Charles E. Roop giving his own forecasts, weather discussions, photos and adventures for the Starkville, MS area, Florida, and beyond.

Sunday, February 19, 2012

Florida Weather Update

What a difference a few hours makes. We have gone from a slight risk of severe weather to just clouds. A look at the radar and satellite imagery show not a whole lot happening. Visible satellite shows cloudcover over most of north and central Florida. The KVAX radar shows some very light precip over north Florida. Surface analysis and the SPC mesoanalysis shows the low over Alabama and Georgia with the front near Tallahassee.

The difference this morning is that forcing seems to be weaker than predicted and the cloudcover over the northern half of Florida will help limit any convection. The PVA appears to be further north. It appears that the severe weather threat that existed is now over.

The clouds will hang around this morning, but there may be some clearing later on this afternoon and the visible satellite is hinting at a clear slot over the gulf (see below) as the clouds move in a northeasterly direction.

Image source: WeatherTAP.com

Winds will switch to a westerly direction as the front passes in the early afternoon. The weather should be clearer tonight with cooler temperatures across the northern part of the state.

Saturday, February 18, 2012

Florida Severe Threat Update

A tornado watch has been issued by the SPC for parts of the Florida panhandle, south Georgia, and extreme southeastern Alabama until 4 a.m. ET. This watch includes the following Florida cities: Tallahassee, Live Oak, Lake City, and Panama City. The SPC is calling for a moderate threat for tornadoes and damaging winds within and close to the watch.

The line of storms are prompting severe thunderstorm warnings across Florida and Georgia, but I haven't seen any tornado warnings issued recently. That doesn't mean that none would be issued, though.

The latest Tallahassee sounding (0Z / 7 pm ET) indicates somewhat of a curved hodograph, but winds are primarily out of the south instead of southeast. Instability may not be as great as daytime heating has ended, but the moisture at the surface remains high (dewpoints are 60F +). The low-level jet isn't around where the action is (yet).

The surface maps from the HPC are showing a second low-pressure center off to the west of the one over the Florida panhandle (see below) at 7 pm ET.

This system is something that the models are picking up on and have as the main system to help bring good rain chances along with a severe weather risk Sunday across north and central Florida. Not much has changed since the last post as the highest threat seems to be damaging winds. I may make a post tomorrow morning as conditions warrant. Stay tuned.

Severe Threat for Gulf Coast Today, North and Central Florida Sunday

Currently, a low pressure system is centered just off the coast of Texas with an associated warm from extends around the middle Gulf of Mexico coast and a cold front moving southwest through the Texas coast. Aloft, 12Z  data analysis showed a trough over western Texas. The latest RUC guidance shows that the trough has moved to the east over central Texas. Surface dewpoints of 60F and greater are currently along the gulf coast while the rain extends from off the Texas coast northeast to Alabama. 

Today's severe weather risk lies along the gulf coast from Louisiana - which warning have already been issued - to the Florida panhandle. Currently, radar is showing a line of potent storms near Slidell, La. and is moving northeasterly (see below).

Storm Relative Helicity numbers are greater behind the lines of storms based on SPC mesoanalysis, but the SRH values where the storms are in the 400-500 range. The lapse rates don't seem too impressive, but the 12Z soundings at KLIX showed a decent southeasterly flow at the surface. The RUC model sounding near Pensacola shows a good curved hodograph, which would show a decent potential for tornadoes. However, that sounding doesn't really scream instability.

For today, the atmospheric motion looks decent for a few tornadoes and strong winds. Instability looks to be a limiting factor in that area as lapse rates from the surface don't look too impressive and daytime heating will be abated due to cloudcover. Regardless, impressive storms are still showing up on radar with the possibility of rotation and damaging winds. 

For Sunday, the threat shifts to north and central Florida. The cold front should be approaching the Florida peninsula gulf coast in the late morning. Helicity values are expected to increase. The NAM sounding profiles near Gainesville and Orlando Sunday late morning/early afternoon show uniderectional hodographs (straight-line wind threat, typically) with steep environmental lapse rates (especially near Orlando by 1 PM ET). However, the NAM is a little more drier aloft at this time and location than the GFS, which could change the amount of instability. The NAM is also showing a decent low-level jet moving into the peninsula early in the afternoon Sunday. 

North and central Florida should be observant tomorrow as straight-line winds and bowing storms could be an issue along with a couple of isolated tornadoes. I might post another weather update tomorrow morning when conditions warrant. 

