SW Louisiana Forecast Discussion...The majority of the forecast area remained dry as expected on this Tuesday. Drier air filtered in in the wake of the pesky elongated Gulf trough which produced numerous shower and thunderstorm activity the last few days. Temperatures also responded as well with readings back into the mid 90s on average today due to more sunshine and less convection. At the same time, we can observe our next synoptic scale weather feature which will have a affect on our weather as we head into the mid-week period. More on that in a moment. In the meantime, any convection which has developed mainly along and South of I-10 and over Acadiana today will quickly cease to exist by sunset. All should be quiet for the overnight hours. Low temperatures will generally run in the mid 70s...have we heard that before at all this summer? Expect Mostly Clear skies for the majority of the forecast area tonight. Our attention will turn to the next synoptic feature at this time.
Rain chances ramp up again Wednesday as another Easterly wave or elongated trough with attendant tropical moisture moves our way. This system is of tropical origins, but is certainly not an organized system, nor will it be. It will be enough of a trigger to enhance shower and thunderstorm activity across the threshold of the forecast area. The aforementioned Easterly wave is currently traversing the Gulf waters from East to West, and will be on our doorstep Wednesday. This is main reason why we've been drier today. We are currently on the subsident (dry) side of this feature. The Easterly wave will generate shower and thunderstorm nocturnally over the coastal waters, and this will be a harbinger of things to come over land areas on Wednesday. The day should start generally on the humid but dry side with some morning sun expected. However, as conditional daytime heating takes effect, showers and thunderstorms will become scattered to numerous across much of the forecast area. The active sea breeze will be enhanced by the Easterly wave, and rain chances should wind up in the likely category. However, in this particular situation I should note that rainfall will not strictly be limited to the afternoon hours. Just remember back to Monday when it rained practically all morning at LCH. As I said previously, nocturnal activity will likely occur over the offshore waters, and as the sun comes up and heats up the land coastal areas will likely see some morning activity, before it spreads further inland as we go through the day. I expect more than half the area to see some rain on Wednesday. Of course, as was the case over the weekend and on Monday, rainfall amounts will vary greatly from location to location. The added moisture and higher chances of rain will translate into cooler high temperatures. Instead of averages running in the mid 90s, expect maximums to be right around the 90 degree threshold...still hot of course. Rainfall amounts could total in excess of 1" in locations which receive a direct hit from one of the tropical downpours.
No severe weather is expected, but in this situation there is certainly the possibility that a tropical funnel cloud or two could be reported. However, in this situation it is generally not more than just a small funnel cloud that forms as the storm is developing. Oft times, a developing or maturing thunderstorm will generate a bit of wind shear in response to the inbound and outbound winds associated with pressure differences. These winds and the downdrafts and updrafts associated with moving air around thunderstorms often generate small amounts of shear briefly, thus a weak funnel cloud forms. These rarely touch down, and I don't expect anything different in this situation. This has occurred today in the New Orleans area with one such funnel cloud spotted near the suburb of Myrtle Grove. Again, these will be short-lived, if they occur at all. The only other threat from the rain on Wednesday would be localized street flooding in areas of heavy rain. It doesn't take too long in these heavy downpours to flood the streets in many urban areas, here in Lake Charles is a prime example. The Easterly wave will generally move onshore right over SW Louisiana or extreme SE Texas, hence the reason why we will be in the moist axis associated with the aforementioned system. All convection should decay with the loss of daytime heating. A few nocturnal storms are possible Wednesday night/early Thursday, but most of us should remain dry with just lots of humidity and mosquitoes to endure. Overnight lows...mid 70s again.
