New Models and Track Posted for Tropical Storm Irene

The National Hurricane Center has shifted the track forecast slightly to the right or east of their 10am track. This shift is most likely in response to the continued shift of computer models to the east. While the shift farther northward may allow Irene to strengthen as it would not be impacted as much by Hispaniola and Cuba, it would also steer the storm farther away from Florida. However, this could also pose a greater risk to Georgia and South Carolina, which could suffer a direct hit.

National Hurricane Center Track, Image: NOAA

Computer Model Tracks, Image: Colorado State Track Model Guidance

Dawn Brown, FOX 8 New Orleans

Don’t “Tie Yourself to One Model”, Irene Threatens US

To track TS Harvey, click here. To track Irene, click here. To track 98L, click here. For an overall look at the tropics, go to MYL’s Hurricane Tracking page.

Tropical Storm Harvey, the 8th storm of the 2011 Hurricane Season, is moving through central Belize tonight. It will likely degenerate over Guatemala and Mexico, but is producing quite a bit of rainfall in and around the center of circulation.

Infrared Satellite, TS Harvey, Image: NOAA

Harvey formed in the central Caribbean and didn’t pose a threat to the United States from its inception. At the same time Harvey or TD 8 was forming, a very unimpressive tropical wave was catching our attention in New Orleans, merely based on the long-range computer models.

The models, mostly notably the GFS, or Global Forecast System, was projecting a major hurricane to form as it approached the Caribbean and making landfall somewhere along the US coastline in the end of August.

In 2006, the GFS predicted a similar occurrence about 10-15 days out.

2006 Hurricane Ernesto, Image: Unisys

It turned into Hurricane Ernesto, a category 1 hurricane, that weakened substantially over western Haiti and eastern Cuba, before hitting Florida as a tropical storm. The only reason I bring up Hurricane Ernesto is to touch on the current unreliability of long range computer models. And really what I mean by long-range, is past 3 or 4 days. As I state this, the global computer models have improved. Last year, I noticed that the GFS was doing a fairly good job of forecasting the inception of a storm, meaning in 10-15 days, the global computer models could pick up on a closed circulation (or a tropical depression) forming. I emailed an expert the National Hurricane Center about it, and they concurred, that they had made some improvements to the GFS. What the GFS could not do and still has trouble telling us, is how strong this system will be when it arrives. However, there is another global computer model that is being heavily relied on by hurricane forecasters that is doing a fairly good job in telling us which storms will strengthen and where they will go.

National Hurricane Center

Last year, while attending the annual Broadcaster’s Conference of the American Meteorological Society in Miami, attendees were privileged to meet, not only the entire staff of hurricane forecasters from the National Hurricane Center, but we also got every insight they could offer to how they put together the forecast. One of the forecasters/researchers also told us the ECMWF, the forecast put other by the European Centre for Medium Range Weather Forecasts had been beating their track forecast for the past couple of years. The percentage was small, but somehow, their global forecasting model was able to beat forecasters with 20-30 years of experience. This may get some guffaws from readers, but keep in mind that the official track by the National Hurricane Center was statistically better than all of the other computer models out there. That means—don’t tie yourself to one model.

Ever since they told me that, I can’t help it.  I rely on the “European”.

But then, last year, I noticed the GFDL, the United States’ global hurricane model, nailing the forecast track as well. I was hopeful, proud. I’m not sure why, but I guess it bothered me a little bit that Europe, which is barely affected by hurricanes, could forecast them better than us! Then the GFDL started really performing well on the track and intensity.

That was last year. This year, I’m back to the European. I don’t know what happened to the GFS and GFDL, but this hurricane season, it’s been having some wild swings when it comes to storm tracks. It also ratchets some storms into a major hurricanes 10-15 days out like it did back in 2006.  The European only goes out 8 days, but in the last few years, I felt confident telling my viewers which way the storm was headed and relatively how strong the storm was going to be when it got there. This year, it’s been guiding me through Arlene, Bret, Cindy, Don and Emily. It forecast Emily forming briefly, dying somewhere north of Hispaniola and then possibly reforming as a weak system before getting carried northeast with a trough of low pressure off the East Coast. Guess what happened? Exactly that. Now, the GFS did eventually forecast a similar scenario. And, it’s much easier to be confident with a forecast when more of the computer models are in alignment.

