July 2017 - TS Emily West of Tampa

[Texaspirate11]

THE WX UPDATE:

A tornado warning is in effect until 4:30 p.m. for Liberty, Polk, San Jacinto, Grimes, Harris and Waller counties.

• An areal flood advisory is in effect until 4:45 p.m. for Grimes, Montgomery and Walker counties.

• An areal flood advisory is in effect until 5 p.m. for central Harris, Brazoria, Fort Bend and Galveston counties.

• A flood advisory is in effect until 5:45 p.m. for Polk, San Jacinto and Trinity counties..

[Katdaddy]

Tornado Warnings for S Central Grimes, NE Waller, NW Harris, S Central San Jacinto, NW Liberty, and S Central Polk Counties expired at 4:30PM.

A summary from both Special Weather Statements from the HOU-GAL NWS:

The storms which prompted the warnings have weakened and no longer appears capable of producing a tornado. Therefore the warnings will be allowed to expire. Strong winds between 30 and 35 miles per hour will still be possible with these storms.

[Katdaddy]

A tornado touched down in Polk County NE of Houston this afternoon:

4 WNW LIVINGSTON POLK TX 3073 9500 TORNADO WAS SPOTTED OFF OF 190 WEST OF LIVINGSTON. THERE WAS REPORTED DAMAGE TO STORAGE FACILITY ROOFS.

[srainhoutx]

Sunday morning briefing from Jeff:

Weakness between the SW US heat ridge and the Bermuda high over the central Atlantic continues across much of the US Gulf coast.

The result is near daily thunderstorms with some days, such as yesterday, seeing much better coverage than others when a weak disturbance is introduced. Morning observations suggest that the widespread activity on Saturday may have overturned the air mass with morning temperatures starting about 10 degrees cooler than yesterday. However, skies are clear and surface heating has commenced while offshore/near coastal activity has remained in that area this morning with local radars showing what appears to be a weak landbreeze and also the old remnant vorticity of TD #4 now approaching the mid TX coast. Position of the 500mb ridge axis over the central plains N of SE TX will help to keep a very moist and general convectively active pattern in place into the early part of the week. Lowest rain chances might actually be today as some slightly drier air is trying to build in from the NE, but radars over NE TX show showers and even a few thunderstorms in this region suggesting another weak disturbance may be approaching from our NE. Air mass will take some time to recover from the development on Saturday and expect temperatures will need to reach near 90 to begin to destabilize the low levels. Storms may also be fighting some residual subsidence from the Saturday disturbance so will cap rain chance in the 40-50% range for this afternoon.

Better rain chances will be possible on Monday as any subsidence is then gone and high moisture levels remain. Main threats both today and Monday will be very heavy rainfall and gusty winds with storms. Certainly could see 1-3 inches of rain in an hour or less, but totals much about that are not likely given the outflow from these slow moving cell undercutting their needed feed of moist air. Cannot rule out a wet microburst, but do not expect a repeat of the tornadic activity seen on Saturday from a few of the storms. Other threat will be frequent cloud to ground lightning…which can be dangerous…a person was struck and injured yesterday by lightning in northern Montgomery County.

Rain chances will gradually lower after Tuesday with a slightly more normal summer pattern of daily seabreeze storms. Upper ridge once again never really gains control over our area and is positioned northward over the plains instead of across TX which may keep us slightly more active than inactive for late July.

Position of the sub-tropical ridges this summer and weakness/trough along the US Gulf coast should be monitored closely as we move into August as long range models continue to forecast above average moisture profiles across the Caribbean Sea and Gulf of Mexico.

ATL 95L:

A weak area of low pressure in the central tropical Atlantic midway between Africa and the Caribbean Sea has a 40% chance of slow development over the next 5 days. The system appears to be embedded with the northern extent of the monsoon trough over the Atlantic Ocean as it moves generally W to WNW. Forecast models show little to any development with this feature, but showers and thunderstorms have increased some over the last 24 hours and overall conditions appear generally favorable for development with dry air located well NE of the area and light winds aloft.

