Daweathablog

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

Thursday, May 28, 2009

Forecast for Friday 05.29.2009

It rained a little earlier than expected today, but it kept coming on and off this afternoon. The UF campus was hit at least three times by isolated thunderstorms with heavy rain at times. It could be the same song and dance Friday.

An upper-level trough will help a cold front slowly push towards our area. This will heighten rain chances for Friday. The GFS and NAM models show "blobs" of precipitation in and around our area, but don't pick up the front very clearly. Still, surface forecasts from the HPC show the front getting as close as Lake City and Live Oak around 8 a.m. Saturday.

For tonight, partly cloudy skies are expected with a morning low near 71. Friday, expect partly cloudy skies in the morning with a good chance of showers and storms during the afternoon (possibly late morning). I'm calling for a high near 88.

The weather looks a little nicer this weekend as the front hangs to our south. The temps will be near average, but it should feel a little less humid. More forecast details tomorrow night.

Wednesday, May 27, 2009

Forecast for Thursday 05.28.2009

So, it didn't rain today in our area. That bombed my forecast. A wake of a mid-level shortwave aided in lowering rain coverage in north Florida according to a SPC convective outlook from the afternoon.

Right now, skies remain mostly clear over the Gainesville area. Tomorrow, here's what the NWS-JAX forecast discussion calls:
THE BIGGEST CHANGES INTO THU WILL BE THE INCREASED GRADIENT WHICH MAY PREVENT SEABREEZE ACTIVITY AT ALL ALONG THE EAST COAST AND THE INCREASED SHORTWAVE ACTIVITY AS LARGER SCALE TROUGH MOVES EASTWARD. OVERALL...WITH LOW LCL`S [lifting condensation level] CONTINUING AND 500 TEMPS WARMING EVER SO SLIGHTLY...WE SHOULD SEE A DAY TYPICAL OF TODAY WITH ACTIVITY FORMING EARLY BUT PERHAPS NOT AS STRONG UNTIL LATE IN THE EVENING SHOULD ANY SEABREEZE FORM ALONG THE [east] COAST.
So...expect some of the same weather as today for Thurdsday. We might see some storms, but don't look for anything crazy until, maybe, in the afternoon. Whether this will affect Gainesville remains to be seen.

Tonight, expect clearer skies with a morning low of 69. The temp at KGNV as of 10 p.m. was 75. It's a little warm, but the clearer skies could aid in some radiational cooling, but it also depends on the amount of moisture in the air tonight (dewpoint was at 71). I won't expect a major cooldown. Thursday, skies should be partly sunny in the morning with a chance of showers and storms. Expect a high of 86.

Keep any eye on my Twitter updates (on the right sidebar) for some of the latest weather updates troughout the day Thursday.

Tuesday, May 26, 2009

Forecast for Wednesday 05.27.2009

I am back from a four-day hiatus and ready to create Wednesday's forecast.

Satellite imagery and models indicate a upper-level trough over the northeast Gulf of Mexico according to the latest NWS-JAX forecast discussion. This could generate some showers tonight. Due to low temps and CAPES, chances of thunderstorms is very low. With the abundant moisture, fog is a possibility but that's dependent on cloud cover over any given area.

Wednesday, things look like the same as today with the west coast sea breeze being the dominant force. Storms, if any, should move into the Gainesville area in the early afternoon and move northeast.

For tonight, some clearing with fog possible. The AM low should be near 67. For Wednesday, partly cloudy with a good chance of showers and thunderstorms in the afternoon. Heavy rain is possible with some of these cells. Expect a high of 86.

Thursday looks to be the same forecast at this point, but check back tomorrow night for details.

Friday, May 22, 2009

Is it tropical or not?

You know that low pressure system that has been pestering us with the rain for the last five days. If you live in Florida, you know you know it. Well, the NHC has raised some suspicions in the last few hours of making this at least a tropical depression soon.

Wait. What? A TD? It's not even hurricane season yet (starts June 1). However, that's not the reason why I am questioning it.

For the last five days, there has been some chatter in the weather community whether this could become a tropical system. It seemed real unlikely due to some technical and other factors. Today, it came up again when the NHC decided to reissue special outlooks regarding the system and giving it less than a 30 percent chance of forming. I've been saying all along that this storm could not do so at this point (and I'll get to why soon).

While watching Weather Center on The Weather Channel this evening, Meteorologist (and UF Geography alumna - WoOt!) Stephanie Abrams read a fresh statement from the NHC changing the likelyhood of formation from low to medium. Wha?

This is why I thought it couldn't. 1) For the last few days this low has been accompanied by a upper level low. Why is this important. Tropical systems are usually aided by high pressure aloft (if you ever see the outer spiral of a hurricane and how it kind of looks like it's going clockwise? That's a clue). It's a way it can vent. But it's not the case with this storm. The upper low would make it more of a cold core system.

