A New Normal Part 2

We are living in a new world and reality, a post-Harvey Texas. Just a week ago, a Category 4 monster, Hurricane Harvey was barreling down towards Rockport. Harvey was the first major hurricane to make landfall on America since Wilma in 2005. I think the National Hurricane Center (NHC) may increase Harvey’s peak to 140 mph 224 km/h 122 knots hurricane. Harvey being the first major hurricane to make landfall since Wilma has been largely overshadowed by the epic flooding that ravaged Houston and Beaumont area. That started on the night of August 26, 2017. A series of core rains that form near the center of Harvey.

One good news, the area of thunderstorms in the Southwest Gulf of Mexico does not pose a threat due to wind shear. It is an area of thunderstorms from a tropical wave. However, a cold front that is passing to Southeast Texas could set off thunderstorms and more rain as it picks up moisture from the tropical wave per NWS Houston.

000
FXUS64 KHGX 020220
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
920 PM CDT Fri Sep 1 2017

.UPDATE...
Forecast for tonight looking on track. Updated temps and
dewpoints for trends.

Beat

&&

.PREV DISCUSSION... /ISSUED 628 PM CDT Fri Sep 1 2017/

AVIATION...
Sea breeze and outflow boundary are working their way inland with not
a whole lot of wind changes. SHRA activity that did develop late this
afternoon has now moved away from LBX. Look for light and variable
winds overnight with some patchy MVFR fog possible again at CXO. Expect
VFR conditions tomorrow with mainly light and variable winds. 42

PREV DISCUSSION... /ISSUED 343 PM CDT Fri Sep 1 2017/

DISCUSSION...
Current satellite is showing the typical afternoon cumulus field
developing across southeast Texas. There is a little enhanced
cumulus along the coast but the weak seabreeze is having trouble
generating enough lift for anything more than very isolated and
weak showers. This is expected again tomorrow and the dry weather
is greatly appreciated.

Models are still showing an upper level trough dropping into North
Texas tomorrow night though a significant change is a stronger
ridge over the southern Plains pinching the trough off from the
westerly flow and retrograding it back to the southwest earlier
than previous model runs. A more westerly position of this trough
means weaker lift and lower PoPs for Saturday night and Sunday.

Tropical moisture in the southern Gulf of Mexico will move north
early next week giving us our next decent chance for rainfall. At
the same time, a western U.S. ridge will amplify and northerly
upper flow will drive a cold front through the area Tuesday night
and early Wednesday. The tropical moisture already in place will
interact with this cold front producing a line of showers and
storms along the front. Fortunately the cold front will be moving
fairly quickly, especially for this time of year, pushing the rain
south by Wednesday afternoon. Behind the front, cool and dry air
will filter into the area bringing very pleasant temperatures with
highs only in the lower 80s Wed/Thu.

Hennig

There is also a tropical wave in the far eastern Atlantic that has a good chance of becoming Jose in the next five days. My main concern is Hurricane Irma, which is a Category 3 hurricane out in the Atlantic. Many are wondering where will Irma go. The latest heat map from various forecast models and GFS ensemble track guidance. The GFS goes up to 10 days.

Most forecast models have Irma moving west southwest direction in the next 5 days. From there, based on GFS ensembles, it could go anywhere. Some have Irma going into the Gulf of Mexico and hitting Louisiana in 10 days. Some have Irma hitting Florida to New York. This is too early too tell and this a low confidence forecast. Anything can happen between now and around September 11, which is the 16th anniversary of horrifying terrorist attacks that killed 3,000 people and destroyed the World Trade Center.

Many on social media may have seen this.

That is bogus. For one, the NHC does not issue forecasts 13 days in advance. They only go up to 5 days in advance. Nobody knows where Irma or any hurricane will go in the next 10 days, let alone 5 days.

The latest intensity forecast are in general agreement that Irma will be a major hurricane. A couple have Irma as a Category 2 fluctuating as Category 3, which happens due to eyewall replacement cycle.