[Electric Lizard]

What's the thinking re: the north central Texas storms making it as far south as western Washington County? This rain event has yielded less than .05" in the Greater Greenvine Metro Area.

[DoctorMu]

Late day t-storms popping up and sliding WSW across the Brazos Valley. I don't think they will reach Houston.

The seabreeze is kicking up from Bay city to League City







FXUS64 KHGX 161722
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1222 PM CDT Sun Jul 16 2017

.AVIATION...
A bit calmer than 24 hrs ago with two areas of convection, the
first of which is affecting the immediate coastline and KGLS and
KLBX. This area of precip is on the periphery of a very weak low
level circulation off the middle coast. A second area of
convection is well to the north and is moving SW and could affect
KCLL and KUTS later this afternoon. Most of the short term
guidance keeps this area of storms north of the Houston terminals.
Daytime heating could still trigger some isolated convection near
both KHOU and KIAH later today. Better rain chances are expected
on Monday with deeper mstr and the area will lie on the east side
of a weak inverted trough. Winds will remain light through the TAF
cycle except in and near storms. 43

&&

.PREV DISCUSSION... /ISSUED 1120 AM CDT Sun Jul 16 2017/

UPDATE...
All of this morning`s shower and storm activity has been focused
around western Gulf lower pressure. Ample early day sun to the
surface will likely allow for the inland development of afternoon
precipitation. Highest rainfall amounts should remain along and
south of the I-10 corridor with widely-scattered latter day
activity blossoming further north. A general height weakness...or
upper shear zone...positioned across the northern Gulf coastline
may not be an actual inverted trough but just enough to initiate
diurnal showers and thunderstorms...forming over the local waters
and then transitioning inland through the daytime hours. An unstable
profile by late morning as surface temperatures achieve the middle
80s with greater than 2 inch PWATs will keep at least 30-40 daytime
POPs in place over the next several days. Diurnal temperatures
should parallel the climo curve with generally no more than a
three degree fluctuation. The only caveats will be possible early
morning patchy fog development over more open (rural) expanses
and maximum afternoon heat indices briefly touching 103 to 107 F
from around 2 through 5 PM. 31

PREV DISCUSSION... /ISSUED 410 AM CDT Sun Jul 16 2017/

DISCUSSION...
The 3AM observations across SE TX are very different from 24 hours
ago. Temperatures are a rain cooled low/mid 70s with Galveston the
warm spot at 78F. There is still no wind but the rain cooled air
has allowed for fog to develop across the area. The good thing is
that you can walk outside the office and not suffocate from the
moisture. Radar shows showers and a few thunderstorms off the
Upper Texas Coast where the airmass remains moist and unstable.

Upper level analysis at 500mb still shows upper level ridge over
the Rockies with troughing through the Great Lakes. Water vapor
imagery shows an elongated shear axis and weakness in the ridge
over the Miss River Valley stretching back towards the Texas Gulf
coast. Yesterday`s vorticity maximum that was over the Mid-South
ended up being more potent than forecast and continues to linger
over the Texas Gulf coast. This feature may still play a role in
today`s forecast but lift may not be as strong.

GOES 16 precipitable water derived imagery shows a broad area of 2
inches or more and the LCH 00Z sounding had 2.2 inches of
precipitable water. Based on the 00Z LCH sounding and model
soundings across the area, convective temperatures should again be
in the low/mid 80s with moist adiabatic lapse rates supporting
very talk and skinny CAPE. Yesterday`s vorticity maximum helped
provide stronger upper level wind so storm motions were to the SW
at a decent speed. While an easterly wind profile is expected,
wind speeds are 10-15 knots with downshear Corfidi vectors at 9
knots. Outflows may be the saving grace to keep storms moving
today and limit the flooding threat. Any storms that form today
will again produce high hourly rain rates and gusty winds. Given
these conditions, the forecast will go with 50 to 60 PoPs along
the coast and 40 PoP for the northern third of the area. Rainfall
amounts will again be in the 1 to 3 inch range but again not
everyone will observe those kinds of rain amounts.

