July 2018: Weekend/Early Next Week Rain Chances

[wxman57]

This morning's European run is much lower with precip on the 4th, only 1/4 inch across Houston. Closer to the GFS, which has about an inch of rain.

[srainhoutx]

Next week appears to bring a change in the Upper Air Pattern as the Upper Ridge weakens enough to allow our 4th of July inverted trough to pass and then additional Easterly waves to march beneath the Upper Ridge far enough to our North to allow for almost daily rain chances to end the upcoming short Holiday Work Week into next weekend. Another area of disturbed weather associated with an Easterly Wave approaches next Thursday/Friday increasing PW's again to the 2.3 range possibly bringing additional unsettled weather to our Region. I see some of the longer range Ensembles are suggesting the Upper Heat Ridge may breakdown further as we near the second full week of July.

[DoctorMu]

Friday morning briefing from Jeff regarding the 4th of July:

Typical summer weather in place over the region with hot and mostly dry conditions with an isolated 20% chance of an afternoon thunderstorm…this will continue for the next couple of days.

Changes appear on the horizon as we start the 4th of July week as vorticity over the SE US begins to dig SSW around the building of a large upper level high pressure system that will bring dangerous heat to the Midwest and NE US this weekend into early next week. Easterly mid and upper level flow will begin to develop along the US Gulf coast early next week on the southern side of the large high pressure cell over the Midwest to NE US. Active weather over the NE Gulf of Mexico is forecasted to begin to shift westward and arrive into SE TX by late Tuesday into Wednesday. This feature will likely consists of an upper level trough and a surge of tropical moisture. Confidence is starting to increase that the period from late Tuesday into Thursday of next week will feature active showers and thunderstorms and some of these storms may contain very heavy rainfall.

Note: the much talked about Saharan Dust will be starting to arrive across SE TX today and encompass the entire area on Saturday into Sunday. Most of this dust is elevated well above the surface…above 5,000 ft, but at times some of the particles can drift to the surface and cause some breathing irritations. Such outbreaks of dust have occurred in past summers resulting in a hazy look to the sky over the area for a few days.

The dust has definitely arrived. I'd be OK if the temp. was lowered, but not such luck,


GFS has a little less rain around the 4th, but we appear to stay underneath the Midwest ridge for another week with a series of retrograde impulses drifting westward over us and south/underneath that ridge. So potentially a week of on and off scattered showers.

We'll see. After 25 years+ in Texas the promise of summer rain in CLL meets with well-worn skepticism. Canadian, ICON, Ensemble also show chances of rain all along the Gulf cast from Florida to Texas from July 4-11, fwiw.

[srainhoutx]

Saturday morning briefing from Jeff:

Confidence continues to increase that rain chances will begin to rise on Tuesday and peak on Wednesday over the region.

An upper level trough will be developing over the NE Gulf of Mexico over the next few days under the southern flank of a very upper level high pressure cell over the Midwest and NE US. Tropical moisture with PWS of 2.0-2.5 inches will become entrained within this trough and both the moisture and the trough will begin to move westward this weekend into early next week. Global forecast models continue to indicate that moisture will begin to increase over SE TX on Tuesday and peak on Wednesday with expected PWS of 2.2-2.5 inches on July 4th. Rain chances will begin to increase Tuesday afternoon from the east and peak on Wednesday with the trough overhead or just to our west.

High moisture levels look to support very heavy rainfall during the period from late on July 3rd through July 4th. Convective trigger temperatures on the 4th will cool into the mid 80’s suggesting little to no heating will be required to produce showers and thunderstorms. The air mass becomes nearly saturated by late on the 3rd and into the 4th with rainfall production in showers and thunderstorms maximized. At this time, it is unclear when and where the greatest rains may occur. The models have been bouncing around within an area from Houston to Lufkin to Lake Charles to offshore the last few days. Based on the incoming air mass and extremely moist conditions high short duration rainfall rates of 2-3 inches in an hour will be possible on the 4th.

Overall 48 hour storm totals (3rd and 4th) will likely averaged 1-3 inches over the area with isolated totals of 5-6 inches in any areas of slow storm motions or cell training.