I would not be surprised if Irma becomes a Category 5 hurricane, especially when it gets around the Caribbean. Hurricanes in that part of the Atlantic rarely become Category 5 hurricanes. Irma will have to be watched for September.

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A New Normal Part 1

Texas and Louisiana are slowly recovering from the ravages of Harvey. It is a national tragedy. Harvey is now a tropical depression over Mississippi dumping heavy rain over Alabama, Mississippi, and Tennessee. They have seen 5 to 8 inches/12.7 to 20.3 centimeters of rain so far. Flooding continues to be a problem for many areas. The Addicks and Barker Reservoir are still bursting at the seams with too much water.

The death toll as of 8/31/2017 is nearly 40. I suspect the death toll is going to be much higher once the flood water recedes. The question is how many. Too early to speculate at this time. If I had to guess, it could be in the hundreds. Katrina claimed more than 1,800 lives, while 9/11 claimed 3,000 lives. 9/11 is a terrorist attack. Harvey could be the deadliest natural disaster since Katrina.

With Harvey no longer a problem, I turn my attention to three areas in the tropics. There are two areas that need to be watched, Hurricane Irma, a low pressure in the Gulf of Mexico, and tropical wave emerging from West Africa. Let’s start with Irma.

Irma is now a major hurricane with 115 mph 184 km/h 100 knots with gusts of 145 mph 232 km/h 126 knots. It is moving westward at this time. Many are wondering where will Irma go. Will Irma enter the Gulf of Mexico, make landfall on the East Coast, or become a fish storm? The latest heat map from various forecast models and GFS ensemble track guidance. The GFS goes up to 10 days.

The forecast models at this point do not have have it getting close to Texas. Some have Irma entering the Gulf of Mexico and hitting the Florida Panhandle. It looks to be a East Coast threat at this point. New York City area is included in the risk area. Again, this is 10 days from now and anything can change between now and next week. Since Irma is a major hurricane, the intensity forecast is interesting.

Most maintain Irma as a Category 3 hurricane. One has it as Category 4 hurricane in two days. Some have Irma as a Category 4 hurricane in three days. I think Irma has the potential to intensify into a Category 5 hurricane, especially when it gets closer to the Caribbean. Irma could be a problem starting next week as it gets closer to land. Irma needs to be watched closely.

Another area of concern is in the Southwest Gulf of Mexico. Here is a discussion from National Hurricane Center (NHC)

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Thu Aug 31 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Hurricane
Irma, located over the eastern Atlantic Ocean. The Weather
Prediction Center is issuing advisories on Tropical Depression
Harvey, located over northern Mississippi.

1. A tropical wave emerging over the far eastern Atlantic is moving
westward at about 15 mph. Environmental conditions are expected to
become more conducive for development over the weekend and early
next week while the system moves well to the south and southwest of
the Cabo Verde Islands.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...40 percent.

2. A area of low pressure could form over the southwestern Gulf of
Mexico by the weekend, however, environmental conditions are
expected to become unfavorable for tropical cyclone formation by
that time. Interests along the Texas and Louisiana coasts are
encouraged to consult products from their local NWS Forecast Office
for more information about impacts from any non-tropical weather
systems.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...10 percent.

Public Advisories on Harvey are issued under WMO header WTNT34 KWNH
and under AWIPS header TCPAT4.

Forecaster Zelinsky

I do no think that will develop into something tropical. However, the moisture from it could be a factor for next week as a cold front passes. The cold front could trigger storms in areas that have been flooded. Not a good thing. That will also have to be watched.

Lastly, there is a tropical wave emerging out of West Africa. I think it will be tagged with an Invest in the next couple of days. It has a moderate chance of developing in the next five days. I would not be surprised if this becomes our next named storm, which would be Jose.

Here is what I think will happen.
-The area of thunderstorms in Southwest Gulf of Mexico bears watching, but I do not think it will develop.
-Irma needs to be watched and may pose a threat somewhere.
-Tropical wave emerging from West Africa needs to be watched. Could be Jose.

