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Posted at 11:20 AM ET, 10/24/2012

Sandy strengthens to hurricane on approach to Jamaica; odds of East Coast impact grow


Hurricane Sandy as of 10:15 a.m. EDT (NOAA)
As of 11 a.m. this morning, Sandy’s maximum sustained winds reached 80 mph, becoming the season’s 10th hurricane. This large, strengthening system may threaten the East Coast of the U.S. although there is a chance the storm turns out to sea before reaching the mid-Atlantic and Northeast.

Already, a tropical storm watch is in effect for southeast Florida, the Florida Keys and southeast Bahamas. Closer to the storm’s center, hurricane warnings cover Jamaica and the eastern half of Cuba while tropical storm warnings have been issued for Haiti and the central and northwest Bahamas.

The center of Sandy is now just 50 miles south of Jamaica and the conditions there reflect that. Sandy is now in range of the radar in Pilon, Cuba, which clearly shows its intense rain bands and increasingly well-defined center. The center will pass directly over Kingston, Jamaica shortly.

Given the storm’s large size (tropical storm winds extend 140 miles from the center), rainbands already extend as far away as the Dominican Republic, Haiti, Cuba, and the Bahamas.


National Hurricane Center 5-day track for Sandy
Sandy’s passage over mountainous (elevations up to 3,000’-5,000’) Jamaica and eastern Cuba will certainly weaken the storm a bit. But the ocean water between the two islands and then north of Cuba is very warm (85F-88F) which may allow for a quick recovery and re-intensification.

The official forecast track from the National Hurricane Center brings Sandy over the Bahamas on Thursday evening into Friday morning, which is also it will be closest to southeast Florida. Then, a turn to the northeast away from the coast is expected as it begins to interact with a strong mid-latitude trough (or cold front). Beyond that time, things could really get interesting as a turn back towards the U.S. East Coast is possible.

Long range track forecasts


Deterministic runs from the global models. (NOAA/EMC)
The deterministic runs from the various global models continue to diverge, with some still showing a track out to sea (GFS and CMC) and some showing a more northerly track into the northeast U.S. coast (ECMWF and NOGAPS). It’s unclear yet which will verify, if any, but the ensembles have been trending westward, with more members now showing a very powerful cyclone (probably not completely tropical) slamming into the mid-Atlantic and Northeast states.

The ominous forecast by last night’s ECMWF deterministic run places an incredibly strong cyclone off the New Jersey coast on Monday evening... with tropical storm to hurricane force winds covering every state between Virginia and Maine (note that the wind speeds on this map are at 5,000’ altitude, not the surface). A scenario such as this would be devastating: a huge area with destructive winds, extensive inland flooding, possibly heavy snow on the west side, and severe coastal flooding and erosion.


Surface pressure and 850mb winds valid next Monday evening, from last night’s ECMWF run. (weatherbellmodels.com)

To provide an update on the ensembles and the spread of scenarios they present, below is the same figure I showed yesterday, but updated by a day. A very obvious difference is that the majority of GFS members now show a westward curve, one or two additional members from the UKMO ensemble joined the westward crowd, and quite a handful of CMC ensemble members actually left the westward crowd.


As I mentioned yesterday, given the model trends and the potential impact a storm like this would have on the U.S., it would be wise to begin basic preparations, particularly in terms of the coastal flooding risk over such a large area. Severe conditions could start affecting the mid-Atlantic states as early as Sunday.

Tony forms

Tropical Depression 19 was upgraded to Tropical Storm Tony as expected. Tony is located approximately 1400 miles southwest of the Azores and heading east-northeast at 16mph. It is only a 45mph tropical storm and is forecast to weaken and become extratropical within a couple of days.

A very active season

This season has now had 19 named storms, which is something very few seasons can claim. In fact, 2012 now ties for third (with four other years) for most on record. Amazingly, the last three years have all had 19 named storm, so three of the busiest 7 years on record have all occcurred in the last three years. The most named storms on record occurred in 2005 (28) and 1933 (20).

Tony is the second earliest 19th named storm to form. The only year during which the “T” storm formed earlier was in 2005 with Tammy on October 4.

Although the 2012 Atlantic hurricane season has seen large numbers of named storms, several of them were short-lived (although Nadine almost set longevity records). As of this morning, the current Accumulated Cyclone Energy (ACE) is 115.5, which is well above average for this date and for an entire season. However, 23 other seasons just since 1950 have ended up with higher ACE values, so we have a long way to go even reach the top 10. Sandy will help nudge the 2012 season up a few places though.

Interesting notes:

* Sandy is just the season’s second hurricane to form south of 20N

* Today is the 7-year anniversary of Wilma’s landfall on Florida in 2005, the last time a major hurricane made landfall in the U.S.

* Brian McNoldy is a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

By Brian McNoldy  |  11:20 AM ET, 10/24/2012

Categories:  Latest, Tropical Weather

 
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