Residents are encouraged to continue to monitor forecasts for the middle of next week as rainfall amounts, timing and locations will likely change over the next few days.

[srainhoutx]

July begins as June ends with hot and dry weather the theme until Tuesday when the upper air pattern changes and rain returns to our sensible weather forecast for the remainder of the first full week of July.

Unfortunately there is a chance for showers and storms on the 4th of July, so have alternate plans ready for that cookout and possibly the area fireworks displays scheduled for Wednesday evening. The GFS is a bit quicker in moving the inverted trough currently seen in the NE Gulf of Mexico through the SE Texas Region possibly bringing the rain to an end before the fireworks displays start. On the other hand, the ECMWF is much slower and actually stronger with its 700/850/500mb vorticity lingering into Wednesday. The latest afternoon Updated 7 Day QPF charts suggest a general 1 to 3 inch amounts with isolated higher total of 4 to near 6 inches possible. The inverted trough passes leaving Thursday a bit drier, but short lived as the next Easterly Wave arrives moving from East to West beneath the Upper Ridge far enough to our North to bring additional rain chances. Rain chance could linger into next weekend as the Upper Ridge remains somewhat displaced far enough North.

A word of caution is probably needed in the coming week expected sensible weather forecast. It appears that there is enough volatility in the very high PW's near 2.5 inches which is in the 90th percentile for our area this time of year that mesoscale features will determine the final rainfall totals. The ECMWF has stayed the course of the last 4 days insisting a stronger vorticity at multiple levels may influence where the heaviest rain may fall. Areas from Lake Charles/Beaumont/Lufkin to Houston have repeatedly been the high precipitation target zones with several runs showing some locations receiving 7 to 10 inches. We'll continue to monitor throughout the rest of the weekend and into early next week, so check back daily and we'll do our best to provide the latest data for the busy 4th of July Holiday. Stay Tuned!

[DoctorMu]

Forecast is generally on track. Trough moves through on the 4th and 5th. Canadian is a little more aggressive about rainfall amounts than GFS (which has backtracked) or ensemble. ICON has a steeper grade with the coast inundated. Weakness persists under the ridge from the 4th to 11th with potential disturbances passing through and isolated/scattered showers.

Ridge may slide southward into Death Ridge position after the 12th per GFS. Ensemble not as sure. Hopefully not.

[DoctorMu]

Holiday rain even seems more modest at the moment. Canadian is still more aggressive than Euro or GFS. (FWIW, Canadian had a better handle on the last rain event). Movement of the ridge in the long-term seems less certain than yesterday.

Good news about the dust - it's beginning to clear away from the area. Yesterday was incredibly hazy, but didn't keep the temps down!

In the meantime, stay cool!

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1033 AM CDT Sun Jul 1 2018

.DISCUSSION...
Upper air analysis shows a strong ridge of high pressure over SE
TX. At 850 mb, a weak area of low pressure was noted over SE New
Mexico with a weak trough extending across the Big bend. Another
area of low pressure was noted over southern Alabama and it`s
this feature that will be heading west early next week and bring
SE TX some much needed rain. 12z soundings support high
temperatures in the mid and upper 90`s today. Moisture profiles
look very dry so not expecting any rain today. Previous forecast
has things covered nicely and other than tweaking some hourly
grids to match observations, no other changes were required.

The Galveston Beach Patrol has indicated that strong rip currents
remain an issue. A Rip Current Statement has been reissued for area
beaches through this evening. 43

&&

.CLIMATE...
June has come to a close and it was another very warm month.
Houston and Hou Hobby had their 6th warmest average June
temperature while Galveston had its 5th warmest June on record.
It was the monthly average low temperature that helped fuel the
warm monthly average. The average June low temperature was the
warmest on record for Houston, third warmest at Galveston, fourth
warmest at Hobby and fifth warmest at College Station. Looking
further back, the average temperature for the months of may and
June are now the warmest on record for Galveston and the 2nd
warmest on record for the city of Houston. A Public Information
Station with June climate information will be issued later today.
43


&&

.PREV DISCUSSION... /ISSUED 642 AM CDT Sun Jul 1 2018/

AVIATION...