Monday and Tuesday look for the moist airmass to linger over the
region support more thunderstorm chances. The upper level ridge
does build over the Plains over this time but think any subsidence
will remain north of the region. There may also be another piece
of vorticity to move over the region in this time frame to aid in
thunderstorm activity.

Precipitable water values finally drop below 2 inches Wednesday
through the rest of the work week but there still may be enough
moisture to support isolated thunderstorm coverage. The upper
level ridge does expand into the region for the end of the week so
the models may be over doing rain chances for the end of the week.
Still there enough confidence to keep 20-30 PoPs in the forecast.
For the end of the week Thursday into Friday there is a piece of
vorticity that shears off along the Atlantic coast and retrogrades
under the ridge across the northern Gulf through Saturday. So
higher rain chances may be needed Saturday should this system
garner a bit more moisture and if the ridge remains north or
northeast of the area.

[jasons2k]

I'm watching this outflow boundary moving through Walker County and into Montgomery County, to see if anything can get going on the outflows. It may collide with the sea breeze later on too.

[DoctorMu]

What's the thinking re: the north central Texas storms making it as far south as western Washington County? This rain event has yielded less than .05" in the Greater Greenvine Metro Area.

Not sure - you'll get an outflow boundary for sure. Skeptical, but it could be close

[jasons2k]

Yeah, so far nothing and the cumulus clouds are evaporating. Subsidence wins today. Still looking up towards Lake Livingston, just in case, but it will probably fall apart.

[Texaspirate11]

Nary a drop in Galveston.

[jasons2k]

hmmm, a couple of spots of convection are appearing now - you just never know.

[Katdaddy]

Another day with isolated showers and thunderstorms across SE TX. Current radar shows scattered showers and thunderstorms offshore that will translate inland with the daytime heating.

[srainhoutx]

SPECIAL WEATHER STATEMENT
National Weather Service HOUSTON/GALVESTON TX
910 AM CDT Tue Jul 18 2017

TXZ199-200-210>214-226-227-235>238-181800-
Montgomery-Liberty-Colorado-Austin-Waller-Harris-Chambers-Wharton-
Fort Bend-Jackson-Matagorda-Brazoria-Galveston-
Including the cities of The Woodlands, Conroe, Willis, Liberty,
Cleveland, Dayton, Columbus, Eagle Lake, Weimar, Sealy,
Bellville, Hempstead, Prairie View, Brookshire, Houston,
Pasadena, Katy, Tomball, Humble, Winnie, Mont Belvieu, Anahuac,
El Campo, Wharton, Pierce, Sugar Land, Missouri City, Richmond,
Rosenberg, Edna, Bay City, Palacios, Pearland, Lake Jackson,
Alvin, Angleton, Freeport, League City, Texas City, Friendswood,
and Galveston
910 AM CDT Tue Jul 18 2017

...FUNNEL CLOUDS POSSIBLE THROUGH THE EARLY AFTERNOON...

VERY MOIST AND BOUYANT AIR COUPLED WITH NUMEROUS LOW LEVEL
BOUNDARIES WILL PRODUCE A FAVORABLE ENVIRONMENT FOR BRIEF FUNNEL
CLOUDS AND POSSIBLE WATERSPOUTS. THESE FEATURES WILL BE SHORT
LIVED AND DIFFICULT TO DETECT ON RADAR. OCCASIONALLY THESE FUNNEL
CLOUDS EXTEND TO THE GROUND AND BECOME WEAK TORNADOES.

Monitor NOAA Weather Radio for the latest information...forecasts
and warnings.

[DoctorMu]

Gulf moisture and elongated trough could trigger t-storms this afternoon - is showers are already getting cranked. Chance of rain could be higher than yesterday IMO. We'll see.

