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FXXX12 KWNP 201230

:Product: Forecast Discussion
:Issued: 2014 Apr 20 1230 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC contact on the Web
#             Forecast Discussion
Solar Activity

.24 hr Summary...
Solar activity remained at low levels with numerous C-class flares
observed over the past 24 hours. The largest flare of the period was a
C6 event at 20/0813 UTC from Region 2033 (N11W78, Hsx/alpha). Associated
with this event was Type II radio emissions with an estimated shock
velocity of 529 km/s. At 20/0848 UTC, LASCO C2 imagery detected a
slow-moving CME (236 km/s line-of-sight velocity) lifting off the NW
limb. It appears the bulk of the material was moving well north of the
ecliptic, but further analysis will be conducted as more imagery becomes

The three largest regions on the disk, Regions 2034, 2035 and 2036, all
exhibited change during the period. Region 2034 (N04W60, Ekc/beta-gamma)
had some consolidation in its leader spots with some new penumbral spot
development south of the leader. Region 2035 (S16W37, Eki/beta-gamma)
indicated some weak spot development north of the large leader spot.
Region 2036 (S17W62, Dac/beta-gamma) exhibited intermediate spot decay.
All three of these regions produced a few low-level (less than C2)
C-class events.

The remainder the spotted regions displayed little change or slight
decay. No new regions were numbered.

Solar activity is expected to be low with moderate (R1-Minor) activity
likely through day one (20 Apr) with a slight chance for R3-Strong or
greater.  Low levels of activity are expected to persist through days
two and three (21-22 Apr) with a chance for moderate (R1-Minor) events
as Regions 2034, 2035 and 2036 approach the west limb.

Energetic Particle

.24 hr Summary...
The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels for the period. Following the M7 event
on 18 Apr, the greater than 10 MeV proton flux at geosynchronous
orbit passed the 10 pfu (S1-Minor)threshold yesterday at 18/1525 UTC.
Flux reached a maximum of 58 pfu at 19/0105 UTC UTC. Flux levels
increased from about 15 pfu to near 30 pfu after the ACE IP shock
passage at 20/1057 UTC.

The greater than 2 MeV electron flux at geosynchronous orbit is expected
to be at normal to moderate levels for the next three days (20-22 Apr).
The greater than 10 MeV proton flux at geosynchronous orbit is expected
to remain above the 10 pfu threshold (S1-Minor) into day one (20 Apr).
S1 events remain likely on day two (21 Apr) with a continued chance on
day three (22 Apr).

Solar Wind

.24 hr Summary...
Solar wind speed at the ACE spacecraft began the period in the upper 400
to lower 500 km/s range through about 19/1800 UTC. During this time, the
Bz component of the IMF fluctuated between -5 nT and +8 nT while Bt
ranged between 1-10 nT.  A small shock was observed at 19/1754 UTC
suggesting the possible arrival of one of the weak CMEs expected late on
19 April. Wind speed subsequently increased from around 460 km/s to 560
km/s and averaged about 525 km/s through about 20/1100 UTC.

At 20/1057 UTC, a second, stronger shock was observed at ACE. Wind
speeds rapidly rose from about 525 km/s to near 600 km/s and further
increased to 764 km/s by 20/1125 UTC. Bt subsequently increased from 6
to 19 nT and further rose to 21 nT by 20/1114 UTC. IMF Bz remained
mostly positive reaching +21 nT at 20/1114 UTC. Since then, and through
the balance of the period, Bz fluctuated between +8 to -7 nT while wind
speeds averaged near 725 km/s. This shock suggests the possible arrival
of the larger 18 April CME.

Phi was in a generally positive (away) sector through about 20/0830 UTC
where a shift to a negative (towards) orientation was observed. Low
energy particle flux continued to rise throughout the period.

With the suspected arrival of the 18 April CME described above,
disturbed conditions are expected to persist for the next three days
(20-22 Apr).


.24 hr Summary...
The geomagnetic field was at quiet to unsettled levels.

WSA-Enlil model output and manual prognosis suggest the back-to-back
arrivals of the CMEs from the 16th and 18th on day one (20 Apr) of the
forecast.  In light of the already disturbed condition of the
geomagnetic field, and the 19 and 20 April shock arrivals at ACE, active
to major (G2) storm conditions are expected on day one (20 Apr) with
localized episodes of severe storm conditions possible at high
latitudes.  Minor (G1) storm conditions are expected to persist into the
early hours of day two (21 Apr) before diminishing to unsettled to
active levels. Unsettled conditions will linger into day three (22 Apr).

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