The forecast models came from NCAR-Tropical Cyclone Guidance and National Hurricane Center. Special thanks to all of them.

This is going to be a long road to recovery. It is a new normal for Texas.

Epic Flood Day 4

Last night, East Texas and Southwest Louisiana got hit hard by heavy rain. Epic flooding that plagued Houston area is now plaguing East Texas and Southwest Louisiana. Here is a rainfall total map.

Many areas saw over 10 inches/25.4 centimeters of rain. The highest total is over 26 inches/66.04 centimeters of rain! Beaumont/Port Arthur got over 26 inches of rain on August 29 and got 3 inches of rain today. That means they saw at least 29 inches of rain!

000
CXUS54 KLCH 300819
CF6BPT
PRELIMINARY LOCAL CLIMATOLOGICAL DATA (WS FORM: F-6)

STATION: BEAUMONT PORT ARTHUR
MONTH: AUGUST
YEAR: 2017
LATITUDE: 29 57 N
LONGITUDE: 94 1 W

TEMPERATURE IN F: :PCPN: SNOW: WIND :SUNSHINE: SKY :PK WND
================================================================================
1 2 3 4 5 6A 6B 7 8 9 10 11 12 13 14 15 16 17 18
12Z AVG MX 2MIN
DY MAX MIN AVG DEP HDD CDD WTR SNW DPTH SPD SPD DIR MIN PSBL S-S WX SPD DR
================================================================================

1 88 77 83 0 0 18 0.07 0.0 0 6.5 15 80 M M 6 19 90
2 86 74 80 -3 0 15 0.29 0.0 0 6.2 16 130 M M 5 138 21 140
3 91 74 83 0 0 18 0.02 0.0 0 5.1 14 30 M M 7 1 17 20
4 90 75 83 0 0 18 0.26 0.0 0 3.6 14 160 M M 5 13 17 160
5 87 74 81 -2 0 16 0.34 0.0 0 4.1 14 150 M M 3 13 20 120
6 92 75 84 1 0 19 0.34 0.0 0 7.5 21 290 M M 3 138 30 240
7 84 74 79 -4 0 14 0.73 0.0 0 4.6 20 280 M M 1 13 26 140
8 87 74 81 -2 0 16 2.42 0.0 0 5.5 20 190 M M 8 13 25 180
9 85 74 80 -3 0 15 0.38 0.0 0 4.5 16 140 M M 7 1 21 140
10 92 75 84 1 0 19 0.00 0.0 0 4.2 14 250 M M 3 1238 26 210
11 91 77 84 1 0 19 0.01 0.0 0 5.8 14 190 M M 1 18 18 180
12 92 74 83 0 0 18 0.00 0.0 0 6.1 14 190 M M 1 12 19 180
13 92 74 83 0 0 18 0.00 0.0 0 6.3 16 180 M M 2 13 24 250
14 93 76 85 2 0 20 0.00 0.0 0 7.7 15 190 M M 2 20 180
15 89 77 83 0 0 18 1.23 0.0 0 7.2 22 200 M M 1 138 31 160
16 91 78 85 2 0 20 0.02 0.0 0 9.0 20 240 M M 2 8 26 260
17 94 76 85 2 0 20 T 0.0 0 7.8 14 190 M M 1 19 220
18 95 76 86 3 0 21 0.00 0.0 0 4.7 14 100 M M 2 13 17 100
19 97 75 86 3 0 21 0.00 0.0 0 3.7 12 180 M M 2 138 15 160
20 92 78 85 2 0 20 0.85 M 0 3.0 8 120 M M 2 13 M M
21 92 77 85 2 0 20 0.01 0.0 0 4.3 17 100 M M 3 38 27 330
22 91 75 83 0 0 18 0.23 0.0 0 3.4 16 110 M M 2 13X 19 100
23 89 76 83 0 0 18 0.02 0.0 0 4.2 17 30 M M 2 13 22 40
24 92 74 83 0 0 18 0.04 0.0 0 7.7 23 70 M M 1 3 29 70
25 80 73 77 -6 0 12 1.23 0.0 0 14.3 23 100 M M 5 13 32 90
26 81 74 78 -5 0 13 2.74 0.0 0 13.1 26 90 M M 8 13 34 90
27 78 73 76 -7 0 11 8.98 0.0 0 15.5 30 110 M M 10 13 42 80
28 82 72 77 -6 0 12 5.52 0.0 0 19.2 28 50 M M 9 13 39 50
29 74 69 72 -10 0 726.03 0.0 0 22.1 35 360 M M 10 13 46 360
================================================================================
SM 2567 2170 0 492 51.76 0.0 216.9 M 114
================================================================================
AV 88.5 74.8 7.5 FASTST M M 4 MAX(MPH)
MISC ----> # 35 360 # 46 360
================================================================================

