June 2017: Typical Summertime WX To End Month

[DoctorMu]

thanks for reply andrew. flooding tropical systems anywhere along the gulf coast need to be monitored. My hope is being this early in the season we wont see any other tropcial action. I can wishcast right!

Indeed, this won't be a major wind event and fortunately not well organized, but caution is necessary, because the time window on effects re: rain and flooding could be in a 48-72 hour range. Models still have a complex forecast to work out re: direction, strength, timing, but folks should be aware of the possibility of a significant rain event...if the system heads towards Texas.

[Scott747]

Too not create any confusion....

92l is the system approaching the eastern Caribbean and not related to 93l which is the system in the NW Caribbean. Probably best to put those updates in the hurricane section.

[Cromagnum]

Bring on the rain and some cooler weather.

[ticka1]

Bring on the rain and some cooler weather.

anything to break the heat BRING ON AUTUMN 95 DAYS!

[weatherguy425]

Well, for what it is worth [a bit less frustration at this point] here is some of the tightest clustering we have seen thus far. Still, a long way to go before any certainty is included with the forecast. To put it simply >> hard for models of any resolution and scale to resolve challenging features individually, let along when they are interacting with one another; ULL, ridges, etc.

[srainhoutx]

Sunday evening briefing from Jeff:

Tropical system in the NW Caribbean Sea organizing

Tropical Storm likely in the Gulf of Mexico as early as tomorrow…chance of development at 90%.

Residents from TX to FL should closely monitor this system as impacts will be widespread and in some cases significant.

Discussion:

While the tropical system over the NW Caribbean Sea has not organized enough to be declared a tropical depression, the overall structure of the system continues to gain slow organization. A mid level vorticity center has developed on the eastern flank of the broad surface low, but an examination of the low level wind field shows SE trades throughout this entire feature suggesting it does not have any low level circulation even though it may look impressive on satellite images. Deep convection around this mid level vort has weakened today and it is unlikely that this will work its way to the surface. Instead the broad sharping wave axis/low along the eastern coast of the Yucatan is likely to become the dominant feature later tonight into Monday as the system moves into the southern Gulf of Mexico on Monday.

The USAF mission this afternoon was cancelled, but the mission planned for Monday is expected to happen to see if a tropical depression is forming.

Track:

Model track guidance has come into better agreement today with the CMC shifting significantly to the west from SC LA to the middle TX coast. The GFS, which has been a strong NE Gulf solution also shifted west and now brings the system toward SE LA and slows it down and then inland over SC LA. The ECWMF and UKMET solutions remain steadfast in their western track toward S TX. It appears for the first time in days we are starting to see gradual model consensus on a track solution toward the W/NW Gulf of Mexico which has been favored. The complicated track factors evolve around the following features:

1) A splitting trough along the US Gulf coast with the west portion of this trough starting to move WSW toward S TX
2) Building sub-tropical highs from both the SW US toward TX and the SE US from the SW Atlantic Ocean
3) A trough across the Great Lakes which is producing a weakness in the height field over the central US Gulf coast from roughly SC LA to the FL panhandle

These three factors will be the ultimate determination of the final outcome for this system. With the trough along the US Gulf showing signs of fracturing today and starting to retrograde (move westward) this is allowing the sub-tropical ridging to begin to build from both the west and east helping to close the weakness over the central US Gulf coast. Latest ECWMF and 18Z NAM show the western portion of this trough becoming an upper level low over S TX which captures 93L’s circulation and draws it N then NW, then W toward the NW Gulf of Mexico. The 18Z NAM shows this very well. Just how fast all this happens and to what extent will determine the track. Feel much more confident that 93L will develop into the SC Gulf tomorrow and track NNW then NW into the NW Gulf by Wednesday. Track guidance has variations of the system nearing the LA coast as soon as 60-72 hours with most others nearing the TX coast in 72-96 hours.

