Daweathablog

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

Monday, October 18, 2010

Forecasting Contest - Glasgow, MT Forecast for Tuesday 10/19

Currently, HPC surface maps show high pressure over Montana bringing quiet conditions to the area. However, satellite is showing mid-level cloudcover that's about to enter the Glasgow area. It might have a slight effect on today's high.

NWS-Glasgow mentioned rising heights for tomorrow in their AFD, which would rise temps a little bit. Model guidance is hinting at this during day Tuesday.

What will make this forecast tricky is the cloudcover and weather that will linger tonight. This could have an affect on overnight lows.

For tonight, expect mid-level cloudiness with some clearing before dawn and a low near 33. I am going to go slightly above guidance. Tuesday, expect partly cloudy skies with a high near 64.

Monday, October 11, 2010

Forecasting Contest - Glasgow, MT Forecast for Tuesday 10/12

Today, I am writing my forecast from my alma mater in Gainesville, FL. We (the class) don't need to do a forecast this weekend since it's fall break, but I figured it wouldn't be a bad idea to keep up with the forecasts.

Our new location to forecast is Glasgow, Montana. Currently, a cold front is passing through the state bringing in showers. Glasgow should get hit with this relatively light rain later on today as the front pushes through. Skies should begin to clear up after the frontal passage based on visible satellite imagery. However, low clouds are showing up on the visible in what appears to be valleys. Therefore, valleys that have experienced some rain today might see some low cloudcover after the passage (You see how much I know about the topography of the west?).

As the night wears on, skies should start to clear out as the front moves out the state and high pressure rolls into the area. This should allow for cooler temperatures to move in. Tuesday should be a nice day as high pressure remains.

Tonight, expect clearer skies late with a low near 39. For Tuesday, expect sunny skies with a high near 60.

Wednesday, October 6, 2010

Forecasting Contest - Brownsville, TX Forecast for Thursday 10/07

Good morning! It seems like I was an idiot yesterday and forgot to place a forecast for this blog and the local competition. Oh, TA stuff. Let's try to get this thing back on track.

The same, boring weather pattern that has been going on since early last week persists in the Brownsville area. Current synoptic-scale analysis shows high pressure centered over northwestern Arkansas, bringing more of a northeast to east flow over the area.

The HPC forecast maps show high pressure moving south and closer to Brownsville over the next day. NWS-BRO and guidance note lower relative humidity levels moving in from the north starting around 12 Z (7 am CDT). This may give a chance for wider temperature values than we have recently observed (which makes forecasting highs and lows a little more difficult).

For tonight, the MOS guidance is hinting between 60 and 62 degrees for a low. BUFKIT is showing more of a northerly flow at the surface as the night wears on with speeds between 3 and 5 knots. This could slightly keep radiational cooling at bay, but the northerly flow will be more of a drier-air advection (unlike a NE flow that'll bring more of a moist air advection from the GOMEX). I think I will stick close to guidance for the low. Tonight, expect mostly clear skies with a low near 60.

For Thursday, expect sunny skies with a high near 87. The winds at the surface should be more out of the northeast around noon.

Monday, October 4, 2010

Forecasting Contest - Brownsville, TX Forecast for Tuesday 10/05

The nice weather pattern in place for the last week is expected to persist on Tuesday. At the synoptic scale, high pressure is over Wisconson and bringing a northeast flow to the Brownsville area. Both the NAM and GFS seem to be in good agreement for this pattern to persist for Tuesday brining a strong northeast to north-northeast flow to the area.

This northeasterly flow could alter temperatures a bit tonight and Tuesday. Expect fair conditions tonight with a low near 67. For Tuesday, expect partly cloudy skies and breezy with a high near 86.

Wednesday, September 29, 2010

Forecasting Contest - Brownsville, TX Forecast for Thursday 09/30

It's going to be the same song-and-dance for Thursday as high pressure at the surface and aloft will continue to hold over the region. This will allow warm temps and mostly clear skies to remain over the area.