The heavy rain that plagued East Texas and Southwest Louisiana happened at night in the form of core rains. The same type of rain that plagued Houston area. Here is the 7 day total.

The rainfall total are from multi-sensor (radar and rain gauge) precipitation estimates obtained from National Weather Service (NWS) River Forecast Centers (RFCs) and mosaicked by National Centers for Environmental Prediction (NCEP). There are areas that have gotten over 50 inches/127 centimeters of rain. Some areas have nearly gotten 60 inches/152.4 centimeters of rain! I would not be surprised by the end of the week, some areas get up over 60 inches/152.4 centimeters of rain! The rainfall data is from Advanced Hydrologic Prediction Service (AHPS).

As things are drying out and we enter September, the tropics are brewing. You did not misread that. There are two areas of concern. Let’s start with the one in the Gulf of Mexico. There is an area of thunderstorms in the Southwest Gulf of Mexico. Yes, that is an area that the National Hurricane Center (NHC) is watching.

The NHC gives that area a low chance of developing in the next 5 days. Here is the discussion from NHC.

ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Wed Aug 30 2017

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical
Depression Harvey, located over central Louisiana and on Tropical
Storm Irma, located over the eastern Atlantic Ocean.

1. An area of low pressure could form over the southwestern Gulf of
Mexico by the weekend. Development, if any, of this system is
expected to be slow to occur as the low moves slowly northward.
If this system does develop, it could bring additional rainfall to
portions of the Texas and Louisiana coasts. However, any rainfall
forecast is uncertain at this time range and it is too soon to
determine any specific impacts. Interests in these areas should
monitor the progress of this system for the next few days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...20 percent.

Public Advisories on Irma are issued under WMO header
WTNT31 KNHC and under AWIPS header MIATCPAT1.
Forecast/Advisories on Irma are issued under WMO header
WTNT21 KNHC and under AWIPS header MIATCMAT1.

Forecaster Avila

Let’s hope that does not develop into something tropical. If it does, that could mean more rain for flood ravaged Texas and Louisiana. That would be very bad. Regardless, I will keep an eye on that area.

There is also newly developed Tropical Storm Irma. The big question is where Irma goes. Here is the latest heat map from various forecast models and GFS ensemble track guidance. The GFS goes up to 10 days.

Looking at the forecast track, it is looking to move more to the northwest. It could affect Bermuda or the East Coast. None of the forecast models have it going into the Gulf of Mexico at this time. Here is the most recent satellite image of Irma.

Looking at Irma, it looks like it is intensifying. The circular pattern and spiral arms suggest that Irma is undergoing rapid intensification. Here is the intensity forecast for Irma.

The forecast models forecasts a Category 1 hurricane in 12 hours. I think Irma could be a major hurricane as early as tomorrow. Frankly, I would not be surprised if Irma becomes a Category 5 hurricane while out in the Atlantic.

Here is what I think will happen.
-The area of thunderstorms in Southwest Gulf of Mexico bears watching.
-Irma will become a major hurricane as early as tomorrow.