Early morning MVFR ceilings at CLL will scatter and lift by mid-
morning, making way for mostly clear skies at all airports today.
A tight surface pressure gradient returns, allowing for some gusty
southerly winds from 17Z-01Z. Southerly winds today will cause
the sea breeze to arrive about an hour earlier at most TAF sites.
Rain chances remain negligible.

22

PREV DISCUSSION... /ISSUED 359 AM CDT Sun Jul 1 2018/

NEAR TERM [Through Today/Tonight]...

Temperatures will reach the mid to upper 90s as the upper level
ridge maintains its influence over our weather in Southeast Texas.
Dew points will once again peak in the mid 70s, bringing maximum
apparent temperatures of 103-107. Will monitor hourly trends
throughout the day to determine whether heat advisory criteria will
be met. Should dew points mix out as they have done the past several
days, we will likely fall just short of criteria.

Otherwise, the morning low level clouds will scatter out to mostly
clear skies this afternoon with occasionally gusty winds. As the
surface low pressure system over the Panhandles remains fairly
stationary, the surface pressure gradient will increase during the
afternoon, leading to wind gusts near 10-15 mph. Although rain
chances remain near zero, today will begin a gradual moistening of
the air mass as the African dust moves northeastward out of our
area. Precipitable water values increase from 1.1" this morning to
1.5" late tonight. According to NASA`s Global Modeling and
Assimilation Office, Galveston reached its peak particulate matter
content yesterday and today will be the peak for Houston. Expect
poor visibility at times and limit outside exposure for sensitive
groups.

22

LONG TERM [Monday Through Sunday]...

Upper air analysis at 500mb for 00Z shows lower heights over
Tallahassee FL at 588dm where models have been forecasting an
inverted trough to develop. Water vapor imagery also shows several
weak areas of vorticity trying to organize near this low. Upper
level ridge had taken shape over the Mid-Atlantic with a weaker
ridge over the NW Gulf. So going forward through the holiday week,
thunderstorm chances still exist for Independence Day.

So what has changed since last few model runs for Wednesday?
- Timing of the rainfall has changed. GFS/NAM and now to some
degree the ECMWF, have all shown thunderstorm activity starting
more Tuesday night/Wednesday morning and ending Wednesday night.
The Canadian is still slower and the ECMWF makes a nice
compromise between all solutions. Forecast leaned more the ECMWF
for timing of the thunderstorm activity. This also means that
firework shows may have a small chance of happening although
crowds may have to deal with wet conditions.
- Rainfall amounts have changed which is to be expected. GFS seems
to be on the same page as the last few runs with a general 1-2
inches. ECMWF has come in line with the GFS amounts and may have
backed off on the 4-6 inch amounts forecasted over E TX. But it
could very well bring that back depending upon now the inverted
trough evolves.

What are we still confident in for the forecast Wednesday?
- Still confident in the inverted trough coming over SE Texas
providing lift.
- Still confident in high precipitable water airmass moving into
the area (2-2.4 inches of PW).
- Confident in scattered to numerous thunderstorms caused by these
conditions - PoPs now 60-70%.
- Growing confidence in timing mentioned above.

What we do not have confidence in for the Wednesday forecast?
- Rainfall amounts - overall think 1-2 inches looks reasonable but
really unsure of any isolated higher amounts. There most likely
will be a few spots with 3-4 inches of rain. There is that
potential.
- Flooding impacts - not seeing really heavy rainfall to cause
flooding other than the typical street/urban flood situations.
But we have little confidence in the isolated higher amounts
which could cause impacts.
- Location of highest rainfall amounts - again models have been
not only all over the place with rainfall amounts but also where
those amounts occur.
- Strength of the inverted trough. Models have been showing
variability in how much vorticity develops with the trough.
With the trough still developing, suspect models are having a
hard time resolving/initializing the feature leading to
different forecasts for rainfall.

Thursday through next Sunday we will need to monitor how the
upper level pattern evolves because this will determine whether we
remain in a wet pattern. The upper level ridge over the Mid-
Atlantic expands and strengths through the middle of the U.S.
through the end of the week. Another inverted trough could reach
the area by Friday/Saturday but models are having more timing
issues with this system. The ridge slides back over the Rockies
for the weekend and a broad weakness in the flow develops from the
Great Lakes down the the Gulf Coast. This may hold up any troughs
riding underneath the ridge. For now the forecast will keep some
type of rain chances going with higher moisture lingering and the
lower upper level heights in place.