The surface wind pattern seems to be variable from NW to NE tonight according to MOS guidance runs, which makes predicting the low a little difficult. Any deviation of wind direction could alter the temp by a couple degrees due to any local advection. Moisture levels will increase as guidance suggests dewpoints in the 60s. I will call for clear skies tonight with a low near 65. For Thursday, expect fair skies with a high near 90.

Quick Update on TD 16

This morning, Tropical Depression 16 is, well, still Tropical Depression 16. It has not intensified since the last blog post and I'm not 100 percent sure if it will before the center of circulation impacts south Florida later today.

The center of circulation is over Cuba at the moment and is expected to move back over the waters later this morning or early afternoon. NHC forecasts have the center hitting south Florida and the upper Keys by this evening. It's then expected to cross southeast Florida and exit over the Atlantic early Thursday morning.

Wind shear is pretty high as the trough and the surface front still hangs nearby. This should keep the cyclone from intensifying too much, if at all.

Impacts from this system are relatively mild as inland flooding is the main concern. Doppler radar storm total estimates show rainfall at 5 or more inches for portions of southeast Florida and the Keys, with some spots picking up as much as 7 inches.

Stay dry, south Florida.

Tuesday, September 28, 2010

Forecasting Contest - Brownsville, TX Forecast for Wednesday 09/29

Today is looking to shape up as a good day in Brownsville with fair skies and temperatures in the low 80s. A similar pattern is expected to remain as high pressure - currently centered over Colorado - remains in control.

Lighter winds with clear skies may allow for a little more radiational cooling tonight than last night since winds were less than 7 mph. However, moisture still on the ground from recent heavy rainfall may keep temperature slightly warmer than what guidance is predicting. I'm calling for fair skies tonight with a low near 61. For Wednesday, expect mostly sunny skies with a high near 89.

Tropical Depression Sixteen (soon to be T.S. Nicole) Looks to Impact S FLA.

This morning, the National Hurricane Center began issuing advisories on Tropical Depression Sixteen in the Caribbean Sea after the disturbance began showing signs of a well-defined closed center of circulation.

As of the 2 pm EDT advisory, winds were at 35 mph as the storm was moving north-northeast at 15 mph. The storm was 160 miles south of Havana, Cuba. This general track is expected to continue according to the NHC outlook. This would place its path towards the south Florida area as early as Wednesday afternoon. The NHC has issued tropical storm warnings from Jupiter Inlet southward to east Cape Sable and Florida Bay as well as the Florida Keys.

Right now, the circulation is a little easier to pick out on visible satellite imagery, but hard to depict on infrared. A lot of the heaviest convection is south of the center of circulation. Moments ago, hurricane reconnaissance aircraft found winds at 35 knots, hinting that this may already be Tropical Storm Nicole. The NHC has yet to confirm this. If it is the case, it will likely be named at the 5 p.m. EDT advisory. One thing may limit its intensification: The trough that is digging into the southeast (and helping to bring some nice, cool weather here in Starkville, MS). Wind shear values north of the depression (~ 20-30 kts) are unfavorable values with regards to intensification.

The trough and associated stationary surface front - which is bringing heavy rain to central Florida - will guide this storm over southeast Florida come Wednesday. The GFS is calling for the TC to move right over inland south Florida. The rest of the guidance models have it going more right and just off the coast of Miami-Dade. Regardless, southeast Florida will deal with gusty winds and heavy rain. Conditions should improve in central and south Florida as early as Thursday morning based on guidance models and HPC surface forecasts.

As to where this system will go beyond Florida, it appears likely that it will lose its tropical characteristics and move north as a mid-latitude low. The 300-mb GFS guidance shows more of a negative tilting in the trough, which could push it towards the Carolinas, as what the HPC seems to be showing starting Thursday night.

In a nutshell, southeast Florida can expect some heavy rain and gusty winds starting Wednesday. I doubt this storm will reach hurricane strength, but it has the chance of being a decent tropical storm.

Keep an eye on my Twitter feed for the latest. I'll post as much as I can as I will be studying for a Calculus II test (fail!).