2) Broad convection. For the last few days, the storm lacked any convection around the center. Instead, the heaviest rain has mostly been far from the center of circulation. Tropical Cyclones (will be noted as TCs for now on) have a closed-center circulation with most of the convection wrapping around it.

3) The wind shear is high over the storm (25-30 kts, the threshold is usually 20 kts or less). Further explained by an excerpt from Divine Wind (Emanuel, 2005, Oxford Press):
"[I]f wind shear is present, the storm tries to move along at an average wind speed, and at some altitudes wind must blow through the storm. This storm-relative flow can import dry air from outside the cloud cluster, destroying the humid column of air that is needed for genesis."
So, what is the National Hurricane Center thinking? A senior hurricane specialist from the NHC was on The Weather Channel via phone to talk about it. Jack Beven had some very valid points that I am now realizing.

1) There is still a upper-level low in place. HOWEVER, it is weakening and not completely for the hell of it. What's happening is that the low is becoming more organized to the point where it is releasing more latent heat in the atmosphere which is helping to weaken the colder upper low.

2) Evidence of strengthening is the amount of convection that has blown up in the last few hours (as shown below from the latest IR satellite at 10:45 PM EDT).



The convection was not this crazy at around 7 p.m.

3) The heaviest convection doesn't always have to completely wrap around the center of circulation. In fact, Beven said that there are some full-blown tropical depressions that do not have all of the thunderstorm activity completely wrapped around it, but it coverage and intensity do play a role. The increased convection will send off more latent heat and modify the system even more.

Both NAM and GFS models have the cut-off upper low disappearing by 8 a.m. Saturday.

Buoy reports have winds near the center at 30 mph, but there is a chance winds might be higher, Beven said.

However, things to consider. If it's strengthening, will it become a TD before landfall Saturday? The models have this system making landfall sometime Saturday afternoon or evening. If it does, will it matter? No matter what happens, the results will be the same: rain, rain, rain in and near the landfall area. There might be a little more wind, but that's it.

Beven was pretty awesome in the interview. He explained things pretty well. I learned some stuff from that interview on TWC. I should have a little more faith in the guys and gals with the Masters and Ph.D's. They might see things that others can't.

Lets see what this thing does.

Thursday, May 21, 2009

Forecast for Friday 05.22.2009

Rain, rain, go away. I'm starting to get a little annoyed with this constant cloud cover over us. I don't mind rain, but if it has to be dreary every minute, it's gets old really quickly. However, the wish of more sun might arrive soon.

The deepening low is still over the eastern Gulf of Mexico but is advancing slowly west with the upper low near the same vicinity. Things do look promising.

The lower-level low is expected to keep moving west while both the NAM and GFS have the upper low disappear tomorrow. The high to our north is expected to weaken and move east, which should decrease the pressure gradient and, in turn, lessen the wind speed. This doesn't mean that it will not rain anymore. We are expected to be on the east side of this low, which will funnel warm and moist tropical air to our area. We should see more broken cloud cover, but any daytime heating will fire up showers and thunderstorms in the Gainesville area. This could bring locally heavy rainfall to places that don't need any more rain.

For tonight, expect cloudy skies with a chance of a shower or two. The AM low should be near 66. Friday, expect mostly cloudy skies with a chance of showers and thunderstorms. I'm calling for a high of 79. We could see a few peaks at the sun...maybe.

Wednesday, May 20, 2009

Forecast for Thursday 05.21.2009

SE SFC

The above image you see is not a hoax. It is reality. The Doppler radar image from NWS-JAX shows the estimated amount of rain at locations across the area since 7:46 AM ET on Saturday, May 16. Where you see the pinks in parts of Flagler and Volusia counties indicates 12 or more inches of rain. Compare that to the Gainesville area where we've seen between an inch and 1.5 inches since Saturday.

Here's the (un)funny part: It's still not over yet.

Surface analysis at 8 p.m. ET continues shows the low in the eastern Gulf of Mexico due east of Naples and due south of Panama City. It's not hugging the coast northern Monroe County like it was last night. It's good news that it's moving, but not quick enough. Also, the upper-level cut off low persists over South Florida according to the latest NWS-JAX forecast discussion.

Bands of rain are still forecast to persist tonight and Thursday around the upper low and the converging flow from the Atlantic according to the discussion. Basically, the synopitc setup will not change very much Thursday. The same 'ol rain dance.

Tonight, periods of on and off rain with a morning low around 65. For Thursday, expect rain with slightly breezy conditions and a high of 77.

The rain might stick around Friday and Saturday, but things might change afterwards. Stay tuned for future forecasts.

Tuesday, May 19, 2009

Forecast for Wednesday 05.20.2009

Rain, rain and more rain will be the story for the next couple of days as the current atmospheric setup is expected to remain mostly static.

