DocNDswamp's WunderBlog

SE LA Brief wx Update... Seasonal Nov temps ahead...

By: DocNDswamp, 11:35 PM GMT on October 28, 2006

Latest W Atlantic Basin AVN / IR Satellite Image

W Atlantic Basin AVN Satellite Image

Thu Nov 2 2006 10:15 AM CST
SE LA wx Update:
Seasonally colder next couple days... and none too soon, as have had high temps in low-mid 80's (84 on Halloween), and plentiful mosquitoes swarming with their threat of West Nile virus... Cold front came thru with very little to no precip... Temps will range up 30's / up 40's to 60's, with highs warming into low-mid 70's by Sat / Sun... strong NLY winds 12-20 mph thru Fri, lessening by weekend and shifting to ELY, then SELY by Sun as cold 1031 mb high pressure slides off to E... Sunny skies will give way to increasing cloudiness by Sun with return flow set-up... Rain chances go up by Sun nite into early next week with another approaching frontal system... Hopefully with no additional hvy rains for SE TX / SW Oct was one of wettest on record there with some stations reporting up to 28" for the month... Only slightly above average here in SE LA with most amts near 3.5 to 4"... 3.65" at my location.

Thu Nov 2 12:30 PM CST:
Quick Tropical Update: Close, but not quite! ...the familiar story of 2006!

Invest 93L continues to edge closer to Belize bringing hvy rain to the region... And low and behold - after 3 days absence - NOAA/SSD finally put the floater back up! ...Today the disturbance has a very well defined rotation and looks better organized... and on RGB sat loop appears to be the closest one since Alberto to becoming a depression in the NW Caribbean... However, most of the energy remains at the mid-levels as winds at the surface have not reached near the criteria... and highest wind gusts around 33 kts have only been reported well away from 1008 mb low pressure center in T-storms... Most probably will not become TD 10 as time is running out - it should continue to move inland next couple days... and upper level subtropical jetstream winds increase... LOL, another close call to add to the long list of "almosts" in 2006.

N Gulf wx nice & dry, less spooky end of October?
Sat Oct 28 2006 6:15 PM CDT
N Gulf Coast Update: A chance to dry out into Halloween with mild seasonal temps... rain chances back in picture Tue nite into Thu with next front... Storm impact reviewed... W Atlantic tropics active?

Well that was another wild wx event for the N Gulf coast region from E TX to FL that started Wed aftn thru today... In the wake of frontal passage, beautiful cool / mild fall wx has returned along with welcome dry air riding in on a NWLY flow... Temps next few days will range upper 40's / low 50's to near 70 / mid 70's, moderating to mid-upper 50's to upper 70's / low 80's by Mon - Wed. With base of large upper trof down over lower MS Valley, steadily shifting E... and high pressure building in at the surface from the west, wx couldn't be nicer this weekend into early next week... and cold air advection will peak here in SE LA tonite into Sunday. By late Mon into Tue however, E / SELY return flow will begin and humidity levels increase (yeah, ya know the deal)... as next frontal system approaches, rain chances go up by Halloween nite (spooky enough, let's hope it's late) and increase more significantly on Wed into early Thu when front is presently slated to pass here... Until then, enjoy the pleasant break.

Have to offer commendation to our NWS Offices in keeping up with developments and issuing timely watches and warnings with the recent difficult to precisely forecast systems coming across this month. In particular, the Lake Charles (KLCH) NWS Office has done a fine job in compiling reports... and ya know they've had a lot to keep up with since their area of responsibility (Extreme E TX / W LA / S Cen LA) has been repeatedly hit the hardest all month... The following is most recent, with abbreviated list of highest rain totals -

400 AM CDT SAT OCT 28 2006

...Yet another Heavy Rain Event brings widespread flooding...

A strong storm system brought yet another heavy rain event to Southeast Texas and Southern Louisiana from Wednesday October 25 through Friday October 27. This latest system is one of several that has brought widespread heavy rainfall and flooding to the region this month.

Most locations across Southeast Texas and Southern Louisiana received between 1 and 5 inches of rainfall from this event. However... a 25 mile wide by 150 mile long area... stretching from near Sour Lake TX to around Port Barre LA... received substantially higher amounts of rainfall from this system. Locations within this swath received three day rainfall totals ranging from 7 to 16 inches.

