7/24/20 Tropical Weather Update – Douglas, Gonzalo, Hanna & the next Wave
Author: Nick Lilja
|| Published: 7/24/2020 at 12:29am
The tropics remain reasonably active as we move through the end of July. Not to say there are multiple monster Hurricanes, but two Tropical Storms and another wave coming off of Africa. Tropical Storm Hanna is in the Gulf of Mexico. Tropical Storm Gonzalo is out in the open Atlantic east of the Windward Islands. And the next wave after that is just coming off the coast of Africa.
Things are lined up – as they should be this time of the year – and the Tropics are keeping meteorologists busy.
Quick Notes on Broken Records
Tropical Storm Hanna becomes the earliest “H” storm to form int eh Atlantic on record. This beat Harvey from 2005. This is another record either broken or tied from the – very – active 2005 Hurricane Season.
The good news is that things are “burning” quickly this season, but not as “hot” as 2005. By this time in 2005, the season had birthed out three Hurricanes and two Major Hurricanes. Of the three hurricanes, Cindy and Dennis bothered the Gulf Coast.
This season, so far, there have been zero Hurricanes.
Tropical Storm Hanna is looking better on satellite tonight. You can see some good anticyclonic venting and cold cloud-tops developing near the center. The storm is getting better organized, and the Hurricane Hunters noted this during their passes through the storm tonight, and the National Hurricane Center digested the data and chose to upgrade Hanna to a Tropical Storm.
As of 10PM:
LOCATION…26.2N 91.4W
ABOUT 385 MI…620 KM ESE OF CORPUS CHRISTI TEXAS
MAXIMUM SUSTAINED WINDS…40 MPH…65 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 7 MPH…11 KM/H
MINIMUM CENTRAL PRESSURE…1002 MB…29.59 INCHES
Courtesy: nhc.noaa.gov
DISCUSSION AND OUTLOOK
At 1000 PM CDT (0300 UTC), the center of Tropical Storm Hanna was located near latitude 26.2 North, longitude 91.4 West. Hanna is moving toward the west-northwest near 7 mph (11 km/h) and a west-northwestward to westward motion is expected during the next couple of days. On the forecast track, the center of the storm is expected to move across the northwestern Gulf of Mexico on Friday and make landfall along the Texas coast on Saturday.
Maximum sustained winds are near 40 mph (65 km/h) with higher gusts. Additional strengthening is expected until the system makes landfall. Steady weakening is expected after Hanna moves inland.
Tropical-storm-force winds extend outward up to 35 miles (55 km) from the center.
The system continues to organize with curved bands becoming better established around the center. The cyclone certainly as the appearance of a tropical storm, and just minutes ago the NOAA Hurricane Hunters found winds to support upgrading the system to a 35-kt tropical storm. Data from the aircraft also show that the minimum pressure has dropped to 1002 mb, indicating that the system is on a developing trend.
Hanna is moving fairly slowly to the west-northwest, with the latest initial motion estimated to be 285/6 kt. This west-northwest motion should continue on Friday, but a turn to the west is expected by Friday night as a subtropical ridge strengthens to the north of the cyclone. This steering flow should take the center of the storm across the southern Texas coast in 36 to 48 hours. After landfall, the storm is forecast to turn south of west across extreme southern Texas and northern Mexico. The models have shifted southward again this cycle, and the NHC track forecast has been adjusted in that direction.
Additional strengthening seems quite likely until the storm makes landfall since it is expected to remain over the very warm Gulf of Mexico waters and in generally low wind shear conditions. After landfall, steady weakening should commence, and the cyclone should dissipate over the rugged terrain of northern Mexico in about 4 days. The NHC intensity forecast is a little above the previous one and at the high end of the guidance given the system’s well organized structure and favorable environment.
Due to the southward shift in the track forecast, the tropical storm warning has been extended southward from Port Mansfield to the Mouth of the Rio Grande.
Tropical Storm Hanna is the earliest 8th storm on record. The previous record was in 2005 when Harvey formed on August 3rd.
HAZARDS AFFECTING LAND
Key messages for Tropical Storm Hanna can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.
— WIND: Tropical storm conditions are expected in the warning area by Friday night or Saturday morning. Tropical storm conditions are possible within the watch area by Friday night or Saturday morning.
