Jerry Forms but Slow to Strengthen, Tropical Storm Watches Issued for the Northern Leeward Islands
Jerry forecast to pass near the northern Leeward Islands as a hurricane tomorrow and Friday but turn well east of the U.S.
Tropical Storm Jerry, the 10th named storm of the hurricane season, formed late Tuesday morning and is forecast to strengthen into a hurricane on Thursday or Friday as it makes its closest pass near or just north of the northern Leeward Islands.
Tropical Storm Watches were issued on Tuesday for the northern Leeward Islands – including places like Antigua and Barbuda, Anguilla, Saint Martin, Sint Maarten, St. Kitts, Nevis, Montserrat, and Guadeloupe – for the possibility of tropical storm conditions (winds of 39 mph or stronger) in the next few days.
Although the official forecast keeps the center of Jerry about 100 miles northeast of the islands during its pass tomorrow and Friday, periphery effects, including gusty winds and squally rainbands that could pose a flash flood risk, will sweep through the Leeward Islands.
Jerry doesn’t pose a direct threat to Puerto Rico or the Virgin Islands, but a tail of trailing moisture as it pulls north Friday may increase rain chances for the weekend.
As we’ve discussed in earlier newsletters, a strong October cold front diving through the southeastern U.S. and into the western Atlantic this weekend will kick Jerry out to sea.
Jerry is expected to turn well east of Bermuda early next week and doesn’t pose a threat to the British Overseas Territory.
Zippy Jerry struggles to strengthen
Since its formation yesterday, Jerry has struggled, with its center peeking out at times from underneath its cover of convection, and persistent west-to-east wind shear knocking its circulation off kilter.
Wind shear is the difference in wind direction or speed with height. Typically in the tropics, the winds on the ocean blow from east to west – the so-called easterly trade winds – but at higher altitudes can blow very quickly from the opposite direction (west to east). Like pruning shears to a garden hedge, this wind shear can lop off the tops of growing thunderstorms before they have a chance to collect and organize.
In most cases, the bigger influence on wind shear comes from stronger west-to-east flowing winds at the jet stream level (around 30,000 to 40,000 feet up), but in the case of Jerry, its unusually fast forward speed is worsening the wind shear at lower levels.
Jerry’s been sailing along at 23 to 24 mph, an extremely fast motion for a tropical storm or hurricane in the deep tropics. In fact, since satellite records began (since 1966), only five named storms have moved as quickly as Jerry in the deep tropics this late in the season, putting Jerry’s forward motion in the top 1% for this part of the Atlantic.
Forecast models show Jerry slowing down as it makes its turn tomorrow and Friday, which should lessen the shear some and allow it to strengthen.
Overall, intensity guidance has fallen since Tuesday – especially with the higher-end scenarios from our high-resolution hurricane models – but our best-performing consensus aids still suggest Jerry will reach hurricane status before the week is out.
Non-tropical nor’easter shaping up for the weekend
As we detailed in Tuesday’s newsletter, a strong coastal storm developing off the southeastern U.S. this weekend will help drag an uncommonly early fall front through South Florida, ushering in some drier, refreshing air through the Florida Straits by Sunday.
Farther up the coast near the Carolinas, the strengthening non-tropical coastal storm will take on characteristics of a nor’easter, an east coast storm powered primarily by strong jet stream winds with persistent onshore winds from the northeast (hence the nor’easter).
The developing nor’easter will likely bring days of strong winds, soaking rains, coastal flooding, and rough surf and beach erosion, first from the Carolinas and Mid-Atlantic this weekend and extending to the northeast and New England for early next week.
If the system sits long enough over the warm Gulf Stream this weekend, it’s possible it takes on some tropical characteristics by Sunday or early next week. A hybrid subtropical storm can’t be ruled out, though not much would change practically, as it would likely still resemble a nor’easter more than it would a full-fledged tropical system.
If it transitioned into a subtropical storm next week, it would receive a name. The next name on the list is Karen.
As always, ty Mr. Lowry ⚘