With grounds already saturated from the heavy rainfall of the past two weeks...this latest heavy rainfall event once again spawned widespread flooding across portions of Southeast Texas...Southwest Louisiana...and South-Central Louisiana. Numerous homes and business were damaged by the flood waters...with several road and school closures.

Below is a preliminary summary of rainfall totals for selected sites during this three day period. (All data is subject to change as post storm analysis is still ongoing.)

LOUISIANA: ...MOSS BLUFF 3NNW (Unofficial but NWS EMPLOYEE) - 15.06"... MOSS BLUFF - 11.37"... SAM HOUSTON JONES S.P. - 11.20"... RAGLEY - 10.50"... OPELOUSAS - 10.20"... GRAND COUTEAU - 9.04"... PORT BARRE - 8.84"... EUNICE - 8.53"... OLD TOWN BAY - 8.50"... OBERLIN FIRE TOWER - 7.79"...

TEXAS: ...ORANGE - 10.65"... LUMBERTON - 9.63"... KOUNTZE - 8.00"... SILSBEE - 7.97"...WARREN - 7.31"

Just a partial list of the heaviest recorded... as widespread 2.5" to 5 - 6" amts fell from near Houston across to east of Baton Rouge... With some of the hard hit areas of SE TX / SW Cen LA having received over 2 feet of rain in Oct, river / tributary flooding will remain a concern for quite awhile... and flash flooding easy to initiate. This is also true further into E TX / N LA over to S MS... SE LA - east of New Iberia and south of New Orleans - missed all of the hvy precip, ranging from trace amts to 1.5"... indeed, my location had .54", bringing my monthly total to 3.65"... Of course, we had the strong straight line winds to deal with as system finally moved east... Some iso areas had winds that gusted 60 - 70 mph causing some damage. Checking several WeatherBug stations along the N Gulf from E TX to N FL indicated common gusts of 30 to 45 mph with the frontal line... and just inland a few F0 - F1 tornadoes were recorded as well with reports of damage, but no serious injuries... In the offshore waters, buoys and oil platforms recorded winds of 40 to 62 mph... LOL, guess it's a good thing the tropics have been quiet this year! ...Ooops, should know better than say that... let's take a look.

Tropical Update:
Substantial late season trop wave (Invest 93L) is moving rapidly thru the E Cen Caribbean... while still disorganized, it has shown defined rotation around a low pressure area - that appeared somewhat more impressive late Fri while moving into Windwards - yet HiRes QuikScat today shows it's still an open wave with winds of 20 - 30 kts, not a closed low... With weak winds aloft dominating the E / Cen Caribbean region, the upper level environment offers favorable low shear under 10 - 15 kts... Currently it's being steered WWD under a broad sfc / mid-level ridge located NE of the Leewards... and zipping along at 15 - 20 mph. That in itself may be the biggest hindrance to development, and those trade winds are expected to increase behind the wave by tomorrow - And that has been another disruptive constant all season along the MDR, as a strong sfc pressure gradient has existed between Atlantic ridging and low pressure over S America... Still, there is some possibility for slow development into Monday. Should be interesting to see how it interacts with frontal trof that's digging into the NW Caribbean...That trof could erode the mid-level ridge, that could allow a more NWLY movement of the wave towards Cuba, getting caught into the trof... will have to see if that occurs or continues WWD. The 12Z GFS was showing possible cyclonic development Mon into Wed all along that trof... from near W Carib... below S FL - that could give hvy rains to S FL and Bahamas by midweek - and NE of Bahamas... However, outside of the Caribbean region strong subtropical jetstream winds remain to rip apart potential tropical systems that migrate NWD... Potent non-tropical low development is just as likely along the frontal trof in time and 18Z GFS also insists it will... But unsure those will become tropical ATT, although 93L certainly could. Beyond that, will keep an eye on area near Panama / W Carib as a climatological favorite into November... So far, everything there has edged into the E Pac and may well continue.

PS - DST ends tonite, set the clocks back... Bah humbug!
Happy Halloween everyone! ...and welcome to November! ...Yay!

Updated: 6:45 PM GMT on November 02, 2006


TX / LA - Serious Flood Threat...again!