Overpeck

[DoctorMu]

Naturally, we should be skeptical of a bullseye (96 hour accumulation) exactly over NW Harris Co., but keep in mind there *could* be LOCALIZED heavy rain with the trough, but no reliable way to precisely predict where that might occur. The max amount of 4 - 4.5 in may be reasonable. Be prepared just in case.

[srainhoutx]

Not seeing much of a change regarding the sensible weather for Wednesday (July 4th into the end of next weekend. HGX has leaned on the slower ECMWF/Canadian solution as the steering flow is much weaker than the fast GFS solution suggests. It still appears High PW's around 2.35 inches, a fully saturated column and low convective temperature will set the stage for scattered to numerous showers/storms. The European and Canadian models hint at domes or pockets of very heavy rainfall, so still think 1 to 3 inches of rain for Wednesday looks reasonable with isolated higher amounts possible.

A brief respite from the rain may be possible on Thursday, but with the weakness in the upper ridge still present and no capping, heat of the showers/storms are possible. A second inverted trough arrives Friday again increasing the chance of widespread showers/storms and a 3rd Easterly wave arrives next Sunday keeping an active weather pattern ahead for the next 7 days.

[jasons2k]

My high today was 99F.

[srainhoutx]

Not seeing any significant changes in the sensible weather forecast tomorrow through next Sunday. Today will be the last dry day we likely will see this coming week and the Saharan Dust is lessening its grip as well. Rain chances increase throughout the day tomorrow from East in Louisiana to West into SE Texas as the inverted trough and its vorticity approaches. The WPC has issued a Marginal Risk for Excessive Rainfall tomorrow and again on Wednesday for our Region. A second inverted trough arrives Thursday into Friday with additional shower/storm chances with a 3rd on Saturday evening into Sunday.

[tireman4]

From Joe Bastardi

[Andrew]

I'm hoping/thinking that by late afternoon there will be enough of a break for a little bit of outdoor activities and even some fireworks at night. Hard to say with complete certainty though because any mesoscale features that setup could wreck havoc on that forecast.

[srainhoutx]

Monday afternoon briefing from Jeff:

An area of low pressure has formed overnight south of the Pensacola/Mobile area over the northern Gulf of Mexico. This is confirmed by both coastal observation sites, coastal radars, and offshore buoys/oil platforms indicating a broad counter clockwise wind field has formed. Land based radar show numerous showers and thunderstorms associated with this feature mainly offshore of the NE Gulf coast.

The National Hurricane Center on its most recent tropical weather outlook gives this feature a 10% chance of additional development before it moves inland over SE LA tonight into Tuesday.

This feature will continue to move westward and arrive into SE TX late Tuesday into Wednesday although that might be a bit fast given the current satellite and radar trends. Expect our currently very dry air mass to become rapidly saturated early on Wednesday with numerous showers and thunderstorms likely, especially in the region between Houston and Lake Charles. PWS surge to near 2.4 inches on Wednesday which will support a heavy rainfall threat.

Current rainfall amounts are expected to average 1-2 inches over the region with isolated much higher amounts. There is still some uncertainty as to where the greatest rainfall amounts may occur, although there has been some indication of the region between Houston and Lake Charles could see some of the heavier rainfall.

Note: Such weak “tropical lows” can become very effective rainfall producers, so it will be important to monitor the forecast over the next 36-48 hours for any changes.

A wet pattern will remain in place with an upper level high to our north resulting in easterly upper level flow over SE TX for the next several days post Wednesday. Tropical waves within this flow will result in good coverage of daily thunderstorms late this week into the weekend.

[wxman57]

Latest European model does indicate that the rain will be ending here around mid to late afternoon on the 4th. Perhaps the evening fireworks will go off as planned.

[unome]

changed to 0/0% over 2/5 days https://www.nhc.noaa.gov/

looking forward to rain, though

in other, happy news - WPC will soon have a secure website - yay !