Currently, a surface low remains near southwest Florida while the warm front (formerly stationary) is moving back north (see 8 p.m. sfc map below). The move of the front is reflected in Gainesville's current temps as they have increased slightly (62 deg as of 11 p.m.).

SE SFC


From looking at satellite imagery, the low is very broad and open with cloud cover extending out hundreds of miles to the east. Showers continue to move onshore with some of the heaviest over Bradford and Clay counties as well as eastern Marion County. East Central Florida will get a heavy batch of rain and a few thunderstorms as the hours wear on. Gainesville could soon get some action from the Bradford and Clay batch, but I am not certain on that at this point.

The low is expected to slowly move to the west Wednesday, but will continue to pump in moisture and keep rain chances very high. The pressure gradient between the high to the north and the low is expected to persist tomorrow and keep things breezy. The upper low over the gulf will too remain nearby until at least Thursday evening when some of the models have it dissipate.

For tonight, expect cloudy skies with periods of rain with an AM low near 63. Wednesday, the same rain song and dance tomorrow with a high near 75. With the warm front lifting through here earlier, I am a little more confident that the 58 degree weather at 4 p.m. in mid-May will be a thing of Monday and today.

The rain in Gainesville hasn't been as bad as other places. Reports of high precip amounts have come in, especially from southern Flagler County where they have received nearly 13 inches since the weekend. GNV Regional Airport only picked up 0.23 inches of rain through 6 p.m. today.

Things may begin to improve after Thursday, but I'll include more details as the time passes.

Quick Weather Update

I have to leave for work soon, so I need to make this short and sweet. Surface maps from the HPC show the front nearly stationary over south Florida with a 1008 mb low between Key West and Cuba with another weak low southeast of Andros Island in the Bahamas (see NOAA/HPC map below).

SE SFC

Radar and satellite imagery show some signs of a counterclockwise turn with this system over Florida. This is bringing a reversal of direction of rain from yesterday - moderate to heavy showers are moving in from the east with the heaviest activity over Flagler County. Expect this heavy activity to move in later this morning and throughout the day.

Due to the tight pressure gradient between the high to the north and the developing low to the south, winds could be a little stronger than ususal today. Winds are expected to be between 15 to 20 mph with gusts as high as 30.

Monday, May 18, 2009

Forecast for Tuesday 05.19.2009

Before I go into tomorrow's outlook, let me discuss today. Holy cow, was it cold for May. The weather played a "switcharoony" today with a low of 59 and a high of 70 (as of 6 p.m.). But it's not what you think. The high of 70 degrees was around 9 a.m. while the low was at 6 p.m.

At 8 p.m., it was 58 degrees at the Gainesville Regional Airport. At 4 p.m., it was 60 degrees. I never thought I would see 60 degrees at 4 o'clock on a mid-May afternoon. It's also damp and cloudy at the same time. What gives?

Something that I didn't catch was the fact that this front would be so potent and that a upper-level trough would be bearing down bringing in cooler weather (trough shown below at 8 a.m. EDT Monday morning)

Upper Air at 8 a.m. EDT
Image Source: NCAR

The guidance models from last night didn't seem to catch this, either. The northerly breeze after the passage of the front aided in the cool feeling today.

Currently, the cold front is nearly stationary to our south with a surface low in the east central Gulf of Mexico. There is also an inverted trough near Florida's east coast according to the NWS-JAX's latest area forecast discussion. These disturbances are bringing light rain to our area, but some of the heaviest rain is off in south Florida, especially Miami-Dade and Broward counties.

The low that is in northern Cuba and the Bahamas is expected to move west and merge with the front and bring in more moisture and rain to the area. The NWS says NAM model predicts the closed low may move across south Florida while the GFS has the low entering through northeast Florida. There is also a slim chance that this low could form into a tropical (or sub-tropical) storm, although I think it's very remote at this point. At the upper levels, the trough that I mentioned earlier might become a cut-off low and sit in the eastern gulf for a few days. The NAM has this cut-off low forming in the gulf as early as tomorrow.

For tomorrow morning, things should be quiet but the rain may begin to return in the afternoon into the evening as the low towards our south begins to interact with the front and push it back towards our area.

Upper Air at 8 a.m. EDT
Forecast for 2 p.m. EDT Tuesday. Image Source: NOAA/HPC

So, in a nut shell (since I might have lost some of you), tonight should be calmer but cloudy with some lingering showers possible. Expect the AM low around 56 with breezy conditions. Due to the high to our north and the low to our south, expect the pressure gradient to keep it breezy. For Tuesday, cloudy in the morning with a chance of light rain followed by a good chance of rain sometime in the afternoon. If the front lifts back up soon enough, it should be a little warmer with a high of 70. Winds should continue to be around 15 mph with possible higher gusts.