A transition unfolds yet again for the latter portion of this work week. The Easterly wave over the area on Wednesday dissolves, and drier air from the NE around the bid ridge builds in again. This will lower rain chances as you would expect. This also means that temperatures will increase once again. The upper ridge pattern that has dominated our weather at times this summer will eventually take over full throttle once again. I will term Thursday a transition day. That means it should essentially be a normal day for this time of year. Expect sea breeze type activity to develop during the peak convective heating hours. About an average coverage day is expected (climo) with about 30% of the local area seeing a shower or storm. The squeeze play will be on between the decaying Easterly wave, and the building ridge. Whichever one ends up being stronger will ultimately dictate just exactly how many storms are able to build up with the effects of daytime heating. High temperatures will be at or slightly above normal in the low to mid 90s. Any hope for relief from shower and thunderstorm activity by Friday will be reduced to a bare minimum. Only about 20% or less of the forecast area stands the chance to see a thermally induced shower or storm Friday. The ridge will have a firm hold on the atmosphere and will largely suppress much vertical growth of the usual cumulus clouds. However, just because of it being a hot, summer afternoon a few storms should still manage to bust the cap and develop. If you are fortunate enough to get cooled off by one of these storms, consider yourself mighty lucky. Most of us will see Partly Cloudy to Mostly Sunny skies and temperatures rising into the mid 90s in most locations. The warmest locales could see the upper 90s, and of course the coast will be a tad cooler because of the marine influence. Expect lower 90s down that way.
The ridge strengthens over the forecast area this weekend, and this will keep rain chances at a minimum. Temperatures will likely average the mid to upper 90s both Saturday and Sunday, but somebody will likely top out near or above 100. Heat indices will be quite nasty as well, and will certainly approach the danger category of 105. The ridge will keep some drier air in place, so dew points may respond in kind, but the drier the air, the hotter the actual temperature will be. Remember to use extreme caution against the oppressive heat. Also, the atmosphere could dry out further depending on what will likely be a tropical entity in the SE Gulf or over Florida by that time. More on this in a moment in the tropical update. Anytime a tropical system is to our East, our weather improves on the backside of the system. Either way, it seems likely that the ridge will dominate our weather this weekend. As we head into the last full week of July, the forecast is entirely up the air really. For now, a standard summer regime is shown and forecast, but much of this hinges on possible tropical developments in the Gulf. Again, see the tropical outlook below. Most forecast models show an influx of tropical moisture over the forecast area by Monday and Tuesday of next week. If so, then rain chances will certainly increase into the likely category once again. Heavy rainfall would also be possible if this scenario plays out, however for now, only a typical 30-40% chance of showers and storms is shown for this time. Temperatures will be very representative of normal for late July as well with lows in the mid 70s and highs reaching the mid 90s as a whole. Beyond the forecast period, the ongoing battle between the Bermuda High and the upper ridge will continue. Also, attention will continue to be on the tropics.
Preliminary Numbers & Zone Forecast:
LCH 76/90 76/93 77/95 20 60 10 30 0 20
LFT 77/90 77/93 76/96 20 60 10 30 0 10
BPT 77/90 76/92 77/94 20 60 10 30 0 20
AEX 73/93 74/95 73/98 10 60 10 30 0 10
POE 74/93 75/95 74/98 10 60 10 30 0 10
ARA 78/89 77/91 77/94 20 60 10 30 0 10
Tonight...Partly Cloudy with a 20% chance of showers & thunderstorms this evening, then Mostly Clear after midnight. Low 76. Light SE wind.
Wednesday...Partly to Mostly Cloudy with showers & thunderstorms likely. Some heavy rainfall possible. High 90. SSE wind 10-15 mph. Chance of rain 60%.
Wednesday Night...Partly Cloudy. Low 76. Light SE wind.
Thursday...Partly Cloudy with a 30% chance of showers & thunderstorms in the afternoon. High 93. SSE wind 10-15 mph.
Thursday Night...Mostly Clear. Low 77. Light SE wind.
Friday...Mostly Sunny to Partly Cloudy with a 20% chance of an afternoon shower or thunderstorm. High 95. SSE wind 10-15 mph. Heat index values 103-108 in the afternoon.
Wednesday 7/21/10 Daily Planner
6a.m.
Weather: Partly Cloudy
Temp: 76
Rain: 20%
Wind: SE 3
9a.m.