And the European only guides me in track and possible strength. It doesn’t give particulars, what’s causing the weakening/strengthening, how weak/strong will the storm be, what areas could suffer torrential downpours or high winds. It’s merely guidance. We still have to do all of our own analysis of the wind shear, upper air pattern, the water vapor (these tropical systems really struggle with dry air), the Saharan Air Layer, everything that tells us what kind of storm we’ll be dealing with. But, it gives me confidence to let me know if I need to be gearing up for a 5-day stretch of spending the night in the weather center. (Technically I got to go home during Gustav—I lived 3 blocks from the station!)

Infrared Satellite, Invest 97L, Image: NOAA

In terms of Invest 97L, it’s been undergoing some interaction with dry air and wind shear that has kept it from developing into Tropical Depression # 9 or Tropical Storm Irene. It looks like it’s going to be a tropical storm in the next 24-hours. It also looks like despite dry air still to its north and west and its possible interaction with Hispaniola and Cuba, it will most likely hit Florida as a tropical storm or possibly even category 1 hurricane.

It looks like the persistent trough off the East Coast will keep it from affecting the northern Gulf Coast states.

I say this in confidence at this point because of my faith in the European. Also-because the other computer models are lining up with a similar forecast.

But… since I live along the Gulf Coast and not along the beaches of the Mediterranean, I still keep my hurricane plan in place until October 15th.

Dawn Brown, FOX 8 New Orleans

P.S. This is my anecdotal account of forecasting with models, Wunderblogger Jeff Masters has a much more studious approach to explaining the performance of models in his blog, click here.

Weak Tropical Storm Arlene on Track for Mexico

Tropical Storm Arlene, Image: NOAA

The National Hurricane Center began issuing advisories on Tropical Storm Arlene at 7pm Central Daylight Time this Tuesday, June 28th. The storm’s satellite presentation isn’t all that impressive, but it’s kicking up some good wave heights in the central Gulf of Mexico (up to 12′). The area of showers and thunderstorms west of the Yucatan Peninsula has been fairly persistent over the last few days and observations near the center of the storms show maximum sustained winds of about 40 miles per hour.

Arlene is expected to make landfall just south of Tampico, Mexico sometime on Thursday. It could provide some heavy rainfall for Tampico, Ciudad Valle and San Luis de La Paz Mexico. This is a mountainous region of central Mexico and tropical storms can dump copious amounts of rain over this region.

For the latest statistics on Arlene, go to the National Hurricane Center website. This is expected to be a fairly active hurricane season.

Dawn Brown, FOX 8 New Orleans

Here Comes The Fog Again

After an unusually cold and dry winter so far across the Gulf South, the pattern has taken a more typical turn.  High pressure is building back in, winds out of the southeast are setting up, and warmer temperatures are ushering back in, but also so is dense overnight fog.  As the pattern stagnates over the next several days, reduced morning visibilities can be expected across portions  of the Gulf states.  In fact Dense Fog Advisories have been issued for the coast of Southeast Louisiana for visibilities below 1/4 mile at times.  Cities that can expect slow morning commutes are places like New Orleans, Baton Rouge, and Biloxi.

Dense Fog Advisory February 15, 2011, Image: NOAA

What’s the deal with this Gulf Coast fog during the Fall, Winter, and Spring?  Well, its something called sea fog and it doesn’t just happen in Louisiana and Mississippi.  In fact, it also occurs in other places in the United States, like San Francisco, and even in other places around the world, like Hong Kong!

Sea Fog Formation, Image: Hong Kong Observatory

Take a look at the image above.  This is what causes sea fog to form.  Winds from a warm and humid source region blow over an area of colder water.  This helps to condense the moisture out of the warm, moist winds as they pass.  This process forms a low cloud.  Those same winds then push the newly-formed cloud over a nearby landmass and voila: fog.

