May 2015 Record Setting May Rainfall Totals For Region

[srainhoutx]

Morning briefing from Jeff:

Significant Severe Weather/Tornado Outbreak:

Factors are coming together for a major severe weather and tornado outbreak across the southern and central plains on Saturday. Main threat region will extend from NC TX to KS. Intense supercell thunderstorms are forecasted to develop Saturday afternoon along a dry line over W OK into NC TX and move ENE Saturday evening. Wind profiles strongly support tornadic supercells with the potential for large long tracked life threatening tornadoes. This will likely be a significant tornado outbreak for OK, KS, and possibly N TX.

Day 2 (Saturday) Severe Weather Outlook:

Sub-tropical storm Ana:

The low pressure system off the SE US coast has acquired enough organization to be classified as a sub-tropical storm and advisories were initiated on the system at 1000pm last night. Overall Ana is lacking much deep convection near its center and drifting (1-2mph) toward the north this morning roughly 170 miles off the Carolinas. While the overall health of the system is not that great, for an early May tropical system it is holding its own this morning.

Ana is in a very weak steering flow within a blocked upper air pattern over the US. This blocking should begin to break down over the weekend allowing the system to gradually move toward the NNW and N and approach/landfall on the SC/NC coasts. There is fairly good agreement on this track reasoning in an otherwise poor steering flow.

Ana is not fully tropical in nature (hence the sub-tropical naming). Without going into great detail on the why behind the tropical versus sub-tropical classifications…the point is that the system will be approaching the coast with gusty winds and heavy rainfall over the weekend. The intensity forecast is slightly more problematic since tropical and sub-tropical system gain their strength from different sources. Ana is sitting over the warm Gulf stream waters and this could allow for more intensification if the system was more tropical in nature…however dry air continues to wrap into the center from the W and SW and this is preventing sustained convection within the inner core region. Overall only slight intensification if any is expected before Ana reaches the coast.

Note: a tropical storm warning may be required later today for portions of the SC/NC coasts.

05082015 Jeff 2 unnamed.gif (43.18 KiB) Viewed 5896 times

Next Week:
Active weather to our west and north has largely missed SE TX over the last several days, but this will change late in the weekend into much of next week. The large upper level storm system currently over CA will slide into the SW US and then into the southern plains early next week. This will push a slow moving frontal boundary into SE TX while at the same time copious moisture surges into the region from the Caribbean Sea. Numerous disturbances will begin to cross the area as early as late Sunday and mid level capping gradually erodes with cooling of the middle levels. A very wet and stormy period appears likely Monday-Wednesday of next week and possibly the entire week. Flooding rainfall appears the primary threat given PWS of 1.8 inches although the severe threat is also present. Possibly a return of our late April active weather pattern by early next week.


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[snowman65]

You can have it all....My trees are doing just fine as well as my grass....take it, please! ...lol

I'll take it. The trees are still under stress and recovering from the drought. Some of the pines are still going through cycles of bursting new needles with rain and them dropping them. There are still a lot in a slow decline cycle and are just now dying off.

Eric Berger's blog (it was either last Monday or the one before) had a writeup about the rain so far this year. Even with all the perceived wetness we are very close to normal. We just forgot what Houston climate is supposed to be like. And all this is with the help of El Niño. It's a little concerning about what lies ahead for us when this El Niño cycle is over. Enjoy the moisture and lack of water restrictions while we have it.

[niner21]

There's no way this is average.

I didn't research it much but it looks to me like April was 2 times as wet as the average. The forecast on the weather channel ap had shown 80% EVERY DAY for about 2 weeks. We have trees falling over because the ground is soooooo wet up here. There's no way we need it, the ground is saturated. They've let water out of lake Conroe 5-6 times already this year.

Like the snowman said, you can have all my rain. Enjoy.

[texoz]

The Central Texas lakes still need A LOT of water. Here in Austin we're above average for the year, but storms have been missing the area 50-200 miles northwest of here where the watersheds are for the highland lakes. Current precip forecasts look somewhat favorable for that region, but the bullseye is farther northeast.

