Starkville Lightning

It's been a few weeks since my last blog post, but I have been pretty busy with packing, preparing for, and moving to Starkville, MS. I've been getting settled in and getting ready for starting my first semester as a graduate meteorology student at Mississippi State.

One week after moving in, I was able to get some photos of lightning associated with a cell that was severe-thunderstorm-warned southwest of Starkville. These aren't my best lightning shots, but are worth of sharing.

Since I will pretty much be taking weather classes for now on (plus calculus and physics - boo), I hope to have more general posts on weather and forecasts on major events surrounding Starkville and my home territory in Florida. Stay tuned.

Tropical Depression 3 Forms Near the Bahamas

Well, it appears that things kicked up a bit overnight. Invest 97L, the tropical wave that now sits over the southern Bahamas has slightly improved and now the National Hurricane Center says it has a closed circulation. To be considered a tropical cyclone, a storm has to have a closed center of circulation. At 11 a.m. EDT, it was upgraded to Tropical Depression 3.

From looking at satellite imagery this morning, it seems that convection has increased. Also, water vapor loops show that dry air isn't invading the circulation as much as it was. However, the heaviest of the thunderstorms remain to the northeast of the center, which indicates the upper-level low still has some influence on the depression, as it can also be seen on water vapor loops. The shear is expected to decrease as time moves forward.

Source: NOAA

Forecast models seem to track the center of circulation a little more to the south - more in the Florida Keys or even further south. For example, the HWRF (see here) has the storm making landfall in the southern Keys Friday morning with 37-knot winds (42 mph, which is tropical storm force).

With the decrease in wind shear and somewhat better development overnight, there is room for slight intensification today and tonight. However, I do not see this as a high-impact wind and surge system. It will mostly be a rainmaker for south Florida.

IMPACTS AT A GLANCE...

- South Florida should start to see affects from TD #3 as early as tonight.

- The Keys will likely get the strongest winds - around 40 knots according to NHC forecasts, with higher gusts possible.

- To the north (Miami-Dade, et al.), some gusts are possible but mostly rain is the main event from this. HPC QPC products show, at most, an inch of rain in some spots in southeast Florida on Friday. In a three-day period, some places can see 1 to 2 inches of rain in south Florida.

- Gainesville will experience better weather, but rain chances will be above normal Saturday as moisture is expected to be pulled in from the depression.

The ridge to the north should keep this storm to the south and not have too much of an impact on central and north Florida.

Interests in south Florida and the Gulf of Mexico need to keep an eye on TD #3. I'll probably make another blog post tonight.

UPDATE: I forgot to mention that there are watches and warnings in effect. From the NHC:

A TROPICAL STORM WARNING IS IN EFFECT FOR... * CENTRAL AND NORTHWESTERN BAHAMAS * FOR THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD INCLUDING THE ENTIRE FLORIDA KEYS AND FLORIDA BAY...AND ALONG THE WEST COAST OF FLORIDA NORTHWARD TO BONITA BEACH  A TROPICAL STORM WATCH IN IN EFFECT FOR... * THE EAST COAST OF FLORIDA NORTH OF GOLDEN BEACH TO JUPITER INLET INCLUDING LAKE OKEECHOBEE

Invest 97L Not So Tough

Since last night, the tropical disturbance that is now located over the southeastern Bahamas has deteriorated a bit. It seems that wind shear from the nearby upper-level low, dry air intrusion, and the center of circulation moving over Hispaniola has affected this disturbance.

Earlier this afternoon, a NOAA G-IV jet inspected the region. Data indicated that upper-level winds are still not favorable for development, according to the National Hurricane Center. Sounding data also showed dry air at the mid levels to the west and north of the system.

A look at infrared and water vapor loops show convection starting to get a little better, but the water vapor clearly shows the upper low to the north.

The NHC thinks that upper-level winds will be "marginally favorable" for development in the next day or two. NAM and GFS models show the upper low moving ahead of 97L in time, but would it move far enough to reduce interfering the wave? Not sure.