Please note: On July 10, 2018, WPC's web site will switch from the "http" protocol to the more secure "https" protocol. Please consider changing any bookmarked pages at that time. We will provide an update if there is a delay in this transition.

[srainhoutx]

Tuesday morning briefing from Jeff:

Heavy rainfall will be possible this evening through Wednesday.

Weak surface low pressure over the northern Gulf of Mexico yesterday has moved inland over SE Louisiana this morning in association with a 500mb inverted trough moving westward along the central US Gulf coast. This feature will continue to move westward and arrive into SE TX late this afternoon and evening. Air mass is starting to moisten from the east this morning and expect this trend to continue today as moisture over the central and eastern Gulf coast states moves westward. PWS will rise to near 2.0 inches by late this afternoon and continue to increase to near 2.4 inches by Wednesday morning. Surface circulation will arrive into SE TX early Wednesday morning helping to concentrate showers and thunderstorms.

Expect a band of strong thunderstorms to develop over SW Louisiana later today and rotate WSW/SW toward SE TX this evening. Meso models show this band reaching the I-45 corridor this evening. This band will be moving into a very warm air mass with temperatures in the mid to upper 90’s and might support an isolated damaging wind threat along any leading outflow boundaries.

Surface low and 500mb trough axis will be overhead late tonight into Wednesday morning. Expect numerous showers and thunderstorms to develop near the center of the surface low late tonight into early Wednesday morning. Some models are indicating the focus of this activity will be around Galveston Bay and then spreading WNW and inland over SE TX early Wednesday morning. Air mass will become saturated by this time, so expect very heavy rainfall. Hourly rainfall rates of 2-3 inches will be possible with this activity.

Overall storm totals will average 1-3 inches over the region with the focus being around Galveston Bay. Isolated totals of 4-6 inches are certainly possible under any areas of cell training or sustained banding. Grounds have had a chance to dry out since the mid June rains and flash flood guidance is fairly high over the region…so think most areas will be able to handle the rainfall although some street flooding will be possible in the more urban areas. With that said these sort of “tropical lows” can produce very heavy rainfall near their center of circulation during the overnight hours and tonight/early Wednesday the circulation center will be somewhere between Houston and Lake Charles.

Extended:
Wet pattern remains in place through the weekend as the area remains in easterly upper level flow and tropical waves will approach and cross the region every 1-2 days enhancing rainfall. Sub-tropical high pressure will build over the western US and looks to remain far enough NW/W of the region to keep rain chances going for the next several days.

[jasons2k]

That line to the NE looks so healthy and juicy right now. Lots of lightning too.

Watch it spit out an outlflow and collapse right before it gets to me. Or some sort of weird split. Or skip. Wait for it....

[Cromagnum]

Lots of prime daytime heating left.

[Ounce]

Severe Thunderstorm Warning
TXC071-291-040100-
/O.NEW.KHGX.SV.W.0064.180703T2356Z-180704T0100Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Houston/Galveston TX
656 PM CDT TUE JUL 3 2018

The National Weather Service in League City has issued a

* Severe Thunderstorm Warning for...
Chambers County in southeastern Texas...
Southern Liberty County in southeastern Texas...

* Until 800 PM CDT.

* At 656 PM CDT, severe thunderstorms were located along a line
extending from Batson to near Stowell, moving southwest at 25 mph.

HAZARD...60 mph wind gusts and penny size hail.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
Liberty, Dayton, Beach City, Mont Belvieu, Anahuac, Old
River-Winfree, Ames, Daisetta, Hardin, Kenefick, Cove, Devers,
Dayton Lakes, Stowell, Oak Island, Hankamer, Moss Hill and
Wallisville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with these storms. Move indoors immediately.
Lightning is one of nature`s leading killers. Remember, if you can
hear thunder, you are close enough to be struck by lightning.

&&

LAT...LON 2966 9436 2960 9472 2966 9470 2975 9469
2975 9471 2974 9471 2979 9473 2979 9474
2976 9482 2972 9486 3021 9507 3029 9466
3011 9460 3011 9454
TIME...MOT...LOC 2356Z 050DEG 22KT 3022 9461 2978 9444

HAIL...0.75IN
WIND...60MPH

$$