The forecast models came from Advanced Hydrologic Prediction Service (AHPS), NCAR-Tropical Cyclone Guidance, National Hurricane Center, Naval Research Laboratory Tropical Cyclone Page, Weather.US, Weather Prediction Center (WPC), and National Weather Service. Special thanks to all of them.

Harvey is not just a Houston area disaster. It is a Texas disaster. A disaster that everyone has feared has come true. A disaster of truly epic proportions of a magnitude that one cannot even imagine.

Epic Flood Day 3

The helicopters flying and boats rescuing people from their flooded out homes. A sight all too common in the Houston area. The Addicks and Barker are bursting with so much water that it has be released to avoid catastrophic and widespread flooding at the cost of flooding neighborhoods. It is on the 12th anniversary of Hurricane Katrina making landfall on Louisiana and Mississippi. I am completely overwhelmed by this disaster as a weather buff. Here is a 7 day rainfall total map from Advanced Hydrologic Prediction Service (AHPS). It is unbelievable amounts I have seen.

The rainfall total are from multi-sensor (radar and rain gauge) precipitation estimates obtained from National Weather Service (NWS) River Forecast Centers (RFCs) and mosaicked by National Centers for Environmental Prediction (NCEP). There are areas that have gotten over 50 inches/127 centimeters of rain. Some areas have nearly gotten 60 inches/152.4 centimeters of rain! I would not be surprised by the end of the week, some areas get up over 60 inches/152.4 centimeters of rain!

Another mind boggling aspect is the large area that received heavy rains.

The green is where at least 10 inches/25.4 centimeters of rain fell. A large area received at least 10 inches/25.4 centimeters or greater! This has to go down as one of the largest rain events in America. We should know once Harvey passes. In the meantime, East Texas and Southwest Louisiana is getting hit by heavy rain. The latest Doppler radar out of NWS Lake Charles shows heavy rain as the storm is over the Gulf of Mexico.

Here is the 24 hour rainfall forecast from GFS, Canadian, EURO, and Weather Prediction Center (WPC).

The forecast models have the heaviest rains east of Houston. This time it is over East Texas and Southwest Louisiana. They have been getting plenty of heavy rain as well.

GFS: 11 inches/27.94 centimeters
Canadian: 10 inches/25.40 centimeters
EURO: 15 inches/38.10 centimeters
WPC: 10.74 inches/27.28 centimeters

As for Houston area, they could see still see rain, including occasional heavy rain. Looking at more moderate rain for Houston. The heavy rain has shifted to East Texas and Southwest Louisiana. Even New Orleans area is getting heavy rain and there is concern for flooding. Some of the pumps are not working, which could flood again like what happened with Katrina.

The million dollar question is where Harvey goes. Here is a heat map from various forecast models.

There is now a consensus among forecast models that Harvey will go northeast after making landfall on Southwest Louisiana as a tropical storm. Here is the latest from the National Hurricane Center. It is as of 10:00 PM or 2200 CDT:
Location: 29.0°N 93.6°W
Moving: NE at 6 mph 9 km/h 5.2 knots
Min pressure: 994 mb
Max sustained: 50 mph 80 km/h 44 knots

I do not think Harvey will intensify as it makes landfall again as a tropical storm. The reason is the core is a swirl of clouds with no thunderstorms. All the thunderstorms are north and east of the center. Once it makes landfall, Harvey moves quickly to the northeast. I say good riddance to Harvey.

Here is what I think will happen.
-Heavy rain at night, especially near and east of the center, which is East Texas and Southwest Louisiana.
-Not ruling out Houston area getting rain again tonight. Looking not as heavy. More like moderate rain.
-Rainfall amounts could range from 10 to 15 inches/25.4 to 38.1 centimeters of rain with isolated totals approaching and exceeding 20 inches/50.8 centimeters.