Monday, September 27, 2010

Forecasting Contest - Brownsville, TX Forecast for Tuesday 09/27

Starting today, participants in the forecasting contest move onto a new location: Brownsville, Texas. The city sits near the US and Mexican border along the gulf coast.

Currently, high pressure rests to the north bringing a northerly flow to the area. For Tuesday, this trend is expected to continue and bring nice weather to the area.

MOS guidance has temps in the low 60s tonight. Skies should be mostly clear with winds slightly decreasing as the night moves on. If clear skies prevail and winds die down enough, radiational cooling would be near prime. Tonight, I will call for mostly clear skies with a low near 62, which is near guidance. Tuesday, skies should be mostly sunny with a high near 87.

Wednesday, September 22, 2010

Forecasting Contest - Atlanta Forecast for Thursday 09/23

Current conditions in Atlanta are essentially a carbon copy of Monday with a deep-layer high to the east of the area (up to about 500 mb). An easterly to southerly flow persists in the area. There is a little more moisture in the air compared to a few days ago with dewpoints currently in the 60s.

The synoptic setup on Thursday is not expected to change much as the high continues to sit to our east. There may be a very slim chance of rain based on NWS-FFC discussions, but I am not confident enough to put it in the forecast for Thursday.

For tonight, expect fair skies with a low near 71 (just a degree or two higher than guidance). For Thursday, expect partly cloudy skies with a high near 90.

Tuesday, September 21, 2010

Forecasting Contest - Atlanta Forecast for Wednesday 09/22

Current surface analysis shows high pressure centered over eastern Pennsylvania. At the upper levels, 12Z analysis shows a high between 850 and 400 mb. This subsistence aloft will help keep rain chances near nil for the today.

Guidance models are forecasting the high over New England to keep sliding east into the Atlantic. This will bring more of a southerly flow tomorrow and pull in more moisture at the surface. High pressure aloft is expected to remain tomorrow and help keep things capped. However, NWS-FFC is keeping a very slim chance of rain for the Atlanta area. I am not very confident of adding a chance of precip to the forecast based on the mid-level high that's expected to remain.

I've been forecasting a little cooler than actual lows; therefore, I might raise the low temp Wednesday morning slightly above MOS guidance. Expect fair conditions tonight with a low near 72. For Wednesday, expect partly cloudy skies, a little muggy with a high near 90.

Monday, September 20, 2010

Forecasting Contest - Atlanta Forecast for Tuesday 09/21

High pressure is currently sitting over the Great Lakes as a frontal system and associated low is over near the Dakotas. A ridge exists in the southeast between 850 mb and 300 mb. SPC forecasts and models note the surface high to move on to the east as the frontal system moves east towards the midwest.

For the Atlanta area, not a whole lot in the weather department is expected. MOS guidance is calling for moisture to decrease as the current northerly flow is expected to persist at least through today. Tomorrow, the high to the north moving off to the east should bring more of a easterly to southeasterly flow. Guidance is hinting at dewpoints to hang around the 60 degree range on Tuesday.

Expect fair skies tonight in the ATL with a low near 69. For Tuesday, expect partly cloudy mostly sunny skies with a high near 92.

Wednesday, September 15, 2010

Forecasting Contest - Atlanta Forecast for Thursday 09/16

Currently, high pressure is centered over extreme western North Carolina. Conditions are mostly clear in the Atlanta area with temps in the 80s.

The high pressure to the northeast of ATL is expected to move offshore today and Thursday. This should usher in more of a southerly flow and should raise the temps above average. I expect temperatures to be a little warmer tonight compared to this morning - fair skies tonight with a low near 68.

During the day, expect partly cloudy skies with a high near 90. Some cloudcover may keep temps slightly cooler than otherwise, but this predicted temp is slightly above guidance.

Tuesday, September 14, 2010

Forecasting Contest - Atlanta Forecast for Wednesday 09/15

Current visible satellite imagery shows mostly clear skies over northern Georgia with temps running in the upper 80s across the area. Surface analysis shows the high pressure in extreme eastern North Carolina. Winds are light and variable for the area, as well.