Friday, February 10, 2012


I'm a Florida native, and this is cold to me. We are not expecting a massive, record-breaking arctic outbreak, but it seems to have been a while since it's been this cold.

Currently, there's a upper-level trough over the southern Great Plains with a noticeable jet streak over the western and central gulf coast, based on the latest RUC run. At the surface, HPC surface analysis shows a low pressure system with an associated cold front over Texas with another front further north. This second front will help chill things out. The aforementioned jet streak will help create lift and bring some rain to the gulf region, but keep Starkville with low POPs.

12Z (7 AM EST) surface analysis (via HPC)

During the next 18 hours, the fronts will pass though the area. The NAM has winds switching out of the north late tonight and picking up speed. The raw NAM has winds at roughly 15 knots across northern Mississippi and Alabama Saturday morning. At this point, the cold air advection will make me be it's (censored) as temps expect to dip near 20 Saturday night. The high Saturday will be hovering around 40, according to guidance. With winds around 15 knots, wind chills can be very high. The winds will die down a bit Saturday night, but any wind at all will make it feel like it's around 10.

If you are going to be out and about this weekend, plan and dress accordingly.

Monday, February 6, 2012

Quick Invest 90L Update

Just as I thought, it ended up being a rain maker...sort of. It has rained a lot in the Florida Keys. In fact, Key West received 4.34 inches of rain Sunday, which broke the 1872 record for that day, according to the National Weather Service office in Key West. Doppler total estimates from the western Keys are in the 1-2 inch range, but it dries off once you head north into Miami-Dade County. Doppler total estimates are pretty much in the trace range, with a few spots in southeast Florida getting at least a half-inch.

The system that has caused the mess seems to be deteriorating based on satellite and radar loops.

The RUC sounding profile for the Miami area looks fairly moist, while the 12Z MFL sounding shows precipitable water at a juicy 1.71 inches and a MLCAPE at roughly a 1000 J/kg.

The cold front in northern Florida is expected to continue to push south while the low will move off to the northeast. Though this low has lost some luster, it's still possible to get some shower activity over southeast Florida. If the sun can break through the clouds, it could help destabilize things a bit and fire up a storm or two. KMFL is thinking about lowering the POPs and I see that as reasonable.

The National Hurricane Center has lowered the chances of tropical or sub-tropical development of this system to near 0 percent.

Sunday, February 5, 2012

Invest 90L in the Yucatan Channel

Many of you reading this are likely thinking of two things: 1) Is he actually wiring a weather blog post? and 2) Isn't this February?

I was taken aback this morning when Tropmet posted that an area of disturbed weather near Cuba and the Yucatan Peninsula has been declared an Invest system. Yes, you are right - it is early February.

But don't panic! People along the eastern Gulf of Mexico don't need to run to Publix and gather water, canned food, and kegs of Miller Lite. I don't expect this to turn into a monster tropical cyclone.

Further analysis shows a little bit of vorticity in the area of the invest, and water temperatures near western Cuba are around 80 degrees F. But vertical wind shear is at least 40 knots, and this will help limit TC development. Still, it looks a little impressive on satellite imagery loops. The radar composite from Cuba is showing the associated precipitation, but no hint at all of a closed center of circulation.

The system isn't moving isn't in a hurry at the moment, but it should start to move a little faster in a northeasterly direction soon. It looks to be a big rain maker for south Florida. The HPC is calling for 24 rainfall totals as much as 2 inches in southeast Florida.

The 12Z (7 am EST) GFS MOS (model output statistics) guidance is showing between 1 to 2 inches of rain in Miami, while the raw (non-statistical) is much drier. The NAM MOS is very dry, as well (maybe a half of an inch within 24 hours). There seems to be disagreement on rainfall from guidance, but I am confident that southeast Florida should see some rain starting tonight. The western Florida Keys are already starting to see rain from Invest 90L based on radar imagery.

Watching the rain on the radar will be a problem as NWS-Miami are currently upgrading to Dual-Pol. Convenient, huh?

In summary, southern Florida can see some wetter weather tonight and tomorrow with conditions beginning to clear out Tuesday. It is interesting to see an invest-declared system this time of year, though.


It turns out there has been a TC this early in the year. Michael Laca posts on Facebook that there was a "Groundhog Day" tropical storm in 1952. Read a little more on this: https://www.facebook.com/vmax135/posts/341037679260193. Thanks, Greg for tweeting this.