SEVERE WEATHER FORECAST SYNOPSIS / INVEST 91L FORECAST SYNOPSIS ISSUED APR. 17, 2017…11:20 A.M. EDT

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!

This is my only available forecast day.  I work tomorrow, have an outpatient procedure Wed., then back to work Thu-Sat.

The SPC has designated the following severe weather risk areas in the Day 1 Outlook as of the 1300Z issuance:

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE HIGH PLAINS…

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS DEEP SOUTH TEXAS…

…SPC SUMMARY…
Very isolated severe thunderstorms with hail and strong wind gusts are expected across parts of the High Plains and south Texas mainly this afternoon and evening.

SPC DAY 1 CONVECTIVE OUTLOOK

Based on the analysis of the outlook, and forecast sounding data from F5 DATA using the current RAP model run, severe thunderstorms should be isolated.  Based on the forecast soundings, indices support the SPC forecast.  The tornado threat should be minimal, with more focus on damaging straight-line winds and hail.  Looking at some of the severe parameters, the RAP model suggests the chance for severe weather may extend through west central Texas, sometime this afternoon, which is outlined in the following map.

F5 DATA RAP MODEL 3:00 P.M. CDT

Indices however, indicate the best probability for isolated supercells and possible isolated tornadoes to occur, will lie within the outlined areas in the SPC outlook maps.

Residents in the outlined SPC risk areas, should monitor NOAA Weather Radio, and local NWS statements for up to date information regarding any necessary actions.

IF A TORNADO WARNING IS ISSUED FOR YOUR AREA…SEEK SHELTER IMMEDIATELY!

The following graphics are linked to their respective sites.  Mouse over and click on the graphics for up to date information.

SPC CONVECTIVE WATCH DISPLAY

SPC MESOSCALE DISCUSSIONS DISPLAY

NWS DOPPLER RADAR SITE MAP

INTELLICAST RADAR SUMMARY (Click local area once map displays to zoom in)

NWS HAZARDS AND WARNINGS DISPLAY (click on graphic, then your area of interest)

ENTER…INVEST 91L:

NOTE:  The NHC issued a Special Tropical Weather Outlook at 12:50 p.m. EDT regarding INVEST91L, indicating a LOW (30%) probability for development over the next 5 days:

An ongoing storm (gale) has been designated INVEST 91L and information is being disseminated through ATCF.  This appears to be the area I mentioned earlier last week, which was forecast to open into a trof, and be kicked out.  Obviously since my last synopsis on the area, conditions have changed.  As of the 12Z ATCF BTK report, the following was available on INVEST 91L:

8:00 PM EDT Mon Apr 17
Location: 32.7°N; 64.8°W
Movement: Nearly stationary
Min pressure: 986 mb/29.12 in
Max sustained: Near 60 mph

NOAA / RAMSDIS SATELLITE LOOP IMAGERY: (CLICK FOR ANIMATION)

Based on my analysis of current information, there appears to be very minimal convection on the west side of this system.  This system is currently baroclinic in nature, and based on analysis of the 06Z TAFB Surface analysis map, this low is associated with a cold occlusion.

NHC TAFB 06Z SURFACE ANALYSIS (CLICK FOR FULL IMAGE)

Albeit wind shear over the system is only 15 kts, and is forecast to become less favorable, then back to favorable after 48 hours, drier air surrounds the outer periphery of the system, SST’s over the area do not support sub-tropical transition, very low levels of TPW (Total Precipitable Water) are indicated, along with zero OHC (Oceanic Heat Content).  The upper level wind pattern is counter-clockwise over the system, in which a low can deepen, however it becomes a very slow process, as opposed to having a clockwise flow aloft.

CIMSS 91L WIND SHEAR PATTERN

CIMSS 91L SST

CIMSS 91L TPW

CIMSS 91L DRY AIR

CIMSS UPPER LEVEL WINDS

IF this takes on sub-tropical characteristics, and becomes a sub-tropical entity, I will be very surprised.

Analysis of current and forecast steering tends to indicate this low should meander about during the next 72 to possibly 96 hours, performing a cyclonic loop, and should slowly weaken and begin to move off slowly to the ENE thereafter.  Shipping interests may wish to monitor the progress of this system over the next 4-5 days.

Elsewhere, Tropical Storm formation is not expected.

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. Bookmark the permalink.

2 Responses to SEVERE WEATHER FORECAST SYNOPSIS / INVEST 91L FORECAST SYNOPSIS ISSUED APR. 17, 2017…11:20 A.M. EDT

  1. dellamom says:

    Thank you, Storm, for doing double duty with winter storms/severe weather and Atlantic disturbances.

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