More Rain Tonight?

The tropical wave is now over Texas. It is a disorganized system, so it is hard to predict where the rain will be tonight. 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 0900Z or 4:00 AM CDT.

The HRRR has heavy rain mostly west and southwest of Houston. The NAM has heavy rain over Matagorda Bay and east of Houston. The RGEM has an axis of heavy rain from Corpus Christi area to East Texas. The WRF-ARW has the heavy rain over Matagorda Bay. The WRF-NMM has heavy rain south of San Antonio. This shows that forecasting where heavy rain will fall tonight is all over the place with this tropical wave.

Looking at the most recent Doppler radar mosaic, there is heavy rain over East Texas and Southwest Louisiana. It is not really active right now.

However, with tropical moisture, thunderstorms tend to form at night, especially near the center of the low pressure system. They are called core rains and they can dump heavy rain in a short time. Harvey, Allison, Claudette, and Thrall 1921 Flood were core rain events as flooding rain fell at night. This system is disorganized, so it will be hard to tell where it will exactly form. Some forecast models want the heavy rain over Matagorda Bay, while some have it over Southeast Texas.

Many are wondering what is the forecasted rain amount. The rainfall forecast models are from GFS, Canadian, EURO, ICON, and Weather Prediction Center (WPC). They are all 7 day rainfall total forecast.

The GFS has 4 inches of rain over Galveston Bay. The area of heaviest rain is east of Houston.

The Canadian has nearly 11 inches of rain just north of Houston. The largest area of heavy rain is north of Houston.

The EURO has backed down on nearly 30 inches of rain. It has nearly 15 inches of rain south of San Antonio. There is a large area of heavy rain southwest of Houston.

The ICON has over 13 inches of rain near Aransas Pass. There is an area of 8 inches of rain west of Houston. Most of the heavy rain is over the Gulf Of Mexico.

The WPC has 10 inches of rain over an Matagorda Bay and Victoria. Houston area has 5 to 7 inches of rain.

The rainfall forecast is all over the place on where it will fall and even the amount. This is a very frustrating forecast. Regardless of forecast models, all forecast heavy rain will fall somewhere.

Here is what I think will happen.
-Someone will see heavy rain tonight.
-Not ruling out Houston area getting heavy rain tonight.
-Rainfall amounts could range from 5 to 10 inches of rain with isolated totals approaching and exceeding 15 inches.

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

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Invest 91L As This Weekend’s Rainmaker?

Invest 91L is over the Gulf of Mexico. Currently on satellite from CIMSS-Tropical Cyclones, it does not look too impressive.

Of course with tropical lows, they tend to fire up at night as they are warmer than the surrounding area. I would not be surprised to see a lot of thunderstorms come morning. As the time passes, where does Invest 91L go?

Most forecast models have it going towards South Texas or Mexico. There is a chance that it could go over Southeast Texas. If it goes into Mexico or South Texas, there is better chance for rain since the northeast side is the wettest as it is the “dirty” side of the tropical low. The intensity forecast models are split.

Some have Invest 91L as a tropical wave. Some have it intensifying into a tropical depression. Some have it becoming a tropical storm. If it becomes a tropical storm, it would be Beryl. Like I say, intensity forecast is not really reliable. At this point, I would be more concerned with the rain than some tropical storm developing.

Various forecast models have different rain amounts, which are from GFS, Canadian, EURO, and Weather Prediction Center (WPC). They are from Weather.US and Weather Prediction Center (WPC)-Quantitative Precipitation Forecasts (QPF). These are 7 day rainfall totals.

The GFS has the heaviest rain over Houston area. It forecasts up to 8 inches of rain. A large area of Southeast Texas has 3 to 6 inches of rain.

The Canadian forecasts rain amounts of up to 6 inches over Austin area and around Halletsville.

The EURO forcasts up to 20 inches of rain southeast of San Antonio. There is 10 inches south of Houston. The EURO is the wettest of the forecast models.

The WPC has up to 5 inches of rain over Southeast Texas. It is the driest of the forecast models.

All the forecast models have rain for Texas. The only difference is the amount. Some are very bullish, while others are not. The plus side is that it will put a dent on the drought in Texas.

Most areas in Texas are in a drought. The rains can alleviate the drought, which is a good thing. This also increases the risk for flooding, which is not good almost a year after Harvey ravaged Texas with epic rainfall.

I think Invest 91L will be more of a rain event this weekend. Tropical development is not likely, but cannot be ruled out. Regardless, Invest 91L needs to be watched as it could be more of a rain event that may cause flooding in some areas.

The forecast models came from NCAR-Tropical Cyclone Guidance. The GIS drought map is from United States Drought Monitor.

A Weakening Bud And Invest 91L

Oh how the mighty have fallen! Yesterday, Bud was a hurricane. Today it is a tropical storm with 50 mph 44 knots 80 km/h winds. It was once a formidable Category 3 hurricane. All the forecast models have Bud weakening.

