July 2019: Warming Trend/Slight Chances For Rain

[LightningBolt]

North America also lacks a true monsoonal cycle/seasonal wind belt shift as seen with other continents like Asia, Africa, and Australia. As a result, the continent remains very much at the mercy of the westerly jet stream, and emanating extremes in weather from its meridonals: Texas summer drought, California winter drought, Central US spring floods, SE US summer floods, etc.

With a more consistent monsoon pattern like in other continents, Texas would have no issues getting summer rain. More consistent easterly disturbances at least. Or even equatorial southwesterlies if the shift is strong enough. At the same time, winters would be milder, more stable, without low pressure disturbances that drag down deep cold air from Canada.

Thanks for your analysis!

[tireman4]

000
FXUS64 KHGX 261130
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
630 AM CDT Fri Jul 26 2019

.AVIATION...
Weak moisture coupled with weak isentropic upglide will create
SCT/BKN deck this morning that will scatter out this afternoon.
VFR ceilings will be possible this morning. Clouds are expected to
thin this evening before another surge of moisture approaches
after 09z. A SCT/BKN deck will be possible near the coast between
09-12z and even a few showers could affect GLS by 12z.

&&

.PREV DISCUSSION... /ISSUED 412 AM CDT Fri Jul 26 2019/

SHORT TERM [Through Sunday]...
With about another 2-3 hours of cooling left, it appears that IAH
might reach a record low temperature this morning (68/1972).

Surface high pressure situated from the Eastern Seaboard into
Texas that has been maintaining our stretch of nice comfortable
July wx will be losing its grip across the area this weekend. Remnant
frontal boundary/trof offshore will be drifting northward back to
the coast and inland. Not expecting much, if any, inland precip
today as deeper moisture remains well off the coast. But as we head
into Saturday PW`s will climb back to around 1.3-1.5" and Sunday
1.8-2.0" so corresponding shra/tstm chances and coverage (mainly
diurnal in nature) will follow that upward trend.

LONG TERM [Sunday Night Through Friday]...
We should generally remain on the eastern periphery of a strong
mid/upper ridge centered over the sw states into early next week.
Though there will be some subsidence to overcome, isolated to
maybe scattered precip remains a possibility each day dependent on
moisture fluctuations. Guidance hints at a disturbance riding
down in the northerly flow aloft Tue/Tue night which will be
something to keep an eye on in regards precip chances. Otherwise,
the ridge makes a slow ene track into NM & western TX/OK as we
head into late next week. Heights don`t look to change all that
much locally...so it`ll probably just be a fcst of persistence as
we head into the month August. 47

MARINE...
A light to moderate northeast flow will become east this afternoon
and SE on Saturday as high pressure over the Ozark plateau moves to
the east. A light to moderate S-SE flow will then continue into
early next week with high pressure over the central Gulf of Mexico
and a weak trough of low pressure in the lee of the Rockies.
Scattered showers and thunderstorms will be possible this weekend as
a weak disturbance moves into the area. Water levels are expected to
remain below critical thresholds and a rip current statement will
not be needed today. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 93 72 94 74 94 / 0 0 10 0 20
Houston (IAH) 92 73 92 75 92 / 0 10 30 10 40
Galveston (GLS) 91 80 90 80 89 / 10 30 40 30 40

&&

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

$$

Discussion...47
Aviation/Marine...43

[tireman4]

Houston Forecast...

[tireman4]

00
FXUS64 KHGX 261731
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1231 PM CDT Fri Jul 26 2019

.AVIATION...

Mainly VFR cigs and visibilities continue through the duration of
the TAF period. Winds will remain out of the E/SE around 5-10 kts
through this evening before shifting more to the SE by tomorrow
morning. With increased moisture advection and the redevelopment
of a more typical summertime flow pattern, high-resolution
model guidence suggests that scattered SHRA/TSRA should form over
the coastal waters tomorrow morning around GLS, progressing
inland towards IAH and HOU by approximately 15Z.

Cady

[Cromagnum]

Some popup showers starting to appear. Maybe we get lucky

[DoctorMu]

Reality hits after 4 gorgeous days in TX in July. Unprecedented really.

The American monsoon doesn't have the source of moisture, temperature gradient, or lift (Tibetan plateau) that the Asian monsoon. Indian Ocean >> Gulf of California

That upper level ridge often extends to Texas and can park over interior regions. The Bermuda High pulls more Gulf moisture into Louisiana, MS, AL, GA than for us. The BH generates easterlies over Florida, where there's an afternoon shower a few days a week.

GoM - can't live with it, can't live without it. Without the Gulf, east Texas would be semi-arid to desert like much of the land at our latitude, not subject to the Asian monsoon.

[mckinne63]

Humidity back for sure. Can't get out of the car or walk out of the store without my glasses fogging up. The 4 days of gorgeous temps are but a memory. But, we have had worse July's. Thankful for air conditioning.

[Cromagnum]

Storming just to my north but not moving this way

[aunneste]

Loved the explanation. I’d rather take my chances at seeing cold weather. I hate Summer, but I’d really hate not having a Winter

Ah, that's fair enough.

[aunneste]

The American monsoon doesn't have the source of moisture, temperature gradient, or lift (Tibetan plateau) that the Asian monsoon. Indian Ocean >> Gulf of California

It's more a matter of lack of land at lower latitudes. Even Australia, a mostly low-elevation continent, still gets stronger monsoonal action than the Americas. The ITCZ just doesn't go poleward in the Americas as it does in the Eastern Hemisphere, the low latitude area is mostly water with slim strips of land.