The NHC has reduced its probability of reaching tropical cyclone criteria to 40 percent. It seems reasonable given how much of a hill this invest has to climb to make it to a depression, or even a storm.

The NAM, GFS, and other models seem to agree on a south Florida initial impact as early as Friday.

SOUTH FLORIDA IMPACTS...

- At this time, it appears that it will mostly be an on-and-off rain event for south Florida. There could be some gusty winds, but nothing to freak out about.

- Rain should start to kick in sometime Friday and last through Saturday...maybe longer as a southerly flow should keep moisture levels high.

GAINESVILLE AREA IMPACTS...

- NWS-JAX is calling for a 50 percent chance of rain for Friday and Saturday. The further north you go, the lower the rain chances. However, this would depend on how far north the tropical wave moves, or how strong it gets.

As time moves forward, it seems this thing might be nothing but a fizzle. Still, it is worth watching. This might be my last update on Invest 97L unless conditions change.

Quick update on Invest 97L...

Source: NOAA

This morning, it appears that the tropical wave that's north of Hispaniola and near the southeastern Bahamas has become disorganized. Wind shear analysis shows that the north part of the wave is still encountering at least 20-to 25-kt wind shear.

Because of the disorganized fashion of this disturbance, the US Air Force has cancelled their scheduled reconnaissance mission today. They may try again tomorrow if conditions warrant.

However, I am now noticing a nice area of convection near the Lesser Antilles in the last few satellite images. This may be convection that's part of the wave - I'm not sure. If any mets are reading this, I am open to input on this.

Regardless, the NHC is still giving this a 60 percent chance of tropical cyclone development in the next 48 hours. Apparently, conditions are expected to improve for development.

Right now, it's expected to be a rain maker for the vicinity, including the Virgin Islands, Puerto Rico, and Hispaniola. The Bahamas should start to see rain starting tomorrow. The models continue to show a south Florida impact this weekend.

As for intensity, I am not sure if this will be developed and named within the next 48 hours. Still, interests in south Florida and the Gulf of Mexico need to watch this for potential development. Regardless of development, expect a wet weekend in south Florida.

I hope to have some time this evening to revisit the models and data to give another update. Stay tuned.

Watching the Tropics: Invest 97L

Wow, it's been a while since I have posted any weather analysis on this blog. I've been pretty occupied for the last few weeks. My load has lightened somewhat to the point where I can sit down and write a post on weather happenings. However, things will be busy again for me soon as I prepare to move to Starkville, MS for at least the next two years for graduate studies at Mississippi State University.

So far in the Atlantic-basin hurricane season, we have had one hurricane that broke some 40-plus-year records for the month of June (Alex). We had one tropical depression, but noting noteworthy on that.

We ("we," as in "weather people") are now watching what could be our next named storm - Bonnie. A tropical disturbance, dubbed Invest 97L, is located near Puerto Rico and Hispaniola and is producing heavy rainfall in the vicinity. NWS-San Juan, PR radar estimates are showing as much as 6 to 7 inches of rain in some parts of extreme eastern Puerto Rico since Saturday. This wave has been moving west-northwestward at about 10 mph and this track is expected to continue for at least the next day or two.

Right now there is at least one feature affecting 97L: Wind shear. Remember that too much wind shear can limit a tropical cyclone's development. There is fairly light shear in the south-end of the wave (as seen here in the analysis). On the north side of the wave, shear is relatively high at 20-25 knots. Satellite imagery picks this up fairly well. This shear is due to an upper-level low, and it can also be seen in initial model runs and in water vapor imagery (see image below from NOAA).

However, the National Hurricane Center is saying that the environment around 97L should improve for further development later on. This tells me that the shear is expected to decrease at least somewhat. About half of the intensity forecast models have the invest at tropical storm status in 12 to 24 hours.

As for the track, the model consensus earlier today has the disturbance moving towards south Florida by the weekend. However, new model runs seem to have it moving a little further south, more in the Florida Keys in about 72 hours.

An area of high pressure currently has a hold over the southeastern United States. The short-term outlooks seem to have this remain in place. This should keep the invest from moving too far north, sort of acting like a blockade.

