PRELIMINARY SEVERE WEATHER OUTLOOK / GOMEX LOW / WINTER STORM SYSTEM FORECAST SYNOPSIS…ISSUED FEB. 22, 2017…4:40 P.M. EST

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.
(T. F. “Storm” Walsh III)

For those who have donated to my site, your help has been greatly appreciated.  For those not aware, donations to my site help me offset my out of pocket expenses…such as some of the model maps you view on here, which are only available due to my subscription to the corresponding sites.  The F5 Data maps I post as well, is another out of pocket expense (monthly subscription).  Updates to software (weather related), and costs for my domain name are also out of pocket to me.  To donate, please click the DONATE button to the right.  Any help you provide is immensely appreciated!

Good day everyone!

The Storm Prediction Center (SPC) has designated the following risk areas regarding the probability for Severe Thunderstorms in the Day 3 Outlook for Friday:

…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL AND NORTHERN INDIANA INTO NORTHWESTERN OHIO AND FAR SOUTHERN LOWER MICHIGAN…

…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF SOUTHERN LOWER MICHIGAN AND MUCH OF THE OHIO VALLEY…

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK…

…SUMMARY…
One or more bands of strong to severe thunderstorms are forecast across the southern Great Lakes and Ohio Valley on Friday and Friday night.

SPC DAY 3 SEVERE THUNDERSTORM OUTLOOK
day3otlk_0830

day3prob_0830

The following is from the SPC outlook:

…SYNOPSIS…
A mid-level trough/low is forecast to move from the middle MO Valley eastward to the western Great Lakes and OH Valley and assume a neutral to slightly negative tilt. As this occurs, a belt of strong and cyclonically curved 500-mb flow is forecast to intensify in excess of 100-kt over the OH Valley late Friday night. A surface low near the MO/IA border will develop northeastward into northern Lower Michigan as a warm front to its east advances northward. A cold front near the MS River around midday Friday will sweep eastward across the OH and TN Valleys by daybreak Saturday.

…Southern Great Lakes and Ohio Valley…
Low-level moisture is forecast to slowly increase on strong southerly flow with boundary-layer dewpoints forecast to range 52-58 degrees F. Although cloud cover will retard strong surface heating, cooling mid-level temperatures to around -19 degrees C will contribute to weak buoyancy (ranging from 250-1000 J/kg MUCAPE) within the northward expanding warm sector during the day. As strong forcing for ascent (DCVA) approaches and overspreads the western parts of the area, a band of thunderstorms will likely develop and intensify. Strong effective shear around 50 kt will act to organize updrafts and strengthening 700-mb flow to the 55-60 kt range will contribute to cold pool’s organization and upscale growth. Downward momentum transport via damaging winds are the predominant severe risk. However, some forecast soundings show relatively moist low levels with strong 0-1 km shear in excess of 25-30 kt. A tornado risk may develop with the maturing squall line and/or pre-frontal supercell(s) that eventually merges with the line. A gradual weakening in buoyancy by the early to mid evening into the overnight will likely lead to a lessening in the damaging-wind risk as storms rapidly move east and northeastward after dark.

…TN and southern Appalachians…
Storm development over this region will likely be inhibited by an initially capped warm sector until stronger 500-mb height falls arrive towards evening. Model guidance suggests a squall line will zipper southward into parts of TN as shear profiles strengthen. Damaging winds will be the primary threat. ..Smith.. 02/22/2017

My following synopsis PRELIMINARY, based on 12Z forecast sounding parameters and indices from F5 DATA using the NAM-WRF, as the RAP model only extends out to 12 hours in time.  Based on analysis of this information, the modeling suggests initiation of any appreciable severe weather to begin approximately near 3:00 p.m. CST on Friday.  Keep in mind, the times I am using in this synopsis, can change between now and then, depending on whether the systems slows down or speeds up.  Forecast sounding parameters indicate the best probability for severe thunderstorms, supercells, and isolated tornadoes could occur within the following outlined area:

NAM-WRF 3:00 P.M. CST
f5data-nam-3pmcst

After 3:00 p.m. CST, the model goes out in 3 hour increments, and suggests by 6:00 p.m. CST through 9:00 p.m. CST that sounding and indices values suggest the best probability for an increased threat for severe thunderstorms, supercells and isolated tornadoes to lie within the following outlined areas:

