Category: Posts EN

 

The 2017 hurricane season in the Atlantic basin was one of the most active and destructive on record (see graphic below). In terms of ACE (Accumulated Cyclone Energy, a measure of the total destructive power of all the cyclones in the season), it was the seventh-most active season on record. Hurricane Harvey became the costliest Atlantic hurricane ever after wrecking the Houston, Texas metro area in late August. Hurricane Irma, the strongest hurricane ever observed outside of the Gulf of Mexico and Caribbean, raked the northern Caribbean and southeast U.S. in early September. Just a few weeks later, Hurricane Maria (lead image, courtesy of astronaut Paolo Nespoli and NASA) devastated Puerto Rico, causing widespread destruction from which the island is still recovering.

 

 

The energetic 2017 season can mostly be blamed on a favorable orientation of the ENSO (El Nino Southern Oscillation) weather pattern. Specifically, it was in the negative phase (La Nina), typically favorable for tropical cyclone development in the Atlantic basin. Sea surface temperatures were also running above normal over the Atlantic, providing fuel for cyclone development.

 

 

The La Nina that developed in Fall 2017 has persisted through the winter, but there are indications that it will swing back towards neutral (see graphic above), or perhaps even rise into the positive (El Nino) phase, albeit weakly positive. El Nino is typically not as favorable for hurricane development in the Atlantic due to increased upper level winds which tend to disrupt hurricane organization. However, even less-active-than-normal seasons in the past have provided devastating landfalls. Hurricanes Hugo in 1989 and Andrew in 1992 both occurred in otherwise quiet seasons. Sea surface temperatures over the Atlantic basin are also expected to remain near to above normal. And seasonal forecasts can change – in 2017, early predictions of a developing El Nino and a quiet hurricane season proved wildly optimistic. The bottom line is that even if 2018 turns out to be a quieter tropical season than 2017, coastal residents shouldn’t be caught unawares when a major hurricane looms.

 

A dynamic springtime weather pattern remains in control across much of the country. A storm system will develop over the Mid-South Thursday night with scattered storms building over the Ozarks. The animation above shows the evolution of Friday storms as depicted by UBIMET’s high-resolution RACE model. The main threats through Friday morning will be large hail and heavy rainfall, leading to flash flooding in spots.

 

 

Later in the day, instability will build with solar heating closer to the Texarkana region. Storms will form into a stronger squall line and move southeast through the afternoon and evening hours. Isolated tornadoes, very large hail, and damaging winds will occur in this time frame. Storms will tend to weaken by early Saturday morning as they approach the Gulf coastal plain.

Severe thunderstorms tore across Texas on Tuesday and Tuesday evening bringing damaging winds and large hail to parts of the state.

Houston’s Hobby airport was hit especially hard with a severe thunderstorm late Tuesday evening. A preliminary storm survey done by the national weather service concluded that winds reached 80 mph (70 kts) at the airport just before midnight.

Those wind speeds caused damage to a private hangar on the airport grounds. 8 planes at the hangar suffered damage, and all totaled damage estimates at the airport are expected to be in the millions of dollars.

The severe weather in Houston was part of a larger severe weather outbreak that stretched from Texas to Pennsylvania. There were several reports of tornadoes, as well as hundreds of large hail and damaging wind reports from 16 states.

Large hail up to the size of baseballs balls (7 cm) fell near Pangburg, Arkansas Tuesday afternoon. Many reports of wind gusts ranging from 60-70 mph (52-61 kts) were observed, causing additional damage and even several injuries.

 

Scattered severe storms have erupted from Texas through the Mississippi Valley to the Ohio Valley today. Currently the storms have consolidated to form a long squall line moving steadily east. High winds will be the most widespread threat going forward, although isolated tornadoes or large hail may still occur.

 

 

Numerous reports of very large hail and high winds (green and blue dots above, respectively) have been received since severe storms developed around midday. Hail stones to three inches (7.5 cm) in diameter were observed near Poplar Grove, Missouri. Gusts upwards of 70 mph (113 kph) have occurred in several places. There have also been several reports of tornadoes (red dots above), including one near Galatia, Illinois that completely destroyed several homes and farm buildings. More reports are likely as the squall line moves east overnight.