It's going to be a wet week, but we need it. Stay tuned.

Sunday, May 17, 2009

Forecast for Monday 05.18.2009

Currently, showers and storms are to our east over the coastal counties and to our north from Sanderson (Baker Co.) southwest to Bell (Gilchrist Co.). There is a chance that Gainesville could get a shower or two before before the night is over. The front is currently north of us in southern Georgia and the western Florida panhandle.

The rainy weather we have seen this afternoon should be a repeat for most of tomorrow. NWS-JAX and the HPC is expecting the front to slowly pass the area later tonight into Monday bringing higher chances of rain. The atmosphere remains very moist and unstable.

For tonight, mostly cloudy skies should persist with a shower or two possible. The morning low should be near 63. For Monday, expect mostly cloudy skies with showers and storms likely. I'm calling for a high of 71. From viewing the short range forecasts, the front may not pass the area until around 2 p.m. ET, but the rain may stick around for most of the day.

Random Weather Update

I've been checked out for the last couple of days and, therefore, no forecasts. However, I have a few minutes to give a heads up on what's coming up.

For today, a front is dragged from Texas to northern Georgia to New England. This front is expected to move southward and (along with daytime heating and the seabreeze) bring a chance of rain to the Gainesville area. This morning's KJAX sounding data shows precipitable water amounts at 1.73 inches with an unstable atmosphere. Storm direction should be northerly

Currently on radar, there are showers and storms forming in Lafayette and Dixie counties (to our north and west of GNV) while lighter showers are spawning in central Putnam County near the St. Johns River.

Things will change a little starting tomorrow. A trough of low pressure is expected to move in from the Caribbean near Florida as the front gets closer. The trough will feed in moisture and will help raise rain chances and aid drought-stricken Florida, especially South Florida. Guidance model forecasts show the low in varying degrees, but the result points to good chances of rain for the state. This will last for at least the first half of the week.

For the rest of the day, expect partly cloudy skies with a 50/50 chance of showers and storms. The high should be around 86.

Five day QPFs from the HPC call for rainfall in Florida about 2-3 inches on average with some higher amounts (see below).

Unisys Weather
Expect the next few days to be umbrella weather.

Thursday, May 14, 2009

Forecast for Friday 05.15.2009

It will be the same song and dance for the next few days as it has been for the last two days. The only influence on our weather here is the sea breeze fronts in the afternoon as we enter a typical summer pattern. Mid to upper level winds will once again be light and, therefore, storms will be slow moving and erratic in direction. Like today, storms should form near the coasts late morning and early afternoon and slowly make their way towards the center of the state. Heavy rainfall and frequent lightning seem to be the main concerns.

For tonight, expect clearing to partly cloudy skies with a morning low near 65. For Friday, showers and thunderstorms will be possible later in the day. The expect the high around 86.

Tuesday, May 12, 2009

Forcast for Wednesday 05.13.2009

The front that I mentioned last night is currently stationary over north Florida. However, for Wednesday, this frontal boundary is expected to remain over the area as well as a moist onshore flow according to the latest NWS-JAX forecast discussion. Conditions will remain favorable for scattered showers and thunderstorms. Weak mid to upper-level flow could keep any storms moving slow to a crawl which could create a flooding risk with heavy rain.

For tonight, expect mostly cloudy skies with a very slight chance of a shower. The morning low should be around 67. For Wednesday, it looks like partly to mostly cloudy skies will persist with a high of 84. NWS-JAX is calling for a 50 percent rain chance in Alachua County while AccuWeather predicts a 40 percent chance.

Rain was possible today, but none hit the Gainesville area so far. A factor was the abundant cloud cover that prevented any daytime heating and, in turn, instability. The severity of any weather (or weather at all) will depend on this factor again Wednesday.

Monday, May 11, 2009

Forecast for Tuesday 05.12.2009

Sorry for the long forecast hiatus. Being real busy plus being on a cruise kept me away from making forecasts. Now, I want to get back into the swing of things.

A front that is to our north is expected be across the Gainesville area sometime Tuesday morning. NWS-JAX and HPC surface forecasts are calling for the front to stall and raise the instability a bit to spawn showers and a few storms. The SPC is not calling for severe threats for the state since there is expected to be little or no shear, but isolated severe hail and wind from stronger cells is a possibility.

The rain is slowly starting to come back to the state. South Florida had a few isolated cells with at least one triggering severe thunderstorm warnings. Some storms were off to the east of Gainesville today.

For tonight, expect partly cloudy skies with a morning low of around 68. During the day, there is a chance of a shower or storm as the front nears and as daytime heating helps fire things up. The high should be around 85. It shouldn't be as hot as it has been for the last few days.

The front is expected to push through Wednesday as the high builds. However, there will be slight chances of rain now that we are starting to enter the typical summer pattern in Florida.