With Bud running into cooler water and closer to land, it is most likely to weaken. The next important question is where Bud goes.

The forecast models are having Bud moving towards Baja California and the Southwestern US as a low pressure system. The moisture from Bud is certainly welcomed in the Southwest as they are very dry.

Almost the entire Four Corners is engulfed in a severe drought. It centers around where the Four Corners meet. There is also a severe drought in the Texas Panhandle region. Any rain is welcomed regardless. This leads to Invest 91L in the Caribbean. Many are asking where 91L will go.

Most of the forecast models have Invest 91L heading towards either Mexico or Deep South Texas. Some have it heading towards Southeast Texas. Regardless of where 91L goes, rain will be the main issue. Since Invest 91L is over an area of warm water, does it have a chance of developing?

Most forecast models have 91L at tropical wave or tropical depression. One has it as a tropical storm. Again, it is too early to tell if it will develop. Tropical waves or low pressure areas in the Caribbean and Gulf of Mexico can form suddenly into a tropical storm or even hurricane. It has happened many times in the past. I am not suggesting it will happen with 91L. It is something to consider.

The Tropical Cyclone Formation Probability Guidance Product does give Invest 91L a chance of developing into a tropical cyclone in the next 48 hours. Again, that is only a small chance of developing.

Since, we are on the topic of tropical weather trouble, it brings rain. Various forecast models have different rain amounts, which are from GFS, Canadian, EURO, and Weather Prediction Center (WPC). They are from Weather.US and Weather Prediction Center (WPC)-Quantitative Precipitation Forecasts (QPF). These are 7 day rainfall totals.

The GFS has less rain for Texas and the Southwest. Southeast Texas has 2 to 4 inches of rain. The Southwest sees 0.50 to 2 inches of rain with 6 inches in the mountains.

The Canadian is not particularly generous for the Southwest. However for Southeast, Texas it has up to 8 inches of rain.

The EURO is generous for Southwest and Texas. The mountains of Arizona, New Mexico, and Colorado have up 8 inches of rain. Most of Arizona is wet as well compared to GFS and Canadian.

The WPC has 2 to 4 inches of rain over Southeast Texas. The Southwest has 0.50 to 1 inches of rain with isolated areas seeing 2 inches of rain.

The forecast models are unanimous on that rain will fall in Texas and the Southwest. They diverge on rain amount. Some forecast lesser amounts, while others forecast higher amounts. We should have a better idea of rain amounts later on.

My take on this. Invest 91L is more likely going to be a rain event. I do not expect 91L will develop at this point, but of course anything can happen. I do not think we will see another Harvey event from 91L. It is not forecasted to linger over Texas, like what Harvey or Allison did. As for Bud, the Southwestern US should welcome the rain with open arms. They will need it for sure.

The forecast models came from NCAR-Tropical Cyclone Guidance. The GIS drought map is from United States Drought Monitor.

Hurricane Bud And Invest 91L

NOAA/NESDIS/STAR GOES-16 ABI BAND 11 OR_ABI-L1b-RadF-M3C11_G16_s20181640230401_e20181640241168_c20181640241232.nc

It is June and the tropics are heating up. We have two areas of interests, Hurricane Bud in the East Pacific and Invest 91L in the Caribbean. Let’s start with Bud.

Hurricane Bud was a powerful Category 3 hurricane that weakened into a Category 2 hurricane with 100 mph 85 knots 161 km/h winds. It is due to cooler water Bud is encountering. Cooler water tends to weaken hurricanes even if there is not a whole of wind shear.

The area of warm water in the East Pacific is not that great. However, two major hurricanes have formed so far, which are Aletta and Bud. East Pacific is one of the most active basins despite its small size. As Bud weakens, where does it go? Here is a heat map forecast for Bud.

Most forecast models have Bud heading towards Baja California later by the end of the week. Where it goes after looks to be heading towards the Southwest. They can certainly use the rainfall as they are in a severe drought. The next question is how strong will Bud be?

Most forecast models have Bud as a tropical storm with one as a Category 1 hurricane around the time it us close to Baja California. From there, it is forecasted to weaken to a tropical depression.

The next problem is closer to home, Invest 91L. It is located off the coast of Honduras in the Caribbean. It is right now just a tropical wave with a cluster of thunderstorms. Many are wondering where will 91L will go? Here is a heat map forecast for 91L.

Most of the forecast models have 91L heading towards the Western Gulf of Mexico. One has it heading towards Florida looping around. It is just one forecast model. The forecast models at this time are heading towards Texas. Since this is a tropical wave, the forecast model is subject to change. The $64,000 question is will 91L become a tropical storm or hurricane, which would be Beryl.

Most forecast models keep 91L at tropical depression. Only one has a tropical storm at this time. Intensity forecast models are unreliable, especially if nothing has developed yet. Some factors do favor development. Let’s look at the water around Invest 91L.

The depth of warm water in Caribbean and Gulf of Mexico is great and over a large area. The heat potential is fairly high in the Gulf of Mexico and Caribbean. Warm water is certainly a factor in tropical development, but not the only one.