While the confidence in the track is starting to increase only a slight deviation of the 3 factors above could result in a different track solution so forecast confidence remains low.

Intensity:

The upper level trough/developing upper low will likely help to continue to impart some degree of shear across the system as it moves northward. In fact the GFS may have been picking up on the mid and upper level portions of 93L shearing off toward FL while the other guidance has been latching onto the low level center moving more westward under the shear. What is interesting is that recent 12Z and 18Z runs are trying to show more intensification than before in what appears to be a fairly hostile environment across the Gulf as the surface low interacts with the upper level low. Such interactions can be favorable for a TC in the correct position of the venting flank of an upper level low, but the surface low must be in the correct position. Tropical Storms Allison (01) and Frances (98) both formed in this manner with the surface system interacting with an upper level low over S TX. Both of these systems had extensive moisture plumes on their eastern flank similar to the forecasted plume across the Gulf this week and both featured significant weather impacts well NE of their surface centers…another likely outcome with 93L. Proof of the deep moisture plume is seen in the ECMWF PWS (total column moisture) of nearly 3.25 inches over the central Gulf of Mexico by mid week…which is “off the charts”.

Impacts:

Broad sprawling nature of this system combined with long fetch deep moisture plume will result in impacts for hundreds of miles north and east of the center. Will not make any changes to the forecast and see if the track solutions can hold and stabilize for the next 12-18 hours. Would also like to get some sort of guidance from NHC although the coordinated NHC/WPC points will likely be the initial advisory track when they decide to upgrade or follow similar procedures as they did with the system east of the Windward Island


It should be noted that the latest NHC Gulf marine forecast has 12 foot swells approaching out 100nm waters by Wednesday.

Note: It is possible that NHC could begin issuing advisories Monday even before a tropical depression or storm is declared due to the new ability to issue advisories, watches/warnings, track within 48 hours of possible impacts.

[DoctorMu]

GFS - Louisiana

GEM - upper Texas

Euro - lower Texas coast sticking to their guns



NAM as rain mentioned has a broad low lurking off the TX coast.

[srainhoutx]

The sloppy mess in the NW Caribbean continues to slowly lift NNW toward the Southern Gulf. A broad surface low is currently just West of Cancun/ inland over the NE tip of the Yucatan Peninsula.

The 06Z GFS continues the Westward shift with sheared low center making Landfall near Vermilion Bay to the SSE of Lafayette. The 00Z Canadian suggests a sheared surface low making Landfall near or just to the West of High Island and finally the 00Z ECMWF suggests a weak surface low S of Corpus spinning an 850mb vorticity into Matagorda Bay.

Hopefully today we will have a better idea exactly where this mess is going, but the heavier rainfall likely will be on the NE quadrant of this disturbance.

Locally a couple of inches of rainfall appears the most likely solution with rainfall totals near or above 8 inches possible across portions of the Central/SE Louisiana and Mississippi Coast.

There remains considerable uncertainty in the sensible weather forecast along the Texas and Louisiana Coastal Areas. Until we see an actual closed surface low develop in the Southern/Central Gulf, the forecasting uncertainty will remain as well as the various modeling solutions.

[Katdaddy]

From this morning's HOU-GAL AFD regarding Invest 93L:

The National Hurricane Center`s most recent Tropical
Weather Outlook continues to say that gradual development of this system is expected when it moves over the southern or central Gulf of Mexico later today and Tuesday where a tropical or subtropical cyclone is likely to form (80% chance of formation through 48 hours and a 90% chance through 5 days). Models continue to show different scenarios on how this will all evolve, and this will probably persist until we get better system organization for the models to handle, hopefully some time later today if the reconnaissance flight can investigate. There could be significant changes to our forecast over the next several days.