OK ridge builds later in the week and we stay on the fringe, reducing chances to isolated and near the coast. Stay cool and hydrated. I've almost forgotten what a "normal" summer is like in SE Texas and the Brazos Valley - we haven't had one in awhile. Sprinklers on stun.




Area Forecast Discussion
National Weather Service Houston/Galveston TX
950 AM CDT Tue Jul 18 2017

.DISCUSSION...
Thunderstorms were occurring mainly along and south of a weak
surface trough and east of Galveston. Satellite PWs were near 2
inches over most of the central and coastal counties. The
surrounding 12Z soundings were uncapped as well. Expect the
convection to work its way inland throughout the day. A model
consensus then shows the coverage to diminish with sunset.

40

&&

.PREV DISCUSSION... /ISSUED 639 AM CDT Tue Jul 18 2017/

AVIATION...
SHRA/TSRA are developing in and around Galveston Bay and also near
the coast, so have included mainly VCSH to start out the 12Z TAFs
in that area. Expect activity to develop further inland during the
day today, so have included VCTS at some sites near the coast this
morning and inland TAF sites this afternoon. Light winds this
morning become SE and S this afternoon, all expected to increase
to around 5 to 10 knots. VFR outside of the rain areas and
MVFR/IFR near the storms. 42

PREV DISCUSSION... /ISSUED 426 AM CDT Tue Jul 18 2017/

DISCUSSION...
Weather will be very typical of mid to late July for the next
several days, with high temperatures near average in the 90s and
lows in the lower to middle 70s. Heat indices will be easily above
100 and many locations look to see max values above 105 if the
current forecast holds deep into the week, so trends there will
need to be watched in the coming days. Scattered showers and
thunderstorms can be expected each day before dissipating in the
evening as the sun goes down. Though convection will be possible
area-wide, especially today, the best potential will be along and
near the incoming seabreeze each afternoon. Seemingly as always,
localized heavy rainfall and potential flooding issues may crop up
with the strongest shower/storm cells for at least the next couple
of days.

NEAR TERM [Through Today]...

Water vapor imagery shows an amplified, but narrow upper trough
focused in far southern Quebec, but with impacts snaking down the
Appalachians, then southwesterly into Texas. Though the Euro puts
the trough axis just south of us, theoretically giving all of
Southeast Texas potential for subsidence, WV imagery really shows
substantial impact ending around the northern edge of our area of
responsibility. Indeed, using the "multi-layer" WV imagery from
GOES-16, this pattern largely seems to hold at all three levels
G-16 samples. For this reason, I`ve tried to keep a relatively
tight PoP gradient around this boundary, with higher precip
potential south of the line than north of it. In other words, to
carry my mid-shift predecessor`s words forward, your odds of
hitting the lotto jackpot will be higher farther south towards the
seabreeze. Storm motion doesn`t look...quite...as bad as it has
recently, and model soundings do show a bit of a dry spot around
500 mb, which may help mitigate heavy rain potential. Despite
that, we`re still looking at relatively slow movers and heaps of
CAPE with a generally saturated profile, so I would still expect
that if you get the wrong cell over the wrong spot, heavy hourly
rain rates could cause some very localized flooding issues. Additionally,
I`ve allowed temperatures farther north where subsidence could be
expected to have a greater impact to drift into the middle 90s,
while the rest of the area stays in the lower 90s.

SHORT TERM [Tonight Through Thursday]...

As you`d probably expect this time of year, look for any rain to
wind itself down through the evening as the sun goes down, with
shower and storm potential shifting offshore overnight with the
slower to cool waters holding onto some of the heat of the day.

Tomorrow looks pretty similar to today, but would focus even more
on the seabreeze for the best rain chances, as high pressure
aloft builds stronger over Oklahoma, and heights corresponding
rise over our area. This should be the start of rain chances
gradually clamping down towards the late week. This also means we
should probably look for modestly warmer temperatures, and heat
indices look to push into the 103-108 range.

