Jeff Masters on NE Weather, Leslie, Michael, & New Waves

Severe weather in the Northeast U.S.; updates on 90L, 91L, Leslie and Michael

Published: 4:07 PM GMT on September 08, 2012

A significant severe weather outbreak is underway today across much of the Northeastern U.S., including metro New York City and Philadelphia. NOAA’s Storm Prediction Center has placed the region in their “Moderate Risk” area for severe weather. A fall-like low pressure system with a very powerful cold front will sweep through the region today, triggering widespread severe thunderstorms that may organize into a “derecho” event with damaging winds covering a large swath of the Northeast. A few tornadoes may accompany the event, and several tornado warnings have already been issued in New York, with a possible tornado touchdown in the Point Breeze section of the Rockaway peninsula in Queens. The same storm system killed four people on Friday in northeast Oklahoma; three of the deaths occurred when strong thunderstorms winds blew a mobile home into a ravine. Record heat was observed in advance of the storm’s cold front yesterday; Wichita Falls, TX hit a record high of 109, the hottest temperature ever recorded there so late in the season. When the cold front blew through at 7 pm CDT, the temperature dropped 15 degrees in 16 minutes, falling to 66 degrees by midnight. Wunderground meteorologist Shaun Tanner has more on the severe weather potential for the Northeast in his blog.

Figure 1. Severe weather potential for Saturday, September 8, 2012.

90L in the Gulf not a threat to develop
A partial remnant of Hurricane Isaac off the coast of the Florida Panhandle, Invest 90L, continues to be disrupted by wind shear, and no longer has time to develop before landfall occurs along the Florida Gulf Coast tonight or Sunday. Visible satellite loops show that 90L has a small area of poorly organized heavy thunderstorms, which will bring some areas of heavy rain to Florida today and Sunday.

Leslie still struggling with cool waters
Tropical Storm Leslie continues to feel the impact of the the cool waters it stirred up due to its long pause south of Bermuda, and remains a 65 mph tropical storm. The storm has no eyewall, as seen on satellite loops, but has cleared out a large cloud-free center. As Leslie continues to move north over warmer water, the storm should be able to build an eyewall and become at least a Category 1 hurricane. However, Leslie is expected to pass far enough to the east of Bermuda today and tonight that top winds of 45 mph will be observed on the island. Bermuda radar shows a large area of heavy rain from Leslie is very close to the island.

Figure 2. Morning radar image of Tropical Storm Leslie from the Bermuda radar.

Forecast for Leslie
The strong trough of low pressure pulling Leslie to the north will bring Leslie very close to Newfoundland, Canada by Tuesday night or Wednesday morning. At that time, Leslie should be weakening due to cooler waters and increased wind shear, and is likely to be a tropical storm. Heavy rain will be the main threat to Newfoundland. The latest 11 am EDT NHC wind probability forecast calls for a 24% chance that Leslie will be a Category 1 or stronger hurricane Wednesday morning at 8 am EDT, when the storm will be near Newfoundland. Even if the core of Leslie misses Newfoundland, the island will still likely experience tropical storm-force winds, since 39+ mph winds will probably extend outward from its center 180 miles to its west on Tuesday and Wednesday. Large swells from Leslie continue to pounding the entire Eastern Seaboard, and are creating beach erosion and dangerous rip currents.

Figure 3. Hurricane Michael as seen by NASA’s Aqua satellite at 11:50 am EDT Friday September 7, 2012. At the time, Michael was a Category 2 hurricane with 105 mph winds. Image credit: NASA.

Hurricane Michael weakens to Category 2
Hurricane Michael remains a Category 2 storm with 105 mph winds, out over the open mid-Atlantic Ocean. Satellite loops show that Michael is still an impressive storm with a well-developed eye. None of the models show that Michael will threaten any land areas during the coming five days, and Michael will likely die at sea over cold waters northeast of Newfoundland in 5 – 7 days.