Some of the models are indicating the high to start to move off the North Carolina coast sometime tomorrow, bringing more a east to southeast flow. Temps should be a little warmer. Otherwise, not much of a change to the status quo.

Tonight's low temp prediction is something I find slightly tricky with the MOS GFS going for 59 and the MOS NAM shooting for 66. The NAM is predicting a little more moisture than the GFS, which could be the reason for the discrepancies. There is not much of a wind flow expected at 1000 mb at 12 Z (8 a.m. EDT), so any moisture or temp advection is a little hard to determine. I think I will stick with current trends from today and may call for a slightly warmer low than this morning. Tonight, expect mostly clear conditions in Atlanta with a low near 63.

Wednesday should be more of the same with mostly sunny skies with a high near 90. There should be more of a southeasterly flow during the day, so my predicted high slightly above MOS guidance.

Monday, September 13, 2010

Forecasting Contest - Atlanta Forecast for Tuesday

Good morning! I am going to do my best to keep up with providing detailed-as-possible weather forecasts for the forecasting contest in my Weather Analysis I class. This week, we start off with Atlanta, Ga...

Currently, high pressure is dominating the southeastern states with the high sitting to the northwest of the ATL area based on HPC surface analysis. Models are expected to move the high to the east today and tonight, which will help usher in a more easterly flow into north Georgia starting no later than tomorrow morning. This will keep temperatures a little more moderated, but keep skies mostly clear and very nice for the area.

A light easterly wind, very little cloudcover and dewpoints in the 40s and 50s will allow good radiational cooling tonight. NWS-Peachtree City is calling for a low near 58 tonight, but I think that's too cool, mostly because of the more easterly flow. I think the low will be a little near MOS guidance and I'll call for a low of 61 tonight with mostly clear skies.

Tuesday will be very nice with the high to the north and maybe slightly east of Atlanta metro. The light easterly flow will continue. I'm calling for a high of 88. No rain is expected for Tuesday.

In a nutshell, expect some nice weather in the A-T-L, so get out an enjoy it!

Tuesday, September 7, 2010

Forecasting Contest Change...

I'm just letting everyone know that there was a change in the weather forecasting contest I mentioned in the previous post. The contest has been delayed due to technical issues. I will start forecasting for the Atlanta area starting next Monday (Sept. 13). I'll try to make Starkville and/or Gainesville updates at least once this week. Stay tuned...

Sunday, September 5, 2010

Warm-up expected soon in Starkville; Forecasting Contest Begins

Good afternoon, everyone! It's been Chamber of Commerce weather here Starkville, MS as sunny skies and drier conditions have persisted. It looks like this weather will sustain itself for the rest of Sunday where temperatures have been in the mid 80s in the Golden Triangle area. Tonight, the dry air and clear skies will allow for optimal radiational cooling. NWS-JAN is calling for Monday morning lows in the mid 50s for Oktibbeha County.

For Monday, HPC forecast surface maps are showing a ridge near the mid-Atlantic coast. The GFS and NAM are hinting at more of a southeasterly flow by 0Z Tuesday (7 pm CDT Monday). Warm air advection from the Gulf of Mexico will help increase moisture and raise temps and dewpoints. A chance of rain exists for most of the week as moisture continues to increase and as a low south of the area begins to inch its way back to the north, per NWS-JAN's forecast discussion.

FORECASTING CONTEST

In Weather Analysis I, students are required to participate in a forecasting contest. Unfortunately for Starkville residents and my friends back in the Gainesville-Ocala area, we are given cities to forecast and they change every so often. In our class, the contest officially begins Tuesday and will start with Wednesday's forecast. However, I will start a day early just to get in the habit of doing it. The first city: Atlanta, Ga.

My desire is to post my forecasts on here for the required four days per week. So, expect a brief discussion on the given city with the predicted high, low, amount of rain and rain amount chances. As usual, I appreciate comments and discussion from blog readers on my forecasts.

I'll make posts on Starkville and beyond as needed. Maybe this will get me back in the habit of noting weather back here and at home. Stay tuned...