That upper level ridge often extends to Texas and can park over interior regions. The Bermuda High pulls more Gulf moisture into Louisiana, MS, AL, GA than for us. The BH generates easterlies over Florida, where there's an afternoon shower a few days a week.

Due to the tendency for Eastern US troughing (which has increased since 2009, hence the US hurricane drought before Harvey), the height-fields are often pinched off into cells, the western of which is often in position to dry Texas out, through elevated dry air from the Rockies. It's not from subsidence, since the areas of Texas in the donut hole during dry spells often aren't where the strongest heights are.

There's obviously similar low-level moisture content in East Texas compared to the Southeast, given the similar high dewpoints/humidity. Texas can get continuous rain so long the high is more continuous longitudinally. The same wind shifts of the North American monsoon also bring rain to Gulf Coastal Mexico, moisture from which delivers heavy rains to Texas. So a stronger monsoon would actually benefit (southern) Texas with summer rainfall, while bringing more continuous rain to the SW desert lowlands/Gulf of California coast.

GoM - can't live with it, can't live without it. Without the Gulf, east Texas would be semi-arid to desert like much of the land at our latitude, not subject to the Asian monsoon.

There could actually be an even further shift of the ITZC northward without the Gulf, since there'd be much landmass at lower latitude. So even if East Texas becomes desert/semi-arid, it may at least come with stronger summer seasonality of rain. See: current parts of Desert SW, Sahel in Africa, Thar Desert of India, etc.

[Katdaddy]

A beautiful tropical sky this afternoon.

[jasons2k]

Yesterday I hit the jackpot. Had a tiny red spec on the radar parked on top my my house and rained itself out. I got a quick .50” of rain.

[mckinne63]

It's raining in Stafford! Woohoo! I saw the skies getting dark and the wind whipping up. Coming down at a good clip too.

[Rip76]

Radar is lit up this morning.

[Cromagnum]

On and off bursts of sideways rain down in Rosharon. Pretty good line moving off towards Alvin and Clear Lake.

[DoctorMu]

Aunneste - would you mind including links and supportive sites with your analyses?

We had a "10 year drought" in Texas. Enhances wind shear and dry air from Texas and Mexico are the mechanisms related to the hurricane "drought" cited by NOAA and from my remembrance. Areas of the SE were unfortunately not under a trough, but suffered rain drought, particularly Georgia.

https://www.weather.gov/bro/hurrprep

https://weather.com/safety/hurricane/ne ... august2016

[Katdaddy]

Picked up a quick well needed .60" of rain here in W League City.

[srainhoutx]

Nothing but a sprinkle in my backyard.

[unome]

we had a nice shower, but I looked at radar &thought, "Jason must be getting dumped on"

https://www.harriscountyfws.org/
https://www.harriscountyfws.org/GageDet ... v=rainfall
https://www.harriscountyfws.org/GageDet ... v=rainfall

some big discrepancies in short distances on the rain map, though

[aunneste]

Aunneste - would you mind including links and supportive sites with your analyses?

Monthly mean precipitation is modified mainly by convective inhibition (CIN) rather than by convective available potential energy (CAPE) or by precipitable water. Excessive CIN is caused by surface dryness and warming at 700 hPa, leading to precipitation deficits on a monthly time scale. While the dewpoint temperature and thermodynamics at the surface are greatly affected by the soil moisture, the temperature at 700 hPa was found to be statistically independent of the surface dewpoint temperature since the 700-hPa temperature represents free-atmospheric processes.
https://journals.ametsoc.org/doi/full/1 ... JCLI2946.1

Some of the results in this section merit further comment. First, subsidence is enhanced in Texas when the influx of diabatically heated particles is dominant, but the elevation of Tlt is caused by the latter rather than the former. This process has been ignored in the previous studies of the 1980 and 1998 droughts that strongly affected Texas. Anticyclonic circulations in the upper troposphere have been assumed to trigger drought by serving as a block to cyclonic activity from the Pacific by displacing storm tracks north of the United States–Canadian border and/or by reducing low-level moisture by interfering with the influx of moist air from the Gulf of Mexico into the Great Plains (Namias 1982). This study finds that anomalous circulations associated with the upper-tropospheric anticyclone induce increased transport of warm air from the elevated terrain into Texas, having a significant impact on initiating and maintaining warm season droughts in Texas by increasing CIN.
https://journals.ametsoc.org/doi/10.1175/2010JCLI2947.1

But it’s not only luck that has been saving our coastlines from major hurricane damage. Over the past 10 years, there has tended to be an area of stronger-than-normal low pressure over the East Coast at the mid-levels of the atmosphere (about 18,000-feet high) during hurricane season.

This is an important feature because the winds at these levels steer hurricanes and determine the final path they take. Winds around this low pressure area help to push storms toward the north where they are picked up by the jet stream and carried away from the United States and out to sea.
https://www.washingtonpost.com/news/cap ... 284bbe5b84

Studies have found that when the NAO is negative, as it is now (Figure 1, above), it can worsen an ongoing summer drought in South Texas. Overall, significantly different ridge/trough patterns develop over North America, depending on the combined phase of ENSO and the NAO. Specifically, winters with El Niño/NAO+ conditions feature positive height anomalies (ridging) over the Great Lakes region, while negative height anomalies troughing) occur from Alaska’s Aleutian Islands to the west coast of North America. This contrasts with the large-scale flow observed in El Niño/NAO– winters, which are characterized by ridging over the western third of North America. The NAO may be an important modulating feature on El Niño impacts in the southwestern United States, namely, variability of winter season precipitation totals.
https://www.weather.gov/bro/2009event_heatwavereasons