Weather: Partly Cloudy
Temp: 82
Rain: 30%
Wind: SSE 8
H.I.: 90
Noon
Weather: Mostly Cloudy
Temp: 88
Rain: 40%
Wind: SSE 12
H.I.: 95
3p.m.
Weather: T-Storms Likely
Temp: 90
Rain: 60%
Wind: SSE 15
H.I.: 103
6p.m.
Weather: Mostly Cloudy
Temp: 87
Rain: 30%
Wind: SSE 11
H.I.: 98
9p.m.
Weather: Mostly Clear
Temp: 83
Rain: 10%
Wind: SSE 4
H.I.: 90
Drew's 7 Day Outlook
Wednesday
7-21-10
Low: 76
High: 90
Rain: 60%
Wind: SSE 10-15
H.I.: 98-103
U.V.: 9- High
Thursday
7-22-10
Low: 76
High: 93
Rain: 30%
Wind: SSE 10-15
H.I.: 100-105
U.V.: 10- High
Friday
7-23-10
Low: 77
High: 95
Rain: 20%
Wind: SSE 10-15
H.I.: 103-108
U.V.: 11- Very High
Saturday
7-24-10
Low: 75
High: 97
Rain: 20%
Wind: S 10-15
H.I.: 103-108
U.V.: 11- Very High
Sunday
7-25-10
Watching the Tropics
Low: 76
Rain: 20%
Wind: S 10-15
H.I.: 102-107
U.V.: 11- Very High
Monday
7-26-10
Watching the Tropics
Low: 76
High: 94
Rain: 30%
Wind: SSE 10-15
H.I.: 100-105
U.V.: 10- High
Tuesday
7-27-10
Low: 77
Rain: 30%
Wind: SSE 15-20
H.I.: 98-103
U.V.: 9- High
...Tropical Update...
The tropics have been quiet for over a week now since we had Tropical Depression 2. This, however, may be changing shortly. An area of disturbed weather (Invest 97L) in the Central Caribbean Sea between Puerto Rico and Hispaniola is getting better organized tonight. This area is lacking a surface low pressure at this time, but the barometric pressure readings are decreasing in this area. The current environment over the Caribbean is one that supports continued development. While the tropical wave sits in a favorable environment for development, some factors are inhibiting further development at this time. The close proximity to land of Invest 97L is a setback for development. The lack of a low-level circulation at present is also one of the key components lacking. The system is moving off to the WNW at around 10 mph, and it will continue to do so through Thursday. Additional strengthening is expected over the next couple of days, and the chances of Invest 97L becoming a tropical cyclone are 70% or greater. A tropical depression may form as early as Wednesday. An Air Force Hurricane Hunter Aircraft will investigate the region on Wednesday if necessary. I believe that if the plane investigates, and finds a definite low-level circulation, then we will likely have Tropical Depression 3. Some wind gusts over 30 mph have been occurring over the islands of the Caribbean for the last 24 hours or so. This is expected to continue along with very heavy rainfall for the next 24 hours. This includes Puerto Rico, Dominican Republic, Haiti, and eventually reaching Jamaica, Grand Cayman, the Bahamas, and Cuba by Thursday. The heavy rainfall over these areas will likely lead to flash flooding and life-threatening mudslides.
The WNW motion should continue for the next few days, and it is likely the system will be approaching South Florida and the Florida Keys by week's end. The major question is what will be the intensity of the system, and where will it ultimately wind up beyond this point. Is it bound for the Gulf or will re-curvature out to sea occur? At this point in time, without having a definitive low-level center it is hard to be specific about the future track and intensity of Invest 97L. However, models have initialized the system, all offer their own scenario for Invest 97L. Observing the synoptic set up out ahead of Invest 97L it seems that there is two likely scenarios. One is that it will continue its steady state progression and intensification and heads towards mainland Florida before ejecting NNE into the SE U.S., and eventually out to sea. The idea of further intensification also suggests that the risk of a named system making landfall on the Florida or SE U.S. this weekend could be realized. Intensity forecast is a crapshoot at best at this juncture. Models suggest that the environment between Hispaniola and Florida is favorable for development, and many of the models do indeed that this will become Bonnie by Thursday. It is conceivably possible that this system could reach hurricane status before approaching the coastline. It remains to be seen, and again without having an actual surface low to focus on there is still so much that could happen. The second scenario, which seems like an outlier at this point, would suggest a track on a WNW heading approaching South Florida or the Florida Keys this weekend, and continue into the SE Gulf of Mexico over the weekend. This would increase the threat to the Gulf coast of course, and landfall could be anywhere from Texas to Florida. There is still so much speculation, but you know I will give you all the latest. I am not overly concerned about this system posing an imminent threat to our area yet, but we must watch it, and no one should let their guard down. A lot more information should become available on Wednesday especially if the hurricane hunter investigates.
