Posts

Doug Simonian

Tropical downpours likely in Northeast US this weekend

/by

Other than a few scattered passing thunderstorms on Wednesday, much of the Northeast US has been devoid of rain over the past several weeks. This is about to change, perhaps dramatically so in some spots. On Sunday, a cold front and associated potent shortwave trough with plenty of vorticity will run into a well established Southeast Ridge, and the remnants of Tropical Storm Julia — two great moisture sources. This combination of energy, dynamics, and moisture — as well as the fact that the ridge and the mid-level flow are parallel to the frontal boundary — will lead to the potential for slow-moving tropical downpours, some of which will train over each other and lead to flash flooding.

As we move towards Autumn, atmospheric troughs can deepen and amplify more than during the warmer summer season. This, combined with tropical moisture and dynamics can lead to impressive meteorological results. This particular shortwave trough is digging from the Great Lakes all the way down to the Tennessee Valley, and is even tilting neutrally or negatively on some guidance. This acts to slow down the atmospheric flow even more, leading to a prolonged fetch of moisture, lift, convergence, and thus heavy downpours.

Read more

John Homenuk

The relentless ridge and its effect on 99L

/by

When meteorologists looked at the medium range forecasts on the first of August, one thing was clear, it appeared: Troughiness would become more likely east of the Mississippi River by the tail end of the month. Brought on by a change in tropical forcing and an overall adjustment in the hemispheric wave pattern, this seemed like a moderate to high confidence forecast. Those ideas were wrong.

Instead, poor modeling and a changed pattern evolution has led to an entirely different outcome: The mid level ridging, which has become a staple of the East Coast weather pattern since early July, will return. Forecast model guidance has altered the hemispheric pattern evolution to support a -PNA (Pacific North American oscillation), or troughiness on the West Coast of the United States. This will only feed the development of a strong ridge from the Southeast United States into the Mid Atlantic.

Read more

John Homenuk

Patricia becomes strongest hurricane ever in satellite era

/by

Hurricane Patricia, located in the Eastern Pacific and in the midst of a catastrophic turn toward Mexico, strengthened this morning, becoming the strongest hurricane on record in the Western Hemisphere. With maximum sustained winds of 200 miles per hour, gusting to 245 miles per hour, and minimum central pressure of 880mb, Patricia is also the strongest hurricane since the satellite era began.

The incredible hurricane has strengthened dramatically — at a near record breaking pace — over the past 24 to 48 hours. The hurricanes maximum sustained winds increased 100 knots within a 24 hour period from 4am CDT on Thursday to 4am CDT on Friday. This morning, Patricia strengthened additionally, becoming the strongest Hurricane ever measured within the National Hurricane Center’s area of responsibility.

Read more

Doug Simonian

Joaquin strengthens, models shift dramatically seaward with track

/by

As it moved through the very warm ocean waters near the Bahamas on Thursday, Hurricane Joaquin strengthened further, reaching Category 4 status on Thursday afternoon. Maximum sustained winds reached 130 miles per hour. The National Hurricane Center suggests additional strengthening is possible, with maximum sustained winds approaching 140 miles per hour.

Computer models have continued their immense struggles with the track and intensity of Joaquin. A storm which was modeled by only a select few to become a major hurricane just days ago, has strengthened far beyond additional expectations. One of the major reasons for this is a farther south track — into warmer waters — which also was not anticipated by modeling until 36-48 hours ago when the ECMWF was the first to suggest a southward jog.

Read more