By: DocNDswamp, 11:39 PM GMT on October 18, 2006

Latest W Atlantic Basin AVN / IR Satellite Image

W Atlantic Basin AVN Satellite Image

Wed Oct 25 2006 10:15 AM CDT:
NW Gulf Update: Additional aggravation to Oct 15 - 16 flooding event possible next 48+ hrs... Flood watches back up for SE TX and SW / Cen LA...

Well folks our beautiful clear skies, dry air and cool temps are leaving us... and what's coming ... isn't pretty. As the record setting cold spell shifts farther east, a developing storm system is poised to bring the chance of hvy rains back over TX and LA beginning today (Wed) thru midday Fri... Flood watches have been issued for areas still saturated across E TX and W / Cen LA as latest guidance indicates timing of progression has slowed... and event duration longer than earlier thought. As the warm front lifts NWD and approaching storm system develops, mostly lite shwrs are currently found... but rising chances for heavier shwrs and T-storms as low - mid levels become more moist and instability increases later today. With the upper level flow becoming more SWLY, additional mid to upper level moisture from the Pacific - remains associated with E Pac's TC Paul - is getting pulled across combining with Gulf moisture... while the storm system coming from west is progressing agonizingly slow... Currently the developing sfc low is in S Cen Plains, while the deepening upper trof lags behind over the West... Rainfall will steadily increase in coverage and intensity overnite into Thu, with heaviest likely from midday Thu into Fri morning... While similar to Oct 15 - 16 event - minus the extremely low pressure and possible tropical storm formation - right now it appears avg rainfall amts will run near 2 - 3" with some 5 - 6" amts possible over the ArkLaTex region... and potential exists for some strong to severe T-storms. Hopefully no one sees rainfall as previous event brought - ATT not expected - or consequences could be horrible... Yet, residents in the flood watch area should stay vigilant next 2 days as it will not take much to initiate flooding... All of this should lessen slightly as it moves EWD in time, the quicker the better. This developing cold front - bringing cool but milder Pacific air - will take midday / aftn Fri before reaching SE LA... and following frontal passage, should remain dry into Mon... Temps behind the front will mostly range 50's to upper 70's / near 80... far milder than recent Canadian cold front... While the cool temps have been pleasant, one bad aspect this time of year from it is... evaporation rate of saturated ground is greatly reduced. What gets wet, stays wet... And this pattern will probably continue. Yep, from drought to flood...

Daylight Savings Time ends this weekend... don't forget to set clocks back... blah, blah, blah... LOL, yeah I hate it. There goes the aftn... SET IT YEAR-ROUND AND LEAVE IT ALONE! Arrrrghhh...

N Gulf wx - Cold front passing - Greatest flood threat diminished...
Thu Oct 19 2006 1:30 PM CDT:
SE LA / N Gulf Update: Hvy rain threat ends for SE TX thru NW / Cen LA as cold front brings cooler drier air... Next front will pass Sat nite / Sun...

*Flash Flood Watch covering SE LA / S MS has been cancelled... Flood Watch for SW LA / S Cen LA has been cancelled...

*River Flood Warning in effect next several days for lower Neches River and tributaries in SE TX... and along Calcasieu River and tributaries in SW LA...

*Small Craft Advisories remain in effect thru early Fri across NW Gulf, ending W to E...

More seasonal wx is on tap... Cold front continuing EWD progress today, with SW to NE oriented line of shwrs and T-storms now stretching from well offshore waters SW of Morgan City, entering Houma to New Orleans into SE MS...toward Mobile... Some strong T-storms embedded in line, but generally weakening.... best potential for additional severe T-storms more likely in NE portion of frcst area of FL Parishes into MS into AL...however, possibility for damaging straight line winds remain as frontal line moves thru... WSW winds will switch to NW at 10 - 18 mph behind the front... and hard hit areas of Cen / W LA to E TX getting cooler, dry relief from flooding rains this week. Cold front will cont into the NE Gulf toward N Cen FL. Temps will trend cooler, more seasonal into next week, ranging from lows of up 40's / mid-up 50's to highs in up 60's to low-mid 70's... especially as secondary reinforcing cold front will pass late Sat thru Sun, also bringing back rain chances, highest POP on Sun... as high pressure coming behind current front will shift E, low may form along frontal boundary in N Gulf and combine with approaching 2nd front - let's hope more over N Cen Gulf than W Gulf, as that area has had enough precip... while SE LA to NW FL could use more... Progressive pattern will continue as another cold front may move thru by late Wed... Hopefully, the record heat (91 tied record in Shreveport Wed) and excessive humidity will be a thing of the past... But, LOL... this IS the South.

