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Little Change in 90L; Tropical Development Still Possible East of Nicaragua

By: Bob Henson 7:17 PM GMT on November 20, 2016

On Sunday, the tropical disturbance dubbed Invest 90L in the southwest Caribbean Sea continued its leisurely evolution toward possible development into a tropical depression or tropical storm over the next few days. Shower and thunderstorm activity in the vicinity of 90L had decreased a bit since Saturday. The system remained without a low-level center of circulation, although there was plenty of spin in the envelope surrounding 90L. Conditions remain favorable for 90L to intensify if and when it develops a low-level center. Sea surface temperatures around 29.5°C (85°F) are roughly 1°C (1.8°F) above average, and a very moist atmosphere surrounds 90L, with mid-level relative humidities around 80%. Vertical shear is moderate, around 15 knots, and it may decrease a bit to 10 - 15 knots over the next several days. Air Force Hurricane Hunters were en route to investigate 90L on Sunday afternoon.

Figure 1. Visible satellite image of 90L east of Central America at 1817Z (1:17 pm EST) Sunday, November 20, 2016. A separate system is located to the northeast of 90L near Hispaniola.

Figure 2. Infrared satellite image of 90L from 1745Z (12:45 pm EST) Sunday, November 20, 2016. Image credit: NASA/MSFC Earth Science Office.

Outlook for 90L
Computer models remain supportive of 90L intensifying over the upcoming week as it drifts around the southwest Caribbean east of Nicaragua. High pressure will be strengthening at upper levels over the northern Caribbean, and a weakening cool front moving into the region may help strengthen the low-level pressure gradient and the associated easterly winds rotating around 90L. All three of our most reliable operational models for tropical cyclone genesis--the European, GFS, and UKMET models--develop 90L into a tropical depression by Tuesday and intensify it to near hurricane strength by Thursday. All three models bring 90L into Nicaragua around the end of the week, with the UKMET distinctly slower than the Euro and GFS. Almost every member of the Euro and GFS ensemble runs from 00Z Sunday develops 90L into a tropical depression by Tuesday. Most of the ensemble members go on to strengthen 90L into Tropical Storm Otto, but only 1 of the 50 Euro ensemble members, and just 1 of the 20 GFS members, produce a hurricane. Both the Euro and GFS ensemble runs agree strongly that 90L will eventually track west toward Nicaragua, reaching the coast around the end of the week. In its 1:00 pm EST Sunday Tropical Weather Discussion, the National Hurricane Center gave 90L 50-50 odds of developing into at least a tropical depression by Tuesday afternoon, with 70 percent odds through Friday afternoon.

Even if it ends up as no more than a tropical depression or tropical storm, 90L will still be capable of causing major trouble in Central America. The slow-moving system will be capable of bringing days of heavy rain to Panama, Costa Rica, and Nicaragua. Torrential rains could spread into parts of Honduras, Belize, and Guatemala by late in the week assuming 90L moves west and strengthens as expected.

Heavy rains lead to national emergency in Dominican Republic
A separate area of showers and thunderstorms along a remnant front several hundred miles northeast of 90L has led to days of heavy rain across the Dominican Republic (see photos in embedded tweet at bottom). At least five people have been killed, with more than 20,000 people displaced and more than 4000 homes damaged, according to government officials. Parts of the Puerta Plata province on the north coast received more than 600 mm (23.62”) of rain from November 6 to 16, according to floodlist.com, which also noted that six provinces were under a state of national emergency.

Figure 3. Projected rainfall (in inches) from the GFS model run at 12Z (7:00 am EST) Sunday for the 180-hour period ending at 00Z Monday, November 28, 2016 (7:00 pm EST Sunday, November 27). Image credit: tropicaltidbits.com.

Figure 4. The first GOES-R satellite lifts off from Kennedy Space Center on Saturday night, November 19, 2016. Image credit: NASA/Kim Shifltett.

GOES-R is a go!
After a one-hour delay, a NASA rocket sent the first entry in NOAA’s Geostationary Operational Environmental Satellite-R series (GOES-R) into space at 6:42 pm EST Saturday, November 19. Once in orbit after about two weeks, GOES-R will be renamed GOES-16. We’ll have more on Monday about the benefits GOES-R is expected to provide to tropical cyclone monitoring and prediction. We will also be covering 90L as it evolves, with posts throughout the holiday week as needed.

Bob Henson

Hurricane Flood

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.