Air Force hurricane reconnaissance aircraft is scheduled to investigate the disturbance on Wednesday, if conditions still warrant (and I think it will).

Also, as other meteorologists - such as Dr. Jeff Masters and Greg Nordstrom - point out on their blogs, we are in an phase known as the Madden-Julian Oscillation. It "is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days" (source, details: http://www.cpc.noaa.gov/products/precip/CWlink/MJO/MJO_1page_factsheet.pdf). We are in a phase now where enhanced convection can take place, and, in turn, higher potential for tropical development. Something to keep in mind.

In a nutshell:

- It has the potential in the next 48 hours to become Tropical Storm Bonnie and move west-northwest in this timeframe. As for Hurricane Bonnie, I think it's too early to say at this point.

- Its exact track is uncertain. It looks like south Florida could at least see some impacts from this disturbance - some wind and heavy rain. If it moves into the Gulf of Mexico, it could spell trouble for oil spill recovery efforts and have room to intensify. This invest needs to be closely monitored for the next few days, as there will be some impacts this weekend.

- Gainesville could only see a greater influx of moisture as the wave approaches and have higher rain chances. However, it depends on what path this wave takes.

- Wednesday's scheduled USAF reconnaissance mission should give us a better clue of what's happening, as well as better data to ingest into forecast models.

I will do my best to keep these updates going. I'm trying to get back into the weather blogging thing and work on my forecasting skills. Also, keep an eye on my Twitter feed (twitter.com/daweathaman) for the latest.

Gainesville Lightning Show

I usually don't place photos on here, but since I am having issues with WordPress (where my photo blog is) I am displaying them on here since they are weather related.

Early this evening, a thunderstorm complex over Jacksonville created an outflow boundary which moved south and southwest (view radar). This line spawned storms over eastern Alachua County and surrounding areas. At least two Severe Thunderstorm Warnings were issued with these storms. The first storm I attempted to find lighting from the storm to the southeast of Gainesville (view radar). However, the lightning show dissipated with this cell by time I perched myself on top of a parking garage near the University of Florida campus. There was hope, though. A tiny cell just east of Williston formed (view radar) and created a nice lightning show for a while and provided all but one of my photos shown here.

Enjoy!

These photos were shot with my Canon EOS 40D with a 50mm f/1.4 lens at 160 ISO.

Rain, Thunderstorms Likely Tuesday

For the last few days in Gainesville, the weather has been fairly hot and muggy. High temps in the low 90s with dewpoints in the 70s have hinted a return of summer to Florida.

To our north and west, a cold front with a trough in the jet stream, along with shortwave energy, is spawning showers and storms. The heaviest of the activity is currently over Georgia and South Carolina.

On Tuesday, NWS-JAX is expecting deep layer moisture along with shortwave energy to move into Georgia. Rain will develop and then move into Florida "by late morning and during the afternoon" according to the latest AFD. The temperatures should be cooler due to the cloudcover and rain.

The severe weather threat looks very low for the area. Weak lapse rates at the mid levels and cloudcover seem to be limiting factors according to the SPC's day 2 discussion.

For Tuesday, I would expect a good chance (about 60-70 percent chance) of showers and maybe a thunderstorm or two across Gainesville. Temps should be a little cooler (80s). Rain chances for Wednesday look to be 50-50 as the front starts to weaken. Slim chances of rain are then expected for the rest of the work week.

For the latest, keep an eye on my Twitter feed: http://www.twitter.com/daweathaman.

Slight Severe Weather Threat Today

The SPC has continued labeling north and central Florida as a slight risk category for today and tonight. The dynamics look decent, but there are a few limitations to the threat.

Skew-T (upper-air sounding) from Jacksonville at 8 am ET (Source: Unisys Weather)

The KJAX skew-t (shown above) gives a snapshot profile of the air above the surface. Shear profiles look good and, according to NWS-JAX, helicity values look good for possible rotation. The lifted index is about -2, which is slightly decent for severe weather formation. There are moist conditions at the surface, but dry at about 900 mb and higher. This might be a sign of convective instability but we would need some daytime heating to get things going. The SPC mesoscale analysis does hint at divergence over the area, which is another factor for making things unstable.