There are other synoptic features that must be observed when forecasting the eventual track of a tropical system. There are a couple of upper level lows traversing the Atlantic basin out ahead of Invest 97L, and also there's the Easterly wave which we will deal with on Wednesday that could eventually have a say so in where the ultimate destination for Invest 97L turns out. These systems are strong enough to generate their own wind flow and current over the Gulf and Caribbean downstream of the system, and they can produce an environment that will carve out a path of least resistance so to speak. The tendency is often such that the tropical system will follow an upper level low, but it is too early to say for sure if that will happen this time. I certainly believe intensification will occur as the environment over the area at least in the short time will support development. I believe there is some question as the system moves downstream on exactly how much shear will be in place. There is a possibility that enough shear will be in place thanks to the upper level lows that the tropical wave will not survive. While it is true that all models initialize the system, they all show it in varying degrees, and they also diverge on a landfall point. Everyone along the Gulf coast and the SE U.S. should continue to monitor the future track of this system. Some graphics follow.
Elsewhere in the tropics, there are a few minor tropical waves traversing the Atlantic basin, but there is nothing even immensely close to developing besides Invest 97L. No additional tropical cyclone formation is anticipated through Thursday.
...Marine Forecast...
Tonight...Southeast winds 10 to 15 knots. Seas 2 feet or less. A chance of showers and thunderstorms.
Wednesday...East winds 10 to 15 knots. Seas 2 to 3 feet. A chance of showers and thunderstorms.
Wednesday Night...Southeast winds 10 to 15 knots. Seas 2 to 3 feet. A slight chance of showers and thunderstorms.
Thursday...Southeast winds 10 to 15 knots. Seas 2 to 3 feet. A chance of showers and thunderstorms.
Thursday Night...Southeast winds 10 to 15 knots. Seas 2 to 3 feet. A slight chance of showers and thunderstorms.
Friday...Southeast winds 5 to 10 knots. Seas 2 to 3 feet. A slight chance of showers and thunderstorms.
...Tide Data...
Wednesday Tides @ Calcasieu Pass
Low: 7:16a.m. 6:37p.m.
High: 2:33a.m. 10:11a.m.
...Toledo Bend Pool Level...
168.20'
...Lake Charles Climate Summary...
Tuesday, July 20, 2010
Low: 75
Normal Low: 75
Record Low: 64-1910
High: 93
Normal High: 91
Record High: 102-1913
Rainfall
Today: 0.00"
Month to Date: 3.04"
Normal Month to Date: 3.44"
Year to Date: 18.56"
Normal Year to Date: 31.55"
Record: 2.67"-1969
Sensible Weather Observed Today:
None
One Year Ago (2009)
Low: 73
High: 88
Rain: 0.19"
5 Years Ago (2005)
Low: 74
High: 91
Rain: 0.94"
10 Years Ago (2000)
Low: 77
High: 98
Rain: 0.00"
Sunrise Wednesday: 6:25a.m.
Sunset Wednesday: 8:13p.m.
...Lunar Table...
Full Moon- Monday July 26
Last Quarter- Tuesday August 3
New Moon- Tuesday August 10
First Quarter- Monday August 16
Have a Great Wednesday & God Bless!
-DM-
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