[srainhoutx]

The latest 12Z GFS and the Weather Prediction Center Extended Range Update continues to suggest a very active weather pattern developing across our Region. Stay Tuned. Rainfall amounts could lead to future Flood Watches being hoisted.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 AM EDT FRI MAY 08 2015

VALID 12Z MON MAY 11 2015 - 12Z FRI MAY 15 2015

...SUBTROPICAL STORM 'ANA' TO IMPACT THE CAROLINAS...
...LARGE RAINFALL AMOUNTS LIKELY ACROSS THE WESTERN GULF
COAST/SOUTH TEXAS...

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
WEST COAST--
HE 8/00Z DETERMINISTIC GUIDANCE HAS INSUFFICIENT AGREEMENT HEADING
INTO THE DAY 4-5 PERIOD. THE CHALLENGE REMAINS TO BE---THE ENTRY
POINT OF THE 500MB CIRCULATION---AND EXPECT TO MAINTAIN AN
ECENS/NAEFS/GEFS APPROACH IN A 50/30/20 BLEND RATIO UNTIL THE
TRANSFER OF PACIFIC ENERGY INLAND (EASTWARD) TO THE NORTHERN
ROCKIES/NORTHERN GREAT BASIN CAN COME IN TO BETTER FOCUS. AT THE
VERY LEAST...THE ENSEMBLES AND THEIR MEANS CAPTURE THE CLOSED
UPPER-LEVEL HIGH FEATURE (PREDOMINANT SOLUTION CLUSTER) OVER
NORTHERN ALBERTA AND A SERIES OF MID-LEVEL WAVES IN A BROAD
NORTHWESTERLY FLOW PATTERN ORIGINATING IN THE GULF OF ALASKA.

THE CENTRAL PLAINS...MIDWEST AND THE ST LAWRENCE VALLEY CYCLONE--
COULD GET AWAY WITH USING ASPECTS OF THE 8/00Z DETERMINISTIC
UKMET/ECMWF FOR DAY 3 TO DAY 4 (11/12Z TO 12/12Z) IF A DEEPER
SURFACE SOLUTION OVER QUEBEC IS PREFERRED. THIS SHOULD NOT RAISE
MANY ISSUES---AS THE MEANS DO MAINTAIN A FLATTER...WESTERLY FLOW
ALOFT OVER NEW ENGLAND---AND CARRY REMNANTS OF 'ANA' OUT TO SEA
WITHOUT MUCH FANFARE.

SOUTHERN PLAINS--
A RETURN FLOW FROM THE WESTERN GULF (A SOUTHEASTERLY UPSLOPE WIND
COMPONENT INLAND) WILL GRADUALLY BROADEN---AND COUPLED WITH AN
'OVER-RUNNING TYPE MID-LEVEL PACIFIC FLOW PATTERN---SHOULD
GENERATE A RE-OCCURRING SCENARIO FOR SLOW-MOVING DIURNAL
CONVECTION ALONG THE DECAYING COLD FRONT.

UPPER-LEVEL DISTURBANCE ALONG THE SOUTHEAST COAST ('ANA')--8/00Z
GUIDANCE WAS CONSISTENT AND STABLE REGARDING THE SYSTEM'S
'MEANDERING' PROGRESSION TOWARDS THE CAROLINAS. THE SYNOPTIC-SCALE
FORECAST PHILOSOPHY REMAINS UNCHANGED AND THE ENSEMBLE MEANS HAVE
HAD A DECENT HANDLE ON THE PATTERN FOR 3 DAYS RUNNING.
PLEASE REFER TO THE NHC FOR THE LATEST INFORMATION CONCERNING THIS
SYSTEM.

...SENSIBLE WEATHER HIGHLIGHTS...
PRECIPITATION AND COOL NORTHEAST ONSHORE FLOW INFLUENCE ALONG THE
MID-ATLANTIC COAST WILL BE THE KEY FEATURES OF THE PATTERN---IN
ASSOCIATION WITH SUB-TS 'ANA'.

WELL-ABOVE NORMAL RAINFALL IS EXPECTED FOR SOUTH AND SOUTHEAST
TEXAS AND THE LOWER MISSISSIPPI VALLEY IN ASSOCIATION WITH A
DECAYING COLD FRONT...OVER-RUNNING WESTERN GULF MOISTURE AND
SLOW-MOVING DIURNAL CONVECTION.
VOJTESAK

[srainhoutx]

The 12Z European also suggests additional shortwaves and potentially yet another closed core upper low drops into the Great Basin next week with a stationary frontal boundary draped across the Southern half of Texas. The pattern next week shows no indications of relaxing through at least Thursday into Friday...if then.

