Olga – Atlantic Ocean

Oct. 28, 2019 – NASA Sees Tropical Cyclone Olga Merge with a Cold Front

Tropical Depression 17 strengthened briefly into a tropical storm on the same day it formed, Oct. 25. NASA’s Terra satellite captured a look at the clouds associated with its remnants merging with a cold front over the southern U.S.

Terra image of Olga
When NASA’s Terra satellite passed over the eastern U.S. on Oct. 26, it found post-tropical cyclone Olga’s clouds spreading into the Mississippi Valley, but there was no discernable center of circulation as the storm became embedded in a cold front. Credit: NASA Worldview

Tropical Depression 17 formed early on Friday, Oct. 25 and by 5 p.m. EDT it had strengthened and organized into a tropical storm and was renamed Olga. However, by 11 p.m. EDT, Olga transitioned again into a post-tropical storm.

The last advisory on Tropical Storm Olga was issued at 11 p.m. EDT on Oct. 25 by the National Hurricane Center or NHC. At that time, the center of Post-Tropical Cyclone Olga was located near latitude 27.8 degrees north and longitude 92.2 degrees west. The post-tropical cyclone was moving toward the northeast near 17 mph (28 kph) and maximum sustained winds were near 50 mph (85 kph) and weakening.

At that time, the NHC discussion said, “Earlier this evening, the last 2 passes through Olga made by an Air Force Reserve Hurricane Hunter aircraft showed that the cyclone had become embedded within a cold front. Strong northwesterly flow was observed within 10 nautical miles northwest of Olga’s center and a sharp temperature and dew point gradient was measured across the cyclone. It does not appear that Olga has separated from the front in any significant way since the plane left. In fact, recent surface observations suggest that either the front passes through the center of the cyclone or its circulation has become poorly defined. Based on all these data, Olga is now classified as post-tropical and this is the last NHC advisory.”

Since Olga became entangled with the front, the winds and seas associated the front were then considered to be representative of the overall system.

Olga’s remnants moved through the Mississippi Valley today and toward the Great Lakes on Sunday, Oct. 27.

By Rob Gutro
NASA’s Goddard Space Flight Center

TD17 – Atlantic Ocean

Oct. 25, 2019 – NASA-NOAA Satellite Catches Development of Gulf Tropical Depression 17

NASA-NOAA’s Suomi NPP satellite passed over the Gulf of Mexico and revealed that a low pressure area was developing into a depression. On Oct. 25, that low pressure area became Tropical Depression 17.

Suomi NPP image of Bualoi
NASA-NOAA’s Suomi NPP satellite passed over the Gulf of Mexico and the VIIRS instrument aboard captured this image of developing Tropical Depression 17 on Oct. 24. Suomi NPP showed that the center of circulation was west of the bulk of clouds. Credit: NASA/NOAA/NRL

On Oct. 24, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard NASA-NOAA’s Suomi NPP satellite captured a visible image of the structure of the low pressure area that became Tropical Depression 17 on Oct. 25. The storm appeared elongated from south to north, but the center was actually located west of all of the clouds and showers. In satellite imagery on Oct. 25, the National Hurricane Center said, “Satellite imagery indicates that the low pressure system in the western Gulf of Mexico has developed a well-defined circulation. In addition, a cluster of strong convection is located near and to the northeast of the low-level center.”

Status of Tropical Depression 17  

At 11 a.m. EDT (1500 UTC) on Oct. 25, the center of Tropical Depression 17 was located near latitude 25.6 degrees north and longitude 94.4 degrees west. That puts the center about 320 miles (515 km) south-southwest of Lake Charles, Louisiana.

The depression was moving toward the north near 16 mph (26 kph).  A motion toward the north-northeast at a faster forward speed is expected later in the day and through Sunday [Oct 27].  Maximum sustained winds are near 35 mph (55 kph) with higher gusts. The estimated minimum central pressure is 1006 millibars.

The National Hurricane Center or NHC said, “Some strengthening is expected and the depression could become a tropical storm later in the day on Oct. 25.  The cyclone is then expected to merge with a cold front and become a post-tropical low with gale-force winds tonight before the center reaches the Gulf coast.”

On the forecast track, the center of the cyclone should move across the northwestern Gulf of Mexico this afternoon and then move over the northern Gulf coast tonight or Saturday morning.

NHC Forecasts Conditions Expected

The NHC noted the following conditions are forecast:  Gale-force winds associated with this system should spread over portions of the northern Gulf coast tonight and Saturday morning. The depression and rainfall ahead of the system along and north of the frontal boundary across the Central Gulf coast is expected to produce total rainfall accumulations of 2 to 4 inches with maximum totals of 8 inches across the Central Gulf coast into the Lower Mississippi Valley through Saturday morning.  These rains may produce flash flooding across the Central Gulf coast into the Lower Mississippi Valley.

Above-normal tides and associated coastal flooding are possible across portions of the northern Gulf coast. A couple tornadoes are possible through tonight across southeast portions of Louisiana and Mississippi into southwest Alabama.

Forecasting a Merge With a Cold Front

The NHC noted, “Since the depression is expected to merge with a cold front and become post-tropical by tonight, hazards related to wind, rainfall and coastal flooding will be covered by products issued by local National Weather Service forecast offices, available at weather.gov.”

Hurricanes are the most powerful weather event on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

By Rob Gutro
NASA’s Goddard Space Flight Center