NAM-WRF 6:00 P.M. CST / 9:00 P.M. CST
f5data-nam-6pm-cst

f5data-nam-9pm-cst

Here are some of the indices I’ve chosen to list for you which lie within the the above outlines:

3:00 P.M. CST:
SBCAPE: 1000 j/k
MLCAPE: 1000-1500 j/k
SWEAT INDEX: 400-450
0-6km SHEAR: 50-60 kts
1km HELICITY: 50 m2/s2
3km HELICITY: 200-250 m2/s2
LIFTED INDEX: -4 to -6

6:00 P.M. CST:
SBCAPE: 500-1000 j/k
MLCAPE: 500-1000 j/k
SWEAT INDEX: 375-425
0-6km SHEAR: 60-70 kts
1km HELICITY: 100-150m2/s2
3km HELICITY: 200-300 m2/s2
LIFTED INDEX: -4

9:00 P.M. CST:
SBCAPE: 500-1000 j/k
MLCAPE: 500-1000 j/k
SWEAT INDEX: 375-450
0-6km SHEAR: 50-60 kts
1km HELICITY: 150-200m2/s2
3km HELICITY: 200-300 m2/s2
LIFTED INDEX: -2 to -4

Again, this is PRELIMINARY information based on ONE SET of forecast soundings, and should be used CAUTIOUSLY.

The following graphics are linked for you to click on, to receive up to date graphics and information regarding Friday’s severe weather threat.  I work tomorrow through Saturday, and will not be able to update.

SPC CONVECTIVE WATCHES DISPLAY
validww

SPC MESOSCALE DISCUSSIONS DISPLAY
validmd

NWS HAZARDS AND WARNINGS DISPLAY

INTELLICAST NWS DOPPLER RADAR

INTELLICAST NWS DOPPLER RADAR SUMMARY

ridge_sitemap

An area of low pressure is centered a few miles offshore in the GOMEX, just south of Fort Walton Beach, FL.  This low is currently responsible for bringing moderate to heavy rains across the Florida Peninsula.

GOMEX RGB SATELLITE LOOP (CLICK FOR LOOP)
rgb-l

RAMSDIS GOES EAST THERMAL IR LOOP
geir404

Analysis of the GFS and NAM models indicates the low should push toward the S-SSE during the day, and is progged to move eastward across the state by later tonight into tomorrow, exiting off the Florida east coast. eventually moving off to the NE and becoming absorbed in about 72 hours, by the next winter storm system that will affect portions of the upper Midwest and northern Rockies .

My initial thoughts were with the low being over the GOMEX, that it could begin to take on sub-tropical characteristics.  However, the low is still baroclinic at the moment, being associated with a trailing cold front.  IF the model path is correct, I do not believe the low to transition to sub-tropical, as based on current SST analysis, SST’s are just below the threshold of 23C required to allow and sustain sub-tropical development.  Analysis of current Cyclone Phase Evolution diagrams indicate the low remains cold core throughout the period.  A slim possibility could exist on the Atlantic side, however I am not anticipating this to occur.

SST ANALYSIS
natl_cdas1

CYCLONE PHASE EVOLUTION ANALYSIS
53-phase1

Another winter system is progged to take aim at portions of the upper Midwest and northern Rockies during the next 36-42 hours.  A low is progged to develop over the southern Plains area, and move NE-NNE, bringing snow and a wintry mix to the area by Fri., with icy precipitation moving north of the Great Lakes, and snow continuing for portions of Nebraska, and NEWD by Fri. evening.

GFS FORECAST
gfs_mslp_uv10m_east_11

gfs_ptype_slp_east_11

NAM FORECAST
nam_mslp_uv10m_east_21

nam_ptype_slp_east_22

The following maps are the 72 hour total snowfall accumulations forecast by the GFS and NAM models.

GFS
gfs_6hr_snow_acc_east_13NAM
nam_3hr_snow_acc_east_25

Please stay safe.

Have a blessed day!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS
CoCoRAHS OBSERVER

 

Advertisements

About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc. I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.
Image | This entry was posted in Severe Weather, Tropical Synopsis, Winter. Bookmark the permalink.

2 Responses to PRELIMINARY SEVERE WEATHER OUTLOOK / GOMEX LOW / WINTER STORM SYSTEM FORECAST SYNOPSIS…ISSUED FEB. 22, 2017…4:40 P.M. EST

  1. dellamom says:

    Thank you, Storm. Prayers to all who are in danger. SE Louisiana understands their concerns.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s