— RAINFALL: Hanna is expected to produce 3 to 5 inches of rain with isolated maximum totals of 10 inches through Monday along the Gulf Coast of the United States from Louisiana to south Texas, and inland to the Mexican states of Coahuila, Nuevo Leon, and northern Tamaulipas. This rain may result in life-threatening flash flooding, rapid rises on small streams, and isolated minor to moderate river flooding.
— SURF: Swells generated by Hanna are expected to increase and affect much of the Texas and Louisiana coasts during the next few days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
Tropical Storm Gonzalo is a peculiar little storm. IT is very small. In fact, I bet it was tough to even pick it out on the map above. Yesterday it was fighting through some weak shear and dry air, and struggled. Today it faired a bit better, but isn’t exactly having a great “go” at it.
As of 10PM:
LOCATION…9.9N 50.6W
ABOUT 730 MI…1170 KM E OF THE SOUTHERN WINDWARD ISLANDS
MAXIMUM SUSTAINED WINDS…60 MPH…95 KM/H
PRESENT MOVEMENT…W OR 275 DEGREES AT 14 MPH…22 KM/H
MINIMUM CENTRAL PRESSURE…1000 MB…29.53 INCHES
Courtesy: nhc.noaa.gov
DISCUSSION AND OUTLOOK
At 1100 PM AST (0300 UTC), the center of Tropical Storm Gonzalo was located near latitude 9.9 North, longitude 50.6 West. Gonzalo is moving toward the west near 14 mph (22 km/h). A westward to west-northwestward motion with an increase in forward speed is expected through the weekend. On the forecast track, the center of Gonzalo will approach the southern Windward Islands Friday night and move across the islands Saturday and into the eastern Caribbean Sea Sunday.
Maximum sustained winds are near 60 mph (95 km/h) with higher gusts. Some strengthening is forecast during the next day or two, and there is still a chance that Gonzalo could become a hurricane. Weakening is expected after Gonzalo moves into the Caribbean Sea and the cyclone is expected to dissipate by the middle of next week.
Tropical-storm-force winds extend outward up to 25 miles (35 km) from the center.
After ingesting a hefty portion of dry high statically stable air this morning, Gonzalo appears to be on the comeback trail. Enhanced infrared BD-curve imagery shows that a small Central Dense Overcast with cloud tops of -80C is redeveloping over the surface center. A compromise of the available subjective and objective satellite intensity estimates supports maintaining 50 kt for this advisory.
This morning’s upper air sounding from Barbados revealed a very dry, high statically stable atmosphere with a mean RH of 23 percent and a CAPE of only 327 J/Kg. Consequently, Gonzalo will be moving into a rather harsh thermodynamic environment over the weekend. As a result, the NHC forecast calls for weakening beyond the 48 hour period as it enters the eastern Caribbean sea and dissipation well south of Hispaniola at day 5, or sooner as a few of the global models suggest. The intensity forecast is basically an update of the previous advisory through 48 hours, indicating a hurricane approaching and moving over the southern Windward Islands, and a faster weakening trend beyond day 2, similar to a consensus of the large-scale models.
The initial motion is estimated to be westward, or 275/12 kt within the stiff mid-tropospheric steering flow provided by an anchored subtropical ridge to the cyclone’s north. The song remains the same, with Gonzalo expected to speed up toward the west and west-northwest through the entire period. The NHC official
forecast is based on a blend of the various consensus aids and is down the middle of the tightly clustered guidance.
HAZARDS AFFECTING LAND
Key messages for Gonzalo can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT2 and WMO header WTNT42 KNHC.
— WIND: Hurricane or tropical storm conditions are possible within the respective watch areas on Saturday.
— RAINFALL: Gonzalo is expected to produce total rain accumulations of 2 to 5 inches, with isolated maximum amounts of 7 inches in Barbados and the Windward Islands from Friday night through Sunday night. Gonzalo is also expected to produce total rain accumulations of 1 to 2 inches in Trinidad and Tobago. Rainfall in Barbados and the Windward Islands could lead to life-threatening flash floods.
The next Tropical wave is just coming off the coast of Africa. This next wave is much larger than Gonzalo. Take a look at this infrared imagery from the College of DuPage:
Courtesy: College of DuPage Meteorology
Gonzalo is the little burst of red convection on the far left-hand side of the image. The next Tropical Wave is, well, just off the coast of Africa.
So far, model guidance is a bit split on this next wave. So far, it looks like it won’t do much until it gets to – roughly – where Gonzalo is right now. Teh European model develops this into a tropical system pretty quickly once is emerges into the Atlantic while the Americna model is a bit more conservative keeping it as an open wave – at best – and never developing anything.
