September: Weekend Rain Chances. 1-2 Inches Possible C/N TX

[Ptarmigan]

With a cold front interacting with the moisture from Ingrid and Manuel, I wonder if we could see widespread heavy rain. I know some flood events happened because of that like in 1994 or 1998.

Invest 95L has a high chance of developing in the next 2 days.

[Katdaddy]

Thunderstorm chances will increase tomorrow with widespread thunderstorms Friday. Locally heavy rainfall with tropical moisture and slow moving thunderstorms Friday. We need it and its been long time since heavy rains have been in the forecast. Invest 95L still likely to become the next tropical cyclone with models still split between MX and the NE GOM. The threat for TX is very slight at this point.

[unome]

from 8am discussion:

A 1005 MB LOW PRESSURE CENTER IS IN THE YUCATAN PENINSULA NEAR 19N89W. NORTHWESTERLY WIND SHEAR IS KEEPING A CLUSTER OF MODERATE/ISOLATED STRONG CONVECTION NE OF THE LOW CENTER FROM 19N-22N BETWEEN 86W-88W. NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS OVER THE NW CARIBBEAN SEA FROM 16N-22N BETWEEN 81W-85W. ENVIRONMENTAL CONDITIONS ARE LIKELY TO BE CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM OVER THE BAY OF CAMPECHE DURING THE NEXT COUPLE OF DAYS AFTER THE LOW MOVES INTO THE REGION ON WEDNESDAY. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM LATER TODAY...IF NECESSARY. REGARDLESS OF TROPICAL CYCLONE FORMATION...THIS DISTURBANCE WILL LIKELY SPREAD HEAVY RAINS OVER EASTERN MEXICO. THESE RAINS COULD CAUSE LIFE-THREATENING FLOODS AND MUDSLIDES OVER AREAS ALREADY IMPACTED BY THE TORRENTIAL RAINS ASSOCIATED WITH INGRID AND MANUEL.

http://www.nhc.noaa.gov/marine/

[srainhoutx]

Morning e-mail from Jeff:

Ingredients coming together to produce a period of potentially heavy rainfall across the area.

Remains and associated moisture from tropical cyclones Ingrid and Manuel will be moving northward over the next 24 hours into TX. At the same time the first “real” cool front of the fall season will be moving down the plains and into TX early Friday. Additionally, deep tropical moisture associated with a complex disturbance (95L) over the Yucatan this morning will also progress NW toward TX by Friday. Lastly, a fairly strong short wave in the upper air flow will carve into the state by Friday afternoon helping to aid in stronger lift of a near completely saturated air mass.

Incoming and slow moving frontal boundary will produce strong surface convergence in a very moist atmosphere with the potential for slow storm motions and training of cells. Moisture values by late Thursday reach to nearly 150% to 175% of normal for this time of year and the forecast soundings show a nearly saturated air column indicating a deep warm layer and near excellent rainfall production (no dry air aloft evaporating falling rain).

Expect scattered to numerous showers and thunderstorms Thursday afternoon, but the main event appears aimed at Friday afternoon and night as the slow moving front crosses the area. Potential for organized heavy rainfall along and ahead of the boundary for several hours starting Friday afternoon. With such a saturated air mass, rainfall rates of 2-3 inches per hour are possible. Storm totals may average 1-3 inches with isolated higher amounts under training cells.

While grounds are dry due to the ongoing drought conditions across the area, short term rainfall rates may easily overwhelm drainage capacities in urban areas leading to quick flooding or roadways. 3-hr flash flood guidance for Harris and surrounding counties is running in the 3.0-4.0 inch range which is relatively high.

95L:
The other item of interest is the tropical system currently nearing the western shore of the Yucatan Peninsula. This well organized system will move over the warm waters of the Bay of Campeche later today where development into a tropical cyclone is likely….80%. This system is forecast to move slowly WNW to NW for the next 48 hours. Thereafter a complex interaction with the front moving off the TX coast makes for a very difficult forecast. Some model guidance turns the system west into MX and others loop the system northward toward TX/LA and yet others send it due east toward FL. Much depends on if 95L becomes captured by the trough along the US Gulf coast. Forecast confidence is extremely low at the moment.

[srainhoutx]

Surface observations, Sabancuy, MX radar and High Resolution Visible satellite imagery suggest the surface feature associated with 95L has move offshore of Campeche, MX into the Bay of Campeche. This is a bit higher in latitude than previous systems have emerged off the Yucatan this year. 95L remains highly sheared with most of the deep convection displaced to the E. Once the upper trough and dry air associated with that troughs weakens later today into tonight, conditions appear favorable for development. I believe we will see TS Jerry in the next 24-36 hours somewhere ESE of Tampico.

[wxman57]

Looks like we might get some decent rain across SE TX Friday into early Saturday morning, mostly from the approaching cold front but also due to increased onshore flow with the TS in the western Gulf by Tampico.

