 
Subtropical Storm Karen Discussion Number   1
NWS National Hurricane Center Miami FL       AL112025
300 AM GMT Fri Oct 10 2025

Over the last 12-18 hours, NHC has been monitoring a small area of 
low pressure (AL96) embedded in a much larger upper-level trough, 
located about 400 n mi to the northwest of the northernmost Azores 
Islands. The system was originally a frontal low that quickly became 
occluded early on 8 October. Since that time, the low has been 
gradually shedding its remaining frontal features as shallow to 
moderate convection formed near the center. Earlier today, there was 
a Sentinel-1A Synthetic Aperture Radar (SAR) pass that indicated the 
system no longer was attached to frontal boundaries and had a 
contracted radius of maximum wind of 20 n mi. Since that time, the 
convective cloud tops have cooled to -50 to -55 C around the center, 
with a distinct warm spot seen near the center. A recent WSFM 
microwave pass also indicated a nearly closed cyan ring on the 
37-GHz channel. 00 UTC subjective satellite classifications on the 
system were a ST1.5/25-30 kt from TAFB, and a T3.0/45 kt from SAB. A 
blend of all of these various data points indicate that the system 
has made the transition to Subtropical Storm Karen. The initial 
intensity is set at 40 kt, in agreement with a recently received 
scatterometer pass which had a peak wind of 38 kt. This also matches 
the special 02 UTC fix of ST 2.5/35-40 kt received from TAFB.

The subtropical storm is moving slowly northeastward, estimated at 
050/8 kt. Karen is already well established in the mid-latitude 
westerlies for being at such a high latitude, and is likely to be 
caught up by another mid-latitude trough that is digging in from the 
west. The track guidance in in pretty good agreement on a 
northeastward motion with a gradual acceleration over the next 24-36 
hours, and the NHC track forecast is roughly in the middle of the 
guidance envelope, close to the simple and corrected consensus 
aids. 

While Karen has made the transition to a subtropical storm, it still 
remains fully embedded in a large upper-level low, so large in fact 
that it has helped the shear over the system remain fairly low and 
has enabled the convection to coalesce near the center. Very cold 
upper-level temperatures also appear to be contributing to the 
convective vigor, allowing cloud tops of -50 C to persist near the 
center. However, even colder sea-surface temperatures lie ahead of 
Karen's path, and it seems like the system only has about a day or 
so before it is quickly overtaken by the next mid-latitude trough. 
The global models show the small cyclone opening up into a trough by 
48 h, and it is also possible the system could become post-tropical 
before then if it loses its current organized convection. This 
intensity forecast is in general agreement with the mean of the 
intensity guidance. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 44.5N  33.0W   40 KT  45 MPH
 12H  10/1200Z 45.6N  31.7W   40 KT  45 MPH
 24H  11/0000Z 47.8N  29.5W   40 KT  45 MPH
 36H  11/1200Z 50.6N  28.0W   35 KT  40 MPH
 48H  12/0000Z...DISSIPATED
 
$$
Forecaster Papin

Upgraded to 60%/60% in latest TWO…

ABNT20 KNHC 092353
TWOAT 

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 PM EDT Thu Oct 9 2025

For the North Atlantic...Caribbean Sea and the Gulf of America:

Active Systems:
The National Hurricane Center is issuing advisories on Tropical 
Storm Jerry, located just southeast of the northern Leeward Islands.

North Atlantic (AL96):
Showers and thunderstorms continue to show signs of organization 
with a small gale-force area of low pressure located several hundred 
miles to the northwest of the Azores. Only a small increase in 
organization could result in the formation of a subtropical 
or tropical storm as soon as tonight, as the system moves slowly 
northwestward. Over the weekend, the system is expected to move 
over cooler waters, ending its chances of further development. For 
more information on this system, including gale warnings, see High 
Seas Forecasts issued by the National Weather Service and Meteo 
France.
* Formation chance through 48 hours...medium...60 percent.
* Formation chance through 7 days...medium...60 percent.

&&
High Seas Forecasts issued by the National Weather Service
can be found under AWIPS header NFDHSFAT1, WMO header FZNT01 
KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

High Seas Forecasts issued by Meteo France can be found under WMO 
header FQNT50 LFPW and available on the web at
https://tgftp.nws.noaa.gov/data/raw/fq/fqnt50.lfpw.txt

$$
Forecaster Papin

A special TWO was issued a little while ago relating to invest AL96 in the North Atlantic (which has been at 45 kt for a while), upgrading it to 40%/40%.

ABNT20 KNHC 092233
TWOAT 

Special Tropical Weather Outlook
NWS National Hurricane Center Miami FL
635 PM EDT Thu Oct 9 2025

For the North Atlantic...Caribbean Sea and the Gulf of America:

Special outlook issued to update information about the gale-force 
low located several hundred miles northwest of the Azores. 

Active Systems:
The National Hurricane Center is issuing advisories on Tropical 
Storm Jerry, located just southeast of the northern Leeward Islands.

North Atlantic (AL96):
Updated: Showers and thunderstorms have become better organized 
today in association with a gale-force area of low pressure located 
several hundred miles to the northwest of the Azores. If these 
development trends continue, a subtropical or tropical storm could 
form as soon as tonight while the system moves slowly northwestward. 
Over the weekend, the system is expected to move over even cooler 
waters, ending its chances of further development. For more 
information on this system, including gale warnings, see High Seas 
Forecasts issued by the National Weather Service and Meteo France.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...40 percent.

&&
High Seas Forecasts issued by the National Weather Service
can be found under AWIPS header NFDHSFAT1, WMO header FZNT01 
KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php

High Seas Forecasts issued by Meteo France can be found under WMO 
header FQNT50 LFPW and available on the web at
https://tgftp.nws.noaa.gov/data/raw/fq/fqnt50.lfpw.txt

$$
Forecaster Papin/Roberts

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