Tropically, old 90L has flared up a bit last 24 hrs - near Virgin Is / N Leewards... as upper level winds have become slightly more favorable... Development still not expected ATT, but will watch for any further organization... By next Tue / Wed strong cold frontal trof dipping SEWD should help lift disturbance N and NEWD and finally away from area. System and interaction with nearby ULL has been enhancing rainfall from Leewards to Puerto Rico for over a week...

NW Gulf - Flooding Rains return in TX/LA! Cooler wx on the way...

Wed Oct 18 2006 6:30 PM CDT:
E TX / LA / N Gulf Update: Renewed flood threat to E TX / LA / MS with cold front on the way... Caution for possible dense fog again overnite if winds slacken.

After starting the day with widespread dense fog covering a large portion of SE CONUS, the combination of saturated ground, residual high moisture content and daytime heating lead to formation of seabreeze type shwrs and T-storms over the area that needs it the least... as by late morning / early aftn hvy rainfall was occurring over extreme E TX across W LA in a line stretching from N of Houston to Baton Rouge and near New Orleans... Already this aftn Flash Flood Watches have been issued from SE TX thru large part of LA to S half MS for those areas that were hit hard on Mon, in anticipation of additional hvy rain as a cold front will move across SE LA by Thu eve... (Extreme SE LA not included in FFW for now... None of Wed's activity has affected my area in S portion of SE LA, but draining of tidal flood waters along the coast has been hampered by returning 10-18 mph S/SWLY winds... W to E line of precip is mostly above 50 miles N of coast)... Cold front will pass thru SE TX by early Thu morn and continue progressing EWD into NW FL by Fri morn...halting SWD progress in Cen FL. Ahead of and along the front, numerous shwrs and strong T-storms - possibly a few severe - are expected, followed by NWLY winds bringing cooler, drier air into Sat (SE LA) ...followed by the approach of another possibly stronger cold front Sat nite / early Sun, although precip expected with 2nd front should be of short duration and have more limited moisture source to feed from... Expect more seasonal temps over weekend, falling somewhat below avg behind 2nd front Mon thru Wed next week... as all along N Gulf get chance to dry out... Let's hope those of us that need rain, get it... and less where already flooded... but set-up favors hvy rain back over worst hit region, and already today another 3 - 5" amts have fallen in parts of SE TX / SW LA.

Besides added flood threat potential... severe T-storms may contain damaging straight line winds, some hail and iso tornadoes as cold front approaches / moves across tonite and on Thu... continuing EWD in time.

Additionally, if winds drop off again tonite... would caution for repeat of dense fog forming late nite / early morning along Gulf coast, esp into FL peninsula...

Tropically - Nothing of concern ATT... as very strong upper winds rotating around massive upper high over Cen Gulf are even ripping over convection and hindering organization in E Pac for now... Weak low near Puerto Rico (old 90L) still hanging around, remains disorganized under upper NLY flow... Shear rules as usual, but will keep an eye on that feature... Such was not the case one year ago tonite - when we witnessed tropical history made as Hurricane Wilma went thru insane intensification down to 882 mb with that extremely tiny vortex with a 2.5 mile wide pinhole eye... to become all time most intense in Atlantic Basin! ...What a Night! What an amazing Tropical Cyclone!!!

Updated: 9:05 PM GMT on October 25, 2006


NW Gulf States - Hvy Rains end / Calm but hot, humid wx returns next 2 days

By: DocNDswamp, 8:04 PM GMT on October 12, 2006

Latest W Atlantic Basin AVN / IR Satellite Image

W Atlantic Basin AVN Satellite Image

Note: Satellite imagery may not display due to heavy usage at SSD.NOAA site.... Sheeeeesh!

Tue Oct 17 2006 1 PM CDT:
SE LA / N Gulf Review / Update: Calmer, but hot wx in store next 2 days...

