The blog will be in short form today because of the holiday and the coverage of Tropical Storm Hermine in the Western Gulf of Mexico.
SW Louisiana Forecast Discussion...The nice weather over the weekend has faded off into the proverbial sunset now. The humidity is back with a vengeance. The cold front which provided one of the nicer starts to football season weather in recent memory lifted Northward from the Gulf of Mexico, and essentially dissolved this morning. At the same time, while we were the beneficiary of the nice reprieve early in the weekend, there was some tropical trouble brewing in the Gulf. An old tropical depression from the East Pacific crossed over Mexico, and the leftover circulation was spinning in the SW Gulf of Mexico (Bay of Campeche), and that same time the previously mentioned cold front helped energize this area of disturbed weather, and allowed thunderstorms to persist in that general vicinity. Persistence is often the key when looking for tropical development, and the Bay of Campeche is a hotbed for development this time of year. Lo and behold, that's exactly what happened Sunday night. The formation of Tropical Depression 10 ensued rather quickly, and became Tropical Storm Hermine formed early this morning. It has steadily strengthened through the day, and is nearing its landfall point in NE Mexico tonight. While it will be the main influence on our weather for the next couple of days, we will not see the direct impacts locally.
The extreme outer fringes of Hermine began affecting the area today as the rain bands on the periphery of the large circulation moved inland off the Gulf. The combination of the retreating front, and being in the NE quadrant of the circulation of Hermine has resulted in a return of deep low-level moisture, and it feels all icky outside again. This Labor Day featured generally Partly to Mostly Cloudy skies with the off and on rain across the area. Rain was heavy at times, but amounts were generally less than an inch or so. We need the rain, so that's good news. We will remain on the edge of Hermine tonight, and rain chances remain in the forecast for the overnight hours. There is not much action ongoing, but re-development is expected over the offshore waters during the night as Hermine makes landfall. Expect the humid conditions to continue with overnight lows in the mid to upper 70s areawide. That is a sharp contrast from the below normal readings we experienced over the weekend. An onshore flow will be maintained as well around the circulation from the cyclone.
Hermine will make landfall in the overnight hours, likely before midnight, in the Rio Grande Valley, and then continue moving Northward from the Rio Grande Valley into the Texas Hill Country by Tuesday afternoon. As Hermine moves inland and weakens, the moisture will spread out and spread Eastward in the deep tropical air mass being pumped into the area around the circulation. The forecast area will remain well entrenched in the onshore flow with the storm in Central Texas. Daytime heating will be thrown into the equation, and the end result will be a high likelihood of shower and thunderstorm activity across the area. The highest chances for rain will be over SE Texas closer to the actual circulation, and rain chances will temper downward the further East you go. Acadiana will still have rain chances in the likely category, but they will certainly be lower than those in SE Texas. Rain will be off and on throughout the day, but activity will be most numerous in the afternoon hours. Some heavy downpours will occur from time to time with the possibility of 1-2" of rain across the forecast area. All of this rain is very much needed across the area, so no issues with flooding are expected. There could be some minor coastal flooding problems on Tuesday due to the stiff SE wind causing higher than normal tides. A Coastal Flood Advisory has been issued accordingly. Other than that, not many effects from Hermine will occur. When it's not raining, skies will be Mostly Cloudy with a few Partly Cloudy intervals. High temperatures will hold in the upper 80s because of the enhanced cloud cover and rain chances. Expect similar weather for the Tuesday night period with rain chances backing off a bit, but a decent probability will still exist. Temperatures will cool off back into the mid to upper 70s with a continued onshore flow.
Rain chances will remain high for mid-week on Wednesday. The moisture from the remnants of Hermine will continue to produce off and on rain across the forecast area. Again, it will be a situation where rain chances are higher across the Western flank of the forecast area, and activity should be more scattered in nature over Acadiana. The actual remnant low will be somewhere into North Texas or South Oklahoma by this time. Moisture will linger over the area, but by late in the day drier air from the East will begin to push back into the area. Rain chances will be lower than that of Tuesday given the drier air punching back into the region as the transition begins. Partly to Mostly Cloudy skies are expected with temperatures warming up to around 90 or so. Again, rain will be most likely during the afternoon hours as the effects of daytime heating are thrown into the equation. The onshore flow will continue, but winds should decrease by then as Hermine will have become a post-tropical entity, and be far enough removed from the coastline to relax the pressure gradient. Thus, the threat for any coastal flooding should be non-existent by this point. An additional inch or so of rain is possible in areas where the heaviest rainfall occurs, but again it will take a lot of rain at this time to cause any flooding issues around here.
