SW Louisiana Forecast Discussion...For all the latest on Bonnie refer to the previous blog entry just below this one. After a nearly normal summer day across the threshold of the forecast area on Thursday, we have some changes on the horizon. This forecast will mostly be dictated by what Bonnie does. There are a couple of significant synoptic features which will come into play that will likely ultimately guide her. The entire forecast I am about to lay out is entirely subject to change, so just keep that in mind.
As I stated a moment ago, Thursday was essentially a normal late July day with a good scattering of shower and thunderstorm activity during the afternoon. An active sea breeze initiated many of the storms, and as temperatures reached near their peak during the afternoon additional showers and storms fired up. Temperatures were very close to average for July 22nd ranging from the low to mid 90s. All convection came to an end with the loss of daytime heating. The nighttime and early morning hours of Friday will be very quiet with lows bottoming out in the usual mid to upper 70s that we have seen so often this summer. On Friday, rain chances will be next to nothing. Subsidence will increase on the backside of the circulation from Bonnie. Bonnie will entering the Gulf late Friday, and anytime there is a tropical system or low for that matter to our East our weather improves. That will be no different this time around. Dry air in the mid and upper levels will take over momentarily, and this will suppress any shower or thunderstorm activity from developing as the subsident zone sets up right overhead. As a result of the drier air and not much chance for a shower or storm, temperatures will be above normal with highs in the mid to upper 90s. Heat indices will flirt with the danger category during the afternoon hours.
The forecast beginning Saturday is even more so dependent on Bonnie. The Westward moving ULL over the Gulf will be passing near the area on Saturday, and this could be enough to generate some shower or thunderstorm activity during the afternoon, despite us still being on the dry, subsident side of Bonnie. Nearly an average chance of shower and thunderstorm activity is expected at this time at least for the daylight hours.After morning lows in the mid to upper 70s once again, afternoon highs should again reach the mid 90s with drier air in the mid and upper levels initially. The forecasted movement of Bonnie suggests that fringe effects will begin to be experienced across portions of the forecast area by Saturday night. The outer rain bands will likely begin moving onshore into SE Louisiana Saturday during the day, and spread Westward approaching Acadiana Saturday night. Thus, rain chances will remain in the forecast for the overnight hours on Saturday. Skies will transition from Partly Cloudy early on during the day to Mostly Cloudy by day's end as the cloud shield on the periphery of Bonnie makes end roads towards the forecast area. Rain chances increase a bit Saturday night as the outer rain bands move through the forecast area, but they should remain out of the likely category for a little while longer as we will still be in the subsidence zone around Bonnie during this period.
The most adverse weather from Bonnie is expected to occur across the forecast area on Sunday and Monday. Rain chances ramp upward into the likely category for both Sunday and Monday as the rain bands from Bonnie affect the region. At this point in time, it is still a bit too early to be very specific about how much rain we will get, and just how adverse the conditions will be. It strictly all hinges on the eventual movement and landfall of Bonnie. Bonnie is expected to remain a tropical storm, and landfall is expected sometime between Sunday afternoon and Monday morning somewhere on the Louisiana coast. An increase in winds and seas is to be expected for the coastline and the coastal waters, while the biggest inland threats will be heavy rain and the possible accompanying flash flooding and tornado threat along and to the East of the center of circulation. Tropical storm conditions could be experienced across a majority of the forecast area in the Sunday-Monday time frame. Someone will certainly stand the chance to see upwards of 5-10" of rain from Bonnie as the tropical downpours persist during this period as Bonnie moves into the state. Further revisions are expected in the coming days. As a result of the increase in moisture and rain chances jumping into the likely category, temperatures decrease as well. High temperatures will likely struggle to reach 90 both Sunday and Monday, while morning lows barely fall below the 80 degree threshold with a very tropical air mass in place. Bonnie should be a quick mover, and conditions should begin to improve late in the day Monday as Bonnie spins down over North Louisiana.
The remainder of the forecast period beyond Monday should be more representative of late July. A transition back to a typical summer regime is expected to take over on Tuesday. Lingering tropical moisture from the decaying Bonnie will certainly aid in the genesis of shower and thunderstorm activity on Tuesday. A better than average chance of showers and thunderstorms is expected on Tuesday as the leftover tropical moisture tries to get scoured out. Temperatures will return to the lower to middle 90s, and heat indices will be near the danger zone with very oppressive dew points thanks (or no thanks) to the departing Bonnie. High pressure over the SE U.S. (Bermuda high) becomes the dominate weather feature by mid-week next week, and this will set the stage for what could essentially be termed as a normal pattern for late July. Wednesday and Thursday will generally see a day where afternoon convection flares up via the sea breeze. This will generate the usual scattering with random locations being selected each day for some relief. Temperatures will also trend above normal once again as the atmosphere begins to dry out with the ridge beginning to intensify once again. Expect maxes in the mid to upper 90s with heat indices accelerating into the danger category once again. This is certainly nothing unusual for late July, and a typical weather pattern is anticipated as we approach August. That is, of course, barring any additional tropical systems which may develop and move into the Gulf, but that's the least of our worries at this time. Let's get rid of Bonnie first. Stay tuned for the latest on Bonnie.