Monday, August 16, 2010

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.

roop_20100815_lightning07

roop_20100815_lightning04

roop_20100815_lightning01

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.

Thursday, July 22, 2010

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

Wednesday, July 21, 2010

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.

Tuesday, July 20, 2010

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.

Friday, June 11, 2010

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.

Monday, May 3, 2010

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.

Sunday, April 25, 2010

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.

Saturday, April 24, 2010

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.

Sunday, March 28, 2010

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.

Saturday, March 27, 2010

Slight Severe Weather Threat Sunday

Good (late) evening, everyone. It's been a while since my last weather post. Schoolwork and the lack of any blog-worthy interesting weather has kept me from writing. However, there looks to be a good reason this time.

I checked out the forecast this morning and noticed a good chance of rain in the forecast as a storm system from the west is expected to approach the area. Later in the afternoon, the Storm Prediction Center issued an update. They raised the severe threat from, well, nothing to slight risk...

...FL PENINSULA...
MULTI-EPISODE/MAJORITY OF THE PERIOD SEVERE POTENTIAL WILL LIKELY EXIST ACROSS THE FL PENINSULA...AND REGION APPEARS TO WARRANT A CATEGORICAL SLIGHT RISK. SEVERE THREAT MAY INITIALLY INCREASE DURING THE AFTERNOON...EITHER VIA INLAND ADVANCEMENT OR PERIPHERAL DEVELOPMENT OF EARLY DAY GULF OF MEXICO TSTMS. THIS MAY ESPECIALLY BE ACROSS THE NORTH CENTRAL FL PENINSULA AMIDST AN INCREASINGLY MOIST/WEAKLY CAPPED BOUNDARY LAYER...WHERE VERTICAL SHEAR PROFILES WOULD SUPPORT SOME SUPERCELLS.

ADDITIONALLY...AS AN UPSTREAM SHORTWAVE TROUGH CROSSES THE GULF COAST AND THE POLAR/SUBTROPICAL JETS COME INTO PHASE SUNDAY NIGHT...STRENGTHENING DEEP LAYER SHEAR /WHILE A CONTINUALLY MOISTENING BOUNDARY LAYER/ AMIDST A STRONGLY DIFFLUENT REGIME COULD ALSO SUPPORT A NOCTURNAL RISK FOR SOME SUPERCELLS/BOWS WITH A DAMAGING WIND/TORNADO RISK.

So, basically we have the following: increasing southerly flow to bring in moisture (with models pointing at dewpoints in the 60s), weak cap to support continuous lifting, and wind shear looking susceptible to some supercell development.


NAM models: 250-mb wind forecast for 8 pm ET Sunday (right) and Temp/Dewpoint forecast for 5 pm ET.
Source: MeteoStar


After dark, things will deteriorate more as guidance models move a squall line into the north Florida area around 8 p.m. ET. The GFS seems to be more aggressive with heavy activity around this time compared to the NAM where more seems to build to the south of Gainesville later at night. The polar jet stream, along with the El Nino-enhanced subtropical jet, will aid in enhancing precipitation along with a "damaging wind/tornado risk."

We shall see what happens. Stay tuned.

Friday, February 12, 2010

Snow Looking Less Likely

Things seem to have changed in the last few hours. There was a slim possibility that parts of northeast Florida could see winter precip tonight. Now, it doesn't seem likely at all according to the NWS in Jacksonville:
WARM LAYER ABOVE THE SURFACE WILL LIKELY KEEP PRECIP ALL RAIN IN
FLORIDA. BY THE TIME THE PROFILE OVER FLORIDA BECOMES COLD ENOUGH
TO SUPPORT SNOW...THE MID AND UPPER LEVEL MOISTURE WILL BE
STRIPPED AWAY AND LACK OF ICE NUCLEATION WILL KEEP ANY PRECIP THAT
FALLS AROUND MIDNIGHT IN THE FORM OF LIGHT DRIZZLE. TEMPS SHOULD
REMAIN ABOVE FREEZING DURING THIS TIMEFRAME SO FREEZING DRIZZLE IS
NOT A CONCERN.
Also, from looking at radar, it seems the storm system is moving out a little faster than forecasts from yesterday revealed. The "back-side" precip is now passing over Gainesville. When this rain moves out, temperatures will still be above freezing and, therefore, winter precip is not likely.