[srainhoutx]

I know many are more interested in the rainfall potential beginning late Thursday into early Saturday. We have seen so many forecasts bust when heavy rain is expected and this complex and complicated pattern is no different. I believe a lot will depend on timing and mesoscale driven storms that guidance cannot anticipate this far out. Anytime we see a very tropical airmass with PW's greater than 2 inches, a shortwave passing across Central Texas with a frontal boundary and a tropical system to our SSW, an eyebrow tends to be raised and daily developments followed a bit more closely than usual. Fingers crossed that everyone that needs the rain, get that much needed rainfall.

[djmike]

Should I begin too worry? The latest QPF from the NWS shows bulk of the rain now in the northern gulf all the way down FL west side. Please tell me we are not slowly losing our chances for abundant rainfall for SETX.

[txflagwaver]

I am going to water as usual, not change any plans..if it rains great...if not everything will still be limping along.

[biffb816]

I am going to water as usual, not change any plans..if it rains great...if not everything will still be limping along.

4 loads of laundry on my old school eco-friendly non-house heating clothes line seems to guarantee rain at my house.

And man, the spaghetti models are living up to their name on this storm.

[djmike]

Can someone post the latest euro and gfs on the precip for this weekend? Thanks!

[srainhoutx]

Morning e-mail from Jeff:

Factors continue to come together for widespread heavy rainfall across much of S, C, SE TX Friday-midday Saturday.

A slow moving frontal boundary will combine with deep tropical moisture from both eastern Pacific Hurricane Manuel and southern Gulf of Mexico tropical disturbance 95L to produce potentially excessive rainfall across the area. This tends to be a classic flash flood setup for the state of TX especially along and E of I-35 into the coastal bend area. Moisture levels are forecast to increase to near +2 SD above normal for mid September by Friday morning (PWS of 2.25 to 2.45 inches). This suggest the air column will be saturated through a deep layer with little evaporation of falling rain. Storm motions will gradually slow from their quick NW motions today to 5-10 mph on Friday out of the SW and WSW which raises the threat for excessive rainfall accumulations. Additionally steering winds and low level boundaries will promote cell training which also increases the flash flood threat.

Coastal convergence early Friday morning (stronger winds over the Gulf colliding with weaker inland winds near the coast) will promote widespread development. Think most of this activity will remain near the coast or possibly work as far inland as US 59, although experience with such tropical air masses suggest the activity will anchor near the coast or the coastal counties. As the front enters the area Friday afternoon along with upper air disturbances from the remains of Manuel, development will become widespread across the entire area and likely last into the overnight hours.

With the air column expected to be saturated through a deep layer, rainfall rates will be on the excessive side. Organized convection will be capable of producing a rapid 1-3 inches in an hour or less. Widespread rainfall amounts of 1-3 inches appear possible with isolate totals up to 5 inches especially under areas a cell training. These types of air masses are very capable of producing some big totals in a short period of time.

Grounds are dry to very dry across the region and flash flood guidance is high which should help mitigate run-off especially in rural areas. Urban areas may suffer more from the high potential rainfall rates with primary drainage systems possibly overwhelmed. With rivers and lakes running below to well below normal, this rainfall is not expected to generate flood flows on area rivers…but hopefully with return them to at least base flow conditions.

Drier air will filter into the region by Saturday afternoon ending he chance of rainfall. Post frontal conditions may allow overnight temperatures to fall into the 60’s for many locations by early next week.

95L:
Area of low pressure over the Bay of Campeche this morning remains fairly well organized, but lacks significant amounts of thunderstorm activity due to some dry air near the system. This system still has a high chance of developing into a tropical cyclone as it drifts WNW toward the eastern coast of Mexico. Latest computer guidance is in much better agreement on a track toward the WNW and NW possibly making landfall in the same region that Ingrid made landfall last week. With a cold front pushing off the TX coast this weekend, this should prevent any northward turn or impacts to our region.

[jasons2k]

Mike - the HPC maps are probably going to be more accurate than model output.

Here is the 5-day rainfall total forecasted by the HPC. Amazingly, it has a small donut of less rain up here on the northside, so it MUST be right or they are reading our forum!!

http://www.hpc.ncep.noaa.gov/qpf/p120i.gif

[djmike]

Mike - the HPC maps are probably going to be more accurate than model output.

Here is the 5-day rainfall total forecasted by the HPC. Amazingly, it has a small donut of less rain up here on the northside, so it MUST be right or they are reading our forum!!

http://www.hpc.ncep.noaa.gov/qpf/p120i.gif

Thanks Jason! I'll still take it! It is better than nothing! I'll take anything really at this point!

[srainhoutx]

The 12Z NAM is likely a bit aggressive with 95L nearing Brownsville, but our neighbors in Central Texas would certainly cheer if that short term meso guidance is correct regarding the rainfall potential. Fingers crossed!