Preliminary Numbers & Zone Forecast:
LCH 76/97 77/96 77/91 0 10 0 30 40 60
LFT 76/98 76/97 77/90 0 10 0 40 50 70
BPT 77/98 77/99 77/92 0 10 0 30 30 60
AEX 75/99 75/99 76/92 0 10 0 30 40 60
POE 75/99 76/99 76/91 0 10 0 30 40 60
ARA 77/95 77/94 78/89 0 10 0 40 50 70
Tonight...Mostly Clear. Low 76. Light SE wind.
Friday...Mostly Sunny to Partly Cloudy. High 97. SSE wind 10-15 mph. Heat indices 102-107 in the afternoon.
Friday Night...Mostly Clear. Low 77. Light SE wind.
Saturday...Partly to Mostly Cloudy with a 30% chance of showers and thunderstorms. High 96. NNE wind 10-15 mph with higher gusts to near 20 mph at times. Heat indices 102-107 in the afternoon.
Saturday Night...Mostly Cloudy with a 40% chance of showers and thunderstorms. Low 77. East wind 10-20 mph and gusty.
Sunday...Mostly Cloudy & Breezy with rain likely in the afternoon. Tropical squalls from Tropical Storm Bonnie. High 91. ENE wind 10-15 mph. Chance of ran 60%.
Friday 7/23/10 Daily Planner
6a.m.
Weather: Clear, A Very Quiet Morning
Temp: 76
Rain: 0%
Wind: SE 2
9a.m.
Weather: Partly Cloudy
Low: 85
Rain: 0%
Wind: SSE 7
H.I.: 93
Noon
Weather: Partly Cloudy
Temp: 91
Rain: 0%
Wind: SSE 12
H.I.: 102
3p.m.
Weather: Partly Cloudy
Temp: 97
Rain: 0%
Wind: SSE 15
H.I.: 106
6p.m.
Weather: Partly Cloudy
Temp: 92
Rain: 0%
Wind: SSE 10
H.I.: 103
9p.m.
Weather: Mostly Clear
Temp: 84
Rain: 0%
Wind: SE 4
Drew's 7 Day Outlook
Friday
7-23-10
Low: 76
High: 97
Rain: 0%
Wind: SSE 10-15
H.I.: 102-107
U.V.: 11- Very High
Saturday
7-24-10
Low: 77
High: 96
Rain: 30%
Wind: NNE 10-15
H.I.: 102-107
U.V.: 11- Very High
Sunday
7-25-10
Watching Bonnie...Tropical Storm Conditions Possible
Low: 77
High: 91
Rain: 60%
Wind: ESE 15-20
H.I.: 95-100
U.V.: 8- High
Monday
7-26-10
Watching Bonnie...Tropical Storm Conditions Possible
Low: 79
High: 89
Rain: 70%
Wind: SSE 20-25
H.I.: 95-100
U.V.: 8- High
Tuesday
7-27-10
Low: 78
High: 92
Rain: 40%
Wind: SSE 10-15
H.I.: 98-103
U.V.: 9- High
Wednesday
7-28-10
Low: 77
High: 94
Rain: 30%
Wind: SSE 10-15
H.I.: 102-107
U.V.: 10- High
Thursday
7-29-10
Low: 76
High: 95
Rain: 30%
Wind: SSE 10-15
H.I.: 105-110
U.V.: 11- Very High
...Tropical Update...
See the previous blog entry for the latest on Tropical Storm Bonnie. Bonnie is affecting the Bahamas early this morning, and will be moving through the Florida Keys and South Florida later today. Bonnie should emerge into the Gulf of Mexico as a minimal tropical storm later today. Stay tuned for all the latest.
...Marine Forecast...
Rest Of Tonight...Southeast winds 10 to 15 knots. Seas 3 feet.
Friday...East winds 5 to 10 knots becoming southeast 10 to 15 knots in the afternoon. Seas subsiding to 2 feet in the afternoon.
Friday Night...Southeast winds 5 to 10 knots. Seas 2 to 3 feet.
Saturday...Northeast winds 5 to 10 knots. Seas building to 3 to 5 feet in the afternoon. A chance of showers and thunderstorms.
Saturday Night...Northeast winds 10 to 15 knots. Seas 4 to 5 feet. A chance of showers.
Sunday...Tropical storm conditions possible. Showers likely.
Good night and God bless!
-DM-
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