In the case of the Gulf South, these winds are southeasterly and pick up warmth and moisture from the Central Gulf of Mexico, where the deep waters still have temperatures well into the 70s.  These rather tropical winds then run northwestward over shallower near-shore waters, that are much more subject to cooling by the cold wintertime land temperatures.  These coastal waters have temperatures only in the 50s.  This helps condense the moisture out of the warm, relatively muggy southeasterly winds.  Hence, a bank of low clouds forms.  The southeasterly winds then push that batch of clouds onshore and there you have it: sea fog and rough morning commutes across the Central Gulf states this week.

My New Gig at FOX 8. Check Out The Weather Lab!

It was a gorgeous day in New Orleans today. Dry, breezy and sunny. It’s the kind of weather we look forward to all year. It’s been a cold winter down here, we’ve been waiting for Spring.

Cirrus Clouds, New Orleans Sunset

On my way to talk to a community group tonight, I shot this photo as I was looking to the southwest. What a gorgeous sunset. Louisiana often has beautiful sunsets and sunrises. Interesting cloud formations reflect the sunlight as the sun rises and falls.

Meanwhile, I’ve been neglected my weather blog. My new job at FOX 8 is creating new and interesting challenges. I love my job. We launched a new show called FOX 8 Morning Call on February 1.

Here’s a picture of Chris Franklin and me from this morning at 5am.

Chris Franklin and Dawn Brown, WVUE New Orleans

We started this new show that’s kind of like the Weather Channel, but it’s focused on Southeast Louisiana. We do the usual temperatures, rain chances, forecast, but then we get to spend extra time talking about the wave heights and sea surface temperatures in the lakes and Gulf of Mexico, the kind of stuff fisherman and mariners are interested in. We have the buoy data from all the Gulf  Coast buoys plotted in our new weather system.

Here’s the pic I took Friday of the current sea surface temperatures on one of our new weather systems.

Sea Surface Temperatures, (3/12/2010)

Here’s Chris at the weather wall. Because I’m usually doing the weather, I never get to see how weird it looks that we’re pointing at a blank green wall.

Chris Franklin, WVUE New Orleans

Our weather graphics are projected onto the wall, and we are “keyed” out of the graphics. We can’t wear green or we would blend right into the graphics. We’ll probably both get pinched on St. Patty’s Day!

It’s awesome having two meteorologists in the mornings. Besides having the extra help with forecasts and graphics, we get to explain basic weather phenomenon, like hail, high pressure systems, sea fog, etc.

Every week, Chris and I also host a segment called “Weather Lab”, where we explain basic weather terms with experiments. Last week, Chris crushed a soda can with air pressure.

I’m having a blast! However, I’ve been remiss with my weather blog and adding new features to my website. I’m getting back on track… bear with me.

Thanks – Dawn Brown

Southern Snow!

Dallas/Fort Worth Snow, Image: NOAA

Snow blanketed the Dallas/Fort Worth area this morning. The pictures above were taken from the National Weather Service Office in Fort Worth. Up to 8″ of snow is expected in some locations northwest of Dallas.

Winter Storm Warnings, Image: NOAA

Winter storm warnings are in effect across Texas, Arkansas, Louisiana and Mississippi today as a Gulf Low slams into a frigid air mass over the Southern Plains. A warm, moist air mass following the southern jet stream is being driven into the cold, dry air mass. Sleet is already being reported in areas outside New Orleans, LA.

Places like Jackson, Mississippi and Shreveport, Louisiana could receive up to 6 inches of snow.

Meanwhile, the East Coast is digging out from the latest pile up of snow. The back to back storms have shut down the nation’s capital.

Snow Depth, Image: NOAA

The graphic above shows the snow depth in the Mid-Atlantic region as of today. The areas in dark blue have recorded more than 30 inches of snow. You can see South Jersey, Southern Pennsylvania, Northern Virginia, Maryland, D.C. and Delaware are covered with 3 feet of snow.

Luckily, it appears the latest gulf storm will track off the coast of the Carolinas, and will not affect the metropolitan areas of D.C., Baltimore and Philadelphia.