Image source: WeatherTap.com

Expect the rain to taper off later this evening with drizzle possible later on. NWS-JAX issued a wind chill advisory for the area from 3 a.m. to 9 a.m. Saturday - which means wind chills in the low to mid 20s are likely. NWS-JAX is calling for a low of 31 tonight in Gainesville. Stay warm.

Thursday, February 11, 2010

SnOMG?!

It has been a few weeks since my last post, which was on the possibility of winter precipitation in the area. Surprisingly, reports of sleet and snow came in from Ocala and Flagler County that early January night. Reports of sleet were even coming in south Florida.

Flash forward to the last couple of days where much of the United States has experienced what some have been calling "Snomagedon" or "Snopocalypse." The last two storm systems have broken many snowfall records and wrecked havoc for millions.

This next storm looks to be interesting, although this system doesn't seem to have many impacts on New England as the last two did. The southeast looks to be under the fire.

What's happening

Surface analysis from the Hydrometeorological Prediction Center (HPC) shows a low pressure system centered near Brownsville, Tx with an associated cold and warm front. Radar shows plenty of rain in southern Texas, southern Louisiana and southern Mississippi while snow is falling in northern Louisiana and north Texas. GFS and NAM guidance is showing a upper-level longwave trough (essentially a trough in the jet stream) over north Texas.

Friday's Synoptic Outlook

The system is expected to intensify and move east over the Gulf of Mexico. Starting Friday before noon, north Florida could start to see rain and pick up in intensity as the day wears on. The HPC forecasts, along with model guidance, seem to agree on the low reaching Florida near Tampa Bay around 7 pm Friday with the warm front remaining south of Gainesville.

So...snow?? Sleet? Anything?

The further north and west you go during the next 36 hours, the better the chances of winter precipitation. Within the last hour or so, sleet was reported in Crestview, FL (western panhandle) was well as Destin. There are some schools of thought of whether Gainesville could see anything.

NWS-Jacksonville is thinking of this (from their latest Area Forecast Discussion)...
SO...THE BEST CHANCE FOR A RA/SNOW MIX WILL EXIST ACROSS OUR NW GA
ZONES BEGINNING FRI MORNING. THE BEST CHANCE FOR POSSIBLE
ACCUMULATIONS WILL BE ACROSS THESE ZONES AFTER 18Z [2 PM EST] FRI AND
CONTINUING THROUGH 06Z [1 AM EST] SAT. THE BEST CHANCE FOR A WINTRY MIX
OF RA/S WILL BE ACROSS NE FL AFTER 21Z [4 PM EST] FRI AND FRI EVENING MAINLY
N OF THE I-10 CORRIDOR. THERE WILL BE A GOOD CHANCE FOR FLURRIES 06Z-12Z
[1 AM - 7 AM EST] SAT ACROSS A LARGE PORTION OF THE AREA DUE TO SHALLOW
WRAP-AROUND MOISTURE...MEAGER LIFT AND STRONG COLD AIR ADVECTION.
In other words, it would be a very slim chance for us. I have been warned by a fellow Twitterite and meteorologist that "warmer air from the Atlantic" could be a limiting factor by "not allowing the lower levels to cool enough." However, my thinking is if the temp is just cool enough below 850mb, we could enough moisture at the surface to have snow fall. He also suggests that the latest GFS and NAM runs don't really show any winter precip for the area.

Based on my look at temperature forecasts with some of the models, chances are slim for winter precip in the area. But that doesn't mean that it's impossible.

The winter precip event early last month had one limitation for Gainesville: surface dry air. During that night, radar indicated light precip in the area but it was not falling to the ground. Why? Too dry - it just evaporated before it even hit the surface.

Here are some examples of temperature profiles for snow (left) and sleet (right).