[srainhoutx]

Monday morning briefing from Jeff:

Tropical storm likely in the Gulf of Mexico this week…a threat to the US Gulf coast

Discussion:
Disorganized tropical wave axis across the eastern Yucatan into the southern Gulf of Mexico this morning has shown little evidence of becoming any better defined overnight. Surface wind analysis shows more of an elongated trough axis than any sort of surface low. Deep convection has been firing across the western Caribbean waters much of the night, but this is well east of the sharp trough axis. The trough has become slightly better defined near the northern coast of the Yucatan where models have been suggesting for days a surface low will form.

Additionally, the upper trough over the NW Gulf of Mexico continues to produce strong shear across the central Gulf and the northern portions of the tropical wave axis. Deep tropical moisture is quickly advancing northward across the eastern gulf.

Track:
While it has been most frustrating watching the most reliable global weather forecasting computer models there is a slow but steady growing consensus on the track of this system. The complicated setup of steering flow across the Gulf of Mexico is the reason for the large spread in the model guidance with each model having its particular favored choice of which atmospheric circulation will ultimately drive the system toward the US Gulf coast. These factors include:

1) A trough over the northern Gulf coast which is fracturing and will form a weakness or upper level low over the western Gulf
2) Building sub-tropical high pressure ridges from both the SW US and the SW Atlantic.
3) A trough of low pressure over the Great Lakes

It is becoming more defined that the dominant steering pattern will evolve around the fracturing and development of an upper level low over the western Gulf of Mexico over the next 24-48 hours with 93L moving northward along the eastern flank of this large scale circulation. In fact there is enough evidence in the model guidance to suggest these two circulations actually interact more and more creating varied solutions. There is general agreement that the sharp trough axis will drift WNW today with a surface low likely forming somewhere within the northern portion of this axis and moving generally N to NNW along the eastern side of the developing upper trough over the western Gulf. This motion will continue on Tuesday as the system moves into the central Gulf of Mexico, but track guidance then becomes split with the GFS tracking 93L NNW toward southern Louisiana while the ECMWF turns 93L almost due west and toward the middle TX coast by Thursday. The CMC is down the middle tracking the system toward the upper TX coast by Thursday. The key to the track will be how much influence the developing upper trough over the western Gulf has over the developing surface low.

There is enough consensus this morning to suggest that the threat for a landfalling tropical storm on the Texas/Louisiana coasts sometime from late Wednesday into late Thursday is likely.

Intensity:
93L is highly disorganized and the atmospheric setup in the Gulf of Mexico does not look very favorable for intensification. Tropical cyclones can and at times do interact with upper level troughs like the one which is forecast to be in the western Gulf this week. The surface low on the eastern side of the large scale trough must find its way into the favorable venting portion of the trough or shear will have a negative effect on the surface low. What is interesting is that several of the global and now meso scale models show such a shearing environment across the central Gulf and then actually show decent upper air conditions as the system nears the coast. Both the high resolution NAM and CMC show a fairly symmetrical system in their 54-84 hours time periods while the GFS and ECMWF show a much more elongated and lopsided presentation.

Several Gulf of Mexico tropical systems have formed in this manner and the end result is almost always a flood event somewhere along and east of the track of a broad ill defined center.

Impacts:
Will raise seas on Tuesday to 3-4 feet across our 20-60nm waters with NHC forecasting 8-12 feet approaching our outer waters on Wednesday. Increasing tides will be possible as early as Wednesday, but will keep them below 2.0 feet total water for now. Addition of larger easterly swell onto the coast on Wednesday will likely start to pile up the water to some degree. It would seem that rain chances need to be raised to at least 50% late Wednesday and this may need additional adjusting upward. Don’t want to get much more specific with impacts at this point until either there is some guidance from NHC or the model track solutions firm up more. A track of the system toward Louisiana would result in a fairly dry and hot forecast for our area while a track toward the TX coast would result in a certainly more wet forecast.

Significant forecast changes may be required for the Wed-Fri period.

Persons along the TX/LA coasts should closely monitor the progress of 93L and be prepared for adverse conditions to potentially begin impacting the coast as early as midday Wednesday.