Wind shear over the Gulf of Mexico is within average and looks to be trending downward. Less wind shear is more favorable for tropical development. If there is strong wind shear over warm water, tropical development is greatly reduced as they blow tops of thunderstorm clouds that forming into something tropical.

At this time, I do not think Invest 91L will develop. It looks to be more of a rainmaker. However, anything can change between now and the end of the week.

The forecast models came from NCAR-Tropical Cyclone Guidance. The tropical heat came from A href=http://www.aoml.noaa.gov/phod/cyclone/data/go.html>Tropical Cyclone Heat Potential (TCHP). Wind shear map came from Tropical Cyclone Formation Probability Guidance Product.

Subtropical Storm Alberto Is Here

Subtropical Storm Alberto formed earlier today, which was Invest 90L. It is clearly a subtropical storm based on satellite image.

A subtropical storm has thunderstorms away from the center, mostly to the east in the Northern Hemisphere or west in the Southern Hemisphere. They look more like extratropical cyclones than tropical cyclones. Tropical cyclones have the most intense thunderstorms near the center.

Tropical storm force winds in Subtropical Storm Alberto are are up to 253 miles 407 kilometers 220 nautical miles across from northeast to southeast quadrant. The winds are east of the center. That is typical of a subtropical storm. The biggest question is where will Alberto go?

This is a heat map from NCAR-Tropical Cyclone Guidance. The heat map is within 300 miles (480 kilometers) from the center. The forecast models have a consensus that Alberto will go somewhere between Southeast Louisiana, Mississippi, Alabama, or Florida Panhandle. There is a small chance it go could deviate. The next question is how strong will Alberto be?

Most forecast model keeps Alberto as a tropical storm. However, one intensifies Alberto into a Category 1 to near Category 2 hurricane. I think Alberto will be a tropical storm at most. A hurricane is very remote at this time. I do not think Alberto will become a hurricane. It will more then likely become a full fledge tropical storm in the Gulf of Mexico. I would be more concerned of heavy rain and flooding from Alberto than wind.

Future Alberto Part 2?

The National Hurricane Center is keeping an eye on Invest 90L. They think in the next 5 days it has a high chance of developing into something tropical.

Interestingly, the intensity forecast keep Invest 90L as a tropical depression. One has it as a tropical storm in 36 hours.

This is not the latest intensity forecast model. It should come out later tonight. The biggest question is where does Invest 90L go?

This is a heat map from data from NCAR-Tropical Cyclone Guidance. The general consensus is it will linger over the Caribbean and possibly move into Mexico or Belize. From there, it goes north. The forecast models tend to congregate around Southeast Louisiana, Mississippi, and Alabama. There is a small risk that Southwest Louisiana and Southeast Texas could get hit by Invest 90L. This is still a rather low confidence forecast of where future Alberto will probably go in the next 5 days.

I would not be surprised we see Tropical Storm Alberto this weekend. The question is where does it go. Everyone in the Gulf of Mexico should keep an eye on Invest 90L. It can go anywhere it wants.

Future Alberto?

The first Invest for the 2018 hurricane season has been tagged as Invest 90L. It is in the Caribbean off the coast of Belize. It is an area of low pressure that is producing a lot of heavy rain. The question is where does it go in the next 5 days.

This is a heat map from data from NCAR-Tropical Cyclone Guidance. It looks like a low confidence forecast as it is all over the place. Some forecast models have it heading towards Alabama. Some have it towards Texas or Florida. It is low confidence because no surface low has formed yet. If a surface low was to form, than we could have a better idea including intensity.

Most forecast models want to keep Invest 90L as a tropical depression. Some want to intensify it to a tropical storm. If 90L is to become a tropical storm, it would be Alberto. I consider the intensity forecast low confidence. Truth is, intensity forecasts are not high confidence for the most part. Forecasting intensity is difficult despite better forecasting technology. I think 90L could become Alberto. Here are my reasons.

Let’s start with the Gulf of Mexico water. The Tropical Cyclone Heat Potential (TCHP) is greatest in the Caribbean, but not so in the Gulf of Mexico. It is May, so the Gulf of Mexico is not going to be this warm.

However, the depth of warm water in the Gulf of Mexico is fairly deep. If the water is very warm at the surface, but not so deep, then that can help weaken tropical cyclone development. If the water is warm, but not super warm, but deep, that is more favorable for tropical development. I would look at depth of warm water more so than surface temperature.

Another factor to look at is wind shear from Tropical Cyclone Formation Probability Guidance Product.

Wind shear over the Gulf of Mexico is below average. More wind shear tends to put a lid on tropical development. Less wind shear is more conducive to tropical development. A tropical wave over very warm and deep warm water with plenty of wind shear is less likely to develop. If it is over not so warm water with low wind shear, it is more conducive to develop into something tropical. Wind shear blows thunderstorm tops off, which inhibits tropical development.

I think Invest 90L could develop this weekend. It bears watching.