From the NHC:
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Thu Jul 23 2020
For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
The National Hurricane Center is issuing advisories on Tropical Storm Gonzalo, located several hundred miles east of the southern Windward Islands.
The National Hurricane Center is also issuing advisories on Tropical Depression Eight, located over the central Gulf of Mexico.
1. A tropical wave located near the west coast of Africa is expected to move westward across the tropical Atlantic during the next several days. Some development of this system is possible early next week when it reaches the western tropical Atlantic.
Courtesy: nhc.noaa.gov
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…30 percent.
So, for now, we are playing the waiting game.
Hurricane Douglas
Courtesy: College of DuPage Meteorology
Over in the Pacific there is Hurricane Douglas. This one scares me. Not because of the storm or anything meteorological. But my high school Track and Cross Country coach was “Coach Douglas” and I still have some unresolved angst from my teenage years, apparently.
Anyway! Back to the storm.
As of 5PM (HST):
LOCATION…14.9N 138.8W
ABOUT 1125 MI…1810 KM ESE OF HILO HAWAII
MAXIMUM SUSTAINED WINDS…130 MPH…215 KM/H
PRESENT MOVEMENT…WNW OR 295 DEGREES AT 18 MPH…30 KM/H
MINIMUM CENTRAL PRESSURE…954 MB…28.17 INCHES
Courtesy: nhc.noaa.gov
DISCUSSION AND OUTLOOK
At 500 PM HST (0300 UTC), the center of Hurricane Douglas was located near latitude 14.9 North, longitude 138.8 West. Douglas is moving toward the west-northwest near 18 mph (30 km/h), and this motion is expected to continue for the next few days with a gradual decrease in forward speed and a slight turn toward the west. On the. forecast track Douglas will approach the Hawaiian Islands Saturday night, and be near those Islands on Sunday.
Maximum sustained winds have increased to near 130 mph (215 km/h) with higher gusts. Douglas is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Gradual weakening expected to begin on Friday and continue through the weekend. Douglas is forecast to be near hurricane strength when it approaches the Hawaiian Islands.
Hurricane-force winds extend outward up to 30 miles (45 km) from the center and tropical-storm-force winds extend outward up to 90 miles (150 km).
Douglas remains a well organized hurricane in visible and infrared satellite imagery. The 15-nmi-wide eye remains very distinct and the surrounding cloud tops have cooled since the previous advisory. Although not evident in conventional satellite imagery, a recent AMSR-2 microwave satellite image showed evidence of concentric eyewalls. Subjective Dvorak T-numbers from TAFB and SAB are 6.0 (115 kt) and recent UW/CIMSS ADT estimates have been creeping upward, and now also close to T6.0. Based on these estimates, the initial wind speed has been raised to 115 kt, making Douglas a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.
Douglas has likely reached its peak intensity as it will be moving over cooler SSTs during the next day or so. Although the predicted track of the hurricane will bring it over warmer waters when Douglas approaches the Hawaiian Islands, vertical shear is forecast to increase at that time. This is expected to result in continued gradual weakening, however Douglas is forecast to be near hurricane strength when it moves close to Hawaii. Despite the slight increase in the initial intensity, the updated NHC wind speed forecast is unchanged from the previous advisory through 36 hours, and then follows the intensity consensus guidance thereafter.
Douglas continues moving quickly west-northwestward or 295/16 kt. The hurricane is forecast to remain on this heading with some slight reduction in forward speed during the next day or so as it remains to the south of a large mid-level ridge. After that time, Douglas is forecast to turn westward to the south of another strong mid-level ridge the is predicted to build well north of the Hawaiian Islands later in the weekend. The new NHC track forecast is very similar to the previous advisory and lies just south of the various consensus aids out of respect of the ECMWF and its ensemble mean which lie along the southern edge of the track envelope.
HAZARDS AFFECTING LAND
— SURF: Swells generated by Douglas are expected to begin affecting portions of the Hawaiian Islands on Saturday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
Nick is former television meteorologist with stints in Amarillo and Hattiesburg. During his time in Hattiesburg, he was also an adjunct professor at the University of Southern Mississippi. He is a graduate of both Oregon State and Syracuse University that now calls Houston home. Now that he is retired from TV, he maintains this blog in his spare time.
