| Above: Tropical Storm Chris at 11:15 am EDT July 9, 2018. At the time, Chris had top winds of 60 mph. Image credit: NOAA/RAMMB. |
Tropical Storm Chris remained stuck in the waters a few hundred miles off of the North Carolina coast early Monday afternoon, having been nearly stationary for over 18 hours. An Air Force hurricane hunter aircraft on Monday morning measured surface winds of 60 mph in Chris, and found a well-organized storm with a compact inner core. Chris was over the warm Gulf Stream current, where sea surface temperatures (SSTs) were near 28°C (82°F), about 1°C (1.8°F) above average. Wind shear was a light 5 - 10 knots—favorable for development. There was dry air to the north of the center, associated with a cold front stalled over North Carolina, and a tendril of this dry air wrapped into the core of Chris on Monday morning, disrupting the storm and halting its intensification. An eye-like feature has been visible on satellite imagery periodically on Monday.
Chris’s strong winds were kicking up high surf along the North Carolina coast, where a High Surf Advisory for waves of 4 – 6 feet was in effect on Monday. Weather radar showed that Chris’s rains were just offshore of the North Carolina Outer Banks early Monday afternoon, and the storm has brought rains of less than 1” to the Outer Banks since Sunday.
#Chris has the classic look of a tropical cyclone suffering from cold water beneath it. Water temperatures at a buoy to the south are indeed falling quickly. This will limit or prevent intensification until the storm begins moving away from this location. pic.twitter.com/lnv4Mn0ZFk
— Levi Cowan (@TropicalTidbits) July 9, 2018
Forecast for Chris
Steering currents for Chris will be very weak through Tuesday, and the storm will meander over the warm waters of the Gulf Stream, a few hundred miles off the North Carolina coast. Stalled storms churn up colder waters from below, cooling the surface and typically causing weakening. Chris has shown signs of this over the past day (see tweet above), but the flow of warm waters from the south along the Gulf Stream is helping keep SSTs under Chris warmer than one might typically see for a stalled storm.
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| Figure 1. Predicted winds for Chris at 11 am EDT Thursday, July 12, 2018, from the 6Z Monday, July 9, 2018, run of the HWRF model. Chris was predicted to be passing south of Halifax, Nova Scotia, Canada, with top winds near 55 kt (65 mph, dark red colors). The HWRF was our best intensity model in 2017. Image credit: Levi Cowan, tropicaltidbits.com. |
A trough of low pressure will pass to the north of Chris on Tuesday through Wednesday, and this trough is expected by all the models to be strong enough to turn the storm to the northeast on Tuesday night, towards the Canadian maritime provinces. Wind shear is predicted by the SHIPS model to remain light to moderate through Wednesday, which should allow Chris to intensify into a Category 1 or 2 hurricane, assuming that Chris can avoid wrapping another slug of dry air into its core. Our top intensity models—the HWRF, DSHIPS, COAMPS-TC, and LGEM—predicted on Monday morning that Chris would reach peak intensity on Wednesday evening or early Thursday morning, with maximum sustained winds in the Category 1 – 2 range: 75 – 105 mph.
Chris is primarily a high surf threat to the U.S. East Coast, and is not expected to bring any significant rainfall to the U.S. coast. High surf and dangerous rip currents are expected to spread from parts of the North Carolina coast up the mid-Atlantic and New England seaboards Wednesday into Thursday. One death from rough surf has already been blamed on Chris--a 62-year-old man that died on Sunday in the waters of North Carolina's Outer Banks.
When Chris moves to the northeast past the latitude of New Jersey, the storm will leave the warm waters of the Gulf Stream, and also encounter high wind shear of 20+ knots. This is expected to occur Thursday morning, and Chris should steadily weaken and transition to an extratropical storm as it speeds over increasingly colder waters towards Nova Scotia and Newfoundland, Canada. Landfall as an extratropical storm in Canada will likely occur Thursday night or Friday morning, posing both a high wind and heavy rainfall threat, but it is possible that Chris will miss making a direct hit on Canada, passing just south of Newfoundland--as predicted by a number of the 70 members of the 0Z Monday GFS and European model ensemble forecasts.
