DC area - especially south and east of the city.
If this type of forecast sounds familiar it's because a hurricane's impact pattern is similar to the large snowstorms we get in the winter. Track means a lot - although exactly where the center travels matters less...especially with a storm this large. That's why the National Hurricane Center cautions people to concentrate less on the line that marks center track and just heed the warnings they issue.
Speaking of which...
We're under a Tropical Storm Warning here in the DC area - mostly for areas near water but including the following counties:
DISTRICT OF COLUMBIA...NORTHERN BALTIMORE...HARFORD... MONTGOMERY...HOWARD...SOUTHERN BALTIMORE...PRINCE GEORGES...ANNE ARUNDEL...CHARLES...CALVERT...PRINCE WILLIAM/MANASSAS/MANASSAS PARK...FAIRFAX...ARLINGTON/FALLS CHURCH/ALEXANDRIA...STAFFORD...
SPOTSYLVANIA AND KING GEORGE.
And in St. Mary's county, the Tropical Storm Warning is now a Hurricane Warning.
So what should we expect?
The storm is likely to move fairly far off the coast so I expect the worst conditions on the Eastern Shore.
Probably 6 inches of rain and winds gusting to 80+ there at times tomorrow.
Here, things start going downhill late tonight. The first bands from Irene could arrive tomorrow morning
and the winds will be increasing all day. Expect winds in the 20-30 MPH range by tomorrow afternoon,
increasing to 30-40 with higher gusts tomorrow night. The worst should be tomorrow evening and
overnight as the storm passes by to our east.
Again, the cutoff for precipitation is expected to be fairly sharp. I'd guess areas around I-95 could pick
up 1-3 inches of rain, more to the east, less to the west. Places out in the Blue Ridge might just have a
cloudy day.
This is a storm to take seriously but in DC, I also don't see the need to go out and buy all the bottled water
you can find. Flooding is possible, power outages are probable and 50 MPH winds with saturated ground
can make trees a problem.
The next official advisory from the National Hurricane Center comes out at 5 PM.
For now, here's an excellent graphic with the forecast storm track:
Boston Globe Irene Tracker
Monday, February 21, 2011
Quick Burst of Snow Tonight Into Tomorrow Morning
It's been a while since anything interesting (aside from some unusually warm weather) has happened around here but tonight we have a fairly unusual situation developing that could cause a quick burst of snow and some minor accumulations around the area.
First up is a cold front which will be moving across our area this afternoon. Precipitation associated with the front will begin as some light rain which will increase a bit in intensity as the afternoon becomes the evening. The cold air will take a little while to catch up but eventually it will move across the area from north to south bringing a changeover in the precipitation that's falling from rain to sleet and eventually over to all snow.
At the same time, a low pressure area will move out of the midwest and cross the region bringing the bulk of our precipitation - especially towards midnight and into the early morning hours Tuesday.
This should be a brief storm but it could be a bigger deal than it even looks now. That "banding" effect we've talked about before could lead to locally heavy precipitation amounts and the model trends have been colder and wetter the last few runs.
Waiting for the afternoon models but I think 2 inches is a good possibility in the immediate DC area, more as you go north and west. There is the potential for more - maybe 4 inches or more - but before we go there, I'd like to see what the afternoon models have to say. But, just to put it out there, here's the GFS 24-hour total precipitation forecast:
You can see we're squarely in the .5-.75 liquid precipitation range. Given that we may lose a bit to rainfall and some sleet, this argues for 4 inches or so.
One thing the precipitation will be fighting is the relatively warm ground temperatures that have developed after the past 5 days or so. On the other hand, the precipitation could be quite heavy later tonight.
Stay tuned...
First up is a cold front which will be moving across our area this afternoon. Precipitation associated with the front will begin as some light rain which will increase a bit in intensity as the afternoon becomes the evening. The cold air will take a little while to catch up but eventually it will move across the area from north to south bringing a changeover in the precipitation that's falling from rain to sleet and eventually over to all snow.
At the same time, a low pressure area will move out of the midwest and cross the region bringing the bulk of our precipitation - especially towards midnight and into the early morning hours Tuesday.
This should be a brief storm but it could be a bigger deal than it even looks now. That "banding" effect we've talked about before could lead to locally heavy precipitation amounts and the model trends have been colder and wetter the last few runs.
Waiting for the afternoon models but I think 2 inches is a good possibility in the immediate DC area, more as you go north and west. There is the potential for more - maybe 4 inches or more - but before we go there, I'd like to see what the afternoon models have to say. But, just to put it out there, here's the GFS 24-hour total precipitation forecast:
You can see we're squarely in the .5-.75 liquid precipitation range. Given that we may lose a bit to rainfall and some sleet, this argues for 4 inches or so.
One thing the precipitation will be fighting is the relatively warm ground temperatures that have developed after the past 5 days or so. On the other hand, the precipitation could be quite heavy later tonight.
Stay tuned...
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