[srainhoutx]

Michael Ventrice‏Verified account @MJVentrice · 35m35 minutes ago
Newest Calibrated ECMWF EPS hot off press- 80% chance of development or higher for both #93L and #92L (Potential Tropical Cyclone 2).

[tireman4]

Dear All,

This is just a heads up. With the Tropical season upon us, make sure ( whether a system is in the waters or not), to go over your hurricane kits and plans of action if an area is threatened. Make sure to stay tuned here with our pro mets (Srain, Wxman 57, Andrew, Brooks, David and Jeff) helping to get you through whatever comes ( Winter/Summer/Spring/Fall). This event, if it ever becomes an event, will be everchanging. Monitor your public sources (tv, NOAA weather radio, the KHOU Forum) and be weather aware. This is my PSA each year. One last item. Make sure to be patient with our mets. They are monitoring all situations and sometimes they cannot give you exact answers for Mother Nature is quite quirky. Remember, to be patient with them and they will do their best to guide you.

[Electric Lizard]

Do y'all think that the MCS pushing south (now near Waco) will make it to SE Texas?

[djmike]

When do you guys think the NHC will add the cone for 93?

[srainhoutx]

Do y'all think that the MCS pushing south (now near Waco) will make it to SE Texas?

We'll need to monitor the outflow boundary across our Northern Areas then a potential seabreeze boundary advancing N from the Coat toward Metro Houston later this afternoon and evening. HGX is currently watching this situation closely and mentioned it in their Updated AFD at 7:00 AM.

[tireman4]

Do y'all think that the MCS pushing south (now near Waco) will make it to SE Texas?

Echoing what Steve said..sorry...LOL


A change in the recently static forecast for aviators today. A
storm system passing across northeastern Texas this morning may
spit out a gust front ahead of a weak larger scale frontal
boundary that will be entering our northern counties just as late
morning temperatures warm into the upper 80s. Lift from a outflow
boundary into a near 90 F and moist air mass will increase the
odds of near noon thunderstorm development across the northern
terminals. Further south...an advancing sea breeze boundary into the
second tier counties by early afternoon may generate late morning
towering cumulus/showers that could transition to more metro area
early to mid afternoon thunderstorm behavior. Late afternoon through
early evening convection will be all mesoscale-driven and northern
storm southern-propagating gust fronts may interact with sea
breeze-driven cells. Inland activity should dwindle down by late
evening with the short range higher resolution models developing
evening (near) coastal county precipitation ahead...or along this
aforementioned larger scale boundary as it becomes more diffuse on
its southern trek to the coast.

[srainhoutx]

Not that we trust the NAM with tropical/sub tropical systems, but...the point remains the same with the reliable guidance.

Michael Ventrice‏Verified account @MJVentrice · 3m3 minutes ago
Extremely messy Gulf of Mexico picture. Many Vorticity maxes interacting; lots of room for model error #slopgyre

[DoctorMu]

Do y'all think that the MCS pushing south (now near Waco) will make it to SE Texas?

I'm prepared for the AggieDome to crush it. leaving us bust again.


It is significant as a marker of the SW ridge drifting east, leaving a gap for the Gulf tropical whatever to move through. We're almost at Nowcasting for this tropical system. Fabulous discussion from Jeff this morning, Srain. Thanks as always for sharing.

The trough axis has emerged nicely along the Yucatan:

[DoctorMu]

Do y'all think that the MCS pushing south (now near Waco) will make it to SE Texas?

We'll need to monitor the outflow boundary across our Northern Areas then a potential seabreeze boundary advancing N from the Coat toward Metro Houston later this afternoon and evening. HGX is currently watching this situation closely and mentioned it in their Updated AFD at 7:00 AM.

Yes - boundary waves are on their way. There will be an eye out this afternoon for any action.

[DoctorMu]

Update: MCV being sandblasted at the Brazos Co. line as expected.



FAQ from HGX up re: 93L if anyone interested.