Yes.... as I've seen it so many times before - that line of T-storms came across S LA, got to my area near 3 AM... and FIZZLED!!! LOL! Oh I got some more rain from it - a meager .61"... along with the .73" on Sun / Mon - had a storm total of 1.34"... Absolutely no surprise... More local Houma-Terrebonne data I could find from event - Highest recorded winds here: sustained at 31 mph... Highest gust - 42 mph... though I'm sure someone had higher... Barometric pressure was lowest of 2006: 1002 - 1003 mb / 29.59" - 29.61", which beat out the Feb 1-2 event when fell to 1004 mb ...Those strong winds dropped off quickly when it got here, which is great news... will allow tidal flooding to recede along the coast, so all looking better but for one exception - it ain't cooling off! Heat and humidity will reign today and Wed before cold front passes on Thu... and will cont much lesser chance for iso / w scat T-storms, although we will be seeing sunshine return today in TX and LA... Which the bad news is - High temps will soar to near record levels of upper 80's - low 90's today and tomorrow and feel quite oppressive in residual high humidity. Yuck...

Impressive rain totals across Cen / W LA and SE TX - one of the highest found was at Kisatchie National Forest Station in Natchitoches Parish - 17.35"! ...and lot of 7 to 13" amts recorded along E TX / W LA border area... Near Houston, Hobby airport recorded over 11" and saw report of Conroe receiving 12.71"... And plenty of 3 - 6" amts elsewhere in E TX / SW-Cen LA... Preliminary Storm Damage Reports from TX / LA / MS NWS Offices are quite an extensive list... of 3 fatalities in Houston area from drowning... flooding from hvy rainfall and / or high coastal tides, the later extending across SE LA to coastal MS ... wind damage from severe T-storms, tornadoes and high pressure gradient winds. It's a good thing upper level winds flying around that huge upper level ridge centered near S MX to Yucatan were too strong to allow tropical development, along with strong upper trof coming across CONUS that pulled disturbance out of Gulf... Offshore Oilrigs and Gulf Buoys recorded tropical storm force winds, the highest I found was 56 mph at Station 42362 (Brutus - Green Canyon Rig)... and wave heights reached 12 ft in N Cen Gulf.

Weakening line of shwrs / T-storms - associated with W Gulf disturbance merged with sfc front / upper level short wave trof - continue to shift EWD... stretch offshore below SE LA across NW FL / GA and Carolinas NWD along Mid-Atlantic coast today...


NW Gulf States - High Winds/Tornadoes/Flooding rain threat continue today...
Mon Oct 16 2006 10:30 AM CDT:
N Gulf wx Update: Hvy rains, strong winds, minor coastal flooding and tornadoes creating havoc...

Tornado watch in place till 1 PM CDT across E TX across S half LA...

Coastal flood warning in place from high tides... SCA's and Inland lakes wind warnings in place into Tue.

Well our disturbance - Non-Tropical Storm X - is lifting up across E TX / LA... along with hvy rain, with some severe supercells formed with embedded tornadoes... which are continuing in W / Cen LA and E TX moving N rapidly... across E TX toward N LA into AR / MS.
Effects have been minimized here in SE LA compared to areas to our west, and rainfall totals generally light - I've only totaled .73" since it began Sun aftn - where parts of SE TX / W / Cen LA have had between 3 to 8"...
However, we weren't completely unscathed - A tornado touched down predawn in Leeville, lower Lafourche Parish flipping mobile homes, injuring 4 people... ripped boats from moorings and gas line ruptured. Also coastal flooding has been a problem as strong SLY winds have driven tides above norm... some roadway flooding across S Lafourche to Grand Isle... this is likely all across immediate coastal S LA to coastal TX. Damage reports continue to come in, more so to my west and NW.

And oh what a tropical airmass in place today - you could cut the heat and humidity with a knife and serve it on a plate (LOL)... Last nite, went outside around 11 PM and watched low level clouds / continuous lite rain racing in with sfc winds up to 30 mph - it felt like a tropical system was nearby... Bar Pressure dropped to 29.69" / 1005 mb here, but drop off more dramatically to the west where core of system passing... many readings from 998 to 1002 mb in SE TX to W / NW LA. High Winds continue at 15 to 25 with gusts over 30 mph and are now shifting from SSE to SSW. ...Rain and T-storms have lifted N of this area (SE LA) for now, but may redevelop later...
Tornado Watch remains until 1 PM CDT across all S LA into E TX... Likely to be extended NWD into N LA as warranted...
Needless to say - there is no longer any possibility of tropical development as strong mid-upper level flow from SW lifting feature NWD out of Gulf...