Basic Vertical Temperature Profile Associated with Snow at the Ground Basic Vertcal Temperature Profile of the Atmosphere Associated with Ice Pellets (Sleet) at the Ground
Image Source: NOAA

Summary

So, will we see snow or any winter precip in the area? Chances are slim, but you can count on dealing with lots of rain for most of your Friday. Bring that umbrella to school or work before you head out the door.

Also, keep any eye on my Twitter feed (twitter.com/daweathaman) for the latest. I might add a new weather post as conditions and free time warrant.

By the way, I always welcome discussion from meteorologists and other weather geeks for their expertise. I'm not too familiar with forecasting winter precip (wonder why?), so any advice would help. Let me know if you have any winter weather reports, too.

Thursday, January 7, 2010

Snow? Here?

For the last few days, most of the United States has been plunged into the deep freeze as a persistent synoptic pattern keeps funneling cold Canadian air southward. For Florida, this trend is expected to continue well into early next week.

For the last few days, abundant discussion on social networking sites and around the proverbial water cooler have been on the $60,000 question: Will it snow in Florida? To most, it would seem like it given that it's been so cold for so long in this state.

Synopsis

An Alberta Clipper system (what's that?) and it's associated front, which is currently over the lower and middle Mississippi River valley, is bringing snow from Wisconsin to northern Mississippi and Alabama while bringing rain for central and southern Mississippi and Alabama and most of Louisiana. High pressure currently remains over the Florida panhandle. This helped keep the winds relatively calm overnight and skies clear to allow temperatures to fall to near-record territory across the state.

Preliminary figures from the NWS suggests that the low in Gainesville this morning was 21 degrees, which would break the old record of 22 set back in 1924. It may have been as low as 21 in Ocala, as well.

At the upper levels, a trough in the jet stream is beginning to fold in the upper Plains and New England while the subtropical jet stream passes over Florida. This may have aided in keeping south Florida mostly cloudy this morning (judging by infrared satellite imagery) and staving off colder weather for that area.


Jet Stream analysis from 1 a.m. ET today (left) and surface analysis at 7 am ET (right).

Later Today through Saturday.

Short-range forecasts from the HPC show the storm system moving east as the high over Florida now moves east. Early Friday morning, the front is expected to be over the panhandle and and be over central Florida at around 7 a.m. The front should be over south Florida by the end of Friday evening.

There are a few things to keep in mind. For starters, will it even be at or close to freezing at the time precipitation will pass through. One tip given (via Weather Prediction) is to see if temps are below freezing at the surface and 850-mb levels (Weather recap for the novice: As elevation increases, the pressure decreases). If so, "snow is the most likely precipitation." Also, it
s good to see what type of thermal advection (movement of air horizontally) is taking place.

With those of many tips given, lets look at the models. Remember, models are not forecasts etched in stone and things can change. These are used as a guidance.

The NAM at 7 pm ET Friday is showing spotty and isolated precip around the north central Florida area. I would count this as a slim chance of precip in the area. At this time, the air temps at 850 mb and 1000 mb are close to freezing. As the night wears on, precip increases over central Florida. For 7 am ET Saturday, temps at 1000 mb are at or below freezing for much of the north central and central Florida while the freezing line at 850 mb is around the I-10 corridor.

The GFS' 06-Zulu run shows the precip associated with the front passing through during the afternoon and evening on Friday. The freezing level at 850 mb is to the north of the Florida/Georgia state line at 7 pm ET Friday while the line is moved south to near Gainesville 12 hours later. The 1000-mb freezing line is over central Florida during the model runs for Friday evening and Saturday morning.

Those are two models with slightly different takes on precip and temperature above the surface. What could be the case? I am not too sure about snow for the northern half of the state. I will be really shocked if we do get it. I can say this: There will be a very slim chance of snow for the north central Florida area. It would depend on the timing of the precipitation.

How about sleet? It would be more plausible than snow, I think. Again, it would depend on the timing of the precipitation. If precip falls at night, it could happen. It also depends on thermal advection.