The high pressure that is steering Hermine to our SW is currently centered over the SE United States with SW Louisiana residing on the Western flank of this high. This will change a bit by the end of the week, and the Thursday-Monday period will be dominated by the persistent SE U.S. anti-cyclone. This will bring in drier air at all levels of the atmosphere, and dramatically reduce rain chances for the remainder of the period. Rain chances will remain in the forecast, but these should be at or below climo for mid-September. It will basically be the presence of an afternoon sea breeze that results in the aforementioned rain chances. A typical late summer period is in offing with hit or miss activity each day. There will be plenty of low-level moisture sticking around. Unfortunately, there is no cold front to come this time around. Partly Cloudy skies should rule the roost in the Thursday-Monday period with seasonable temperatures with morning lows in the mid 70s on average, while afternoon highs average the lower 90s. Heat indices will creep back up towards the century mark thanks to the beaucoup amounts of low-level moisture. No large scale weather systems are on the horizon once we get Hermine out of the way. AS we head towards mid-September, you gotta figure the first real cool front isn't too far away. We shall see!
Preliminary Numbers & Zone Forecast:
LCH 77/89 76/90 77/92 40 80 40 60 30 30
LFT 77/90 76/92 76/93 30 70 30 50 30 30
BPT 78/88 77/89 77/91 60 90 60 70 40 30
AEX 74/91 74/93 74/93 40 70 30 60 30 30
POE 75/91 75/93 74/93 40 80 30 60 30 30
ARA 78/89 77/90 77/92 50 70 30 50 30 30
Tonight...Mostly Cloudy with a 40% chance of showers and thunderstorms mainly after midnight. Low 77. SSE wind 10-15 mph.
Tuesday...Mostly Cloudy with rain and thunderstorms likely. Rain heavy at times. High 89. SSE wind 10-15 mph. Chance of rain 80%.
Tuesday Night...Mostly Cloudy with a 40% chance of showers and thunderstorms. Low 76. SSE wind 10 mph.
Wednesday...Partly to Mostly Cloudy with a good chance of rain and thunderstorms. Rain heavy at times. High 90. SSE wind 10-15 mph. Chance of rain 60%.
Wednesday Night...Partly to Mostly Cloudy with a 30% chance of showers & thunderstorms. Low 77. SSE wind 10 mph.
Thursday...Partly Cloudy with a 30% chance of scattered showers & thunderstorms. High 92. SSE wind 10 mph.
Drew's 7 Day Outlook
Tuesday
9-7-10
Low: 77
High: 89
Rain: 80%
Wind: SSE 10-15
H.I.: 93-98
U.V.: 8- High
Wednesday
9-8-10
High: 90
Rain: 60%
Wind: SSE 10-15
H.I.: 95-100
U.V.: 9- High
Thursday
9-9-10
Low: 77
High: 92
Rain: 30%
Wind: SSE 10-15
H.I.: 95-100
U.V.: 10- High
Friday
9-10-10
Low: 75
High: 93
Rain: 20%
Wind: S 10
H.I.: 100-105
U.V.: 11- Very High
Saturday
9-11-10
9 Year Anniversary of the Terror Attacks...Patriot Day!
Low: 76
High: 94
Rain: 20%
Wind: S 10
H.I.: 100-105
U.V.: 11- Very High
Sunday
9-12-10
High: 93
Rain: 20%
Wind: SSE 10
H.I.: 100-105
U.V.: 11- Very High
Monday
9-13-10
Low: 75
High: 92
Rain: 20%
Wind: S 10-15
H.I.: 98-103
U.V.: 11- Very High
...Tropical Update...
Tropical Storm Hermine is at landfall over Extreme NE Mexico in the Rio Grande Valley. The cyclone will move Northerly into South Texas within the next 12 hours, and rains will overspread much of Texas with rainfall extending into Louisiana. Hermine is a strong tropical storm which would have made it to hurricane status if it had more time over water. Complete details on Hermine can be found in the post above this one in the latest tropical update.
Elsewhere, in the tropics...the remnant low from the former Tropical Storm Gaston is near the Northern Leeward Islands tonight. It continues to show some organization, but no re-development is imminent at this time. There is a chance it could become a tropical cyclone again in a day or two as it moves Westward into the Caribbean Sea.
All else is quiet at this time.
...Marine Forecast...
Tonight...Southeast winds 20 knots and gusty. Seas 4 to 6 feet. A chance of showers and thunderstorms.
Tuesday...Southeast winds 20 knots and gusty. Seas 4 to 6 feet. Showers and thunderstorms likely.
Tuesday Night...Southeast winds 15 to 20 knots. Seas 4 to 5 feet. A chance of showers and thunderstorms.
Wednesday...Southeast winds 10 to 15 knots. Seas 4 to 5 feet subsiding to 3 to 4 feet in the afternoon. 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...South winds around 10 knots. Seas 2 feet. A chance of showers and thunderstorms.
Good night, have a great Tuesday & be sure to view the tropical weather outlook above this post! God bless!
-DM-
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