The forecast models came from NCAR-Tropical Cyclone Guidance, Weather.US, National Hurricane Center, and National Weather Service. Special thanks to all of them.

I am at total loss of words of with Harvey. I cannot imagine what people are going through. This a disaster that I cannot comprehend. It defies any description.

Epic Flood Day 2

Houston and the surrounding area is under water from the heavy rains of Harvey. So many people are being rescued from their flooded out homes as I type. I am so utterly stunned and horrified at what has been going on. Here is a 7 day rainfall total map from Advanced Hydrologic Prediction Service (AHPS). It is unbelievable amounts I have seen.

The highest is total is over 45 inches/114.3 centimeters! That is over Liberty County. The area of heavy rain is much larger than Allison. Heavy rain from South, Central, and East Texas. This is easily one of the largest flood events in Texas and possibly in American history. Let that all sink in. With more rain forecasted tonight and tomorrow, the total is most certainly going to rise. The forecast of 50 to 60 inches/127 to 152.4 centimeters of rain is not so far-fetched. Let’s look at the ever important rainfall forecast totals up to Friday. They are from GFS, Canadian, EURO, and Weather Prediction Center (WPC).

All of them have more rain coming. The location and amount varies.
GFS: 31 inches/78.74 centimeters
Canadian: 18 inches/45.72 centimeters
EURO: 21 inches/53.34 centimeters
WPC: 17.80 inches/45.21 centimeters

The GFS has the highest, while WPC has the lowest. The GFS and WPC have heaviest rain over Houston area. Canadian has two areas of heavy rain over Houston area and East Texas. The EURO has the heaviest over East Texas. Looks like more heavy rain will fall in the next few days from Harvey. Just the amount and where is the problem.

The million dollar question is where Harvey goes. Here is a heat map from various forecast models.

If there is some good news, the forecast models are on consensus that Harvey is eventually going to move out of Texas. The previous forecast models were low confidences as they were all over the place on where Harvey would go. This time looks Harvey is heading northeastward. However, Harvey is over the Gulf of Mexico, which allows the core to redevelop, which could mean more rain for Houston area. That is a very bad thing. Also, it could allow Harvey to reintensify and head back to land as a tropical storm. Another million dollar question, how strong will Harvey be?

Most forecast models keep Harvey as a tropical storm. Harvey has strengthened somewhat to 45 mph 72 km/h 40 knots. Some have Harvey intensifying, while a couple have Harvey becoming a strong tropical storm. I do no think Harvey will be a hurricane again despite being over the Gulf of Mexico on Tuesday. Let’s hope not.

What will tonight be like? Let’s look at High-Resolution Rapid Refresh (HRRR), North American Mesoscale Forecast System (NAM), Regional Model (RGEM), and Weather Research and Forecast (WRF-ARW, and WRF-NMM). They are at 0800Z or 3:00 AM CDT. The RGEM has it at 0900Z or 4:00 AM.

All the forecast models agree that there will be thunderstorms firing up near the center of Harvey. The locations vary by forecast model. HRRR has the heaviest rain over Beaumont area and East Texas. NAM has it over Houston area. RGEM has heaviest rain over Houston and Beaumont area. WRF-ARW has heaviest rain over Texas and Louisiana border. WRF-NMM has heaviest rain northeast of Houston. The WRF-ARW and WRF-NMM have the center of Harvey over land, which is not the case as of right now. Heavy rain is possible again tonight, but the forecast models are split on where it will happen. Like I mentioned before with tropical systems, the thunderstorms flare up at night due to the warm core and cooler surrounding temperature.

Here is what I think will happen.
-Heavy rain at night, especially near and east of the center.
-Not ruling out Houston area getting more heavy rain again tonight.
-Rainfall amounts could range from 5 to 10 inches/12.7 to 25.4 centimeters of rain with isolated totals approaching and exceeding 15 inches/38.1 centimeters.

The forecast models came from NCAR-Tropical Cyclone Guidance, Tropical Tidbits, National Hurricane Center, Weather.US, and National Weather Service. Special thanks to all of them.