91L off the coast of Africa
A tropical wave that emerged off the coast of Africa on Friday has been designated Invest 91L by NHC today. Most of the reliable computer models are predicting that 91L will develop into a tropical depression by Wednesday. None of the reliable computer models foresee that this storm will be a threat to the Lesser Antilles Islands, but it is still early to be assuming that 91L will recurve harmlessly out to sea.

Hurricane Potential in The Gulf

Gulf of Mexico disturbance 96L poorly organized, but may develop
Posted by: Dr. Jeff Masters, on June 22, 2012 +27
An area of low pressure and heavy thunderstorms in the Southern Gulf of Mexico (designated 96L by NHC Thursday afternoon) is a threat to become a tropical depression this weekend, and all interests along the Gulf of Mexico coast should pay attention to the progress of this disturbance. The disturbance is bringing occasional heavy rains to Western Cuba, South Florida, and Mexico’s Yucatan Peninsula. Top winds measured in the surrounding ocean areas this morning were 27 mph, gusting to 34 mph, at the Yucatan Basin buoy between Mexico’s Yucatan Peninsula and the Cayman Islands. Our wundermap for the surrounding ocean areas show a ship that measured sustained winds of 30 mph near the western tip of Cuba this morning. Satellite-based surface wind measurements from the newly-available Oceansat-2 scatterometer, courtesy of India, show no signs of a surface circulation. Visible satellite loops show that 96L is less organized than it was Thursday evening, with only a little low-level spin apparent, and a modest area of disorganized thunderstorms. The decrease in organization is probably due to the moderate to high levels of wind shear of 15 – 25 knots over the region. Water vapor satellite loops show a modest region of dry air over the Central Gulf of Mexico, which is interfering with development. Ocean temperatures are 81 – 83°F in the Western Caribbean and Southern Gulf of Mexico, which is about 1°F above average, and warm enough to support formation of a tropical storm. A hurricane hunter mission is scheduled to investigate 96L this afternoon, but this mission will probably be cancelled due to the disturbance’s lack of organization.

Figure 1. Morning satellite image of the tropical disturbance 96L in the Southern Gulf of Mexico.

Forecast for 96L
Wind shear is predicted to remain in the moderate range through Saturday night, which is likely low enough to allow 96L to develop into a tropical depression; NHC gave 96L a 70% chance of developing into a tropical depression by Sunday morning, in their 8am EDT Tropical Weather Outlook. By Sunday, wind shear is predicted to increase, limiting 96L’s potential for intensification. Where the storm might go is anybody’s guess. The GFS model has consistently been predicting that a trough of low pressure pushing off of the U.S. East Coast will be capable of grabbing the disturbance and accelerating it to the northeast across Florida north of Tampa Bay on Sunday or Monday. However, an ensemble of forecasts from the model created by running the model with slight perturbations to the initial conditions shows a wide range of possible tracks, both to the east over Florida, and to the west towards Texas and Louisiana (Figure 2.) The latest ECMWF model run (00 UTC) predicts that the trough will not be strong enough to pull 96L northeastwards across Florida. The ECMWF predicts that a ridge of high pressure will build in over the Southern U.S., forcing the disturbance westwards across the Gulf of Mexico and into South Texas by Thursday. The UKMET model also favors a track west towards Texas. The NOGAPS model takes 96L to the northwest into Louisiana/Texas by Monday.

Figure 2. Which way will 96L go? The GFS model, when run at low resolution with 20 slightly different perturbations to the initial conditions in order to generate an ensemble of different forecasts, shows two distinct possibilities: a sharp east turn to move over Florida, or a west or northwest motion towards Louisiana or Texas. The high-resolution official GFS forecast is shown in white.

Jeff Masters


Severe Weather & Tornadoes — Why Now?

Why So Many Tornadoes Are Striking the US

Brett Israel, OurAmazingPlanet Staff Writer
Date: 02 March 2012 Time: 05:55 PM ET


Wind speed at 18,000 feet in the atmosphere. The darkest shade represents winds of up to 150 mph.
Wind speed at 18,000 feet in the atmosphere. The darkest shade represents winds of up to 150 mph.