[srainhoutx]

It looks like a fairly healthy upper air disturbance is heading ENE out of Mexico. Showers and isolated stronger storms are firing across portions of S Central Texas generally headed toward SE Texas this afternoon.

[srainhoutx]

The overnight guidance continues to suggest our Region is heading toward a multi-day heavy rainfall event that could last into next weekend. The much talked about blocking pattern of a Ridge to the East and a trough to our West creates a pattern conducive for deep tropical moisture to stream N from the Western Caribbean into the Western Gulf then inland over Texas. This synoptic pattern appears stuck and should linger into at least next Saturday...possibly longer.

The very cold core upper low to our West that has been responsible for the Severe Weather Outbreak this week should eventually lift NE into the Central Plains by Monday. The Storm Prediction Center has outlined an Enhanced Risk for Severe Storms Sunday across portions of East Texas into Arkansas and a Slight Risk for Severe Storms on Monday across portions of Central and SE Texas extending NE into Louisiana and the Mississippi River Valley. What Central and SE Texas has been missing as a 'trigger' or a focal point for generating enough lift for storm development will be present Sunday well into next week. A stalling frontal boundary somewhere near or just N of the I-10 Corridor will be the culprit for an extended period of heavy rainfall. The upper ridge that eventually will turn Ana NE after making landfall along the Carolinas looks to build while the next in a series of upper lows drop SE from the Gulf of Alaska into the Great Basin allowing the very pesky upper trough to remain entrenched from Northern Mexico into the Great Plains. Embedded disturbances both from the Eastern Pacific and the Gulf of Alaska look to continue dropping into the base of the upper trough and stream ENE across Mexico into Texas next week. PW's steadily increase to near or above 2 inches which is about 2 and half Standard Deviation above normal for this time of year, appears locked in place across at least the Southern half of Texas into late next week.

Embedded disturbances are suggested by all available computer models throughout next week, but are extremely difficult to forecast beyond 6 to 12 hours in advance. The upcoming pattern will be mesoscale driven, so expect a lot of day to day changes on exactly who and where the greatest threat for heavy rainfall could occur. The overnight QPF guidance suggests a large area of 10 inch rainfall amounts with some isolated totals approaching15+ inches potential through next Friday, but has shifted both East and West the past several cycles as the guidance attempts to resolve this very complicated pattern. Strong to severe storms are possible developing across the Sierra Madre mountains of Mexico and spreading ENE from the Rio Grande Valley on into Central and SE Texas almost daily next week. It does appear that the Hill Country Lakes could see some significant replenishment during the week as both upstream flooding from very heavy rainfall late this week moves down stream and very heavy possibly training storms develop this coming week across the Region. I urge those of you that are weather savoy to advise those that may not be so weather wise to pay attention to the weather during the next several days into next week. Stay Tuned!

[srainhoutx]

Briefing from Jeff last evening:

Potentially prolonged excessive rainfall event for a large part of TX next week.

Factors will be coming together over the weekend to produce several days of excessive rainfall across a large part of TX starting on Sunday and lasting through almost all of next week. Potential for river flooding and flash flooding is increasingly possible.

A slow moving and strong upper level storm system will settle into the SW US over the weekend while a strong fetch of southeasterly winds begins to bring deep tropical moisture from the Caribbean Sea NW across the Gulf of Mexico and into TX by late Sunday. Upper level flow aloft will become increasingly SW over time allowing jet stream disturbances to ride across the region starting on Sunday and lasting all next week. Most important a slow moving/stalling front boundary will enter into the picture Monday and linger across the region much of next week interacting with the copious moisture in place and the disturbances aloft.

Expect numerous rounds of excessive rainfall starting as early as late Sunday, but most likely on Monday and lasting through all next week. Will not attempt at this point to indicate any time period for better rainfall production over another at this range. I am concerned with some of the model guidance attempting to develop a 850mb circulation over SC/C TX around Wednesday which would likely be somewhat warm core and behave like a tropical system in such a tropical air mass. Such systems in the past have produced “incredible” rainfall amounts and some of the most devastating floods in the past.

Total rainfall amounts from Sunday-next Friday will likely average 4-5 inches over much of SE/SC/C TX with isolated totals of 10-15 inches possible.

Hydro:
Grounds are already soggy over much of the state east of I-35 and several river systems are elevated from recent rainfall…especially the Brazos and Trinity. Forecasted rainfall next week along with the widespread nature on top of saturated grounds and elevated rivers is cause for concern. Such forecasted rainfall amounts on near normal flow conditions would likely result in rises to flood stage, so a very close watch on area rivers and watersheds will be needed next week.

Rainfall rates will be potentially excessive in the short term with PWS surging to 1.8 inches or greater early next week. Could easily see 2-4 inches per hour or even greater in slow moving/training convection leading to rapid flash flooding across C TX and in urban areas.

Of all the forecasted rainfall events this spring (and there have been several) this one has me the most concerned due to the stalling frontal boundary and deep tropical moisture suggesting repeat rounds of excessive rainfall.

7-Day Forecasted Rainfall Totals (QPF):

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[srainhoutx]

Morning briefing from Jeff:

Heavy Rainfall Event increasingly likely next week.

Factors, including a slow moving/stalling cool front/surface trough, deep tropical moisture from both the Pacific and Caribbean Sea, and a slow moving upper level storm system, point to a very active period of weather from late Sunday-Friday of next week.

Moisture levels greatly increase Sunday into Monday as a slow moving frontal system stalls across the region Tuesday-Thursday. Expect numerous rounds of heavy thunderstorms with excessive rainfall rates of 2-3 inches per hour or greater. Air mass will be extremely moist and capable of some really big rainfall totals in a short period of time. Threat is there for slow storm motions and cell training making the overall situation worse in the face of widespread excessive rainfall totals over the next 7 days.

Forecasted Rainfall Amounts:
Rainfall amounts Monday-Friday will likely average 4-5 inches with isolated totals of 8-10 inches possible. Current WPC rainfall forecast attached below shows a very large area of excessive rainfall over a large portion of central and SE TX. Should these rainfall totals verify over the middle Colorado River basin, significant improvement would likely occur in the long term hydrologic drought on the Highland Lakes including Lake Travis.

The highest totals will be in strong relation to cell training and this is impossible to determine much more than a few hours in advance.

There is some potential for the trough axis to morph into a closed 850mb low over central TX toward the middle of the week. Such systems in a very tropical air mass can act like a decaying tropical cyclone and take on the daily rainfall pattern of intense nocturnal rainfall events in the late evening and early morning hours near/around the low center at which time the center of any such low pressure would become critical in forecasting where the greatest rainfall would likely occur.

Hydro:
Harris County watersheds are near base flow today and will likely be near base flow at the onset of the rainfall at some point on Monday. Repeated rounds of storms will raise watershed levels over time, but the main question is how long are the breaks between rounds and does any cell training setup over Harris County. Short term rainfall rates of 2-3 inches per hour support urban street flooding and ponding and this will be possible all week.

Rivers:
Area rivers are already high from the recent rainfall especially the Brazos and Trinity and the forecasted rainfall amounts and widespread nature of the event will support significant rises on area rivers with some likely going above flood stage. Only the San Jacinto River affects Harris County however persons traveling outside of Harris County especially toward central TX should be aware of the river/flash flood threat and messaging should encourage “Turn around don’t drown” as this is the type of rainfall setup that has in the past resulted in loss of life in normally dry river bottoms in central TX and at low water crossings.

Tides:
ESE fetch has really increased overnight in response to lowering pressures over NW TX. Nearshore buoys have been running 20-25mph this morning and this has resulted in higher than expected waves along the Gulf beaches. Tides are already running about 1-1.5 feet above normal and when combined with the current lunar cycle total water levels along the Gulf beaches and in Galveston Bay are nearing 3.0 ft. Currently the Galveston North Jetty is running at 2.6ft and Morgan’s Point is 1.6ft. There has been some wave run-up on Bolivar this morning pushing water levels near the top of the beaches. For the most part tides will remain at or below the 3.0 ft mark today and Sunday. Winds will weaken as the frontal boundary approaches Monday and this should begin to slowly lower tide levels.

