Hermine "Pulling an Humberto?"
Afternoon September 6,
Tropical Storm Hermine has managed to rapidly form and develop in the southwestern Gulf of Mexico from the remnants of eastern Pacific Tropical Depression 11-E. There has been a "tropical wave drought" in the Gulf and eastern Pacific regions recently, and most tropical cyclones in this part of the world develop due to tropical waves originating from Africa. The "tropical wave drought" (or lack of tropical waves) in this region has been due to the fact that the most recent string of wave disturbances from Africa have developed into Danielle, Earl, Fiona, and Gaston in that order, and so far neither of those systems have made there way toward the eastern Pacific or Gulf regions (were still watching the remnants of Gaston, we'll see if in the very long range if Gaston makes it to the Gulf, too early to tell). In my synoptic history of 11-E/Hermine below, you can see how this system managed to form from the ITCZ (intertropical convergence zone) instead of an African tropical wave.
Below my 11-E/Hermine synoptic history below, I have also posted my synoptic history of Humberto I wrote about 3 years ago. Like Hermine, Humberto was a rapidly developing September tropical storm in the Gulf of Mexico. Humberto was so impressive in that it went from tropical depression to hurricane in the same day (Sept. 12, 2007) and took residents in High Island, Texas by surprise do to its rapid development off the coast (they not expecting hurricane conditions when the system was just a tropical depression early in the day). Hermine's recent rapid development today makes us ask, could Hermine be "pulling off an Humberto?" However, unlike Humberto which hit the east Texas coast, Hermine is headed for northeast Mexico just south of the Texas/Mexico border. Small, rapidly developing storms like Humberto and Hermine have small wind fields, so the worst winds will be tightly confined to the center. Hermine though will be producing rains at and away from the center, and will be the third tropical cyclone to affect the Rio Grande region near the Texas/Mexico border this season, after Alex and TD 2 had done so back-to-back in June. Lets hope that Hermine doesn't causing another flood in this region after Alex & TD 2 has already caused problems in the area early this season.
I am forecasting that Hermine's center will make landfall later this evening in northeastern Mexico while exhibiting maximum sustained winds ranging from 65 mph (strong tropical storm) to as strong as 80 mph winds (cat. 1 hurricane). If Hermine reaches hurricane strength tonight, it will only be the second Atlantic tropical cyclone on record to go from tropical depression to hurricane in the same day while so close to land, a feat only achieved by Humberto to date. Hermine is running out of time to do this as it has just recently flattened out in intensification, not strengthening beyond 60 mph winds between 1 PM and 4 PM CDT. However, the central pressure has dropped from 995 to 992 mb between those hours, so I think it'll strengthen at least a little more before tonight's landfall.
Tropical Storm Hermine
(Eastern Pacific Tropical Depression Eleven-E)
Dates: September 5 to Present (September 3 to 4)
Maximum winds: 60 mph (35 mph)
Minimum pressure: 992 mb (1005 mb)
Synoptic situation: Tropical depression Eleven-E of the 2010 Eastern Pacific Hurricane Season developed from enhanced storm activity along the ITCZ (intertropical convergence zone) that began on September 2 to the south of the Isthmus of Tehuentepec of southeastern Mexico. A strong upper trough over the United States was located at the longitude of the disturbance on this day, and it seems plausible that relatively higher pressures south of the upper trough perhaps allowed for anticyclonic upper ridging than enhanced the outflow over the area such that the ITCZ storms were regionally enhanced. This led to a broad east-west area of low pressure along the ITCZ on September 3 that rapidly organized into tropical depression Eleven-E later that day. The depression drifted northward into the low-level ridge weakness associated with the United States upper trough, making landfall across the Isthmus of Tehuentepec early on September 4 and weakening into a broad remnant low. The northern side of the remnant low produced strong storm clusters across the Bay of Campeche later that day, with the storm activity organizing about the remnant low as it moved into the western portion of the Bay early on September 5. As the center of circulation became better defined while continuing northward into the southwestern Gulf of Mexico, it was upgraded to tropical depression ten during the late evening.
A subtropical ridge to the north was building in the wake of the United States upper trough, which allowed for an increasingly westward component to the northward track of the depression on the 6th. Over warm waters and under low shear, tropical depression ten briskly intensified into Tropical Storm Hermine during the early morning, and was already a strong tropical storm by the afternoon hours.