LONG TERM [Thursday Night Through Tuesday]...

Through the rest of the workweek, we should look for that ridge
aloft to peak in strength, but then begin to moderate some. 850
flow also begins to modestly veer a little towards southwesterly.
In general, you`d think things would start to dry out in the
scenario, and to some extent, the forecast indicates this.
However, the GFS and the Euro both to some extent cut off a chunk
of vorticity from the upper trough mentioned up top and drag it
back over Texas along the edge of this ridge (more the GFS than
Euro). This will likely keep midlevel heights from rising quite
as high, and dampen subsidence aloft. Because of this, I`m loath
to go totally dry, but continuing to focus the best chances right
on the seabreeze boundary as I gradually taper PoPs down.

Another thing I`ve got my eye on going into the weekend will be
yet another pinched off vort max from this trough - this time off
the Georgia coast, will move back into the northern Gulf. The GFS
is similarly much more enamored of this blob of vorticity than
the Euro, but both show the feature in some way or another. Key
thing to remember: neither model does a whole lot with it other
than drag it across the northeast Gulf coast, and enhance shower
potential in that area. But, I`m also not going to completely
trust midlevel vorticity hanging out over the Gulf in July with
only some modest shear, so I`ll watch things so you don`t have to.
Likely there will be little worth mentioning anyway.

[DoctorMu]

The Yin and Yang of mid-summer...


Area Forecast Discussion
National Weather Service Houston/Galveston TX
315 PM CDT Tue Jul 18 2017

.DISCUSSION...
The convection which occurred over areas along and south of the
I-10 corridor earlier today has diminished. Scattered showers and
thunderstorms were occurring along the northward and westward
moving outflow boundaries at 3:00 PM. Tweaked the rain chances
for the southwestern and northern counties for the rest of this
afternoon to account for these ongoing storms. Could see an
isolated shower or thunderstorm to redevelop to the south and
southeast but with the cirrus shield overhead think these will be
limited.

The deep layer weak trough overhead of SE Texas will likely linger
overhead one more day before the deep layer upper level ridge in
the Plains edges southward. This pattern should lead to slightly
warmer temperatures and less rain chances. On both Wednesday and
thursday the maximum heat indices could reach into the 105 to 107
for a lot of locations with some isolated locations reaching 108.
Do think that the best chances for rain will be on Wednesday;
however, enough moisture will linger overhead to keep daily shower
and thunderstorm chances in place for Thursday and Friday. By
Saturday the general upper level troughiness over the Atlantic
Region will again extend into the Upper Texas coastal areas. Both
the GFS and ECMWF show a 500 mb low pressure area over the Mid
Atlantic moving southwestward into at least the lower Mississippi
Valley during the weekend. Both models differ on the evolution of
this system early next week but both show the weak trough again
developing either overhead SE Texas or near the Upper Texas coast.
For this reason, kept daily chances for showers and thunderstorms
in place for most areas through Tuesday.

[srainhoutx]

The newest Upgraded version of the GFS will be operational and available today with the 12Z run. Stay Hydrated over the next several days. Heat Indices could push 108F in some locales.

[tireman4]

000
FXUS64 KHGX 191720
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1220 PM CDT Wed Jul 19 2017

.AVIATION...
Satellite & radar pix show some sct precip developing along the
seabreeze/baybreeze. This activity should gradually make its way
inland this afternoon then die off with the loss of heating.
Forecast soundings do show a bit of an inverted-v this afternoon
indicative of the potential for some decent wind gusts should any
strong cells manage to develop overhead. Otherwise, continued VFR
overnight with a landbreeze developing toward morning.
Rinse/repeat on Thurs. 47