Sat Oct 14 2006 11:30 PM CDT:
TX - LA / N Gulf wx Update: Potent low / retreating warm front likely to bring hvy flooding rain potential to E TX / LA

Big changes are on the way for our area, as a potent low pressure system has formed in W Gulf along the stationary cold front, off the MX coast. While it was a pleasant partly sunny Saturday (55 low, 78 high) with low / mod humidity, signs of those changes were evident as ENE winds increased to 12 to 20 mph from gradient between sfc high to our NE and the developing sfc low in the W Gulf. As cold high pressure slides EWD, warm front and low pressure system will lift NWD - also in response to EWD advancing upper low storm system coming from CA - bringing abundant deep moisture into TX and LA with hvy rains and strong T-storms Sun / Mon... and very gusty E / SELY winds. Looking at the 0Z model runs, the NAM - which brings heaviest rains over E TX / W LA up into ARKLATEX... and the GFS which earlier had a near tropical storm into SW / S Cen LA late Sun / early Mon and into MS and TN Valley by Tue... are more in agreement in latest runs, although the GFS still hints at a vortex coming ashore into LA. We'll just have watch as somewhere between the two seems most probable... The other question is could we see a tropical cyclone form of the current 1008 mb non-tropical low as it slides up the W Gulf... Well, I would not rule out the possibility, but timing of the progression would seem to contradict. Here's why...

Currently upper level winds rotating around the broad up ridge located over S MX right below the disturbance are likely too high to allow tropical development very far to the N... although center of that ridge (with lower shear values of 5 - 15 kts) will be shifting NNE over next 48 hrs that could allow tropical development. The problem is the sfc low will probably move too fast NWD, outrunning favorable conditions by lifting into higher 30 - 40 kt shear environment found in N perimeter of ridge. The scenario with this low is somewhat reminiscent of tropical disturbance event back on July 23 - 26 near same location... when that sfc low remained just inland, precluding tropical development as it hugged the coast moving NWD.

Primary threat from this disturbance will be the potential for concentrated hvy rainfall causing floods as shrws and T-storms may have training effect over parts of SE TX and into LA during the day, particularly late Sun into early Tue. However, over the open waters of the W to N Cen Gulf... breezy conditions and gusty E / SELY winds could likely reach tropical storm force as system moves NNE. As I stated since Fri nite, residents of E TX and LA need to be aware of this potential flood threat thru Tue... when combined systems will shift into mid-South toward E Coast and likely weaken some as rains and warmth return there. Next strong cold front will arrive late week, bringing cooler, drier seasonal conditions back for the weekend. In between, chances for scat shwrs and T-storms continue... along with high humidity and very warm temps, which may be near record levels in 90's Wed / Thu... Yuck!!! What a roller coaster of a ride...

Fri Oct 13 2006 1:30 PM CDT:
And in N Gulf weather news....

Had a few severe wx reports from yesterday aftn as strong T-storms formed ahead of front in SW LA... some iso structural damage, trees and powerlines from either tornado or straight line winds in Deridder to Oberlein... no injuries...
Cold front passed thru this morning with a few shwrs and T-storms as advertised... received .59" precip and low temp plunged from 67 to 54 (coolest yet)... now holding low-mid 60's, could reach near 70, clouds holding temps back for now... Partial clearing giving a few peeks of sun through remnant low level clouds. Forecast going as expected, although projected lows tonite dependent on clearing cloudiness... range of either low to up 50's to near 60 on the coast. Fairly rapid warm-up Sat under PC / MC skies and rain chances increasing the next 24 hrs with return flow ...remaining Sun thru next week, esp for S to E TX thru LA on Sun / Mon shifting NEWD across South.
12Z GFS backing slightly on developing sfc cyclone in Gulf by Sun - still a hint of it - and becoming more in line with NAM solution - shwrs and T-storms break out along returning warm front in Gulf main storm system forms in S TX moves ENE in response to Pacific low / weak frontal boundary coming across...which will stall / wash out... likely followed by another weak cool front late week, which may also stall due to more zonal flow our area... back to Indian Summer with above norm temps - lows in low-mid 70's, highs mid-80's... plenty of humidity and lots of rain ops... maybe another slim break to cooler, drier air next weekend... ;-(

Thu Oct 12 2006 2:30 PM CDT:
SE LA / N Gulf wx Update: Another short-lived cool down coming...