[srainhoutx]

Actually I am a bit more encouraged to see the GFS trend toward the slower less strong frontal passage than the American model had been suggesting earlier in the week. The GFS is now suggesting the frontal boundary is not as strong or extends as deep into the Gulf shown in earlier runs. Also the Manuel moisture from the EPAC remains a wildcard in the forecast and is often under or over estimated. Also of note is the GFS is now suggesting and easterly wave moves W bound across the Gulf next week bringing additional moisture into our Region. It is also somewhat interesting to see the sheared 95L moisture streaming NW toward the Texas Coast with its 2.5 PW's. Talk about a complicated and complex forecast.

[srainhoutx]

LOL @ the Canadian...it take 95L up to near Brownsville, stalls then drifts E just S of Louisiana and then brings it back W making landfall near Freeport/Jamaica Beach next week.

[srainhoutx]

The general trend via the 12Z suite of guidance including the Euro suggests that Manuel's moisture may be a bit too strong over Texas and the trough and frontal boundary may be much weaker that expected and have a lot of trouble making it too far S. Most of the Operational and even the GFS ensemble guidance suggest the front will stall along or just S of I-10 and linger. The Euro also suggests that 95L will become trapped or stall just SE of Brownsville and linger S of Texas through hour 168.

WPC Model Diagnostic Discussion:

TROPICAL DISTURBANCE IN THE BAY OF CAMPECHE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: DRIFT UP THE MEXICAN COAST
CONFIDENCE: BELOW AVERAGE -- SEE NHC OUTLOOKS

THE NATIONAL HURRICANE CENTER -- NHC -- GIVES THIS SYSTEM AN 80%
CHANCE OF BECOMING A TROPICAL CYCLONE OVER THE NEXT FIVE DAYS AS
IT DRIFTS ACROSS THE WESTERN GULF OF MEXICO. A PORTION OF THE
SUBTROPICAL RIDGE -- AND ASSOCIATED UNDERLYING TRADE WINDS --
GUIDES THE SYSTEM NORTHWEST FOR A COUPLE DAYS, BEFORE AN UPPER
TROUGH MOVING ACROSS THE GREAT LAKES FLATTENS THE SUBTROPICAL
RIDGE OUT OF EXISTENCE AND LEAVING THE SYSTEM IN A REGION OF
DOLDRUMS WITHIN BECALMED FLOW BELAYING MUCH FORWARD MOTION. WEAK
UPPER TROUGHING -- ADVERTISED BY THE NON-GFS GUIDANCE -- ALONG THE
GULF COAST OPENS THE DOOR TO AN EASTWARD DRIFT IN A FEW DAYS. A
WEAK SURFACE LOW MOVING THROUGH THE SOUTHEAST WILL PLUNDER SOME OF
THE GULF SYSTEM'S MOISTURE, LEADING TO A PRE-TYPE PRECIPITATION
EVENT IN 2-3 DAYS, DEPENDING UPON ITS MAGNITUDE. SEE WPC QPF
GRAPHICS AND DISCUSSIONS FOR MORE DETAILS ON THE RAINFALL FORECAST.

EVEN THOUGH THE NON-GFS GUIDANCE PARROTS ONE ANOTHER IN RECURVING
THE SYSTEM OFFSHORE TEXAS, NHC WAS SPELLBOUND BY THE SIREN SONG OF
THE PAST COUPLE GFS RUNS DURING THE 17Z MEDIUM RANGE COORDINATION
CALL, WITH A FORECAST TRACK THAT WOULD PILLAGE PORTIONS OF THE
NORTHEAST MEXICAN COAST INTO MONDAY MORNING BEFORE THE SYSTEM'S
DISSIPATION. A BULK OF THE 00Z GLOBAL ENSEMBLE SUPPORT LEAVE THE
SYSTEM FOUNDERING OVER THE GULF FOR DAYS, WHICH REMAINS A VIABLE
ALTERNATIVE SCENARIO. THE NHC SOLUTION IS PREFERRED BY DEFAULT
WITH BELOW AVERAGE CONFIDENCE DUE TO FORECAST UNCERTAINTY. SEE
NHC OUTLOOKS FOR THE LATEST ON THE SYSTEM'S STATUS.

[srainhoutx]

Methinks some pirates may have intervened in the 2:40 pm Model Diagnostic Discussion... http://www.wpc.ncep.noaa.gov/discussion ... isc=pmdhmd

WPC Forecaster Roth does have a sense of humor...

[Kludge]

[quote="Ed Mahmoud]
Methinks some pirates may have intervened in the 2:40 pm Model Diagnostic Discussion... http://www.wpc.ncep.noaa.gov/discussion ... isc=pmdhmd
[/quote]

That's what happens when you spend too much time looking at the radARRRRRRR....