However, the NWS is noting low lapse rates as a limiting factor. Also, the cloudcover over northern Florida would limit daytime heating in the area. However, that could change later on.

Florida visible satellite image (Source: WeatherTap.com)

As for timing and arrival, NWS-JAX wrote this at 9:38 this morning...

THE LINE IS EXPECTED TO SPLINTER AS IT APPROACHES THE COAST THIS AFTN...THEN REDEVELOPMENT OCCURS ACRS THE SRN PORTION LATER IN THE AFTN AS STORMS MOVE IN DIRECTLY FROM THE GULF. EVEN SO THE COASTAL ZONES AND REMAINDER OF NE FL ARE NOT OUT OF THE WOODS AS STRONG TO SEVERE STORMS ARE POSSIBLE AND RISK FOR TORNADOES STILL EXISTS.

Based on the sounding and profile readings, storm motion should be out of the west-southwest at about 30-40 knots.

So, it's a wait and see. Keep an eye on the Twitter feed during the day as I try to both watch this and study for a physics final exam. Stay tuned.

Slight Severe Weather Risk in North Florida on Sunday

Severe weather risk for today. (Source: SPC/NOAA)

Good morning, everyone. Today isn't (or is) a good day to be in the southeast (depending if you are a weather nut or a storm chaser). There is a very-rare high risk for severe weather in parts of Alabama and Mississippi according to the Storm Prediction Center (SPC). A low over the Midwest with an associated cold front, a sufficient low-level jet, steep lapse rate potential, a negative tilting trough, and many other factors are allowing for this rare weather setup across the deep south. Multiple tornado watches are in effect along with many tornado warnings currently in effect. Reports of possible tornado and thunderstorm wind damage are flooding my Twitter feed as I write this.

This same storms system will continue to move on into the east and will affect areas from central Florida to the mid-Atlantic states on Sunday. The SPC has issued a slight risk of severe weather for the aforementioned area. Here are some factors the SPC is laying out for the risk (with links to their definitions by meteorologist Jeff Haby):

- Southerly to Southwesterly low-level jet within the pre-frontal warm sector

- MLCAPE of 1000 to 2000 J/Kg

- Increased dynamic forcing ahead of a upper trough

- Increased wind shear environment

Severe Weather Risk for Sunday (Source: SPC/NOAA)

Among these, daytime heating will help enhance the setup as the day advances. The National Weather Service in Jacksonville also noted in their last full Area Forecast Discussion (AFD) that the southern jet stream will also strengthen tonight. As Sunday begins, multiple lifting mechanisms (cold front, upper-level divergence - which allows more air to replace the diverged air in the upper levels - smaller impulses and disturbances) will add to the potential.

We will have to wait until Sunday morning when more data comes in and forecasts solidify before determining what exactly will happen. Timing will also be key since the intensity will depend on how much daytime heating would be allowed. So much for focusing on the Physics II final exam.

There may be an update on this blog Sunday morning or as early as tonight. Keep an eye on my Twitter feed for the latest information.

Watching the Gulf of Mexico

Good morning! Things have changed slightly since last night's weather post. From viewing satellite imagery, HPC surface observations and discussions, a warm frontal boundary in the eastern Gulf of Mexico has formed and, therefore, spawned some showers and likely thunderstorms (judging by the cold cloudtops on infrared sat imagery). Some views of this cluster can be seen on composite radar, but I am not taking too much credence of the reflectivity values just yet due to the distances of the coldest cloudtops (on the west side of the complex) from the NEXRAD sites.

Overcast conditions have now taken over Gainesville and will likely continue as this cluster of storms moves east.


Images: IR satellite (left, via WeatherTap.com); Surface MSLP/wind (right, via NOAA/SPC)

This cloudcover may take down the instability a notch because of the lack of daytime heating. Dewpoints in GNV has yet to reach 60 while places such as Ocala and southward have hit or surpassed that mark.

Rain should start affecting the area later on today. However, expect another batch of rain and storms later on tonight as the front nears and dynamics improve.

More later.