WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

90L Near Nicaragua Closer to Tropical Depression Status; GOES-R Going Up

By: Jeff Masters 8:30 PM GMT on November 19, 2016

An area of disturbed weather in the extreme southern Caribbean off the coast of Nicaragua (Invest 90L) became much more organized on Saturday morning and afternoon, and is likely to develop into a tropical depression by Tuesday. Satellite loops on Saturday afternoon showed a considerable increase in 90L’s heavy thunderstorm activity, and the storm had plenty of spin—though no low-level circulation center was present. The disturbance had plenty of moisture to work with (about 75% relative humidity at mid-levels of the atmosphere), and water vapor satellite imagery showed no large-scale areas of dry air that 90L might have to contend with. Wind shear was marginally favorable for development, about 15 - 20 knots. Sea surface temperatures (SSTs) were very warm, near 29.5°C (85°F), which was about 1°C (1.8°F) above average.

Figure 1. MODIS satellite image of 90L taken late Saturday morning, November 19, 2016. Image credit: NASA.

Track forecast: 90L a heavy rain threat to Central America
Steering currents are weak in the region, and 90L will move erratically over the next five days. Most of the models predict a slow westward motion by Wednesday and Thursday, which would bring 90L ashore over Nicaragua late in the week. Heavy rains over Panama, Costa Rica and Nicaragua are a major concern from 90L, as even a weak tropical depression or tropical storm meandering in this area for multiple days could cause significant flooding and landslides.

Our three reliable models for prediction of tropical storm genesis—the European, GFS and UKMET models—continued to forecast in their 12Z Saturday operational runs that 90L would develop into a tropical depression by Tuesday. At least 65% of the 70 forecasts from the 0Z Saturday European and GFS model ensembles predicted that 90L would eventually become Tropical Storm Otto. However, less than 10% of these forecasts showed 90L becoming a hurricane. In their 1 pm EST Saturday Tropical Weather Outlook, NHC gave 90L 2-day and 5-day development odds of 50% and 70%, respectively. An Air Force hurricane hunter aircraft is scheduled to investigate 90L on Sunday afternoon.

GOES-R launch is today!
The new GOES-R satellite is scheduled to be launched at 5:42 pm EST Saturday. Sky and Telescope has details on how to watch the launch in person or online. I’m super excited to see this bird go up!

Jeff Masters


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