-Dawn Brown

Advection Fog

Fog is a cloud that is actually on the ground!  There are many different ways that fog forms.  What’s behind advection fog, though, is pretty interesting.  Advection fog is most common along the West Coast of The United States during the spring and first few months of summer.  In fact, most of the fog that affects San Francisco, and the nearby coastal areas, is due to the advection fog process.  Namely the fog that affects the West Coast is known as sea fog,  Advection fog may last for hours, or even days.

Advection Fog From Above

The way advection fog, or more specifically sea fog, is winds blow over warm water that is relatively far out to sea.  There, the air picks up warmth and moisture.  The winds then take that air and drag it over cooler water nearer to the coast.  This process condenses the water vapor out of the air and develops the cloud.  The winds then take the cloud, which is near the surface of the water, and drag it over the near-shore areas of the land.

Advection fog can also occur in interactions between warmer water and cool landmass areas.

In fact, advection fog can occur during other seasons and in other parts of the country.  On a smaller scale, advection sea fog occurs in the Gulf South during the wintertime months.  Here, winds out of the southeast drag air over the warm waters of the central Gulf of Mexico and eventually over much cooler near-shore waters developing fog over places like New Orleans and Southeastern Louisiana.  In fact, sea fog will be socking in Boothville in far southeast Louisiana prompting fog advisories through Friday morning.

US Watches & Warnings, Image: NOAA

Southern & Western Wallop

Yet another El Nino system is pulling into the California coast.  One to three inches of rain has already fallen across the foothills surrounding the Sacramento Valley and more is on the way, creating flooding across many of the lower elevations.  Up in the mountains near Lake Tahoe, near blizzard conditions are happening right now with a good 8 to 16 inches of snow on the way for skiers.

National Satellite Image, Image: NOAA

Click here for the latest national satellite imagery.

In the meantime, yet another El Nino storm is moving through the Deep South. This has provided for a couple of inches of rain across the central Gulf Coast and tornado watches from just north of New Orleans, all the way up into Mississippi, east Texas, and southern Arkansas.  Tornadoes were even spotted Wednesday afternoon over portions of Southeastern Louisiana.  Tornado Watches are in effect for cities like Jackson, MS.

US Watches & Warnings, Image: NOAA

Flash Flood Watches Out Again For Gulf Coast, Carolina Snow

A storm system developing over the western Gulf of Mexico will spread yet another batch of 1″ to 2,” with locally up to 4,” of rain across the Central Gulf Coast Thursday through Friday.

New Orleans Radar, Image: NOAA (Image is OLD!)

Click for the latest New Orleans Radar.

With up to nearly 2 feet of rain on the month so far in places like New Orleans, Louisiana and widespread flash flooding over the past week, any additional rain could cause more flooding issues.

National Watches and Warnings, Image: NOAA (Image is OLD!)

Click for the latest watches and warnings.

Flood Watches have already been posted for portions of southeastern Louisiana and coastal Mississippi through as far east as southern Georgia.

The same system will then go on to affect much of the rest of the Deep South Friday into Saturday, primarily with rain, but snow may mix in in the higher terrain of North Carolina.  Winter Storm Watches are posted for the end of the week into the weekend for the Carolinas as far south as Greenville/Spartanburg, SC east as Charlotte and Raleigh/Durham in North Carolina.  The storm is expected to produce as much as 4-6″ of snow in the North Carolina mountains near Asheville., but a wintry mix of snow, sleet, and freezing rain, and rain are even looking likely in the Charlotte and Raleigh/Durham area with light accumulations of snow and ice.

Southern Snow!

December 2009 Snow Storm Katy, Texas, Image: Susan Walpole

December 2009 Snow Storm Katy, Texas Image: Susan Walpole

A fast moving storm has dumped snow across Houston and other portions of East Texas, and Southern Louisiana. Since the storm is quickly exiting to the east, winter weather advisories have now been issued for portions of central Alabama, Tennessee, the Virginias, Maryland and D.C.. From there, the storm is expected to move out to sea. 

-Dawn Brown