A warm spell and a low-dipping jet stream are fueling the monster storms that are spawning tornadoes today across a wide swath of the country, weather experts said.

Today, the Storm Prediction Center has received 311 reports of severe weather, including 48 reported tornadoes and a few reported fatalities. This massive storm system also spawned deadly tornadoes on Leap Day, which raked Kansas, Nebraska, Illinois, Indiana, Missouri, Kentucky and Tennessee. The severe storms killed at least 12 people and included a strong EF-4 twister in Harrisburg, Ill., a rarity for February.

As of this morning, the severe storm risk area covered an estimated 162 million people, or 56 percent of the United States, according to weather experts at the National Oceanic and Atmospheric Administration (NOAA).

While the main tornado season runs from spring to early summer, this year’s early outbreaks show that tornadoes can form under a variety of conditions and strike during fall and winter, too. This year’s mild winter and warm start to meteorological spring has upped the risk of dangerous storms.

“We’ve been in a very warm pattern all winter,” said meteorologist Mark Rose of the National Weather Service in Birmingham, Ala. “Because it has been so mild, it increases our chances for severe weather.”

Also behind this week’s twisters is a low-dipping jet stream. The jet stream is moving at a blistering pace today across the Mid-South and Ohio River Valley. NOAA satellites clocked the jet stream at 150 mph (241 kph) across these regions. The jet stream is bringing cold air from Canada to mix with the warm, moist air from the Gulf of Mexico. Where these two differing air masses meet is often an area of severe weather, hail, winds and even tornadoes. [Infographic: 2012’s Active Tornado Season]

The warm air and rapid jet stream will keep fueling the storms thru tonight and into the weekend, according to NOAA. Weather experts continue to warn that dangerous tornado outbreaks could explode throughout the evening and overnight hours across the Mid- and Deep South and Ohio River Valley.

“We actually are looking at a risk from the Gulf Coast to the Great Lakes to west of the Mississippi to the East Coast,” Craig Fugate, director of the Federal Emergency Management Agency, told the Weather Channel. “And these storms are moving fast.”


Southern Plains Severe Weather Alert

Severe weather, including Tornadoes likely on Monday for the South U.S. Plains

Published on November 5, 2011 9:40 am PT
– By TWS Senior Meteorologist
– Edited by Staff Editor

( – A storm system will move out of Southern California through Arizona on Sunday. This system will move eastward and impact Northwest Texas to Western Oklahoma in the form of supercells with a tornado setup developing. 

We usually want to wait for these things to get a bit closer for details to run the numbers for the Tornado Risk Model and this seems about the right time to get a ‘general’ idea of the setup

An upper level jet streak will be moving through the New Mexico and Western Texas border on Monday evening. This will provide the needed upper level divergence across the Eastern Texas Panhandle, down to Childress.

This upper level divergence, strong instability, good dewpoint/temp value, low level shear, and even convergence at the surface will make for a severe weather setup, including tornadoes on Monday evening.

This zone will be narrowed down and does issue Tornado Watches on this site for viewers that are interested. Those watches appear on the top right of all articles and the main page when issued and one might be needed on Monday should trends continue.

The main threat will be hail, but the Tornado Model numbers indicate a yellow/red value which is good enough for EF1 to EF2 type tornadoes on the south end of the storm system, over and around Childress, Texas.


Severe Weather on the Way

10/5/2011– Tornaodes in Texas & Snow out west = severe coming to midwest / east coast soon

Posted on October 5, 2011 by sincedutch


As the low pressure system moves in from the west / northwest .. it is pulling cold air to the south.. also.. the southern arm of the system is pulling warm air up from the south.. mixing in North Texas.. producing tornadoes / tornadic cells.

here is the video:

to see the video and for more, go to: