Tuesday, August 24, 2010

Drier Air & Lower Dew Points by Mid-Week...Second Hurricane of the 2010 Season Develops in Atlantic...

Monday, August 23, 2010

SW Louisiana Forecast Discussion...It's been so hot for so long. Of course, it's supposed to be, it is August after all. However, it has been bordering on ridiculous at times this summer. The summer of 2010 will certainly go down as one of the hottest in recent memory. Today was no exception to the rule as it was another day of Partly Cloudy skies, very humid and hot conditions. Highs exceeding the mid 90s were commonplace once again. The actual normal high for this time of year is in the lower 90s, but we've not seen too much normalcy this summer. A few late day scattered storms developed in response to daytime heating as per usual. The storm development was aided by a rare but weak August cool front which is sagging into the forecast area. I briefly mentioned this front last week. All convection has ceased tonight, and the weak boundary is lined up from NE to SW across the area, and it will continues its slow sag Southward overnight. Overnight lows will be in the mid to upper 70s yet again with a light onshore flow prevailing.

Tuesday will offer up another very similar late August day. Very hot weather is anticipated once again with highs reaching the mid to upper 90s. The feeble frontal boundary will remain in close proximity, and with the effects of daytime heating will cause some isolated afternoon showers and storms. A few could be strong with gusty winds, but any rain will be much needed and very welcomed across the area. Most everyone will miss out on the rain of course as drier air in the mid and upper levels keeps the atmosphere will remain largely capped. The frontal boundary will slowly evacuate into the coastal waters, and drier air in the lower levels of the atmosphere will filter into the region. This drier air will not be that noticeable on Tuesday as it will lag behind the front a bit. However, for Northern portions of the area, afternoon dew points may drop a few degrees, and the drier air will be a bit more noticeable. This will help keep heat indices below the danger level of 105. It will certainly still be hot, but any relief is a blessing this time of year. We are still about a month away from the first official day of fall, and the average first "true" cold front usually occurs in the middle of September. We have plenty of summer heat left to say the least.  By Tuesday night, drier air will infiltrate the entire region, and clear skies will be in store. Somewhat cooler temperatures (near normal) in the lower 70s will suffice for a minimum. A light offshore flow will develop, and transport the breath of fresh air into the region.

The mid-week period for Wednesday and Thursday will be dominated by the drier air in the wake of the diffuse frontal boundary. Lower dew points will make it more bearable during the afternoon hours. Mostly Sunny skies are expected both days, with hot conditions continuing. Above normal high temperatures in the mid 90s will still be realized, but with the lower dew points 95 will fill a lot more like 95 than it has all summer. This will come after a morning start of around 70 to the lower 70s. Dare I say, some mid to upper 60s could actually occur across the Northern portions of the forecast area with the drier air in place. No rainfall is expected Wednesday or Thursday as limited boundary layer moisture will exist. A light offshore flow will prevail. The overnight lows will continue to be in the lower 70s for Wednesday night into Thursday morning, so another pleasant night under clear skies is in the offing for this period.

The drier air will quickly be supplanted by moist air once again. High pressure in control at all levels will begin to break down across the area as we head into Friday. At the same time, models suggest the development of an Eastern Gulf low. I would suspect that if this low forms it will be off of the decaying frontal boundary. It remains to be seen if Gulf cyclogenesis will occur, but for now this forecast will hinge on this idea occurring. Either way, moisture levels will increase over the area beginning Friday as ridging processes break down over the area. Boundary layer moisture will increase, and with the return of an onshore flow and the effects of daytime heating the prospects for scattered afternoon convection will move back into the equation. About an average chance for shower and thunderstorm activity is expected for the afternoon hours on Friday. Temperatures will respond in tandem as well with readings dropping from the mid 90s back to the lower 90s. The influx of moisture will certainly lead to more cloud cover as well, and the Mostly Sunny skies of Wednesday and Thursday will give way to Partly Cloudy skies once again. Should Gulf cyclogenesis occur, the low will gradually move Westward off of Florida's West Coast. A dry forecast is retained for Friday night as all daytime convection ceases with the loss of daytime heating. This is important because this is the beginning of the High School Football season with all the area jamborees being held this weekend. Warm and humid conditions with no threat of rain should suffice for game time.

The forecast for the last weekend of August is one that will be highly dependent on the possibility of Gulf cyclogenesis. Moisture levels will certainly be on the high side, regardless, with the brief period of dry air at mid-week nothing but a fast fading memory by this time. The projected weak Gulf low should move Westward to the South of the Louisiana coast towards Lower Texas or Northern Mexico late in the weekend. This will in turn send of a slug of moisture up towards the Northern Gulf Coast. Therefore, increased cloud cover and a chance for some showers and thunderstorms are expected this weekend. Rain chances could end up in the likely category depending on the motion of the forecasted low. For now, a better than average chance of scattered convection is reflected. Temperatures will continue to remain closer to the normal levels as well in response to the increased low-level moisture. Lows for both weekend days should be in the mid 70s while afternoon highs range from the upper 80s to lower 90s across the forecast area. This is essentially normal for late August. The same general pattern continues into early next week as we round out this forecast period. Enhanced moisture will keep a chance for mainly afternoon convection going for Monday with seasonal temperatures. Skies will generally range from Partly to Mostly Cloudy. The long range forecast as we head into the first few days of September, if you can believe that, shows the opportunity for some more much needed rainfall. This, as a very moist air mass remains in place in the lower levels thanks to a persistent onshore flow around the periphery of the Bermuda High, which should become the dominant weather forecast by that time. Seasonal temperatures are forecast, and hopefully we are turning the corner, and are on the downside of our long summer season as September nears. The official peak of hurricane season is still to come, and the tropics are heating up this week.


Preliminary Numbers & Zone Forecast:


LCH  76/96  70/95  70/95  10 10 10 0 0 0
LFT   77/97  71/96  70/95  10 10 10 0 0 0
BPT   78/97  72/96  71/95  10 10 10 0 0 0
AEX  73/99  67/96  68/95  10 10 10 0 0 0
POE  73/99  68/96  67/95  10 10 10 0 0 0
ARA  77/96  72/95  71/95  10 10 10 0 0 0


Today...Partly Cloudy to Mostly Sunny with an isolated storm or two possible. High 96. Light NE wind.

Tonight...Clear and Cooler. Low 70. Light NE wind.

Wednesday...Mostly Sunny. High 95. NE wind 5-10 mph.

Wednesday Night...Mostly Clear. Low 71. Light NE wind.

Thursday...Mostly Sunny. High 95. East wind 5-10 mph.


Drew's 7 Day Outlook


Tuesday
8-24-10











Low: 76
High: 96
Rain: 10%
Wind: NE 3-8
H.I.: 101-106
U.V.: 11- Very High


Wednesday
8-25-10










Low: 70
High: 95
Rain: 0%
Wind: NE 5-10
H.I.: 95-100
U.V.: 11- Very High


Thursday
8-26-10
18 Year Anniversary of Hurricane Andrew




Low: 71
High: 95
Rain: 0%
Wind: E 5-10
H.I.: 97-102
U.V.: 11- Very High


Friday
8-27-10


Low: 72
High: 92
Rain: 30%
Wind: SE 10-15
H.I.: 100-105
U.V.: 10- High


Saturday
8-28-10











Low: 75
High: 91
Rain: 40%
Wind: SSE 10-15
H.I.: 98-103
U.V.: 10- High


Sunday
8-29-10
5 Year Anniversary of Hurricane Katrina











Low: 76
High: 91
Rain: 40%
Wind: SSE 10-15
H.I.: 98-103
U.V.: 9- High


Monday
8-30-10











Low: 75
High: 92
Rain: 30%
Wind: SSE 10-15
H.I.: 100-105
U.V.: 10- High


...Tropical Update...


The tropics are heating up right on cue. We are in prime time now through September. Tropical Depression 6 formed over the weekend, and became Tropical Storm Danielle Sunday and a hurricane Monday afternoon. Danielle continues to strengthen, and is on her way on becoming a true Cape Verde storm. Danielle will likely become the season's first major hurricane later this week, but the good news is that while atmospheric conditions support continued strengthening for Danielle, the steering currents will steer it away from all landmasses. It poses no threat to the United States. It could threaten Bermuda over the weekend, but right now it is forecast to bypass the tiny island nation in the Atlantic with no more than just a few squalls and some increased winds and seas. I will not be as in depth with Danielle as I was for Alex and Bonnie because Danielle will simply not be a Gulf storm. I will certainly mention it each day while its an active storm, but there is no need to worry about Danielle posing a threat to anyone in the United States. The latest advisory and some graphics follow.


Hurricane Danielle Advisory

10p.m. Monday, August 23, 2010

...Danielle Strengthening...on Track to Become Season's First Major Hurricane Later This Week...No Threat to Land...


Latitude: 15.6 N

Longitude: 43.2 W

This is 1,205 miles E of the Lesser Antilles.

Maximum Sustained Winds: 85 mph with higher gusts. This makes Danielle a category 1 hurricane on the Saffir-Simpson scale. Danielle is forecast to continue strengthening and will likely become a major hurricane by Tuesday night or Wednesday morning. Hurricane force winds extend outward to 25 miles from the center, while tropical storm force winds extend outward to 85 miles from the center.

Movement: WNW or 285 degrees @ 20 mph. This motion is forecast to continue Tuesday morning with a turn towards the NW expected by late Tuesday.

Pressure: 29.00" or 982 mb.


Danielle will remain over the open waters of the Atlantic, and affect no more than just shipping interests. The cyclone continues to be steered by an anticyclone to its North. A weakness will develop in this ridge over the next couple of days as Danielle zooms off to the WNW and NW, and this weakness will ultimately steer Danielle around the periphery of the anticyclone, and keep it a fish storm. It might pose a threat to Bermuda over the weekend, but even this remains a stretch at this point. The storm will continue to gain latitude as it turns more Northerly over the weekend in response to an advancing Eastern U.S. trough. It will accelerate out to sea next week. The only impacts to the United States should be increased swells along the East coast this weekend and early next week.


Elsewhere in the tropics, a vigorous tropical wave has just emerged off the West Coast of Africa. It is located to the South of the Cape Verde Islands. It is well organized based on satellite representation, and it seems poised to become a tropical cyclone within a day or two. Conditions over the Eastern Atlantic are certainly conducive to support development. This system is moving to the WNW around 15 mph, and this motion should continue through Tuesday. There is about a 70% chance that this system will become the next classified tropical system. I believe it will become Tropical Depression 7 on Tuesday, and ultimately become Tropical Storm Earl later this week. It is too early to tell for sure what path this system will ultimately take, but the early projections are for this to follow closely in Danielle's footsteps and become a fish storm. We will watch it as usual.




















Elsewhere, no tropical cyclone formation is expected through Wednesday.


...Marine Forecast...


Tuesday
...Northeast winds around 5 knots becoming east in the afternoon. Seas 1 foot. A slight chance of showers and thunderstorms.

Tuesday Night...Southeast winds 5 to 10 knots becoming east after midnight. Seas 1 foot. A slight chance of showers and thunderstorms.

Wednesday...Northeast winds around 10 knots becoming 5 to 10 knots in the afternoon. Seas 1 foot. A slight chance of showers and thunderstorms.

Wednesday Night...East winds 5 to 10 knots becoming northeast after midnight. Seas 1 foot. A slight chance of showers and thunderstorms.

Thursday...Northeast winds 10 to 15 knots becoming east in the afternoon. Seas 1 to 2 feet. A slight chance of showers and thunderstorms.


Have a great Tuesday and God bless!
-DM-

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