I am at total loss of words of with Harvey. I cannot imagine what people are going through. This a disaster that I cannot comprehend. It defies any description.

Epic Flooding

The heavy rain that struck Houston area has been nothing short of epic. I am at total loss of words. This is an event that we all so feared and has come to reality. So much rain fell over a large area in a short time. Here is a rainfall total map.

Many areas got over 10 inches of rain since last night. The highest total is over 26 inches of rain. However, NWS Houston has reported 30 inches of rain has fallen, which is no surprise.

000
FXUS64 KHGX 271101
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
601 AM CDT Sun Aug 27 2017

...FLASH FLOOD EMERGENCY FOR LIFE-THREATENING CATASTROPHIC FLOODING...

.DISCUSSION...
Epic and catastrophic flooding has occurred in and around the
Houston and Galveston areas and surrounding communities overnight,
and very heavy rains continue falling across these areas early
this morning. Rainfall totals between Saturday evening and early
this morning have totaled 15 to 30 inches. Tropical Storm Harvey
is approximately 50 miles east southeast of San Antonio and has
remained nearly stationary all night long. Showers and thunderstorms
along Harvey`s feeder bands have spread 4 to 6 inch per hour producing
rainfall rates resulting in this historic event. Activity continues
spreading across already devastated areas with hourly rainfall
rates averaging around 4 to 5 inches in the Matagorda-Brazoria
County storms and around 6 to 7 inches in the Galveston-Harris
County area storms. We might get a break from the rain some time
later today, but additional storm development is likely overnight.
It is possible that these new storms could become concentrated a
little further westward than this morning`s activity. However,
with Harvey expected to remain in the same general area between
its current location and the coast over the next several days,
additional life-threatening rainfall totals of 15 to 25 inches
with isolated higher amounts are possible across the Flash Flood
Watch area over the next several days, and results could be
devastating if any of these rains fall where catastrophic flooding
has already occurred. 42
&&

.HYDROLOGY...
There have been record crests across numerous bayous across southern
Harris County overnight. Due to the heavy rain, we are expecting
record crests during the week ahead. 43
&&

.MARINE...
Tropical Storm Harvey will move very little in the coming days and
this will maintain a tight enough northeast to east pressure
gradient across the local waters to keep small craft advisory flags
up through at least mid week. Bands of heavy rainfall with embedded
thunderstorms will periodically track across the waters...moving in
from the south and west. Gale force wind gusts and quickly agitated
seas will occur in and around any passing strong thunderstorm cell.
Waterspouts will also be a threat within Harvey`s outer bands. East
to southeast winds will range between 20 to 30 knots with average
wave heights of between 5 to 7 feet with occasional 8 to 9 foot
heights.

Extreme to strong rip currents will continue for a few more days.
Currents and river(s) discharge(s) into the bays will also remain
problematic for navigation for at least a few days (possibly into
next weekend) given this record setting rainfall that has led to
the extreme inland flooding. 31

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 79 71 81 70 82 / 90 80 70 60 60
Houston (IAH) 79 73 79 72 82 / 90 80 80 70 60
Galveston (GLS) 80 76 82 77 84 / 90 80 80 70 70

&&

The forecast models of where Harvey is going has been nothing but an adventure in frustration. It is depicted in this heat map from various forecast models.

It could either linger over Texas for the next several days. Some models have Harvey going over the Gulf of Mexico and going over Houston area. This is nothing short of frustrating. I am most concern is will it rain again like last night. Let’s look at High-Resolution Rapid Refresh (HRRR), North American Mesoscale Forecast System (NAM), Regional Model (RGEM), and Weather Research and Forecast (WRF-ARW, and WRF-NMM). They are at 0800Z or 3:00 AM CDT.