&&

.PREV DISCUSSION... /ISSUED 1012 AM CDT Wed Jul 19 2017/
Deep layer weak east-to-west trough was still located over the
coastal areas at mid morning. The upper level ridge has drifted
southward a bit as compared to yesterday and the PW field has
drifted southward in response. Satellite derived PWs are in line
with the area 12Z soundings: 2 to 2.1 inches along the coastal
counties; 1.8 inches over the central counties; and 1.6 over the
northern areas. MUCAPE values range from 3500 near the coast to
2500 over the northern areas. Liked how the high resolution models
keep the best chances along and off the coast this morning with
isolated to scattered coverage mainly from the central areas
southeastward this afternoon. Tweaked the forecast rain chances
and temperatures to account for the latest model trends. 40

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 98 76 98 76 98 / 10 20 10 10 10
Houston (IAH) 95 77 95 77 94 / 30 10 30 10 30
Galveston (GLS) 90 81 90 82 89 / 20 10 20 10 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.

&&

$$

[DoctorMu]

The Death Ridge is lurking now at our doorstep in CLL...with a heat index of 106°F. It's grip should ease on Friday. Isolated showers and sea breeze continue for HOU.

Could use more rain...but could be worse. Maybe a shower this weekend, if we're lucky...


Area Forecast Discussion
National Weather Service Houston/Galveston TX
Issued by National Weather Service LAKE CHARLES LA
248 PM CDT Wed Jul 19 2017

.DISCUSSION...
Seabreeze & baybreeze boundaries helped to trigger a few showers
and thunderstorms this morning and afternoon with resulting storm
outflows continuing to push the activity a little further inland.
Higher pressure aloft across our northern zones helped to dampen
development except for an isolated shower or thunderstorm.
Temperatures this afternoon manage to get up into the low 90s
along the coast to the mid 90s across our inland zones.

Most of this afternoon convection should begin to dissipate with loss
of daytime heating around 7 pm. Any remaining isolated shower or
thunderstorm should be gone by midnight.

Looking at the big picture...a large dome of high pressure centered
across the central United States was allowing temperatures to
soar up into the low to mid 100`s across northern Nebraska with
strong subsidence resulting in no chance of rain to cool those
unfortunate souls off. Our county warning areas is on the fringe
of the high pressure ridge spreading across our northern areas. We
do expect to see the high pressure ridge sinking a little further
south on Thursday which may limit thunderstorm activity
especially across northern areas. Heat Indices are expected to
rise tomorrow starting by mid morning at 100 degree in some
locations and climbing into the 105 to near 108 heat indices
between 3 and 4 pm. While the criteria is not met for heat
advisory or heat warning...those folks venturing or working
outside should drink plenty of water and seek shelter inside a
cool room so that the body can cool down. Be cool folks...stay
cool and hydrated!

The upper level dome of high pressure will move east on Friday which
should allow for lower pressure aloft and therefore likely to see
a slow increase in thunderstorm activity Friday and Saturday and
again Sunday especially across our eastern zones where a weak east
to west upper level disturbance is expected to trigger a few more
storms Sunday.

As we enter into next week...expect Monday and Tuesday to be a little
active as the upper level high pressure builds back into area. By
mid week though...could see some additional storms develop as
southeast Texas will be between high pressure to the northwest and
southeast putting us in a weak area of low pressure.

So...in general warm days in the mid to upper 90s and lows in the
mid to upper 70s will prevail. Rain chances are near normal to
perhaps slightly above normal through the 7 day forecast. Heat
Indices will generally hit the century mark by 10 am across parts
of the area each day accelerating into the 105 to 108 degrees
range by maximum heating time between 3 and 4 pm. Heat Indices
will be slow to fall not reaching below 100 most areas until about
8 pm each day. Summer appears to be more of the normal from here
on out except for brief reprieve from seabreeze/baybreeze activity
each day.

[Katdaddy]

Another hot and humid SE TX day with isolated scattered tropical showers and thunderstorms. The heat index will be running between 104F and 107F as well today.

[brooksgarner]

With the death ridge tightening its grip next week, alllllllll we need is a slight southwest component or a loosening of the southeast onshore gradient to pump the first 100° temps in Houston. Are we rooting for that? haha