Visible satellite image of intensifying Tropical Storm Hermine taken during the afternoon hours of September 6
Warnings: At the formation of tropical depression Eleven-E close to the south Pacific-facing coast of Mexico on September 3, a tropical storm warning was immediately issued from Boca de Pijijiapan to Puerto Angel. Warnings were dropped after the depression made landfall and dissipated into a remnant low early on the 4th.
A tropical storm warning was immediately issued for the east Gulf-facing coast of Mexico, from Tampico northward to the mouth of the Rio Grande River, when tropical depression ten formed during the late evening of September 5. The warning was extended northward to Baffin Bay, Texas early on the 6th when the depression intensified to Tropical Storm Hermine. With Hermine intensifying quickly during the morning hours, a hurricane watch was issued from Baffin Bay, Texas southward to Rio San Fernando, Mexico. The tropical storm warning was discontinued south of La Cruz, Mexico and extended northward to Port O’ Connor, Texas as Hermine had tracked a little more toward the north than initially forecast.
Impacts: Hermine has yet to make landfall as of this writing. No major impacts so far, but Hermine is likely to produce a tight area of high winds at landfall tonight, and produce rainfall in and south of the Rio Grande Region inland after landfall.
Dates: September 12 to 13, 2007
Maximum winds: 85 mph (Category 1)
Minimum pressure: 985 mb
Synoptic situation: The precursor to this cyclone was the same decaying frontal boundary that produced the pre-Gabrielle surface low. The southern portion of the front decayed into a surface trough over Florida. The surface trough moved westward with an associated broad storm cluster across the Yucatan and southern Gulf of Mexico on the 8th through the 10th. The trough consolidated as a weak surface low just southeast of Texas on the 11th, and conditions were generally favorable with warm waters and low shear under a deep-layered ridge to the north dominating the southern United States. A large frontal system moving into the southern United States eroded the ridging to the north except for a small upper ridge directly over the surface low that provided a favorable outflow environment for storms to develop over the surface low. The storm activity quickly organized around the center, and tropical depression nine formed just off of the Texas coast by late morning on the 12th.
The depression quickly became Tropical Storm Humberto in the early afternoon while developing in the favorable outflow aloft. Low-level ridging to the east was driving the new storm northward into the Texas coast. Humberto developed unusually fast, forming a tight core of hurricane winds just before landfall in southeastern Texas. Humberto continued strengthening till landfall, reaching a peak of 85 mph winds while the center crossed just east of High Island very early on the 13th. This was the first time on record for a cyclone so close to landfall to develop from a tropical depression to a hurricane in the same day.
The large frontal system just north of Humberto stalled, and the upper ridge that had been over Humberto had been pushed further south into the Gulf while expanding. Hurricane Humberto made an eastward turn on the north side of the upper ridge and just south of the front. The hurricane finally weakened to an inland tropical storm in southwestern Louisiana by the late morning of September 13. During the afternoon, Humberto quickly weakened to a dissipating tropical depression moving eastward across Louisiana, and the National Hurricane Center issued its final advisory.
The remnant low of Humberto soon merged with the stalled front to the north on the 14th, and the low tracked eastward into Mississippi on the north side of the expanding Gulf ridge to the south. While moving across northern Alabama, the remnant low became indistinct along the frontal zone later on the 14th.
Tropical Storm Humberto forms off of the Texas coast on September 12. The above visible satellite image was taken during the early afternoon. Humberto became a hurricane that evening.
Warnings: A tropical storm warning was immediately required as tropical depression nine was declared just off of the Texas coast. The warning was issued in eastern Texas and parts of southwestern Louisiana. Tropical storm watches extended further east into Louisiana. This watch was upgraded to a warning hours later. Humberto’s record development before landfall was not anticipated, and a small hurricane warning for the tight hurricane wind core was issued as Humberto was upgraded. This only provided a couple of hours warning time, far short of the ideal 24 hours for a warning. As tropical storm and hurricane conditions cleared from the coast after landfall, all coastal warnings were removed.
Impacts: The most notable impacts from Humberto occurred in a small swath in the southeastern corner of Texas and the southwestern corner of Louisiana as the hurricane had a tight core. The peak storm surge was measured at 4.87 ft, with a 2 to 4 ft average near the landfall site. Hurricane force winds occurred in a tight area near the landfall site, with some notable wind damage in High Island, Texas that was initially assessed to be from a tornado. The highest rainfall total from the storm was 14.13 at East Bay Bayou, Texas, and a narrow swath of 3 to 5 inches spreads from this area into central Louisiana. As a remnant low, Humberto produced locally heavy rains across the southeastern United States. The total damage from Humberto is estimated at $50 million, with costs coming from flood damage and also winds damaging trees and power lines.