Here's what the National Weather Service in Jacksonville (NWS-JAX) has written in an earlier Area Forecast Discussion:

DUE TO THE SLOWER PROGRESSION OF PRECIP...HAVE ALSO INDICATED SOME
MIXED PRECIP DURING FRI MORNING ACROSS EXTREME SE GA WITH A COLD
RAIN EXPECTED ELSEWHERE. HOWEVER...WOULD NOT BE SURPRISED TO GET
REPORTS OF SOME SLEET MIXED WITH RAIN INTO EXTREME NE FL. NO
ACCUMULATIONS ARE EXPECTED...BUT STILL CONCERNED ABOUT WET ROADS
FREEZING DURING THE EARLY MORNING HOURS ON FRI IN SE GA AS COLDER
AIR FILTERS IN BEHIND THE FRONT. DAY SHIFT ISSUED A SPECIAL WX
STATEMENT ADDRESSING THIS...AND WILL REFRESH THIS PRODUCT WITH THE
LATEST THINKING.

MODELS STILL INDICATING SOME LINGERING MOISTURE OVER THE EXTREME
SE ZONES AS A DISTURBANCE MOVES ACROSS CENTRAL FL EARLY SAT. HAVE
INCLUDED A SLIGHT CHANCE OF RAIN OR SNOW OVER THIS AREA WITH A
SMALL AREA OF FLURRIES BEHIND IT GENERALLY SE OF A ST AUGUSTINE TO
OCALA LINE. AGAIN...MEASURABLE AMOUNTS ARE NOT EXPECTED.

Bottom line: Very, very low chance of snow. Sleet possible depending on temperatures aloft and timing of precipitation. Chances would be greater the farther north you go. However, just as NWS-JAX keeps mentioning in their forecast discussions: "Measurable amounts [of winter precip] are not expected."

The Next 24 Hours

Expect temps to increase slightly today into the 50s for the Gainesville area today with mostly sunny skies. Tonight, things will begin to change with a chance of showers and a low in the low 30s. Based on temp profiles aloft with guidance, I don't see much of a chance tonight for any winter precip. Friday, things will get interesting and may change. I might write another post if updates are necessary. Otherwise, keep any eye on my Twitter feed for the latest at twitter.com/daweathaman.

Friday, January 1, 2010

New Year Brings Cold

Good afternoon and Happy New Year, everyone. It's been a while since my last weather blog post. I am kind of making it a New Year's resolution to make more posts on here - at least once every few days. Hope it sticks.

At the moment, a cold front with associated showers have passed the Gainesville area late this morning. Skies continue to be mostly cloudy, but judging by visible satellite imagery clearing is expected in the area real soon as the cloud cover passes with the front.

At the upper levels, a deep trough in the jet stream, along with the passage of the surface low and its flow, will bring colder air to much of the midwest and eastern U.S. for the next few days according to guidance models. NWS-JAX is considering this as "one of the longest duration cold spells in quite some time" in this morning's Area Forecast Discussion.

However, the big question: How cold? NWS-JAX calls for lows in Gainesville in the low 30s tonight, but MOS guidance is mostly hinting in the upper 20s except for the NAM. I would have to agree with the NWS at this time since, based on experience, it might take a little longer for the coldest air to reach here after the passage of the front. Plus, winds created by pressure gradients after the passage of the low and associated cold front will inhibit radiational cooling and keep air temperatures a little warm. However, with any wind, it may feel colder.

Starting Saturday, the pressure gradient is expected to weaken and bring colder nighttime temps to much of Florida. NAM guidance seems to be treating this a little warm while GFS is calling for temps near 20. For now, I would wait before I call for an exact temperature reading. Regardless, by Florida standards, temperatures are expected to be very cold with below freezing temps each morning through at least Wednesday. Highs are expected to not get close to 60 degrees through Wednesday.

For now, I call for clearing skies in the area today with highs reaching into the upper 50s. Continued clearing with some wind is expected tonight in Titletown with a Saturday morning low near 32. Keep any eye on my Twitter and Facebook feeds for my predictions for the next few nights. Stay warm.