HRRR and NAM have the heaviest rain east of Houston, mostly around Beaumont area. The RGEM, WRF-AWW, and WRF-NMM have the heaviest rains over Houston again. It is not unanimous like last night on where it will happen. However, the forecast models are unanimous on that more heavy rain could fall again tonight. The forecast models got it right last night. I am not ruling out another core rain event again.

Here is what I think will happen.
-Heavy rain at night, especially east of the center.
-Rainfall amounts could range from 10 to 15 inches/25.4 to 38.1 centimeters of rain with isolated totals approaching and exceeding 20 inches/50.8 centimeters.
-Not ruling out Houston area getting more heavy rain again tonight.

This is a very concerning event. As long as Houston area is on the northeast side of Harvey, heavy rain will be a severe problem. Also, if Harvey moves closer to the coast, it can pull in more moisture from the Gulf of Mexico. Harvey’s core can get more moisture as there is dry air. Regardless of what happens, any more rain is going to make flooding worse.

The forecast models came from NCAR-Tropical Cyclone Guidance, Tropical Tidbits, National Hurricane Center, National Weather Service, and Advanced Hydrologic Prediction Service (AHPS). Special thanks to all of them.

Harvey Trudges Along

Hurricane Harvey made landfall around Rockport last night. Now, it is a tropical storm that is lingering over Texas. The question is where Harvey goes. Here is a heat map from various forecast models.

This is a low confidence forecast. The forecast models are all over the place on where Harvey will go in the next 5 days. This shows that this is far from over. Since the winds have died down, heavy rain and dangerous flooding will be the main problem. My main concern is what is going to happen tonight. Let’s look at the short term mesoscale forecast models. They are High-Resolution Rapid Refresh (HRRR), North American Mesoscale Forecast System (NAM), Regional Model (RGEM), and Weather Research and Forecast (WRF-ARW, and WRF-NMM). They are at 0900Z or 4:00 AM CDT.

All the forecast models show show large areas of feeder bands over the Houston area in the early morning hour. The mesoscale forecast models are on board for more heavy rain tonight. This is not surprising as heavy rain is more likely to fall at night with tropical systems. Looking at the most recent Doppler radar mosaic, I can see numerous feeder bands heading towards Houston area.

I would not be surprised to see more rain tonight and tomorrow. This could be a very stormy night. NWS Houston has this very concerning forecast.

000
FXUS64 KHGX 262154
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
454 PM CDT Sat Aug 26 2017

...Catastrophic and life-threatening flooding expected due to
prolonged heavy rainfall from Harvey...

.DISCUSSION...
With Harvey meandering just west of the forecast area, rain and
feeder bands will move over Southeast Texas until the storm moves
out of the area. Short term high resolution models show the
potential for rain bands to produce 10 to 15 inches of rain just
tonight and Sunday morning. Rainfall of 10 to 15 inches within 6
or 12 hours will produce flash flooding. In addition, rainfall
rates could exceed 4 inches per hour. If these intense rain bands
with these amounts occur over the metro areas, flooding could
impact homes, roadways, and the highway system.

In addition, isolated tornadoes will continue to be possible. A
tornado watch continues in effect through 2:00 AM Sunday.

With Harvey pretty much stuck in very weak upper level steering,
the potential for heavy rainfall will persist into Wednesday.
Global models continue to show the rainfall potential from tonight
through Wednesday evening of 15 to 25 inches. Isolated maximum
amounts of up to 40 inches for the entire event is possible.

It should be stressed that anyone planning to travel should check
with TXDOT, Houston TranStar, or other trusted sources for road
conditions prior to travel. Rainfall of this magnitude could cause
major flooding of the highway system.

40

&&

Here is what I think will happen.
-Heavy rain will likely fall at night, especially east of the center.
-Rainfall amounts could range from 10 to 15 inches/25.4 to 38.1 centimeters of rain with isolated totals approaching 20 inches/50.8 centimeters.

The forecast models came from NCAR-Tropical Cyclone Guidance, Weather.US, Tropical Tidbits, National Hurricane Center, and National Weather Service. Special thanks to all of them.