Forecasted Rainfall Totals (Next 7 Days):

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[Ptarmigan]

May has seen big floods in the past like in 1907, 1929, 1989, and 2006.

Houston Flood History
http://www.wxresearch.com/almanac/houflood.html

[unome]

tornado, flood, winter storm and a tropical storm warnings all at once - can't say I ever remember seeing that before

[srainhoutx]

Looks like an active Mother's Day is developing across the Region.

[srainhoutx]

The overall thinking has not changed today as to what our sensible weather will bring beginning today across the Hill Country into San Antonio and Austin. The Storm Prediction Center extended a Moderate Risk for Severe Storms mainly N and E of Metro Austin into the Temple/Killeen/Waco areas and into the portions of the Metroplex.

Storms look to begin firing across the Edwards Plateau and across the Hill Country within an hour or two developing into a slow moving squall line approaching the I-35 Corridor somewhere around 8:00 PM.

The updated Quantitative Precipitation Forecast (QPF) continues to suggest some folks could receive up to 9 inches of rain during the next 5 days. Water Vapor imagery is showing a rather robust disturbance moving ENE off the Pacific Ocean nearing the Baja Peninsula. It is possible that mid/upper level energy will arrive tomorrow into early Tuesday as the slow moving frontal boundary pulls up stationary. Exactly where, when and what locations will see the heaviest rainfall cannot be determined this far out in time, so we will could to monitor for both Severe Weather episodes tonight into tomorrow and the flooding threat that may develop.

[Andrew]

KCLL special sounding

[unome]

KCLL special sounding

will you interpret that for us novices Andrew - muchas gracias

[Andrew]

KCLL special sounding

will you interpret that for us novices Andrew - muchas gracias

Yea, it basically shows an overall favorable profile for all three types of severe weather. Plenty of CAPE for strong updrafts for hail (and wind) with a vertical wind profile that supports the possibility for tornadoes. Of course though this was a couple of hours ago and as we head into the evening CAPE will slowly decrease through the evening. Furthermore, the multicellular nature of storms so far will limit any tornado chances and keep it more limited to straight line winds and hail as we head into the overnight hours.

[jeff]

KCLL special sounding

will you interpret that for us novices Andrew - muchas gracias

Yea, it basically shows an overall favorable profile for all three types of severe weather. Plenty of CAPE for strong updrafts for hail (and wind) with a vertical wind profile that supports the possibility for tornadoes. Of course though this was a couple of hours ago and as we head into the evening CAPE will slowly decrease through the evening. Furthermore, the multicellular nature of storms so far will limit any tornado chances and keep it more limited to straight line winds and hail as we head into the overnight hours.

And there remains capping to be overcome in the 850-650mb range...thus far it has held over all SC and SE TX today. Should begin to erode with greater forcing overnight helping to maintain NC TX line of convection at least into our NW counties...some debate on the high res models how far some this line makes it...and its outflow.

Main show for SE TX is really looking like Monday afternoon/evneing with stalled outflow boundary and approach of strong disturbance (currently nearing Baja) in SE TX near/after peak heating.

[Andrew]

KCLL special sounding

will you interpret that for us novices Andrew - muchas gracias

Yea, it basically shows an overall favorable profile for all three types of severe weather. Plenty of CAPE for strong updrafts for hail (and wind) with a vertical wind profile that supports the possibility for tornadoes. Of course though this was a couple of hours ago and as we head into the evening CAPE will slowly decrease through the evening. Furthermore, the multicellular nature of storms so far will limit any tornado chances and keep it more limited to straight line winds and hail as we head into the overnight hours.

And there remains capping to be overcome in the 850-650mb range...thus far it has held over all SC and SE TX today. Should begin to erode with greater forcing overnight helping to maintain NC TX line of convection at least into our NW counties...some debate on the high res models how far some this line makes it...and its outflow.

Main show for SE TX is really looking like Monday afternoon/evneing with stalled outflow boundary and approach of strong disturbance (currently nearing Baja) in SE TX near/after peak heating.[/quote]

Yea with that sounding capping should be eroded enough for convection to initialize with the right trigger mechanism, but I suspect surface obs are in question somewhat and greater convergence remains off to the west. Either way mid/low level lift from the trough should be enough to spark storms across the region later this evening/overnight.

[unome]

thank you both, gentlemen - very helpful info !