Uncertainties abound with our short - medium range forecast... but one thing is sure - we on the N Gulf coast will cool down next couple days, but will not get as cold as thought from guidance 5 - 7 days ago... and we can thank the strong subtropical jet stream cutting across for it... High temps on Fri - Sat will likely run low-mid 70's to near 80 with coldest lows Sat morn varying widely from mid-up 40's interior to low 50's closer to coast. While a cold early season arctic air mass is pooled over the Great Lakes and diving SWD today, the coldest air will remain N of our area as it also shifts east thru the weekend... as the subtropical jet will effectively limit the polar air mass' southward advance into the Gulf. Keep in mind, as is typical with such arctic air masses, the farther N one's location is under the high pressure regime... the more significantly colder the temps, often in relatively short distances with tightly packed isotherms... and often are more dramatic in winter than fall.

In the upper levels, the subtropical jet represents the gradient region between the deep polar low over Great Lakes / E Canada and broad upper ridge over S MX, with a cut-off low off CA coast helping to pull Pacific moisture across. The sunny to partly cloudy skies today following yesterday's passage of weak Pacific front will become mostly cloudy ahead of the arctic front that will move thru overnite... bringing chance of shwrs / T-storms poss thru early Fri as it progresses EWD... and poss brief clearing. More likely areas of the E portion forecast region may enjoy the clearing and sunny skies longer (i.e. - to NE FL)... as return flow will set-up over S TX / W Gulf by late Sat / Sun along with rain chances. One of the biggest uncertainties lies in whether a strong sfc low will form on the tail of front in Cen Gulf south of LA... as the GFS keeps trying to. Either way, wet weather and back to mild to warm temps will be the rule as we go into next week... and strongest upper winds relax some with a flattening to more zonal flow... Ha! ...What, you thought this was Winter setting in? ...Think again! The latest CPC / NOAA winter outlook calls for another mild winter with a few brief arctic intrusions, though slightly cooler overall than last winter... what we see now in this current front could be a preview of things to come... Wetter wx along W to N Cen Gulf seems likely as several impulses move into the area from the west.

Thu Oct 12 2006 2:30 PM CDT:
Tropical Update: TD 10 possible?

Tropical wave that flared up near N Windwards last couple days had a short window of opportunity as it moves WNW across Windwards / Leewards toward Puerto Rico. That window may be closing as system remains disorganized. The farther WNW it moves, the more hostile upper winds it will encounter, thwarting development... Biggest concern is potential for flash flooding rains over islands high terrain next 3 days, along with breezy conditions with some possible gusts to near tropical storm strength... With lack of developed sfc low, earlier model runs for it's track may be dubious - had it continuing WWD near the Greater Antilles... or going WNW / NW, getting caught in the trof that will lie between the Atlantic ridge and building high over E CONUS behind cold front...Also was thought possible trof could lift out before disturbance reaches it with sfc high pressure building over above it. However, it appears N portion has already merged with the convection associated with the trof...and LLC has yet to become established. Viewing RGB sat loop this aftn, looks like a LLC is trying to form well north of P.R., away from the wave...while another may be trying to form much farther to south - between Barbados and St. Lucia... If feature N of P.R. becomes dominant, would not be surprised to find all of this whisked away to the N... Bottom line - still a disorganized wave with the slightest of potential. Beyond 72 - 84 hrs, if stays in Caribbean will soon encounter strong NLY upper winds circulating around massive upper high centered over S MX... This small system is almost reminiscent of TS Chris, and as we said before in that case - such can easily ramp up under good enviro conditions... and just as quickly - get ripped to shreds... Again - greatest realistic threat is from hvy rainfall over Windwards, Leewards, Virgin Is and Puerto Rico to E Dominican Republic next 3-4 days... if it holds together. Don't ya just love all this interaction with upper trofs and high shear values!

Elsewhere, tropical cyclone formation does not appear evident... As usual will keep an eye on W Caribbean / S Gulf and tail end of fronts. Strong westerlies associated with subtropical jetstream may relax somewhat as it lifts... and sprawling upper ridge currently over S MX expands back N and E over SW / Cen Gulf by next week. Other than what is likely indicated to be a non-tropical low on the front in the Gulf, tropical development is not depicted ATT on model runs... Will be watching for any October surprises, however.

Updated: 6:13 PM GMT on October 17, 2006


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